Move routines to manipulate WAL into PostgreSQL::Test::Cluster

[pgsql.git] / src / interfaces / libpq / fe-exec.c

/*-------------------------------------------------------------------------
 *
 * fe-exec.c
 *        functions related to sending a query down to the backend
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        src/interfaces/libpq/fe-exec.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"

#include <ctype.h>
#include <fcntl.h>
#include <limits.h>

#ifdef WIN32
#include "win32.h"
#else
#include <unistd.h>
#endif

#include "libpq-fe.h"
#include "libpq-int.h"
#include "mb/pg_wchar.h"

/* keep this in same order as ExecStatusType in libpq-fe.h */
char       *const pgresStatus[] = {
        "PGRES_EMPTY_QUERY",
        "PGRES_COMMAND_OK",
        "PGRES_TUPLES_OK",
        "PGRES_COPY_OUT",
        "PGRES_COPY_IN",
        "PGRES_BAD_RESPONSE",
        "PGRES_NONFATAL_ERROR",
        "PGRES_FATAL_ERROR",
        "PGRES_COPY_BOTH",
        "PGRES_SINGLE_TUPLE",
        "PGRES_PIPELINE_SYNC",
        "PGRES_PIPELINE_ABORTED",
        "PGRES_TUPLES_CHUNK"
};

/* We return this if we're unable to make a PGresult at all */
static const PGresult OOM_result = {
        .resultStatus = PGRES_FATAL_ERROR,
        .client_encoding = PG_SQL_ASCII,
        .errMsg = "out of memory\n",
};

/*
 * static state needed by PQescapeString and PQescapeBytea; initialize to
 * values that result in backward-compatible behavior
 */
static int      static_client_encoding = PG_SQL_ASCII;
static bool static_std_strings = false;


static PGEvent *dupEvents(PGEvent *events, int count, size_t *memSize);
static bool pqAddTuple(PGresult *res, PGresAttValue *tup,
                                           const char **errmsgp);
static int      PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery);
static bool PQsendQueryStart(PGconn *conn, bool newQuery);
static int      PQsendQueryGuts(PGconn *conn,
                                                        const char *command,
                                                        const char *stmtName,
                                                        int nParams,
                                                        const Oid *paramTypes,
                                                        const char *const *paramValues,
                                                        const int *paramLengths,
                                                        const int *paramFormats,
                                                        int resultFormat);
static void parseInput(PGconn *conn);
static PGresult *getCopyResult(PGconn *conn, ExecStatusType copytype);
static bool PQexecStart(PGconn *conn);
static PGresult *PQexecFinish(PGconn *conn);
static int      PQsendTypedCommand(PGconn *conn, char command, char type,
                                                           const char *target);
static int      check_field_number(const PGresult *res, int field_num);
static void pqPipelineProcessQueue(PGconn *conn);
static int      pqPipelineSyncInternal(PGconn *conn, bool immediate_flush);
static int      pqPipelineFlush(PGconn *conn);


/* ----------------
 * Space management for PGresult.
 *
 * Formerly, libpq did a separate malloc() for each field of each tuple
 * returned by a query.  This was remarkably expensive --- malloc/free
 * consumed a sizable part of the application's runtime.  And there is
 * no real need to keep track of the fields separately, since they will
 * all be freed together when the PGresult is released.  So now, we grab
 * large blocks of storage from malloc and allocate space for query data
 * within these blocks, using a trivially simple allocator.  This reduces
 * the number of malloc/free calls dramatically, and it also avoids
 * fragmentation of the malloc storage arena.
 * The PGresult structure itself is still malloc'd separately.  We could
 * combine it with the first allocation block, but that would waste space
 * for the common case that no extra storage is actually needed (that is,
 * the SQL command did not return tuples).
 *
 * We also malloc the top-level array of tuple pointers separately, because
 * we need to be able to enlarge it via realloc, and our trivial space
 * allocator doesn't handle that effectively.  (Too bad the FE/BE protocol
 * doesn't tell us up front how many tuples will be returned.)
 * All other subsidiary storage for a PGresult is kept in PGresult_data blocks
 * of size PGRESULT_DATA_BLOCKSIZE.  The overhead at the start of each block
 * is just a link to the next one, if any.  Free-space management info is
 * kept in the owning PGresult.
 * A query returning a small amount of data will thus require three malloc
 * calls: one for the PGresult, one for the tuples pointer array, and one
 * PGresult_data block.
 *
 * Only the most recently allocated PGresult_data block is a candidate to
 * have more stuff added to it --- any extra space left over in older blocks
 * is wasted.  We could be smarter and search the whole chain, but the point
 * here is to be simple and fast.  Typical applications do not keep a PGresult
 * around very long anyway, so some wasted space within one is not a problem.
 *
 * Tuning constants for the space allocator are:
 * PGRESULT_DATA_BLOCKSIZE: size of a standard allocation block, in bytes
 * PGRESULT_ALIGN_BOUNDARY: assumed alignment requirement for binary data
 * PGRESULT_SEP_ALLOC_THRESHOLD: objects bigger than this are given separate
 *       blocks, instead of being crammed into a regular allocation block.
 * Requirements for correct function are:
 * PGRESULT_ALIGN_BOUNDARY must be a multiple of the alignment requirements
 *              of all machine data types.  (Currently this is set from configure
 *              tests, so it should be OK automatically.)
 * PGRESULT_SEP_ALLOC_THRESHOLD + PGRESULT_BLOCK_OVERHEAD <=
 *                      PGRESULT_DATA_BLOCKSIZE
 *              pqResultAlloc assumes an object smaller than the threshold will fit
 *              in a new block.
 * The amount of space wasted at the end of a block could be as much as
 * PGRESULT_SEP_ALLOC_THRESHOLD, so it doesn't pay to make that too large.
 * ----------------
 */

#define PGRESULT_DATA_BLOCKSIZE         2048
#define PGRESULT_ALIGN_BOUNDARY         MAXIMUM_ALIGNOF /* from configure */
#define PGRESULT_BLOCK_OVERHEAD         Max(sizeof(PGresult_data), PGRESULT_ALIGN_BOUNDARY)
#define PGRESULT_SEP_ALLOC_THRESHOLD    (PGRESULT_DATA_BLOCKSIZE / 2)


/*
 * PQmakeEmptyPGresult
 *       returns a newly allocated, initialized PGresult with given status.
 *       If conn is not NULL and status indicates an error, the conn's
 *       errorMessage is copied.  Also, any PGEvents are copied from the conn.
 *
 * Note: the logic to copy the conn's errorMessage is now vestigial;
 * no internal caller uses it.  However, that behavior is documented for
 * outside callers, so we'd better keep it.
 */
PGresult *
PQmakeEmptyPGresult(PGconn *conn, ExecStatusType status)
{
        PGresult   *result;

        result = (PGresult *) malloc(sizeof(PGresult));
        if (!result)
                return NULL;

        result->ntups = 0;
        result->numAttributes = 0;
        result->attDescs = NULL;
        result->tuples = NULL;
        result->tupArrSize = 0;
        result->numParameters = 0;
        result->paramDescs = NULL;
        result->resultStatus = status;
        result->cmdStatus[0] = '\0';
        result->binary = 0;
        result->events = NULL;
        result->nEvents = 0;
        result->errMsg = NULL;
        result->errFields = NULL;
        result->errQuery = NULL;
        result->null_field[0] = '\0';
        result->curBlock = NULL;
        result->curOffset = 0;
        result->spaceLeft = 0;
        result->memorySize = sizeof(PGresult);

        if (conn)
        {
                /* copy connection data we might need for operations on PGresult */
                result->noticeHooks = conn->noticeHooks;
                result->client_encoding = conn->client_encoding;

                /* consider copying conn's errorMessage */
                switch (status)
                {
                        case PGRES_EMPTY_QUERY:
                        case PGRES_COMMAND_OK:
                        case PGRES_TUPLES_OK:
                        case PGRES_COPY_OUT:
                        case PGRES_COPY_IN:
                        case PGRES_COPY_BOTH:
                        case PGRES_SINGLE_TUPLE:
                        case PGRES_TUPLES_CHUNK:
                                /* non-error cases */
                                break;
                        default:
                                /* we intentionally do not use or modify errorReported here */
                                pqSetResultError(result, &conn->errorMessage, 0);
                                break;
                }

                /* copy events last; result must be valid if we need to PQclear */
                if (conn->nEvents > 0)
                {
                        result->events = dupEvents(conn->events, conn->nEvents,
                                                                           &result->memorySize);
                        if (!result->events)
                        {
                                PQclear(result);
                                return NULL;
                        }
                        result->nEvents = conn->nEvents;
                }
        }
        else
        {
                /* defaults... */
                result->noticeHooks.noticeRec = NULL;
                result->noticeHooks.noticeRecArg = NULL;
                result->noticeHooks.noticeProc = NULL;
                result->noticeHooks.noticeProcArg = NULL;
                result->client_encoding = PG_SQL_ASCII;
        }

        return result;
}

/*
 * PQsetResultAttrs
 *
 * Set the attributes for a given result.  This function fails if there are
 * already attributes contained in the provided result.  The call is
 * ignored if numAttributes is zero or attDescs is NULL.  If the
 * function fails, it returns zero.  If the function succeeds, it
 * returns a non-zero value.
 */
int
PQsetResultAttrs(PGresult *res, int numAttributes, PGresAttDesc *attDescs)
{
        int                     i;

        /* Fail if argument is NULL or OOM_result */
        if (!res || (const PGresult *) res == &OOM_result)
                return false;

        /* If attrs already exist, they cannot be overwritten. */
        if (res->numAttributes > 0)
                return false;

        /* ignore no-op request */
        if (numAttributes <= 0 || !attDescs)
                return true;

        res->attDescs = (PGresAttDesc *)
                PQresultAlloc(res, numAttributes * sizeof(PGresAttDesc));

        if (!res->attDescs)
                return false;

        res->numAttributes = numAttributes;
        memcpy(res->attDescs, attDescs, numAttributes * sizeof(PGresAttDesc));

        /* deep-copy the attribute names, and determine format */
        res->binary = 1;
        for (i = 0; i < res->numAttributes; i++)
        {
                if (res->attDescs[i].name)
                        res->attDescs[i].name = pqResultStrdup(res, res->attDescs[i].name);
                else
                        res->attDescs[i].name = res->null_field;

                if (!res->attDescs[i].name)
                        return false;

                if (res->attDescs[i].format == 0)
                        res->binary = 0;
        }

        return true;
}

/*
 * PQcopyResult
 *
 * Returns a deep copy of the provided 'src' PGresult, which cannot be NULL.
 * The 'flags' argument controls which portions of the result will or will
 * NOT be copied.  The created result is always put into the
 * PGRES_TUPLES_OK status.  The source result error message is not copied,
 * although cmdStatus is.
 *
 * To set custom attributes, use PQsetResultAttrs.  That function requires
 * that there are no attrs contained in the result, so to use that
 * function you cannot use the PG_COPYRES_ATTRS or PG_COPYRES_TUPLES
 * options with this function.
 *
 * Options:
 *       PG_COPYRES_ATTRS - Copy the source result's attributes
 *
 *       PG_COPYRES_TUPLES - Copy the source result's tuples.  This implies
 *       copying the attrs, seeing how the attrs are needed by the tuples.
 *
 *       PG_COPYRES_EVENTS - Copy the source result's events.
 *
 *       PG_COPYRES_NOTICEHOOKS - Copy the source result's notice hooks.
 */
PGresult *
PQcopyResult(const PGresult *src, int flags)
{
        PGresult   *dest;
        int                     i;

        if (!src)
                return NULL;

        dest = PQmakeEmptyPGresult(NULL, PGRES_TUPLES_OK);
        if (!dest)
                return NULL;

        /* Always copy these over.  Is cmdStatus really useful here? */
        dest->client_encoding = src->client_encoding;
        strcpy(dest->cmdStatus, src->cmdStatus);

        /* Wants attrs? */
        if (flags & (PG_COPYRES_ATTRS | PG_COPYRES_TUPLES))
        {
                if (!PQsetResultAttrs(dest, src->numAttributes, src->attDescs))
                {
                        PQclear(dest);
                        return NULL;
                }
        }

        /* Wants to copy tuples? */
        if (flags & PG_COPYRES_TUPLES)
        {
                int                     tup,
                                        field;

                for (tup = 0; tup < src->ntups; tup++)
                {
                        for (field = 0; field < src->numAttributes; field++)
                        {
                                if (!PQsetvalue(dest, tup, field,
                                                                src->tuples[tup][field].value,
                                                                src->tuples[tup][field].len))
                                {
                                        PQclear(dest);
                                        return NULL;
                                }
                        }
                }
        }

        /* Wants to copy notice hooks? */
        if (flags & PG_COPYRES_NOTICEHOOKS)
                dest->noticeHooks = src->noticeHooks;

        /* Wants to copy PGEvents? */
        if ((flags & PG_COPYRES_EVENTS) && src->nEvents > 0)
        {
                dest->events = dupEvents(src->events, src->nEvents,
                                                                 &dest->memorySize);
                if (!dest->events)
                {
                        PQclear(dest);
                        return NULL;
                }
                dest->nEvents = src->nEvents;
        }

        /* Okay, trigger PGEVT_RESULTCOPY event */
        for (i = 0; i < dest->nEvents; i++)
        {
                /* We don't fire events that had some previous failure */
                if (src->events[i].resultInitialized)
                {
                        PGEventResultCopy evt;

                        evt.src = src;
                        evt.dest = dest;
                        if (dest->events[i].proc(PGEVT_RESULTCOPY, &evt,
                                                                         dest->events[i].passThrough))
                                dest->events[i].resultInitialized = true;
                }
        }

        return dest;
}

/*
 * Copy an array of PGEvents (with no extra space for more).
 * Does not duplicate the event instance data, sets this to NULL.
 * Also, the resultInitialized flags are all cleared.
 * The total space allocated is added to *memSize.
 */
static PGEvent *
dupEvents(PGEvent *events, int count, size_t *memSize)
{
        PGEvent    *newEvents;
        size_t          msize;
        int                     i;

        if (!events || count <= 0)
                return NULL;

        msize = count * sizeof(PGEvent);
        newEvents = (PGEvent *) malloc(msize);
        if (!newEvents)
                return NULL;

        for (i = 0; i < count; i++)
        {
                newEvents[i].proc = events[i].proc;
                newEvents[i].passThrough = events[i].passThrough;
                newEvents[i].data = NULL;
                newEvents[i].resultInitialized = false;
                newEvents[i].name = strdup(events[i].name);
                if (!newEvents[i].name)
                {
                        while (--i >= 0)
                                free(newEvents[i].name);
                        free(newEvents);
                        return NULL;
                }
                msize += strlen(events[i].name) + 1;
        }

        *memSize += msize;
        return newEvents;
}


/*
 * Sets the value for a tuple field.  The tup_num must be less than or
 * equal to PQntuples(res).  If it is equal, a new tuple is created and
 * added to the result.
 * Returns a non-zero value for success and zero for failure.
 * (On failure, we report the specific problem via pqInternalNotice.)
 */
int
PQsetvalue(PGresult *res, int tup_num, int field_num, char *value, int len)
{
        PGresAttValue *attval;
        const char *errmsg = NULL;

        /* Fail if argument is NULL or OOM_result */
        if (!res || (const PGresult *) res == &OOM_result)
                return false;

        /* Invalid field_num? */
        if (!check_field_number(res, field_num))
                return false;

        /* Invalid tup_num, must be <= ntups */
        if (tup_num < 0 || tup_num > res->ntups)
        {
                pqInternalNotice(&res->noticeHooks,
                                                 "row number %d is out of range 0..%d",
                                                 tup_num, res->ntups);
                return false;
        }

        /* need to allocate a new tuple? */
        if (tup_num == res->ntups)
        {
                PGresAttValue *tup;
                int                     i;

                tup = (PGresAttValue *)
                        pqResultAlloc(res, res->numAttributes * sizeof(PGresAttValue),
                                                  true);

                if (!tup)
                        goto fail;

                /* initialize each column to NULL */
                for (i = 0; i < res->numAttributes; i++)
                {
                        tup[i].len = NULL_LEN;
                        tup[i].value = res->null_field;
                }

                /* add it to the array */
                if (!pqAddTuple(res, tup, &errmsg))
                        goto fail;
        }

        attval = &res->tuples[tup_num][field_num];

        /* treat either NULL_LEN or NULL value pointer as a NULL field */
        if (len == NULL_LEN || value == NULL)
        {
                attval->len = NULL_LEN;
                attval->value = res->null_field;
        }
        else if (len <= 0)
        {
                attval->len = 0;
                attval->value = res->null_field;
        }
        else
        {
                attval->value = (char *) pqResultAlloc(res, len + 1, true);
                if (!attval->value)
                        goto fail;
                attval->len = len;
                memcpy(attval->value, value, len);
                attval->value[len] = '\0';
        }

        return true;

        /*
         * Report failure via pqInternalNotice.  If preceding code didn't provide
         * an error message, assume "out of memory" was meant.
         */
fail:
        if (!errmsg)
                errmsg = libpq_gettext("out of memory");
        pqInternalNotice(&res->noticeHooks, "%s", errmsg);

        return false;
}

/*
 * pqResultAlloc - exported routine to allocate local storage in a PGresult.
 *
 * We force all such allocations to be maxaligned, since we don't know
 * whether the value might be binary.
 */
void *
PQresultAlloc(PGresult *res, size_t nBytes)
{
        /* Fail if argument is NULL or OOM_result */
        if (!res || (const PGresult *) res == &OOM_result)
                return NULL;

        return pqResultAlloc(res, nBytes, true);
}

/*
 * pqResultAlloc -
 *              Allocate subsidiary storage for a PGresult.
 *
 * nBytes is the amount of space needed for the object.
 * If isBinary is true, we assume that we need to align the object on
 * a machine allocation boundary.
 * If isBinary is false, we assume the object is a char string and can
 * be allocated on any byte boundary.
 */
void *
pqResultAlloc(PGresult *res, size_t nBytes, bool isBinary)
{
        char       *space;
        PGresult_data *block;

        if (!res)
                return NULL;

        if (nBytes <= 0)
                return res->null_field;

        /*
         * If alignment is needed, round up the current position to an alignment
         * boundary.
         */
        if (isBinary)
        {
                int                     offset = res->curOffset % PGRESULT_ALIGN_BOUNDARY;

                if (offset)
                {
                        res->curOffset += PGRESULT_ALIGN_BOUNDARY - offset;
                        res->spaceLeft -= PGRESULT_ALIGN_BOUNDARY - offset;
                }
        }

        /* If there's enough space in the current block, no problem. */
        if (nBytes <= (size_t) res->spaceLeft)
        {
                space = res->curBlock->space + res->curOffset;
                res->curOffset += nBytes;
                res->spaceLeft -= nBytes;
                return space;
        }

        /*
         * If the requested object is very large, give it its own block; this
         * avoids wasting what might be most of the current block to start a new
         * block.  (We'd have to special-case requests bigger than the block size
         * anyway.)  The object is always given binary alignment in this case.
         */
        if (nBytes >= PGRESULT_SEP_ALLOC_THRESHOLD)
        {
                size_t          alloc_size = nBytes + PGRESULT_BLOCK_OVERHEAD;

                block = (PGresult_data *) malloc(alloc_size);
                if (!block)
                        return NULL;
                res->memorySize += alloc_size;
                space = block->space + PGRESULT_BLOCK_OVERHEAD;
                if (res->curBlock)
                {
                        /*
                         * Tuck special block below the active block, so that we don't
                         * have to waste the free space in the active block.
                         */
                        block->next = res->curBlock->next;
                        res->curBlock->next = block;
                }
                else
                {
                        /* Must set up the new block as the first active block. */
                        block->next = NULL;
                        res->curBlock = block;
                        res->spaceLeft = 0; /* be sure it's marked full */
                }
                return space;
        }

        /* Otherwise, start a new block. */
        block = (PGresult_data *) malloc(PGRESULT_DATA_BLOCKSIZE);
        if (!block)
                return NULL;
        res->memorySize += PGRESULT_DATA_BLOCKSIZE;
        block->next = res->curBlock;
        res->curBlock = block;
        if (isBinary)
        {
                /* object needs full alignment */
                res->curOffset = PGRESULT_BLOCK_OVERHEAD;
                res->spaceLeft = PGRESULT_DATA_BLOCKSIZE - PGRESULT_BLOCK_OVERHEAD;
        }
        else
        {
                /* we can cram it right after the overhead pointer */
                res->curOffset = sizeof(PGresult_data);
                res->spaceLeft = PGRESULT_DATA_BLOCKSIZE - sizeof(PGresult_data);
        }

        space = block->space + res->curOffset;
        res->curOffset += nBytes;
        res->spaceLeft -= nBytes;
        return space;
}

/*
 * PQresultMemorySize -
 *              Returns total space allocated for the PGresult.
 */
size_t
PQresultMemorySize(const PGresult *res)
{
        if (!res)
                return 0;
        return res->memorySize;
}

/*
 * pqResultStrdup -
 *              Like strdup, but the space is subsidiary PGresult space.
 */
char *
pqResultStrdup(PGresult *res, const char *str)
{
        char       *space = (char *) pqResultAlloc(res, strlen(str) + 1, false);

        if (space)
                strcpy(space, str);
        return space;
}

/*
 * pqSetResultError -
 *              assign a new error message to a PGresult
 *
 * Copy text from errorMessage buffer beginning at given offset
 * (it's caller's responsibility that offset is valid)
 */
void
pqSetResultError(PGresult *res, PQExpBuffer errorMessage, int offset)
{
        char       *msg;

        if (!res)
                return;

        /*
         * We handle two OOM scenarios here.  The errorMessage buffer might be
         * marked "broken" due to having previously failed to allocate enough
         * memory for the message, or it might be fine but pqResultStrdup fails
         * and returns NULL.  In either case, just make res->errMsg point directly
         * at a constant "out of memory" string.
         */
        if (!PQExpBufferBroken(errorMessage))
                msg = pqResultStrdup(res, errorMessage->data + offset);
        else
                msg = NULL;
        if (msg)
                res->errMsg = msg;
        else
                res->errMsg = libpq_gettext("out of memory\n");
}

/*
 * PQclear -
 *        free's the memory associated with a PGresult
 */
void
PQclear(PGresult *res)
{
        PGresult_data *block;
        int                     i;

        /* As a convenience, do nothing for a NULL pointer */
        if (!res)
                return;
        /* Also, do nothing if the argument is OOM_result */
        if ((const PGresult *) res == &OOM_result)
                return;

        /* Close down any events we may have */
        for (i = 0; i < res->nEvents; i++)
        {
                /* only send DESTROY to successfully-initialized event procs */
                if (res->events[i].resultInitialized)
                {
                        PGEventResultDestroy evt;

                        evt.result = res;
                        (void) res->events[i].proc(PGEVT_RESULTDESTROY, &evt,
                                                                           res->events[i].passThrough);
                }
                free(res->events[i].name);
        }

        free(res->events);

        /* Free all the subsidiary blocks */
        while ((block = res->curBlock) != NULL)
        {
                res->curBlock = block->next;
                free(block);
        }

        /* Free the top-level tuple pointer array */
        free(res->tuples);

        /* zero out the pointer fields to catch programming errors */
        res->attDescs = NULL;
        res->tuples = NULL;
        res->paramDescs = NULL;
        res->errFields = NULL;
        res->events = NULL;
        res->nEvents = 0;
        /* res->curBlock was zeroed out earlier */

        /* Free the PGresult structure itself */
        free(res);
}

/*
 * Handy subroutine to deallocate any partially constructed async result.
 *
 * Any "saved" result gets cleared too.
 */
void
pqClearAsyncResult(PGconn *conn)
{
        PQclear(conn->result);
        conn->result = NULL;
        conn->error_result = false;
        PQclear(conn->saved_result);
        conn->saved_result = NULL;
}

/*
 * pqSaveErrorResult -
 *        remember that we have an error condition
 *
 * In much of libpq, reporting an error just requires appending text to
 * conn->errorMessage and returning a failure code to one's caller.
 * Where returning a failure code is impractical, instead call this
 * function to remember that an error needs to be reported.
 *
 * (It might seem that appending text to conn->errorMessage should be
 * sufficient, but we can't rely on that working under out-of-memory
 * conditions.  The OOM hazard is also why we don't try to make a new
 * PGresult right here.)
 */
void
pqSaveErrorResult(PGconn *conn)
{
        /* Drop any pending result ... */
        pqClearAsyncResult(conn);
        /* ... and set flag to remember to make an error result later */
        conn->error_result = true;
}

/*
 * pqSaveWriteError -
 *        report a write failure
 *
 * As above, after appending conn->write_err_msg to whatever other error we
 * have.  This is used when we've detected a write failure and have exhausted
 * our chances of reporting something else instead.
 */
static void
pqSaveWriteError(PGconn *conn)
{
        /*
         * If write_err_msg is null because of previous strdup failure, do what we
         * can.  (It's likely our machinations here will get OOM failures as well,
         * but might as well try.)
         */
        if (conn->write_err_msg)
        {
                appendPQExpBufferStr(&conn->errorMessage, conn->write_err_msg);
                /* Avoid possibly appending the same message twice */
                conn->write_err_msg[0] = '\0';
        }
        else
                libpq_append_conn_error(conn, "write to server failed");

        pqSaveErrorResult(conn);
}

/*
 * pqPrepareAsyncResult -
 *        prepare the current async result object for return to the caller
 *
 * If there is not already an async result object, build an error object
 * using whatever is in conn->errorMessage.  In any case, clear the async
 * result storage, and update our notion of how much error text has been
 * returned to the application.
 *
 * Note that in no case (not even OOM) do we return NULL.
 */
PGresult *
pqPrepareAsyncResult(PGconn *conn)
{
        PGresult   *res;

        res = conn->result;
        if (res)
        {
                /*
                 * If the pre-existing result is an ERROR (presumably something
                 * received from the server), assume that it represents whatever is in
                 * conn->errorMessage, and advance errorReported.
                 */
                if (res->resultStatus == PGRES_FATAL_ERROR)
                        conn->errorReported = conn->errorMessage.len;
        }
        else
        {
                /*
                 * We get here after internal-to-libpq errors.  We should probably
                 * always have error_result = true, but if we don't, gin up some error
                 * text.
                 */
                if (!conn->error_result)
                        libpq_append_conn_error(conn, "no error text available");

                /* Paranoia: be sure errorReported offset is sane */
                if (conn->errorReported < 0 ||
                        conn->errorReported >= conn->errorMessage.len)
                        conn->errorReported = 0;

                /*
                 * Make a PGresult struct for the error.  We temporarily lie about the
                 * result status, so that PQmakeEmptyPGresult doesn't uselessly copy
                 * all of conn->errorMessage.
                 */
                res = PQmakeEmptyPGresult(conn, PGRES_EMPTY_QUERY);
                if (res)
                {
                        /*
                         * Report whatever new error text we have, and advance
                         * errorReported.
                         */
                        res->resultStatus = PGRES_FATAL_ERROR;
                        pqSetResultError(res, &conn->errorMessage, conn->errorReported);
                        conn->errorReported = conn->errorMessage.len;
                }
                else
                {
                        /*
                         * Ouch, not enough memory for a PGresult.  Fortunately, we have a
                         * card up our sleeve: we can use the static OOM_result.  Casting
                         * away const here is a bit ugly, but it seems best to declare
                         * OOM_result as const, in hopes it will be allocated in read-only
                         * storage.
                         */
                        res = unconstify(PGresult *, &OOM_result);

                        /*
                         * Don't advance errorReported.  Perhaps we'll be able to report
                         * the text later.
                         */
                }
        }

        /*
         * Replace conn->result with saved_result, if any.  In the normal case
         * there isn't a saved result and we're just dropping ownership of the
         * current result.  In partial-result mode this restores the situation to
         * what it was before we created the current partial result.
         */
        conn->result = conn->saved_result;
        conn->error_result = false; /* saved_result is never an error */
        conn->saved_result = NULL;

        return res;
}

/*
 * pqInternalNotice - produce an internally-generated notice message
 *
 * A format string and optional arguments can be passed.  Note that we do
 * libpq_gettext() here, so callers need not.
 *
 * The supplied text is taken as primary message (ie., it should not include
 * a trailing newline, and should not be more than one line).
 */
void
pqInternalNotice(const PGNoticeHooks *hooks, const char *fmt,...)
{
        char            msgBuf[1024];
        va_list         args;
        PGresult   *res;

        if (hooks->noticeRec == NULL)
                return;                                 /* nobody home to receive notice? */

        /* Format the message */
        va_start(args, fmt);
        vsnprintf(msgBuf, sizeof(msgBuf), libpq_gettext(fmt), args);
        va_end(args);
        msgBuf[sizeof(msgBuf) - 1] = '\0';      /* make real sure it's terminated */

        /* Make a PGresult to pass to the notice receiver */
        res = PQmakeEmptyPGresult(NULL, PGRES_NONFATAL_ERROR);
        if (!res)
                return;
        res->noticeHooks = *hooks;

        /*
         * Set up fields of notice.
         */
        pqSaveMessageField(res, PG_DIAG_MESSAGE_PRIMARY, msgBuf);
        pqSaveMessageField(res, PG_DIAG_SEVERITY, libpq_gettext("NOTICE"));
        pqSaveMessageField(res, PG_DIAG_SEVERITY_NONLOCALIZED, "NOTICE");
        /* XXX should provide a SQLSTATE too? */

        /*
         * Result text is always just the primary message + newline.  If we can't
         * allocate it, substitute "out of memory", as in pqSetResultError.
         */
        res->errMsg = (char *) pqResultAlloc(res, strlen(msgBuf) + 2, false);
        if (res->errMsg)
                sprintf(res->errMsg, "%s\n", msgBuf);
        else
                res->errMsg = libpq_gettext("out of memory\n");

        /*
         * Pass to receiver, then free it.
         */
        res->noticeHooks.noticeRec(res->noticeHooks.noticeRecArg, res);
        PQclear(res);
}

/*
 * pqAddTuple
 *        add a row pointer to the PGresult structure, growing it if necessary
 *        Returns true if OK, false if an error prevented adding the row
 *
 * On error, *errmsgp can be set to an error string to be returned.
 * If it is left NULL, the error is presumed to be "out of memory".
 */
static bool
pqAddTuple(PGresult *res, PGresAttValue *tup, const char **errmsgp)
{
        if (res->ntups >= res->tupArrSize)
        {
                /*
                 * Try to grow the array.
                 *
                 * We can use realloc because shallow copying of the structure is
                 * okay. Note that the first time through, res->tuples is NULL. While
                 * ANSI says that realloc() should act like malloc() in that case,
                 * some old C libraries (like SunOS 4.1.x) coredump instead. On
                 * failure realloc is supposed to return NULL without damaging the
                 * existing allocation. Note that the positions beyond res->ntups are
                 * garbage, not necessarily NULL.
                 */
                int                     newSize;
                PGresAttValue **newTuples;

                /*
                 * Since we use integers for row numbers, we can't support more than
                 * INT_MAX rows.  Make sure we allow that many, though.
                 */
                if (res->tupArrSize <= INT_MAX / 2)
                        newSize = (res->tupArrSize > 0) ? res->tupArrSize * 2 : 128;
                else if (res->tupArrSize < INT_MAX)
                        newSize = INT_MAX;
                else
                {
                        *errmsgp = libpq_gettext("PGresult cannot support more than INT_MAX tuples");
                        return false;
                }

                /*
                 * Also, on 32-bit platforms we could, in theory, overflow size_t even
                 * before newSize gets to INT_MAX.  (In practice we'd doubtless hit
                 * OOM long before that, but let's check.)
                 */
#if INT_MAX >= (SIZE_MAX / 2)
                if (newSize > SIZE_MAX / sizeof(PGresAttValue *))
                {
                        *errmsgp = libpq_gettext("size_t overflow");
                        return false;
                }
#endif

                if (res->tuples == NULL)
                        newTuples = (PGresAttValue **)
                                malloc(newSize * sizeof(PGresAttValue *));
                else
                        newTuples = (PGresAttValue **)
                                realloc(res->tuples, newSize * sizeof(PGresAttValue *));
                if (!newTuples)
                        return false;           /* malloc or realloc failed */
                res->memorySize +=
                        (newSize - res->tupArrSize) * sizeof(PGresAttValue *);
                res->tupArrSize = newSize;
                res->tuples = newTuples;
        }
        res->tuples[res->ntups] = tup;
        res->ntups++;
        return true;
}

/*
 * pqSaveMessageField - save one field of an error or notice message
 */
void
pqSaveMessageField(PGresult *res, char code, const char *value)
{
        PGMessageField *pfield;

        pfield = (PGMessageField *)
                pqResultAlloc(res,
                                          offsetof(PGMessageField, contents) +
                                          strlen(value) + 1,
                                          true);
        if (!pfield)
                return;                                 /* out of memory? */
        pfield->code = code;
        strcpy(pfield->contents, value);
        pfield->next = res->errFields;
        res->errFields = pfield;
}

/*
 * pqSaveParameterStatus - remember parameter status sent by backend
 */
void
pqSaveParameterStatus(PGconn *conn, const char *name, const char *value)
{
        pgParameterStatus *pstatus;
        pgParameterStatus *prev;

        /*
         * Forget any old information about the parameter
         */
        for (pstatus = conn->pstatus, prev = NULL;
                 pstatus != NULL;
                 prev = pstatus, pstatus = pstatus->next)
        {
                if (strcmp(pstatus->name, name) == 0)
                {
                        if (prev)
                                prev->next = pstatus->next;
                        else
                                conn->pstatus = pstatus->next;
                        free(pstatus);          /* frees name and value strings too */
                        break;
                }
        }

        /*
         * Store new info as a single malloc block
         */
        pstatus = (pgParameterStatus *) malloc(sizeof(pgParameterStatus) +
                                                                                   strlen(name) + strlen(value) + 2);
        if (pstatus)
        {
                char       *ptr;

                ptr = ((char *) pstatus) + sizeof(pgParameterStatus);
                pstatus->name = ptr;
                strcpy(ptr, name);
                ptr += strlen(name) + 1;
                pstatus->value = ptr;
                strcpy(ptr, value);
                pstatus->next = conn->pstatus;
                conn->pstatus = pstatus;
        }

        /*
         * Save values of settings that are of interest to libpq in fields of the
         * PGconn object.  We keep client_encoding and standard_conforming_strings
         * in static variables as well, so that PQescapeString and PQescapeBytea
         * can behave somewhat sanely (at least in single-connection-using
         * programs).
         */
        if (strcmp(name, "client_encoding") == 0)
        {
                conn->client_encoding = pg_char_to_encoding(value);
                /* if we don't recognize the encoding name, fall back to SQL_ASCII */
                if (conn->client_encoding < 0)
                        conn->client_encoding = PG_SQL_ASCII;
                static_client_encoding = conn->client_encoding;
        }
        else if (strcmp(name, "standard_conforming_strings") == 0)
        {
                conn->std_strings = (strcmp(value, "on") == 0);
                static_std_strings = conn->std_strings;
        }
        else if (strcmp(name, "server_version") == 0)
        {
                /* We convert the server version to numeric form. */
                int                     cnt;
                int                     vmaj,
                                        vmin,
                                        vrev;

                cnt = sscanf(value, "%d.%d.%d", &vmaj, &vmin, &vrev);

                if (cnt == 3)
                {
                        /* old style, e.g. 9.6.1 */
                        conn->sversion = (100 * vmaj + vmin) * 100 + vrev;
                }
                else if (cnt == 2)
                {
                        if (vmaj >= 10)
                        {
                                /* new style, e.g. 10.1 */
                                conn->sversion = 100 * 100 * vmaj + vmin;
                        }
                        else
                        {
                                /* old style without minor version, e.g. 9.6devel */
                                conn->sversion = (100 * vmaj + vmin) * 100;
                        }
                }
                else if (cnt == 1)
                {
                        /* new style without minor version, e.g. 10devel */
                        conn->sversion = 100 * 100 * vmaj;
                }
                else
                        conn->sversion = 0; /* unknown */
        }
        else if (strcmp(name, "default_transaction_read_only") == 0)
        {
                conn->default_transaction_read_only =
                        (strcmp(value, "on") == 0) ? PG_BOOL_YES : PG_BOOL_NO;
        }
        else if (strcmp(name, "in_hot_standby") == 0)
        {
                conn->in_hot_standby =
                        (strcmp(value, "on") == 0) ? PG_BOOL_YES : PG_BOOL_NO;
        }
        else if (strcmp(name, "scram_iterations") == 0)
        {
                conn->scram_sha_256_iterations = atoi(value);
        }
}


/*
 * pqRowProcessor
 *        Add the received row to the current async result (conn->result).
 *        Returns 1 if OK, 0 if error occurred.
 *
 * On error, *errmsgp can be set to an error string to be returned.
 * (Such a string should already be translated via libpq_gettext().)
 * If it is left NULL, the error is presumed to be "out of memory".
 */
int
pqRowProcessor(PGconn *conn, const char **errmsgp)
{
        PGresult   *res = conn->result;
        int                     nfields = res->numAttributes;
        const PGdataValue *columns = conn->rowBuf;
        PGresAttValue *tup;
        int                     i;

        /*
         * In partial-result mode, if we don't already have a partial PGresult
         * then make one by cloning conn->result (which should hold the correct
         * result metadata by now).  Then the original conn->result is moved over
         * to saved_result so that we can re-use it as a reference for future
         * partial results.  The saved result will become active again after
         * pqPrepareAsyncResult() returns the partial result to the application.
         */
        if (conn->partialResMode && conn->saved_result == NULL)
        {
                /* Copy everything that should be in the result at this point */
                res = PQcopyResult(res,
                                                   PG_COPYRES_ATTRS | PG_COPYRES_EVENTS |
                                                   PG_COPYRES_NOTICEHOOKS);
                if (!res)
                        return 0;
                /* Change result status to appropriate special value */
                res->resultStatus = (conn->singleRowMode ? PGRES_SINGLE_TUPLE : PGRES_TUPLES_CHUNK);
                /* And stash it as the active result */
                conn->saved_result = conn->result;
                conn->result = res;
        }

        /*
         * Basically we just allocate space in the PGresult for each field and
         * copy the data over.
         *
         * Note: on malloc failure, we return 0 leaving *errmsgp still NULL, which
         * caller will take to mean "out of memory".  This is preferable to trying
         * to set up such a message here, because evidently there's not enough
         * memory for gettext() to do anything.
         */
        tup = (PGresAttValue *)
                pqResultAlloc(res, nfields * sizeof(PGresAttValue), true);
        if (tup == NULL)
                return 0;

        for (i = 0; i < nfields; i++)
        {
                int                     clen = columns[i].len;

                if (clen < 0)
                {
                        /* null field */
                        tup[i].len = NULL_LEN;
                        tup[i].value = res->null_field;
                }
                else
                {
                        bool            isbinary = (res->attDescs[i].format != 0);
                        char       *val;

                        val = (char *) pqResultAlloc(res, clen + 1, isbinary);
                        if (val == NULL)
                                return 0;

                        /* copy and zero-terminate the data (even if it's binary) */
                        memcpy(val, columns[i].value, clen);
                        val[clen] = '\0';

                        tup[i].len = clen;
                        tup[i].value = val;
                }
        }

        /* And add the tuple to the PGresult's tuple array */
        if (!pqAddTuple(res, tup, errmsgp))
                return 0;

        /*
         * Success.  In partial-result mode, if we have enough rows then make the
         * result available to the client immediately.
         */
        if (conn->partialResMode && res->ntups >= conn->maxChunkSize)
                conn->asyncStatus = PGASYNC_READY_MORE;

        return 1;
}


/*
 * pqAllocCmdQueueEntry
 *              Get a command queue entry for caller to fill.
 *
 * If the recycle queue has a free element, that is returned; if not, a
 * fresh one is allocated.  Caller is responsible for adding it to the
 * command queue (pqAppendCmdQueueEntry) once the struct is filled in, or
 * releasing the memory (pqRecycleCmdQueueEntry) if an error occurs.
 *
 * If allocation fails, sets the error message and returns NULL.
 */
static PGcmdQueueEntry *
pqAllocCmdQueueEntry(PGconn *conn)
{
        PGcmdQueueEntry *entry;

        if (conn->cmd_queue_recycle == NULL)
        {
                entry = (PGcmdQueueEntry *) malloc(sizeof(PGcmdQueueEntry));
                if (entry == NULL)
                {
                        libpq_append_conn_error(conn, "out of memory");
                        return NULL;
                }
        }
        else
        {
                entry = conn->cmd_queue_recycle;
                conn->cmd_queue_recycle = entry->next;
        }
        entry->next = NULL;
        entry->query = NULL;

        return entry;
}

/*
 * pqAppendCmdQueueEntry
 *              Append a caller-allocated entry to the command queue, and update
 *              conn->asyncStatus to account for it.
 *
 * The query itself must already have been put in the output buffer by the
 * caller.
 */
static void
pqAppendCmdQueueEntry(PGconn *conn, PGcmdQueueEntry *entry)
{
        Assert(entry->next == NULL);

        if (conn->cmd_queue_head == NULL)
                conn->cmd_queue_head = entry;
        else
                conn->cmd_queue_tail->next = entry;

        conn->cmd_queue_tail = entry;

        switch (conn->pipelineStatus)
        {
                case PQ_PIPELINE_OFF:
                case PQ_PIPELINE_ON:

                        /*
                         * When not in pipeline aborted state, if there's a result ready
                         * to be consumed, let it be so (that is, don't change away from
                         * READY or READY_MORE); otherwise set us busy to wait for
                         * something to arrive from the server.
                         */
                        if (conn->asyncStatus == PGASYNC_IDLE)
                                conn->asyncStatus = PGASYNC_BUSY;
                        break;

                case PQ_PIPELINE_ABORTED:

                        /*
                         * In aborted pipeline state, we don't expect anything from the
                         * server (since we don't send any queries that are queued).
                         * Therefore, if IDLE then do what PQgetResult would do to let
                         * itself consume commands from the queue; if we're in any other
                         * state, we don't have to do anything.
                         */
                        if (conn->asyncStatus == PGASYNC_IDLE ||
                                conn->asyncStatus == PGASYNC_PIPELINE_IDLE)
                                pqPipelineProcessQueue(conn);
                        break;
        }
}

/*
 * pqRecycleCmdQueueEntry
 *              Push a command queue entry onto the freelist.
 */
static void
pqRecycleCmdQueueEntry(PGconn *conn, PGcmdQueueEntry *entry)
{
        if (entry == NULL)
                return;

        /* recyclable entries should not have a follow-on command */
        Assert(entry->next == NULL);

        if (entry->query)
        {
                free(entry->query);
                entry->query = NULL;
        }

        entry->next = conn->cmd_queue_recycle;
        conn->cmd_queue_recycle = entry;
}


/*
 * PQsendQuery
 *       Submit a query, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *                      0 if error (conn->errorMessage is set)
 *
 * PQsendQueryContinue is a non-exported version that behaves identically
 * except that it doesn't reset conn->errorMessage.
 */
int
PQsendQuery(PGconn *conn, const char *query)
{
        return PQsendQueryInternal(conn, query, true);
}

int
PQsendQueryContinue(PGconn *conn, const char *query)
{
        return PQsendQueryInternal(conn, query, false);
}

static int
PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
{
        PGcmdQueueEntry *entry = NULL;

        if (!PQsendQueryStart(conn, newQuery))
                return 0;

        /* check the argument */
        if (!query)
        {
                libpq_append_conn_error(conn, "command string is a null pointer");
                return 0;
        }

        if (conn->pipelineStatus != PQ_PIPELINE_OFF)
        {
                libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
                                                                "PQsendQuery");
                return 0;
        }

        entry = pqAllocCmdQueueEntry(conn);
        if (entry == NULL)
                return 0;                               /* error msg already set */

        /* Send the query message(s) */
        /* construct the outgoing Query message */
        if (pqPutMsgStart(PqMsg_Query, conn) < 0 ||
                pqPuts(query, conn) < 0 ||
                pqPutMsgEnd(conn) < 0)
        {
                /* error message should be set up already */
                pqRecycleCmdQueueEntry(conn, entry);
                return 0;
        }

        /* remember we are using simple query protocol */
        entry->queryclass = PGQUERY_SIMPLE;
        /* and remember the query text too, if possible */
        entry->query = strdup(query);

        /*
         * Give the data a push.  In nonblock mode, don't complain if we're unable
         * to send it all; PQgetResult() will do any additional flushing needed.
         */
        if (pqFlush(conn) < 0)
                goto sendFailed;

        /* OK, it's launched! */
        pqAppendCmdQueueEntry(conn, entry);

        return 1;

sendFailed:
        pqRecycleCmdQueueEntry(conn, entry);
        /* error message should be set up already */
        return 0;
}

/*
 * PQsendQueryParams
 *              Like PQsendQuery, but use extended query protocol so we can pass parameters
 */
int
PQsendQueryParams(PGconn *conn,
                                  const char *command,
                                  int nParams,
                                  const Oid *paramTypes,
                                  const char *const *paramValues,
                                  const int *paramLengths,
                                  const int *paramFormats,
                                  int resultFormat)
{
        if (!PQsendQueryStart(conn, true))
                return 0;

        /* check the arguments */
        if (!command)
        {
                libpq_append_conn_error(conn, "command string is a null pointer");
                return 0;
        }
        if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
        {
                libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
                                                                PQ_QUERY_PARAM_MAX_LIMIT);
                return 0;
        }

        return PQsendQueryGuts(conn,
                                                   command,
                                                   "",  /* use unnamed statement */
                                                   nParams,
                                                   paramTypes,
                                                   paramValues,
                                                   paramLengths,
                                                   paramFormats,
                                                   resultFormat);
}

/*
 * PQsendPrepare
 *       Submit a Parse message, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *                      0 if error (conn->errorMessage is set)
 */
int
PQsendPrepare(PGconn *conn,
                          const char *stmtName, const char *query,
                          int nParams, const Oid *paramTypes)
{
        PGcmdQueueEntry *entry = NULL;

        if (!PQsendQueryStart(conn, true))
                return 0;

        /* check the arguments */
        if (!stmtName)
        {
                libpq_append_conn_error(conn, "statement name is a null pointer");
                return 0;
        }
        if (!query)
        {
                libpq_append_conn_error(conn, "command string is a null pointer");
                return 0;
        }
        if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
        {
                libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
                                                                PQ_QUERY_PARAM_MAX_LIMIT);
                return 0;
        }

        entry = pqAllocCmdQueueEntry(conn);
        if (entry == NULL)
                return 0;                               /* error msg already set */

        /* construct the Parse message */
        if (pqPutMsgStart(PqMsg_Parse, conn) < 0 ||
                pqPuts(stmtName, conn) < 0 ||
                pqPuts(query, conn) < 0)
                goto sendFailed;

        if (nParams > 0 && paramTypes)
        {
                int                     i;

                if (pqPutInt(nParams, 2, conn) < 0)
                        goto sendFailed;
                for (i = 0; i < nParams; i++)
                {
                        if (pqPutInt(paramTypes[i], 4, conn) < 0)
                                goto sendFailed;
                }
        }
        else
        {
                if (pqPutInt(0, 2, conn) < 0)
                        goto sendFailed;
        }
        if (pqPutMsgEnd(conn) < 0)
                goto sendFailed;

        /* Add a Sync, unless in pipeline mode. */
        if (conn->pipelineStatus == PQ_PIPELINE_OFF)
        {
                if (pqPutMsgStart(PqMsg_Sync, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        goto sendFailed;
        }

        /* remember we are doing just a Parse */
        entry->queryclass = PGQUERY_PREPARE;

        /* and remember the query text too, if possible */
        /* if insufficient memory, query just winds up NULL */
        entry->query = strdup(query);

        /*
         * Give the data a push (in pipeline mode, only if we're past the size
         * threshold).  In nonblock mode, don't complain if we're unable to send
         * it all; PQgetResult() will do any additional flushing needed.
         */
        if (pqPipelineFlush(conn) < 0)
                goto sendFailed;

        /* OK, it's launched! */
        pqAppendCmdQueueEntry(conn, entry);

        return 1;

sendFailed:
        pqRecycleCmdQueueEntry(conn, entry);
        /* error message should be set up already */
        return 0;
}

/*
 * PQsendQueryPrepared
 *              Like PQsendQuery, but execute a previously prepared statement,
 *              using extended query protocol so we can pass parameters
 */
int
PQsendQueryPrepared(PGconn *conn,
                                        const char *stmtName,
                                        int nParams,
                                        const char *const *paramValues,
                                        const int *paramLengths,
                                        const int *paramFormats,
                                        int resultFormat)
{
        if (!PQsendQueryStart(conn, true))
                return 0;

        /* check the arguments */
        if (!stmtName)
        {
                libpq_append_conn_error(conn, "statement name is a null pointer");
                return 0;
        }
        if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
        {
                libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
                                                                PQ_QUERY_PARAM_MAX_LIMIT);
                return 0;
        }

        return PQsendQueryGuts(conn,
                                                   NULL,        /* no command to parse */
                                                   stmtName,
                                                   nParams,
                                                   NULL,        /* no param types */
                                                   paramValues,
                                                   paramLengths,
                                                   paramFormats,
                                                   resultFormat);
}

/*
 * PQsendQueryStart
 *      Common startup code for PQsendQuery and sibling routines
 */
static bool
PQsendQueryStart(PGconn *conn, bool newQuery)
{
        if (!conn)
                return false;

        /*
         * If this is the beginning of a query cycle, reset the error state.
         * However, in pipeline mode with something already queued, the error
         * buffer belongs to that command and we shouldn't clear it.
         */
        if (newQuery && conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        /* Don't try to send if we know there's no live connection. */
        if (conn->status != CONNECTION_OK)
        {
                libpq_append_conn_error(conn, "no connection to the server");
                return false;
        }

        /* Can't send while already busy, either, unless enqueuing for later */
        if (conn->asyncStatus != PGASYNC_IDLE &&
                conn->pipelineStatus == PQ_PIPELINE_OFF)
        {
                libpq_append_conn_error(conn, "another command is already in progress");
                return false;
        }

        if (conn->pipelineStatus != PQ_PIPELINE_OFF)
        {
                /*
                 * When enqueuing commands we don't change much of the connection
                 * state since it's already in use for the current command. The
                 * connection state will get updated when pqPipelineProcessQueue()
                 * advances to start processing the queued message.
                 *
                 * Just make sure we can safely enqueue given the current connection
                 * state. We can enqueue behind another queue item, or behind a
                 * non-queue command (one that sends its own sync), but we can't
                 * enqueue if the connection is in a copy state.
                 */
                switch (conn->asyncStatus)
                {
                        case PGASYNC_IDLE:
                        case PGASYNC_PIPELINE_IDLE:
                        case PGASYNC_READY:
                        case PGASYNC_READY_MORE:
                        case PGASYNC_BUSY:
                                /* ok to queue */
                                break;

                        case PGASYNC_COPY_IN:
                        case PGASYNC_COPY_OUT:
                        case PGASYNC_COPY_BOTH:
                                libpq_append_conn_error(conn, "cannot queue commands during COPY");
                                return false;
                }
        }
        else
        {
                /*
                 * This command's results will come in immediately. Initialize async
                 * result-accumulation state
                 */
                pqClearAsyncResult(conn);

                /* reset partial-result mode */
                conn->partialResMode = false;
                conn->singleRowMode = false;
                conn->maxChunkSize = 0;
        }

        /* ready to send command message */
        return true;
}

/*
 * PQsendQueryGuts
 *              Common code for sending a query with extended query protocol
 *              PQsendQueryStart should be done already
 *
 * command may be NULL to indicate we use an already-prepared statement
 */
static int
PQsendQueryGuts(PGconn *conn,
                                const char *command,
                                const char *stmtName,
                                int nParams,
                                const Oid *paramTypes,
                                const char *const *paramValues,
                                const int *paramLengths,
                                const int *paramFormats,
                                int resultFormat)
{
        int                     i;
        PGcmdQueueEntry *entry;

        entry = pqAllocCmdQueueEntry(conn);
        if (entry == NULL)
                return 0;                               /* error msg already set */

        /*
         * We will send Parse (if needed), Bind, Describe Portal, Execute, Sync
         * (if not in pipeline mode), using specified statement name and the
         * unnamed portal.
         */

        if (command)
        {
                /* construct the Parse message */
                if (pqPutMsgStart(PqMsg_Parse, conn) < 0 ||
                        pqPuts(stmtName, conn) < 0 ||
                        pqPuts(command, conn) < 0)
                        goto sendFailed;
                if (nParams > 0 && paramTypes)
                {
                        if (pqPutInt(nParams, 2, conn) < 0)
                                goto sendFailed;
                        for (i = 0; i < nParams; i++)
                        {
                                if (pqPutInt(paramTypes[i], 4, conn) < 0)
                                        goto sendFailed;
                        }
                }
                else
                {
                        if (pqPutInt(0, 2, conn) < 0)
                                goto sendFailed;
                }
                if (pqPutMsgEnd(conn) < 0)
                        goto sendFailed;
        }

        /* Construct the Bind message */
        if (pqPutMsgStart(PqMsg_Bind, conn) < 0 ||
                pqPuts("", conn) < 0 ||
                pqPuts(stmtName, conn) < 0)
                goto sendFailed;

        /* Send parameter formats */
        if (nParams > 0 && paramFormats)
        {
                if (pqPutInt(nParams, 2, conn) < 0)
                        goto sendFailed;
                for (i = 0; i < nParams; i++)
                {
                        if (pqPutInt(paramFormats[i], 2, conn) < 0)
                                goto sendFailed;
                }
        }
        else
        {
                if (pqPutInt(0, 2, conn) < 0)
                        goto sendFailed;
        }

        if (pqPutInt(nParams, 2, conn) < 0)
                goto sendFailed;

        /* Send parameters */
        for (i = 0; i < nParams; i++)
        {
                if (paramValues && paramValues[i])
                {
                        int                     nbytes;

                        if (paramFormats && paramFormats[i] != 0)
                        {
                                /* binary parameter */
                                if (paramLengths)
                                        nbytes = paramLengths[i];
                                else
                                {
                                        libpq_append_conn_error(conn, "length must be given for binary parameter");
                                        goto sendFailed;
                                }
                        }
                        else
                        {
                                /* text parameter, do not use paramLengths */
                                nbytes = strlen(paramValues[i]);
                        }
                        if (pqPutInt(nbytes, 4, conn) < 0 ||
                                pqPutnchar(paramValues[i], nbytes, conn) < 0)
                                goto sendFailed;
                }
                else
                {
                        /* take the param as NULL */
                        if (pqPutInt(-1, 4, conn) < 0)
                                goto sendFailed;
                }
        }
        if (pqPutInt(1, 2, conn) < 0 ||
                pqPutInt(resultFormat, 2, conn))
                goto sendFailed;
        if (pqPutMsgEnd(conn) < 0)
                goto sendFailed;

        /* construct the Describe Portal message */
        if (pqPutMsgStart(PqMsg_Describe, conn) < 0 ||
                pqPutc('P', conn) < 0 ||
                pqPuts("", conn) < 0 ||
                pqPutMsgEnd(conn) < 0)
                goto sendFailed;

        /* construct the Execute message */
        if (pqPutMsgStart(PqMsg_Execute, conn) < 0 ||
                pqPuts("", conn) < 0 ||
                pqPutInt(0, 4, conn) < 0 ||
                pqPutMsgEnd(conn) < 0)
                goto sendFailed;

        /* construct the Sync message if not in pipeline mode */
        if (conn->pipelineStatus == PQ_PIPELINE_OFF)
        {
                if (pqPutMsgStart(PqMsg_Sync, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        goto sendFailed;
        }

        /* remember we are using extended query protocol */
        entry->queryclass = PGQUERY_EXTENDED;

        /* and remember the query text too, if possible */
        /* if insufficient memory, query just winds up NULL */
        if (command)
                entry->query = strdup(command);

        /*
         * Give the data a push (in pipeline mode, only if we're past the size
         * threshold).  In nonblock mode, don't complain if we're unable to send
         * it all; PQgetResult() will do any additional flushing needed.
         */
        if (pqPipelineFlush(conn) < 0)
                goto sendFailed;

        /* OK, it's launched! */
        pqAppendCmdQueueEntry(conn, entry);

        return 1;

sendFailed:
        pqRecycleCmdQueueEntry(conn, entry);
        /* error message should be set up already */
        return 0;
}

/*
 * Is it OK to change partial-result mode now?
 */
static bool
canChangeResultMode(PGconn *conn)
{
        /*
         * Only allow changing the mode when we have launched a query and not yet
         * received any results.
         */
        if (!conn)
                return false;
        if (conn->asyncStatus != PGASYNC_BUSY)
                return false;
        if (!conn->cmd_queue_head ||
                (conn->cmd_queue_head->queryclass != PGQUERY_SIMPLE &&
                 conn->cmd_queue_head->queryclass != PGQUERY_EXTENDED))
                return false;
        if (pgHavePendingResult(conn))
                return false;
        return true;
}

/*
 * Select row-by-row processing mode
 */
int
PQsetSingleRowMode(PGconn *conn)
{
        if (canChangeResultMode(conn))
        {
                conn->partialResMode = true;
                conn->singleRowMode = true;
                conn->maxChunkSize = 1;
                return 1;
        }
        else
                return 0;
}

/*
 * Select chunked results processing mode
 */
int
PQsetChunkedRowsMode(PGconn *conn, int chunkSize)
{
        if (chunkSize > 0 && canChangeResultMode(conn))
        {
                conn->partialResMode = true;
                conn->singleRowMode = false;
                conn->maxChunkSize = chunkSize;
                return 1;
        }
        else
                return 0;
}

/*
 * Consume any available input from the backend
 * 0 return: some kind of trouble
 * 1 return: no problem
 */
int
PQconsumeInput(PGconn *conn)
{
        if (!conn)
                return 0;

        /*
         * for non-blocking connections try to flush the send-queue, otherwise we
         * may never get a response for something that may not have already been
         * sent because it's in our write buffer!
         */
        if (pqIsnonblocking(conn))
        {
                if (pqFlush(conn) < 0)
                        return 0;
        }

        /*
         * Load more data, if available. We do this no matter what state we are
         * in, since we are probably getting called because the application wants
         * to get rid of a read-select condition. Note that we will NOT block
         * waiting for more input.
         */
        if (pqReadData(conn) < 0)
                return 0;

        /* Parsing of the data waits till later. */
        return 1;
}


/*
 * parseInput: if appropriate, parse input data from backend
 * until input is exhausted or a stopping state is reached.
 * Note that this function will NOT attempt to read more data from the backend.
 */
static void
parseInput(PGconn *conn)
{
        pqParseInput3(conn);
}

/*
 * PQisBusy
 *       Return true if PQgetResult would block waiting for input.
 */

int
PQisBusy(PGconn *conn)
{
        if (!conn)
                return false;

        /* Parse any available data, if our state permits. */
        parseInput(conn);

        /*
         * PQgetResult will return immediately in all states except BUSY.  Also,
         * if we've detected read EOF and dropped the connection, we can expect
         * that PQgetResult will fail immediately.  Note that we do *not* check
         * conn->write_failed here --- once that's become set, we know we have
         * trouble, but we need to keep trying to read until we have a complete
         * server message or detect read EOF.
         */
        return conn->asyncStatus == PGASYNC_BUSY && conn->status != CONNECTION_BAD;
}

/*
 * PQgetResult
 *        Get the next PGresult produced by a query.  Returns NULL if no
 *        query work remains or an error has occurred (e.g. out of
 *        memory).
 *
 *        In pipeline mode, once all the result of a query have been returned,
 *        PQgetResult returns NULL to let the user know that the next
 *        query is being processed.  At the end of the pipeline, returns a
 *        result with PQresultStatus(result) == PGRES_PIPELINE_SYNC.
 */
PGresult *
PQgetResult(PGconn *conn)
{
        PGresult   *res;

        if (!conn)
                return NULL;

        /* Parse any available data, if our state permits. */
        parseInput(conn);

        /* If not ready to return something, block until we are. */
        while (conn->asyncStatus == PGASYNC_BUSY)
        {
                int                     flushResult;

                /*
                 * If data remains unsent, send it.  Else we might be waiting for the
                 * result of a command the backend hasn't even got yet.
                 */
                while ((flushResult = pqFlush(conn)) > 0)
                {
                        if (pqWait(false, true, conn))
                        {
                                flushResult = -1;
                                break;
                        }
                }

                /*
                 * Wait for some more data, and load it.  (Note: if the connection has
                 * been lost, pqWait should return immediately because the socket
                 * should be read-ready, either with the last server data or with an
                 * EOF indication.  We expect therefore that this won't result in any
                 * undue delay in reporting a previous write failure.)
                 */
                if (flushResult ||
                        pqWait(true, false, conn) ||
                        pqReadData(conn) < 0)
                {
                        /* Report the error saved by pqWait or pqReadData */
                        pqSaveErrorResult(conn);
                        conn->asyncStatus = PGASYNC_IDLE;
                        return pqPrepareAsyncResult(conn);
                }

                /* Parse it. */
                parseInput(conn);

                /*
                 * If we had a write error, but nothing above obtained a query result
                 * or detected a read error, report the write error.
                 */
                if (conn->write_failed && conn->asyncStatus == PGASYNC_BUSY)
                {
                        pqSaveWriteError(conn);
                        conn->asyncStatus = PGASYNC_IDLE;
                        return pqPrepareAsyncResult(conn);
                }
        }

        /* Return the appropriate thing. */
        switch (conn->asyncStatus)
        {
                case PGASYNC_IDLE:
                        res = NULL;                     /* query is complete */
                        break;
                case PGASYNC_PIPELINE_IDLE:
                        Assert(conn->pipelineStatus != PQ_PIPELINE_OFF);

                        /*
                         * We're about to return the NULL that terminates the round of
                         * results from the current query; prepare to send the results of
                         * the next query, if any, when we're called next.  If there's no
                         * next element in the command queue, this gets us in IDLE state.
                         */
                        pqPipelineProcessQueue(conn);
                        res = NULL;                     /* query is complete */
                        break;

                case PGASYNC_READY:
                        res = pqPrepareAsyncResult(conn);

                        /*
                         * Normally pqPrepareAsyncResult will have left conn->result
                         * empty.  Otherwise, "res" must be a not-full PGRES_TUPLES_CHUNK
                         * result, which we want to return to the caller while staying in
                         * PGASYNC_READY state.  Then the next call here will return the
                         * empty PGRES_TUPLES_OK result that was restored from
                         * saved_result, after which we can proceed.
                         */
                        if (conn->result)
                        {
                                Assert(res->resultStatus == PGRES_TUPLES_CHUNK);
                                break;
                        }

                        /* Advance the queue as appropriate */
                        pqCommandQueueAdvance(conn, false,
                                                                  res->resultStatus == PGRES_PIPELINE_SYNC);

                        if (conn->pipelineStatus != PQ_PIPELINE_OFF)
                        {
                                /*
                                 * We're about to send the results of the current query.  Set
                                 * us idle now, and ...
                                 */
                                conn->asyncStatus = PGASYNC_PIPELINE_IDLE;

                                /*
                                 * ... in cases when we're sending a pipeline-sync result,
                                 * move queue processing forwards immediately, so that next
                                 * time we're called, we're prepared to return the next result
                                 * received from the server.  In all other cases, leave the
                                 * queue state change for next time, so that a terminating
                                 * NULL result is sent.
                                 *
                                 * (In other words: we don't return a NULL after a pipeline
                                 * sync.)
                                 */
                                if (res->resultStatus == PGRES_PIPELINE_SYNC)
                                        pqPipelineProcessQueue(conn);
                        }
                        else
                        {
                                /* Set the state back to BUSY, allowing parsing to proceed. */
                                conn->asyncStatus = PGASYNC_BUSY;
                        }
                        break;
                case PGASYNC_READY_MORE:
                        res = pqPrepareAsyncResult(conn);
                        /* Set the state back to BUSY, allowing parsing to proceed. */
                        conn->asyncStatus = PGASYNC_BUSY;
                        break;
                case PGASYNC_COPY_IN:
                        res = getCopyResult(conn, PGRES_COPY_IN);
                        break;
                case PGASYNC_COPY_OUT:
                        res = getCopyResult(conn, PGRES_COPY_OUT);
                        break;
                case PGASYNC_COPY_BOTH:
                        res = getCopyResult(conn, PGRES_COPY_BOTH);
                        break;
                default:
                        libpq_append_conn_error(conn, "unexpected asyncStatus: %d", (int) conn->asyncStatus);
                        pqSaveErrorResult(conn);
                        conn->asyncStatus = PGASYNC_IDLE;       /* try to restore valid state */
                        res = pqPrepareAsyncResult(conn);
                        break;
        }

        /* Time to fire PGEVT_RESULTCREATE events, if there are any */
        if (res && res->nEvents > 0)
                (void) PQfireResultCreateEvents(conn, res);

        return res;
}

/*
 * getCopyResult
 *        Helper for PQgetResult: generate result for COPY-in-progress cases
 */
static PGresult *
getCopyResult(PGconn *conn, ExecStatusType copytype)
{
        /*
         * If the server connection has been lost, don't pretend everything is
         * hunky-dory; instead return a PGRES_FATAL_ERROR result, and reset the
         * asyncStatus to idle (corresponding to what we'd do if we'd detected I/O
         * error in the earlier steps in PQgetResult).  The text returned in the
         * result is whatever is in conn->errorMessage; we hope that was filled
         * with something relevant when the lost connection was detected.
         */
        if (conn->status != CONNECTION_OK)
        {
                pqSaveErrorResult(conn);
                conn->asyncStatus = PGASYNC_IDLE;
                return pqPrepareAsyncResult(conn);
        }

        /* If we have an async result for the COPY, return that */
        if (conn->result && conn->result->resultStatus == copytype)
                return pqPrepareAsyncResult(conn);

        /* Otherwise, invent a suitable PGresult */
        return PQmakeEmptyPGresult(conn, copytype);
}


/*
 * PQexec
 *        send a query to the backend and package up the result in a PGresult
 *
 * If the query was not even sent, return NULL; conn->errorMessage is set to
 * a relevant message.
 * If the query was sent, a new PGresult is returned (which could indicate
 * either success or failure).
 * The user is responsible for freeing the PGresult via PQclear()
 * when done with it.
 */
PGresult *
PQexec(PGconn *conn, const char *query)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendQuery(conn, query))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQexecParams
 *              Like PQexec, but use extended query protocol so we can pass parameters
 */
PGresult *
PQexecParams(PGconn *conn,
                         const char *command,
                         int nParams,
                         const Oid *paramTypes,
                         const char *const *paramValues,
                         const int *paramLengths,
                         const int *paramFormats,
                         int resultFormat)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendQueryParams(conn, command,
                                                   nParams, paramTypes, paramValues, paramLengths,
                                                   paramFormats, resultFormat))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQprepare
 *        Creates a prepared statement by issuing a Parse message.
 *
 * If the query was not even sent, return NULL; conn->errorMessage is set to
 * a relevant message.
 * If the query was sent, a new PGresult is returned (which could indicate
 * either success or failure).
 * The user is responsible for freeing the PGresult via PQclear()
 * when done with it.
 */
PGresult *
PQprepare(PGconn *conn,
                  const char *stmtName, const char *query,
                  int nParams, const Oid *paramTypes)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendPrepare(conn, stmtName, query, nParams, paramTypes))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQexecPrepared
 *              Like PQexec, but execute a previously prepared statement,
 *              using extended query protocol so we can pass parameters
 */
PGresult *
PQexecPrepared(PGconn *conn,
                           const char *stmtName,
                           int nParams,
                           const char *const *paramValues,
                           const int *paramLengths,
                           const int *paramFormats,
                           int resultFormat)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendQueryPrepared(conn, stmtName,
                                                         nParams, paramValues, paramLengths,
                                                         paramFormats, resultFormat))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * Common code for PQexec and sibling routines: prepare to send command
 */
static bool
PQexecStart(PGconn *conn)
{
        PGresult   *result;

        if (!conn)
                return false;

        /*
         * Since this is the beginning of a query cycle, reset the error state.
         * However, in pipeline mode with something already queued, the error
         * buffer belongs to that command and we shouldn't clear it.
         */
        if (conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        if (conn->pipelineStatus != PQ_PIPELINE_OFF)
        {
                libpq_append_conn_error(conn, "synchronous command execution functions are not allowed in pipeline mode");
                return false;
        }

        /*
         * Silently discard any prior query result that application didn't eat.
         * This is probably poor design, but it's here for backward compatibility.
         */
        while ((result = PQgetResult(conn)) != NULL)
        {
                ExecStatusType resultStatus = result->resultStatus;

                PQclear(result);                /* only need its status */
                if (resultStatus == PGRES_COPY_IN)
                {
                        /* get out of a COPY IN state */
                        if (PQputCopyEnd(conn,
                                                         libpq_gettext("COPY terminated by new PQexec")) < 0)
                                return false;
                        /* keep waiting to swallow the copy's failure message */
                }
                else if (resultStatus == PGRES_COPY_OUT)
                {
                        /*
                         * Get out of a COPY OUT state: we just switch back to BUSY and
                         * allow the remaining COPY data to be dropped on the floor.
                         */
                        conn->asyncStatus = PGASYNC_BUSY;
                        /* keep waiting to swallow the copy's completion message */
                }
                else if (resultStatus == PGRES_COPY_BOTH)
                {
                        /* We don't allow PQexec during COPY BOTH */
                        libpq_append_conn_error(conn, "PQexec not allowed during COPY BOTH");
                        return false;
                }
                /* check for loss of connection, too */
                if (conn->status == CONNECTION_BAD)
                        return false;
        }

        /* OK to send a command */
        return true;
}

/*
 * Common code for PQexec and sibling routines: wait for command result
 */
static PGresult *
PQexecFinish(PGconn *conn)
{
        PGresult   *result;
        PGresult   *lastResult;

        /*
         * For backwards compatibility, return the last result if there are more
         * than one.  (We used to have logic here to concatenate successive error
         * messages, but now that happens automatically, since conn->errorMessage
         * will continue to accumulate errors throughout this loop.)
         *
         * We have to stop if we see copy in/out/both, however. We will resume
         * parsing after application performs the data transfer.
         *
         * Also stop if the connection is lost (else we'll loop infinitely).
         */
        lastResult = NULL;
        while ((result = PQgetResult(conn)) != NULL)
        {
                PQclear(lastResult);
                lastResult = result;
                if (result->resultStatus == PGRES_COPY_IN ||
                        result->resultStatus == PGRES_COPY_OUT ||
                        result->resultStatus == PGRES_COPY_BOTH ||
                        conn->status == CONNECTION_BAD)
                        break;
        }

        return lastResult;
}

/*
 * PQdescribePrepared
 *        Obtain information about a previously prepared statement
 *
 * If the query was not even sent, return NULL; conn->errorMessage is set to
 * a relevant message.
 * If the query was sent, a new PGresult is returned (which could indicate
 * either success or failure).  On success, the PGresult contains status
 * PGRES_COMMAND_OK, and its parameter and column-heading fields describe
 * the statement's inputs and outputs respectively.
 * The user is responsible for freeing the PGresult via PQclear()
 * when done with it.
 */
PGresult *
PQdescribePrepared(PGconn *conn, const char *stmt)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendTypedCommand(conn, PqMsg_Describe, 'S', stmt))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQdescribePortal
 *        Obtain information about a previously created portal
 *
 * This is much like PQdescribePrepared, except that no parameter info is
 * returned.  Note that at the moment, libpq doesn't really expose portals
 * to the client; but this can be used with a portal created by a SQL
 * DECLARE CURSOR command.
 */
PGresult *
PQdescribePortal(PGconn *conn, const char *portal)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendTypedCommand(conn, PqMsg_Describe, 'P', portal))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQsendDescribePrepared
 *       Submit a Describe Statement command, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *                      0 if error (conn->errorMessage is set)
 */
int
PQsendDescribePrepared(PGconn *conn, const char *stmt)
{
        return PQsendTypedCommand(conn, PqMsg_Describe, 'S', stmt);
}

/*
 * PQsendDescribePortal
 *       Submit a Describe Portal command, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *                      0 if error (conn->errorMessage is set)
 */
int
PQsendDescribePortal(PGconn *conn, const char *portal)
{
        return PQsendTypedCommand(conn, PqMsg_Describe, 'P', portal);
}

/*
 * PQclosePrepared
 *        Close a previously prepared statement
 *
 * If the query was not even sent, return NULL; conn->errorMessage is set to
 * a relevant message.
 * If the query was sent, a new PGresult is returned (which could indicate
 * either success or failure).  On success, the PGresult contains status
 * PGRES_COMMAND_OK. The user is responsible for freeing the PGresult via
 * PQclear() when done with it.
 */
PGresult *
PQclosePrepared(PGconn *conn, const char *stmt)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendTypedCommand(conn, PqMsg_Close, 'S', stmt))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQclosePortal
 *        Close a previously created portal
 *
 * This is exactly like PQclosePrepared, but for portals.  Note that at the
 * moment, libpq doesn't really expose portals to the client; but this can be
 * used with a portal created by a SQL DECLARE CURSOR command.
 */
PGresult *
PQclosePortal(PGconn *conn, const char *portal)
{
        if (!PQexecStart(conn))
                return NULL;
        if (!PQsendTypedCommand(conn, PqMsg_Close, 'P', portal))
                return NULL;
        return PQexecFinish(conn);
}

/*
 * PQsendClosePrepared
 *       Submit a Close Statement command, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *                      0 if error (conn->errorMessage is set)
 */
int
PQsendClosePrepared(PGconn *conn, const char *stmt)
{
        return PQsendTypedCommand(conn, PqMsg_Close, 'S', stmt);
}

/*
 * PQsendClosePortal
 *       Submit a Close Portal command, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *                      0 if error (conn->errorMessage is set)
 */
int
PQsendClosePortal(PGconn *conn, const char *portal)
{
        return PQsendTypedCommand(conn, PqMsg_Close, 'P', portal);
}

/*
 * PQsendTypedCommand
 *       Common code to send a Describe or Close command
 *
 * Available options for "command" are
 *       PqMsg_Close for Close; or
 *       PqMsg_Describe for Describe.
 *
 * Available options for "type" are
 *       'S' to run a command on a prepared statement; or
 *       'P' to run a command on a portal.
 *
 * Returns 1 on success and 0 on failure.
 */
static int
PQsendTypedCommand(PGconn *conn, char command, char type, const char *target)
{
        PGcmdQueueEntry *entry = NULL;

        /* Treat null target as empty string */
        if (!target)
                target = "";

        if (!PQsendQueryStart(conn, true))
                return 0;

        entry = pqAllocCmdQueueEntry(conn);
        if (entry == NULL)
                return 0;                               /* error msg already set */

        /* construct the Close message */
        if (pqPutMsgStart(command, conn) < 0 ||
                pqPutc(type, conn) < 0 ||
                pqPuts(target, conn) < 0 ||
                pqPutMsgEnd(conn) < 0)
                goto sendFailed;

        /* construct the Sync message */
        if (conn->pipelineStatus == PQ_PIPELINE_OFF)
        {
                if (pqPutMsgStart(PqMsg_Sync, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        goto sendFailed;
        }

        /* remember if we are doing a Close or a Describe */
        if (command == PqMsg_Close)
        {
                entry->queryclass = PGQUERY_CLOSE;
        }
        else if (command == PqMsg_Describe)
        {
                entry->queryclass = PGQUERY_DESCRIBE;
        }
        else
        {
                libpq_append_conn_error(conn, "unrecognized message type \"%c\"", command);
                goto sendFailed;
        }

        /*
         * Give the data a push (in pipeline mode, only if we're past the size
         * threshold).  In nonblock mode, don't complain if we're unable to send
         * it all; PQgetResult() will do any additional flushing needed.
         */
        if (pqPipelineFlush(conn) < 0)
                goto sendFailed;

        /* OK, it's launched! */
        pqAppendCmdQueueEntry(conn, entry);

        return 1;

sendFailed:
        pqRecycleCmdQueueEntry(conn, entry);
        /* error message should be set up already */
        return 0;
}

/*
 * PQnotifies
 *        returns a PGnotify* structure of the latest async notification
 * that has not yet been handled
 *
 * returns NULL, if there is currently
 * no unhandled async notification from the backend
 *
 * the CALLER is responsible for FREE'ing the structure returned
 *
 * Note that this function does not read any new data from the socket;
 * so usually, caller should call PQconsumeInput() first.
 */
PGnotify *
PQnotifies(PGconn *conn)
{
        PGnotify   *event;

        if (!conn)
                return NULL;

        /* Parse any available data to see if we can extract NOTIFY messages. */
        parseInput(conn);

        event = conn->notifyHead;
        if (event)
        {
                conn->notifyHead = event->next;
                if (!conn->notifyHead)
                        conn->notifyTail = NULL;
                event->next = NULL;             /* don't let app see the internal state */
        }
        return event;
}

/*
 * PQputCopyData - send some data to the backend during COPY IN or COPY BOTH
 *
 * Returns 1 if successful, 0 if data could not be sent (only possible
 * in nonblock mode), or -1 if an error occurs.
 */
int
PQputCopyData(PGconn *conn, const char *buffer, int nbytes)
{
        if (!conn)
                return -1;
        if (conn->asyncStatus != PGASYNC_COPY_IN &&
                conn->asyncStatus != PGASYNC_COPY_BOTH)
        {
                libpq_append_conn_error(conn, "no COPY in progress");
                return -1;
        }

        /*
         * Process any NOTICE or NOTIFY messages that might be pending in the
         * input buffer.  Since the server might generate many notices during the
         * COPY, we want to clean those out reasonably promptly to prevent
         * indefinite expansion of the input buffer.  (Note: the actual read of
         * input data into the input buffer happens down inside pqSendSome, but
         * it's not authorized to get rid of the data again.)
         */
        parseInput(conn);

        if (nbytes > 0)
        {
                /*
                 * Try to flush any previously sent data in preference to growing the
                 * output buffer.  If we can't enlarge the buffer enough to hold the
                 * data, return 0 in the nonblock case, else hard error. (For
                 * simplicity, always assume 5 bytes of overhead.)
                 */
                if ((conn->outBufSize - conn->outCount - 5) < nbytes)
                {
                        if (pqFlush(conn) < 0)
                                return -1;
                        if (pqCheckOutBufferSpace(conn->outCount + 5 + (size_t) nbytes,
                                                                          conn))
                                return pqIsnonblocking(conn) ? 0 : -1;
                }
                /* Send the data (too simple to delegate to fe-protocol files) */
                if (pqPutMsgStart(PqMsg_CopyData, conn) < 0 ||
                        pqPutnchar(buffer, nbytes, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        return -1;
        }
        return 1;
}

/*
 * PQputCopyEnd - send EOF indication to the backend during COPY IN
 *
 * After calling this, use PQgetResult() to check command completion status.
 *
 * Returns 1 if successful, or -1 if an error occurs.
 */
int
PQputCopyEnd(PGconn *conn, const char *errormsg)
{
        if (!conn)
                return -1;
        if (conn->asyncStatus != PGASYNC_COPY_IN &&
                conn->asyncStatus != PGASYNC_COPY_BOTH)
        {
                libpq_append_conn_error(conn, "no COPY in progress");
                return -1;
        }

        /*
         * Send the COPY END indicator.  This is simple enough that we don't
         * bother delegating it to the fe-protocol files.
         */
        if (errormsg)
        {
                /* Send COPY FAIL */
                if (pqPutMsgStart(PqMsg_CopyFail, conn) < 0 ||
                        pqPuts(errormsg, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        return -1;
        }
        else
        {
                /* Send COPY DONE */
                if (pqPutMsgStart(PqMsg_CopyDone, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        return -1;
        }

        /*
         * If we sent the COPY command in extended-query mode, we must issue a
         * Sync as well.
         */
        if (conn->cmd_queue_head &&
                conn->cmd_queue_head->queryclass != PGQUERY_SIMPLE)
        {
                if (pqPutMsgStart(PqMsg_Sync, conn) < 0 ||
                        pqPutMsgEnd(conn) < 0)
                        return -1;
        }

        /* Return to active duty */
        if (conn->asyncStatus == PGASYNC_COPY_BOTH)
                conn->asyncStatus = PGASYNC_COPY_OUT;
        else
                conn->asyncStatus = PGASYNC_BUSY;

        /* Try to flush data */
        if (pqFlush(conn) < 0)
                return -1;

        return 1;
}

/*
 * PQgetCopyData - read a row of data from the backend during COPY OUT
 * or COPY BOTH
 *
 * If successful, sets *buffer to point to a malloc'd row of data, and
 * returns row length (always > 0) as result.
 * Returns 0 if no row available yet (only possible if async is true),
 * -1 if end of copy (consult PQgetResult), or -2 if error (consult
 * PQerrorMessage).
 */
int
PQgetCopyData(PGconn *conn, char **buffer, int async)
{
        *buffer = NULL;                         /* for all failure cases */
        if (!conn)
                return -2;
        if (conn->asyncStatus != PGASYNC_COPY_OUT &&
                conn->asyncStatus != PGASYNC_COPY_BOTH)
        {
                libpq_append_conn_error(conn, "no COPY in progress");
                return -2;
        }
        return pqGetCopyData3(conn, buffer, async);
}

/*
 * PQgetline - gets a newline-terminated string from the backend.
 *
 * Chiefly here so that applications can use "COPY <rel> to stdout"
 * and read the output string.  Returns a null-terminated string in `buffer`.
 *
 * XXX this routine is now deprecated, because it can't handle binary data.
 * If called during a COPY BINARY we return EOF.
 *
 * PQgetline reads up to `length`-1 characters (like fgets(3)) but strips
 * the terminating \n (like gets(3)).
 *
 * CAUTION: the caller is responsible for detecting the end-of-copy signal
 * (a line containing just "\.") when using this routine.
 *
 * RETURNS:
 *              EOF if error (eg, invalid arguments are given)
 *              0 if EOL is reached (i.e., \n has been read)
 *                              (this is required for backward-compatibility -- this
 *                               routine used to always return EOF or 0, assuming that
 *                               the line ended within `length` bytes.)
 *              1 in other cases (i.e., the buffer was filled before \n is reached)
 */
int
PQgetline(PGconn *conn, char *buffer, int length)
{
        if (!buffer || length <= 0)
                return EOF;
        *buffer = '\0';
        /* length must be at least 3 to hold the \. terminator! */
        if (length < 3)
                return EOF;

        if (!conn)
                return EOF;

        return pqGetline3(conn, buffer, length);
}

/*
 * PQgetlineAsync - gets a COPY data row without blocking.
 *
 * This routine is for applications that want to do "COPY <rel> to stdout"
 * asynchronously, that is without blocking.  Having issued the COPY command
 * and gotten a PGRES_COPY_OUT response, the app should call PQconsumeInput
 * and this routine until the end-of-data signal is detected.  Unlike
 * PQgetline, this routine takes responsibility for detecting end-of-data.
 *
 * On each call, PQgetlineAsync will return data if a complete data row
 * is available in libpq's input buffer.  Otherwise, no data is returned
 * until the rest of the row arrives.
 *
 * If -1 is returned, the end-of-data signal has been recognized (and removed
 * from libpq's input buffer).  The caller *must* next call PQendcopy and
 * then return to normal processing.
 *
 * RETURNS:
 *       -1    if the end-of-copy-data marker has been recognized
 *       0         if no data is available
 *       >0    the number of bytes returned.
 *
 * The data returned will not extend beyond a data-row boundary.  If possible
 * a whole row will be returned at one time.  But if the buffer offered by
 * the caller is too small to hold a row sent by the backend, then a partial
 * data row will be returned.  In text mode this can be detected by testing
 * whether the last returned byte is '\n' or not.
 *
 * The returned data is *not* null-terminated.
 */

int
PQgetlineAsync(PGconn *conn, char *buffer, int bufsize)
{
        if (!conn)
                return -1;

        return pqGetlineAsync3(conn, buffer, bufsize);
}

/*
 * PQputline -- sends a string to the backend during COPY IN.
 * Returns 0 if OK, EOF if not.
 *
 * This is deprecated primarily because the return convention doesn't allow
 * caller to tell the difference between a hard error and a nonblock-mode
 * send failure.
 */
int
PQputline(PGconn *conn, const char *string)
{
        return PQputnbytes(conn, string, strlen(string));
}

/*
 * PQputnbytes -- like PQputline, but buffer need not be null-terminated.
 * Returns 0 if OK, EOF if not.
 */
int
PQputnbytes(PGconn *conn, const char *buffer, int nbytes)
{
        if (PQputCopyData(conn, buffer, nbytes) > 0)
                return 0;
        else
                return EOF;
}

/*
 * PQendcopy
 *              After completing the data transfer portion of a copy in/out,
 *              the application must call this routine to finish the command protocol.
 *
 * This is deprecated; it's cleaner to use PQgetResult to get the transfer
 * status.
 *
 * RETURNS:
 *              0 on success
 *              1 on failure
 */
int
PQendcopy(PGconn *conn)
{
        if (!conn)
                return 0;

        return pqEndcopy3(conn);
}


/* ----------------
 *              PQfn -  Send a function call to the POSTGRES backend.
 *
 *              conn                    : backend connection
 *              fnid                    : OID of function to be called
 *              result_buf              : pointer to result buffer
 *              result_len              : actual length of result is returned here
 *              result_is_int   : If the result is an integer, this must be 1,
 *                                                otherwise this should be 0
 *              args                    : pointer to an array of function arguments
 *                                                (each has length, if integer, and value/pointer)
 *              nargs                   : # of arguments in args array.
 *
 * RETURNS
 *              PGresult with status = PGRES_COMMAND_OK if successful.
 *                      *result_len is > 0 if there is a return value, 0 if not.
 *              PGresult with status = PGRES_FATAL_ERROR if backend returns an error.
 *              NULL on communications failure.  conn->errorMessage will be set.
 * ----------------
 */

PGresult *
PQfn(PGconn *conn,
         int fnid,
         int *result_buf,
         int *result_len,
         int result_is_int,
         const PQArgBlock *args,
         int nargs)
{
        *result_len = 0;

        if (!conn)
                return NULL;

        /*
         * Since this is the beginning of a query cycle, reset the error state.
         * However, in pipeline mode with something already queued, the error
         * buffer belongs to that command and we shouldn't clear it.
         */
        if (conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        if (conn->pipelineStatus != PQ_PIPELINE_OFF)
        {
                libpq_append_conn_error(conn, "%s not allowed in pipeline mode", "PQfn");
                return NULL;
        }

        if (conn->sock == PGINVALID_SOCKET || conn->asyncStatus != PGASYNC_IDLE ||
                pgHavePendingResult(conn))
        {
                libpq_append_conn_error(conn, "connection in wrong state");
                return NULL;
        }

        return pqFunctionCall3(conn, fnid,
                                                   result_buf, result_len,
                                                   result_is_int,
                                                   args, nargs);
}

/* ====== Pipeline mode support ======== */

/*
 * PQenterPipelineMode
 *              Put an idle connection in pipeline mode.
 *
 * Returns 1 on success. On failure, errorMessage is set and 0 is returned.
 *
 * Commands submitted after this can be pipelined on the connection;
 * there's no requirement to wait for one to finish before the next is
 * dispatched.
 *
 * Queuing of a new query or syncing during COPY is not allowed.
 *
 * A set of commands is terminated by a PQpipelineSync.  Multiple sync
 * points can be established while in pipeline mode.  Pipeline mode can
 * be exited by calling PQexitPipelineMode() once all results are processed.
 *
 * This doesn't actually send anything on the wire, it just puts libpq
 * into a state where it can pipeline work.
 */
int
PQenterPipelineMode(PGconn *conn)
{
        if (!conn)
                return 0;

        /* succeed with no action if already in pipeline mode */
        if (conn->pipelineStatus != PQ_PIPELINE_OFF)
                return 1;

        if (conn->asyncStatus != PGASYNC_IDLE)
        {
                libpq_append_conn_error(conn, "cannot enter pipeline mode, connection not idle");
                return 0;
        }

        conn->pipelineStatus = PQ_PIPELINE_ON;

        return 1;
}

/*
 * PQexitPipelineMode
 *              End pipeline mode and return to normal command mode.
 *
 * Returns 1 in success (pipeline mode successfully ended, or not in pipeline
 * mode).
 *
 * Returns 0 if in pipeline mode and cannot be ended yet.  Error message will
 * be set.
 */
int
PQexitPipelineMode(PGconn *conn)
{
        if (!conn)
                return 0;

        if (conn->pipelineStatus == PQ_PIPELINE_OFF &&
                (conn->asyncStatus == PGASYNC_IDLE ||
                 conn->asyncStatus == PGASYNC_PIPELINE_IDLE) &&
                conn->cmd_queue_head == NULL)
                return 1;

        switch (conn->asyncStatus)
        {
                case PGASYNC_READY:
                case PGASYNC_READY_MORE:
                        /* there are some uncollected results */
                        libpq_append_conn_error(conn, "cannot exit pipeline mode with uncollected results");
                        return 0;

                case PGASYNC_BUSY:
                        libpq_append_conn_error(conn, "cannot exit pipeline mode while busy");
                        return 0;

                case PGASYNC_IDLE:
                case PGASYNC_PIPELINE_IDLE:
                        /* OK */
                        break;

                case PGASYNC_COPY_IN:
                case PGASYNC_COPY_OUT:
                case PGASYNC_COPY_BOTH:
                        libpq_append_conn_error(conn, "cannot exit pipeline mode while in COPY");
        }

        /* still work to process */
        if (conn->cmd_queue_head != NULL)
        {
                libpq_append_conn_error(conn, "cannot exit pipeline mode with uncollected results");
                return 0;
        }

        conn->pipelineStatus = PQ_PIPELINE_OFF;
        conn->asyncStatus = PGASYNC_IDLE;

        /* Flush any pending data in out buffer */
        if (pqFlush(conn) < 0)
                return 0;                               /* error message is setup already */
        return 1;
}

/*
 * pqCommandQueueAdvance
 *              Remove one query from the command queue, if appropriate.
 *
 * If we have received all results corresponding to the head element
 * in the command queue, remove it.
 *
 * In simple query protocol we must not advance the command queue until the
 * ReadyForQuery message has been received.  This is because in simple mode a
 * command can have multiple queries, and we must process result for all of
 * them before moving on to the next command.
 *
 * Another consideration is synchronization during error processing in
 * extended query protocol: we refuse to advance the queue past a SYNC queue
 * element, unless the result we've received is also a SYNC.  In particular
 * this protects us from advancing when an error is received at an
 * inappropriate moment.
 */
void
pqCommandQueueAdvance(PGconn *conn, bool isReadyForQuery, bool gotSync)
{
        PGcmdQueueEntry *prevquery;

        if (conn->cmd_queue_head == NULL)
                return;

        /*
         * If processing a query of simple query protocol, we only advance the
         * queue when we receive the ReadyForQuery message for it.
         */
        if (conn->cmd_queue_head->queryclass == PGQUERY_SIMPLE && !isReadyForQuery)
                return;

        /*
         * If we're waiting for a SYNC, don't advance the queue until we get one.
         */
        if (conn->cmd_queue_head->queryclass == PGQUERY_SYNC && !gotSync)
                return;

        /* delink element from queue */
        prevquery = conn->cmd_queue_head;
        conn->cmd_queue_head = conn->cmd_queue_head->next;

        /* If the queue is now empty, reset the tail too */
        if (conn->cmd_queue_head == NULL)
                conn->cmd_queue_tail = NULL;

        /* and make the queue element recyclable */
        prevquery->next = NULL;
        pqRecycleCmdQueueEntry(conn, prevquery);
}

/*
 * pqPipelineProcessQueue: subroutine for PQgetResult
 *              In pipeline mode, start processing the results of the next query in the queue.
 */
static void
pqPipelineProcessQueue(PGconn *conn)
{
        switch (conn->asyncStatus)
        {
                case PGASYNC_COPY_IN:
                case PGASYNC_COPY_OUT:
                case PGASYNC_COPY_BOTH:
                case PGASYNC_READY:
                case PGASYNC_READY_MORE:
                case PGASYNC_BUSY:
                        /* client still has to process current query or results */
                        return;

                case PGASYNC_IDLE:

                        /*
                         * If we're in IDLE mode and there's some command in the queue,
                         * get us into PIPELINE_IDLE mode and process normally.  Otherwise
                         * there's nothing for us to do.
                         */
                        if (conn->cmd_queue_head != NULL)
                        {
                                conn->asyncStatus = PGASYNC_PIPELINE_IDLE;
                                break;
                        }
                        return;

                case PGASYNC_PIPELINE_IDLE:
                        Assert(conn->pipelineStatus != PQ_PIPELINE_OFF);
                        /* next query please */
                        break;
        }

        /*
         * Reset partial-result mode.  (Client has to set it up for each query, if
         * desired.)
         */
        conn->partialResMode = false;
        conn->singleRowMode = false;
        conn->maxChunkSize = 0;

        /*
         * If there are no further commands to process in the queue, get us in
         * "real idle" mode now.
         */
        if (conn->cmd_queue_head == NULL)
        {
                conn->asyncStatus = PGASYNC_IDLE;
                return;
        }

        /*
         * Reset the error state.  This and the next couple of steps correspond to
         * what PQsendQueryStart didn't do for this query.
         */
        pqClearConnErrorState(conn);

        /* Initialize async result-accumulation state */
        pqClearAsyncResult(conn);

        if (conn->pipelineStatus == PQ_PIPELINE_ABORTED &&
                conn->cmd_queue_head->queryclass != PGQUERY_SYNC)
        {
                /*
                 * In an aborted pipeline we don't get anything from the server for
                 * each result; we're just discarding commands from the queue until we
                 * get to the next sync from the server.
                 *
                 * The PGRES_PIPELINE_ABORTED results tell the client that its queries
                 * got aborted.
                 */
                conn->result = PQmakeEmptyPGresult(conn, PGRES_PIPELINE_ABORTED);
                if (!conn->result)
                {
                        libpq_append_conn_error(conn, "out of memory");
                        pqSaveErrorResult(conn);
                        return;
                }
                conn->asyncStatus = PGASYNC_READY;
        }
        else
        {
                /* allow parsing to continue */
                conn->asyncStatus = PGASYNC_BUSY;
        }
}

/*
 * PQpipelineSync
 *              Send a Sync message as part of a pipeline, and flush to server
 */
int
PQpipelineSync(PGconn *conn)
{
        return pqPipelineSyncInternal(conn, true);
}

/*
 * PQsendPipelineSync
 *              Send a Sync message as part of a pipeline, without flushing to server
 */
int
PQsendPipelineSync(PGconn *conn)
{
        return pqPipelineSyncInternal(conn, false);
}

/*
 * Workhorse function for PQpipelineSync and PQsendPipelineSync.
 *
 * immediate_flush controls if the flush happens immediately after sending the
 * Sync message or not.
 */
static int
pqPipelineSyncInternal(PGconn *conn, bool immediate_flush)
{
        PGcmdQueueEntry *entry;

        if (!conn)
                return 0;

        if (conn->pipelineStatus == PQ_PIPELINE_OFF)
        {
                libpq_append_conn_error(conn, "cannot send pipeline when not in pipeline mode");
                return 0;
        }

        switch (conn->asyncStatus)
        {
                case PGASYNC_COPY_IN:
                case PGASYNC_COPY_OUT:
                case PGASYNC_COPY_BOTH:
                        /* should be unreachable */
                        appendPQExpBufferStr(&conn->errorMessage,
                                                                 "internal error: cannot send pipeline while in COPY\n");
                        return 0;
                case PGASYNC_READY:
                case PGASYNC_READY_MORE:
                case PGASYNC_BUSY:
                case PGASYNC_IDLE:
                case PGASYNC_PIPELINE_IDLE:
                        /* OK to send sync */
                        break;
        }

        entry = pqAllocCmdQueueEntry(conn);
        if (entry == NULL)
                return 0;                               /* error msg already set */

        entry->queryclass = PGQUERY_SYNC;
        entry->query = NULL;

        /* construct the Sync message */
        if (pqPutMsgStart(PqMsg_Sync, conn) < 0 ||
                pqPutMsgEnd(conn) < 0)
                goto sendFailed;

        /*
         * Give the data a push.  In nonblock mode, don't complain if we're unable
         * to send it all; PQgetResult() will do any additional flushing needed.
         * If immediate_flush is disabled, the data is pushed if we are past the
         * size threshold.
         */
        if (immediate_flush)
        {
                if (pqFlush(conn) < 0)
                        goto sendFailed;
        }
        else
        {
                if (pqPipelineFlush(conn) < 0)
                        goto sendFailed;
        }

        /* OK, it's launched! */
        pqAppendCmdQueueEntry(conn, entry);

        return 1;

sendFailed:
        pqRecycleCmdQueueEntry(conn, entry);
        /* error message should be set up already */
        return 0;
}

/*
 * PQsendFlushRequest
 *              Send request for server to flush its buffer.  Useful in pipeline
 *              mode when a sync point is not desired.
 */
int
PQsendFlushRequest(PGconn *conn)
{
        if (!conn)
                return 0;

        /* Don't try to send if we know there's no live connection. */
        if (conn->status != CONNECTION_OK)
        {
                libpq_append_conn_error(conn, "no connection to the server");
                return 0;
        }

        /* Can't send while already busy, either, unless enqueuing for later */
        if (conn->asyncStatus != PGASYNC_IDLE &&
                conn->pipelineStatus == PQ_PIPELINE_OFF)
        {
                libpq_append_conn_error(conn, "another command is already in progress");
                return 0;
        }

        if (pqPutMsgStart(PqMsg_Flush, conn) < 0 ||
                pqPutMsgEnd(conn) < 0)
        {
                return 0;
        }

        /*
         * Give the data a push (in pipeline mode, only if we're past the size
         * threshold).  In nonblock mode, don't complain if we're unable to send
         * it all; PQgetResult() will do any additional flushing needed.
         */
        if (pqPipelineFlush(conn) < 0)
                return 0;

        return 1;
}

/* ====== accessor funcs for PGresult ======== */

ExecStatusType
PQresultStatus(const PGresult *res)
{
        if (!res)
                return PGRES_FATAL_ERROR;
        return res->resultStatus;
}

char *
PQresStatus(ExecStatusType status)
{
        if ((unsigned int) status >= lengthof(pgresStatus))
                return libpq_gettext("invalid ExecStatusType code");
        return pgresStatus[status];
}

char *
PQresultErrorMessage(const PGresult *res)
{
        if (!res || !res->errMsg)
                return "";
        return res->errMsg;
}

char *
PQresultVerboseErrorMessage(const PGresult *res,
                                                        PGVerbosity verbosity,
                                                        PGContextVisibility show_context)
{
        PQExpBufferData workBuf;

        /*
         * Because the caller is expected to free the result string, we must
         * strdup any constant result.  We use plain strdup and document that
         * callers should expect NULL if out-of-memory.
         */
        if (!res ||
                (res->resultStatus != PGRES_FATAL_ERROR &&
                 res->resultStatus != PGRES_NONFATAL_ERROR))
                return strdup(libpq_gettext("PGresult is not an error result\n"));

        initPQExpBuffer(&workBuf);

        pqBuildErrorMessage3(&workBuf, res, verbosity, show_context);

        /* If insufficient memory to format the message, fail cleanly */
        if (PQExpBufferDataBroken(workBuf))
        {
                termPQExpBuffer(&workBuf);
                return strdup(libpq_gettext("out of memory\n"));
        }

        return workBuf.data;
}

char *
PQresultErrorField(const PGresult *res, int fieldcode)
{
        PGMessageField *pfield;

        if (!res)
                return NULL;
        for (pfield = res->errFields; pfield != NULL; pfield = pfield->next)
        {
                if (pfield->code == fieldcode)
                        return pfield->contents;
        }
        return NULL;
}

int
PQntuples(const PGresult *res)
{
        if (!res)
                return 0;
        return res->ntups;
}

int
PQnfields(const PGresult *res)
{
        if (!res)
                return 0;
        return res->numAttributes;
}

int
PQbinaryTuples(const PGresult *res)
{
        if (!res)
                return 0;
        return res->binary;
}

/*
 * Helper routines to range-check field numbers and tuple numbers.
 * Return true if OK, false if not
 */

static int
check_field_number(const PGresult *res, int field_num)
{
        if (!res)
                return false;                   /* no way to display error message... */
        if (field_num < 0 || field_num >= res->numAttributes)
        {
                pqInternalNotice(&res->noticeHooks,
                                                 "column number %d is out of range 0..%d",
                                                 field_num, res->numAttributes - 1);
                return false;
        }
        return true;
}

static int
check_tuple_field_number(const PGresult *res,
                                                 int tup_num, int field_num)
{
        if (!res)
                return false;                   /* no way to display error message... */
        if (tup_num < 0 || tup_num >= res->ntups)
        {
                pqInternalNotice(&res->noticeHooks,
                                                 "row number %d is out of range 0..%d",
                                                 tup_num, res->ntups - 1);
                return false;
        }
        if (field_num < 0 || field_num >= res->numAttributes)
        {
                pqInternalNotice(&res->noticeHooks,
                                                 "column number %d is out of range 0..%d",
                                                 field_num, res->numAttributes - 1);
                return false;
        }
        return true;
}

static int
check_param_number(const PGresult *res, int param_num)
{
        if (!res)
                return false;                   /* no way to display error message... */
        if (param_num < 0 || param_num >= res->numParameters)
        {
                pqInternalNotice(&res->noticeHooks,
                                                 "parameter number %d is out of range 0..%d",
                                                 param_num, res->numParameters - 1);
                return false;
        }

        return true;
}

/*
 * returns NULL if the field_num is invalid
 */
char *
PQfname(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return NULL;
        if (res->attDescs)
                return res->attDescs[field_num].name;
        else
                return NULL;
}

/*
 * PQfnumber: find column number given column name
 *
 * The column name is parsed as if it were in a SQL statement, including
 * case-folding and double-quote processing.  But note a possible gotcha:
 * downcasing in the frontend might follow different locale rules than
 * downcasing in the backend...
 *
 * Returns -1 if no match.  In the present backend it is also possible
 * to have multiple matches, in which case the first one is found.
 */
int
PQfnumber(const PGresult *res, const char *field_name)
{
        char       *field_case;
        bool            in_quotes;
        bool            all_lower = true;
        const char *iptr;
        char       *optr;
        int                     i;

        if (!res)
                return -1;

        /*
         * Note: it is correct to reject a zero-length input string; the proper
         * input to match a zero-length field name would be "".
         */
        if (field_name == NULL ||
                field_name[0] == '\0' ||
                res->attDescs == NULL)
                return -1;

        /*
         * Check if we can avoid the strdup() and related work because the
         * passed-in string wouldn't be changed before we do the check anyway.
         */
        for (iptr = field_name; *iptr; iptr++)
        {
                char            c = *iptr;

                if (c == '"' || c != pg_tolower((unsigned char) c))
                {
                        all_lower = false;
                        break;
                }
        }

        if (all_lower)
                for (i = 0; i < res->numAttributes; i++)
                        if (strcmp(field_name, res->attDescs[i].name) == 0)
                                return i;

        /* Fall through to the normal check if that didn't work out. */

        /*
         * Note: this code will not reject partially quoted strings, eg
         * foo"BAR"foo will become fooBARfoo when it probably ought to be an error
         * condition.
         */
        field_case = strdup(field_name);
        if (field_case == NULL)
                return -1;                              /* grotty */

        in_quotes = false;
        optr = field_case;
        for (iptr = field_case; *iptr; iptr++)
        {
                char            c = *iptr;

                if (in_quotes)
                {
                        if (c == '"')
                        {
                                if (iptr[1] == '"')
                                {
                                        /* doubled quotes become a single quote */
                                        *optr++ = '"';
                                        iptr++;
                                }
                                else
                                        in_quotes = false;
                        }
                        else
                                *optr++ = c;
                }
                else if (c == '"')
                        in_quotes = true;
                else
                {
                        c = pg_tolower((unsigned char) c);
                        *optr++ = c;
                }
        }
        *optr = '\0';

        for (i = 0; i < res->numAttributes; i++)
        {
                if (strcmp(field_case, res->attDescs[i].name) == 0)
                {
                        free(field_case);
                        return i;
                }
        }
        free(field_case);
        return -1;
}

Oid
PQftable(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return InvalidOid;
        if (res->attDescs)
                return res->attDescs[field_num].tableid;
        else
                return InvalidOid;
}

int
PQftablecol(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return 0;
        if (res->attDescs)
                return res->attDescs[field_num].columnid;
        else
                return 0;
}

int
PQfformat(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return 0;
        if (res->attDescs)
                return res->attDescs[field_num].format;
        else
                return 0;
}

Oid
PQftype(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return InvalidOid;
        if (res->attDescs)
                return res->attDescs[field_num].typid;
        else
                return InvalidOid;
}

int
PQfsize(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return 0;
        if (res->attDescs)
                return res->attDescs[field_num].typlen;
        else
                return 0;
}

int
PQfmod(const PGresult *res, int field_num)
{
        if (!check_field_number(res, field_num))
                return 0;
        if (res->attDescs)
                return res->attDescs[field_num].atttypmod;
        else
                return 0;
}

char *
PQcmdStatus(PGresult *res)
{
        if (!res)
                return NULL;
        return res->cmdStatus;
}

/*
 * PQoidStatus -
 *      if the last command was an INSERT, return the oid string
 *      if not, return ""
 */
char *
PQoidStatus(const PGresult *res)
{
        /*
         * This must be enough to hold the result. Don't laugh, this is better
         * than what this function used to do.
         */
        static char buf[24];

        size_t          len;

        if (!res || strncmp(res->cmdStatus, "INSERT ", 7) != 0)
                return "";

        len = strspn(res->cmdStatus + 7, "0123456789");
        if (len > sizeof(buf) - 1)
                len = sizeof(buf) - 1;
        memcpy(buf, res->cmdStatus + 7, len);
        buf[len] = '\0';

        return buf;
}

/*
 * PQoidValue -
 *      a perhaps preferable form of the above which just returns
 *      an Oid type
 */
Oid
PQoidValue(const PGresult *res)
{
        char       *endptr = NULL;
        unsigned long result;

        if (!res ||
                strncmp(res->cmdStatus, "INSERT ", 7) != 0 ||
                res->cmdStatus[7] < '0' ||
                res->cmdStatus[7] > '9')
                return InvalidOid;

        result = strtoul(res->cmdStatus + 7, &endptr, 10);

        if (!endptr || (*endptr != ' ' && *endptr != '\0'))
                return InvalidOid;
        else
                return (Oid) result;
}


/*
 * PQcmdTuples -
 *      If the last command was INSERT/UPDATE/DELETE/MERGE/MOVE/FETCH/COPY,
 *      return a string containing the number of inserted/affected tuples.
 *      If not, return "".
 *
 *      XXX: this should probably return an int
 */
char *
PQcmdTuples(PGresult *res)
{
        char       *p,
                           *c;

        if (!res)
                return "";

        if (strncmp(res->cmdStatus, "INSERT ", 7) == 0)
        {
                p = res->cmdStatus + 7;
                /* INSERT: skip oid and space */
                while (*p && *p != ' ')
                        p++;
                if (*p == 0)
                        goto interpret_error;   /* no space? */
                p++;
        }
        else if (strncmp(res->cmdStatus, "SELECT ", 7) == 0 ||
                         strncmp(res->cmdStatus, "DELETE ", 7) == 0 ||
                         strncmp(res->cmdStatus, "UPDATE ", 7) == 0)
                p = res->cmdStatus + 7;
        else if (strncmp(res->cmdStatus, "FETCH ", 6) == 0 ||
                         strncmp(res->cmdStatus, "MERGE ", 6) == 0)
                p = res->cmdStatus + 6;
        else if (strncmp(res->cmdStatus, "MOVE ", 5) == 0 ||
                         strncmp(res->cmdStatus, "COPY ", 5) == 0)
                p = res->cmdStatus + 5;
        else
                return "";

        /* check that we have an integer (at least one digit, nothing else) */
        for (c = p; *c; c++)
        {
                if (!isdigit((unsigned char) *c))
                        goto interpret_error;
        }
        if (c == p)
                goto interpret_error;

        return p;

interpret_error:
        pqInternalNotice(&res->noticeHooks,
                                         "could not interpret result from server: %s",
                                         res->cmdStatus);
        return "";
}

/*
 * PQgetvalue:
 *      return the value of field 'field_num' of row 'tup_num'
 */
char *
PQgetvalue(const PGresult *res, int tup_num, int field_num)
{
        if (!check_tuple_field_number(res, tup_num, field_num))
                return NULL;
        return res->tuples[tup_num][field_num].value;
}

/* PQgetlength:
 *      returns the actual length of a field value in bytes.
 */
int
PQgetlength(const PGresult *res, int tup_num, int field_num)
{
        if (!check_tuple_field_number(res, tup_num, field_num))
                return 0;
        if (res->tuples[tup_num][field_num].len != NULL_LEN)
                return res->tuples[tup_num][field_num].len;
        else
                return 0;
}

/* PQgetisnull:
 *      returns the null status of a field value.
 */
int
PQgetisnull(const PGresult *res, int tup_num, int field_num)
{
        if (!check_tuple_field_number(res, tup_num, field_num))
                return 1;                               /* pretend it is null */
        if (res->tuples[tup_num][field_num].len == NULL_LEN)
                return 1;
        else
                return 0;
}

/* PQnparams:
 *      returns the number of input parameters of a prepared statement.
 */
int
PQnparams(const PGresult *res)
{
        if (!res)
                return 0;
        return res->numParameters;
}

/* PQparamtype:
 *      returns type Oid of the specified statement parameter.
 */
Oid
PQparamtype(const PGresult *res, int param_num)
{
        if (!check_param_number(res, param_num))
                return InvalidOid;
        if (res->paramDescs)
                return res->paramDescs[param_num].typid;
        else
                return InvalidOid;
}


/* PQsetnonblocking:
 *      sets the PGconn's database connection non-blocking if the arg is true
 *      or makes it blocking if the arg is false, this will not protect
 *      you from PQexec(), you'll only be safe when using the non-blocking API.
 *      Needs to be called only on a connected database connection.
 */
int
PQsetnonblocking(PGconn *conn, int arg)
{
        bool            barg;

        if (!conn || conn->status == CONNECTION_BAD)
                return -1;

        barg = (arg ? true : false);

        /* early out if the socket is already in the state requested */
        if (barg == conn->nonblocking)
                return 0;

        /*
         * to guarantee constancy for flushing/query/result-polling behavior we
         * need to flush the send queue at this point in order to guarantee proper
         * behavior. this is ok because either they are making a transition _from_
         * or _to_ blocking mode, either way we can block them.
         *
         * Clear error state in case pqFlush adds to it, unless we're actively
         * pipelining, in which case it seems best not to.
         */
        if (conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        /* if we are going from blocking to non-blocking flush here */
        if (pqFlush(conn))
                return -1;

        conn->nonblocking = barg;

        return 0;
}

/*
 * return the blocking status of the database connection
 *              true == nonblocking, false == blocking
 */
int
PQisnonblocking(const PGconn *conn)
{
        if (!conn || conn->status == CONNECTION_BAD)
                return false;
        return pqIsnonblocking(conn);
}

/* libpq is thread-safe? */
int
PQisthreadsafe(void)
{
        return true;
}


/* try to force data out, really only useful for non-blocking users */
int
PQflush(PGconn *conn)
{
        if (!conn || conn->status == CONNECTION_BAD)
                return -1;
        return pqFlush(conn);
}

/*
 * pqPipelineFlush
 *
 * In pipeline mode, data will be flushed only when the out buffer reaches the
 * threshold value.  In non-pipeline mode, it behaves as stock pqFlush.
 *
 * Returns 0 on success.
 */
static int
pqPipelineFlush(PGconn *conn)
{
        if ((conn->pipelineStatus != PQ_PIPELINE_ON) ||
                (conn->outCount >= OUTBUFFER_THRESHOLD))
                return pqFlush(conn);
        return 0;
}


/*
 *              PQfreemem - safely frees memory allocated
 *
 * Needed mostly by Win32, unless multithreaded DLL (/MD in VC6)
 * Used for freeing memory from PQescapeBytea()/PQunescapeBytea()
 */
void
PQfreemem(void *ptr)
{
        free(ptr);
}

/*
 * PQfreeNotify - free's the memory associated with a PGnotify
 *
 * This function is here only for binary backward compatibility.
 * New code should use PQfreemem().  A macro will automatically map
 * calls to PQfreemem.  It should be removed in the future.  bjm 2003-03-24
 */

#undef PQfreeNotify
void            PQfreeNotify(PGnotify *notify);

void
PQfreeNotify(PGnotify *notify)
{
        PQfreemem(notify);
}


/*
 * Escaping arbitrary strings to get valid SQL literal strings.
 *
 * Replaces "'" with "''", and if not std_strings, replaces "\" with "\\".
 *
 * length is the length of the source string.  (Note: if a terminating NUL
 * is encountered sooner, PQescapeString stops short of "length"; the behavior
 * is thus rather like strncpy.)
 *
 * For safety the buffer at "to" must be at least 2*length + 1 bytes long.
 * A terminating NUL character is added to the output string, whether the
 * input is NUL-terminated or not.
 *
 * Returns the actual length of the output (not counting the terminating NUL).
 */
static size_t
PQescapeStringInternal(PGconn *conn,
                                           char *to, const char *from, size_t length,
                                           int *error,
                                           int encoding, bool std_strings)
{
        const char *source = from;
        char       *target = to;
        size_t          remaining = length;

        if (error)
                *error = 0;

        while (remaining > 0 && *source != '\0')
        {
                char            c = *source;
                int                     len;
                int                     i;

                /* Fast path for plain ASCII */
                if (!IS_HIGHBIT_SET(c))
                {
                        /* Apply quoting if needed */
                        if (SQL_STR_DOUBLE(c, !std_strings))
                                *target++ = c;
                        /* Copy the character */
                        *target++ = c;
                        source++;
                        remaining--;
                        continue;
                }

                /* Slow path for possible multibyte characters */
                len = pg_encoding_mblen(encoding, source);

                /* Copy the character */
                for (i = 0; i < len; i++)
                {
                        if (remaining == 0 || *source == '\0')
                                break;
                        *target++ = *source++;
                        remaining--;
                }

                /*
                 * If we hit premature end of string (ie, incomplete multibyte
                 * character), try to pad out to the correct length with spaces. We
                 * may not be able to pad completely, but we will always be able to
                 * insert at least one pad space (since we'd not have quoted a
                 * multibyte character).  This should be enough to make a string that
                 * the server will error out on.
                 */
                if (i < len)
                {
                        if (error)
                                *error = 1;
                        if (conn)
                                libpq_append_conn_error(conn, "incomplete multibyte character");
                        for (; i < len; i++)
                        {
                                if (((size_t) (target - to)) / 2 >= length)
                                        break;
                                *target++ = ' ';
                        }
                        break;
                }
        }

        /* Write the terminating NUL character. */
        *target = '\0';

        return target - to;
}

size_t
PQescapeStringConn(PGconn *conn,
                                   char *to, const char *from, size_t length,
                                   int *error)
{
        if (!conn)
        {
                /* force empty-string result */
                *to = '\0';
                if (error)
                        *error = 1;
                return 0;
        }

        if (conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        return PQescapeStringInternal(conn, to, from, length, error,
                                                                  conn->client_encoding,
                                                                  conn->std_strings);
}

size_t
PQescapeString(char *to, const char *from, size_t length)
{
        return PQescapeStringInternal(NULL, to, from, length, NULL,
                                                                  static_client_encoding,
                                                                  static_std_strings);
}


/*
 * Escape arbitrary strings.  If as_ident is true, we escape the result
 * as an identifier; if false, as a literal.  The result is returned in
 * a newly allocated buffer.  If we fail due to an encoding violation or out
 * of memory condition, we return NULL, storing an error message into conn.
 */
static char *
PQescapeInternal(PGconn *conn, const char *str, size_t len, bool as_ident)
{
        const char *s;
        char       *result;
        char       *rp;
        int                     num_quotes = 0; /* single or double, depending on as_ident */
        int                     num_backslashes = 0;
        int                     input_len;
        int                     result_size;
        char            quote_char = as_ident ? '"' : '\'';

        /* We must have a connection, else fail immediately. */
        if (!conn)
                return NULL;

        if (conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        /* Scan the string for characters that must be escaped. */
        for (s = str; (s - str) < len && *s != '\0'; ++s)
        {
                if (*s == quote_char)
                        ++num_quotes;
                else if (*s == '\\')
                        ++num_backslashes;
                else if (IS_HIGHBIT_SET(*s))
                {
                        int                     charlen;

                        /* Slow path for possible multibyte characters */
                        charlen = pg_encoding_mblen(conn->client_encoding, s);

                        /* Multibyte character overruns allowable length. */
                        if ((s - str) + charlen > len || memchr(s, 0, charlen) != NULL)
                        {
                                libpq_append_conn_error(conn, "incomplete multibyte character");
                                return NULL;
                        }

                        /* Adjust s, bearing in mind that for loop will increment it. */
                        s += charlen - 1;
                }
        }

        /* Allocate output buffer. */
        input_len = s - str;
        result_size = input_len + num_quotes + 3;       /* two quotes, plus a NUL */
        if (!as_ident && num_backslashes > 0)
                result_size += num_backslashes + 2;
        result = rp = (char *) malloc(result_size);
        if (rp == NULL)
        {
                libpq_append_conn_error(conn, "out of memory");
                return NULL;
        }

        /*
         * If we are escaping a literal that contains backslashes, we use the
         * escape string syntax so that the result is correct under either value
         * of standard_conforming_strings.  We also emit a leading space in this
         * case, to guard against the possibility that the result might be
         * interpolated immediately following an identifier.
         */
        if (!as_ident && num_backslashes > 0)
        {
                *rp++ = ' ';
                *rp++ = 'E';
        }

        /* Opening quote. */
        *rp++ = quote_char;

        /*
         * Use fast path if possible.
         *
         * We've already verified that the input string is well-formed in the
         * current encoding.  If it contains no quotes and, in the case of
         * literal-escaping, no backslashes, then we can just copy it directly to
         * the output buffer, adding the necessary quotes.
         *
         * If not, we must rescan the input and process each character
         * individually.
         */
        if (num_quotes == 0 && (num_backslashes == 0 || as_ident))
        {
                memcpy(rp, str, input_len);
                rp += input_len;
        }
        else
        {
                for (s = str; s - str < input_len; ++s)
                {
                        if (*s == quote_char || (!as_ident && *s == '\\'))
                        {
                                *rp++ = *s;
                                *rp++ = *s;
                        }
                        else if (!IS_HIGHBIT_SET(*s))
                                *rp++ = *s;
                        else
                        {
                                int                     i = pg_encoding_mblen(conn->client_encoding, s);

                                while (1)
                                {
                                        *rp++ = *s;
                                        if (--i == 0)
                                                break;
                                        ++s;            /* for loop will provide the final increment */
                                }
                        }
                }
        }

        /* Closing quote and terminating NUL. */
        *rp++ = quote_char;
        *rp = '\0';

        return result;
}

char *
PQescapeLiteral(PGconn *conn, const char *str, size_t len)
{
        return PQescapeInternal(conn, str, len, false);
}

char *
PQescapeIdentifier(PGconn *conn, const char *str, size_t len)
{
        return PQescapeInternal(conn, str, len, true);
}

/* HEX encoding support for bytea */
static const char hextbl[] = "0123456789abcdef";

static const int8 hexlookup[128] = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
        -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

static inline char
get_hex(char c)
{
        int                     res = -1;

        if (c > 0 && c < 127)
                res = hexlookup[(unsigned char) c];

        return (char) res;
}


/*
 *              PQescapeBytea   - converts from binary string to the
 *              minimal encoding necessary to include the string in an SQL
 *              INSERT statement with a bytea type column as the target.
 *
 *              We can use either hex or escape (traditional) encoding.
 *              In escape mode, the following transformations are applied:
 *              '\0' == ASCII  0 == \000
 *              '\'' == ASCII 39 == ''
 *              '\\' == ASCII 92 == \\
 *              anything < 0x20, or > 0x7e ---> \ooo
 *                                                                              (where ooo is an octal expression)
 *
 *              If not std_strings, all backslashes sent to the output are doubled.
 */
static unsigned char *
PQescapeByteaInternal(PGconn *conn,
                                          const unsigned char *from, size_t from_length,
                                          size_t *to_length, bool std_strings, bool use_hex)
{
        const unsigned char *vp;
        unsigned char *rp;
        unsigned char *result;
        size_t          i;
        size_t          len;
        size_t          bslash_len = (std_strings ? 1 : 2);

        /*
         * empty string has 1 char ('\0')
         */
        len = 1;

        if (use_hex)
        {
                len += bslash_len + 1 + 2 * from_length;
        }
        else
        {
                vp = from;
                for (i = from_length; i > 0; i--, vp++)
                {
                        if (*vp < 0x20 || *vp > 0x7e)
                                len += bslash_len + 3;
                        else if (*vp == '\'')
                                len += 2;
                        else if (*vp == '\\')
                                len += bslash_len + bslash_len;
                        else
                                len++;
                }
        }

        *to_length = len;
        rp = result = (unsigned char *) malloc(len);
        if (rp == NULL)
        {
                if (conn)
                        libpq_append_conn_error(conn, "out of memory");
                return NULL;
        }

        if (use_hex)
        {
                if (!std_strings)
                        *rp++ = '\\';
                *rp++ = '\\';
                *rp++ = 'x';
        }

        vp = from;
        for (i = from_length; i > 0; i--, vp++)
        {
                unsigned char c = *vp;

                if (use_hex)
                {
                        *rp++ = hextbl[(c >> 4) & 0xF];
                        *rp++ = hextbl[c & 0xF];
                }
                else if (c < 0x20 || c > 0x7e)
                {
                        if (!std_strings)
                                *rp++ = '\\';
                        *rp++ = '\\';
                        *rp++ = (c >> 6) + '0';
                        *rp++ = ((c >> 3) & 07) + '0';
                        *rp++ = (c & 07) + '0';
                }
                else if (c == '\'')
                {
                        *rp++ = '\'';
                        *rp++ = '\'';
                }
                else if (c == '\\')
                {
                        if (!std_strings)
                        {
                                *rp++ = '\\';
                                *rp++ = '\\';
                        }
                        *rp++ = '\\';
                        *rp++ = '\\';
                }
                else
                        *rp++ = c;
        }
        *rp = '\0';

        return result;
}

unsigned char *
PQescapeByteaConn(PGconn *conn,
                                  const unsigned char *from, size_t from_length,
                                  size_t *to_length)
{
        if (!conn)
                return NULL;

        if (conn->cmd_queue_head == NULL)
                pqClearConnErrorState(conn);

        return PQescapeByteaInternal(conn, from, from_length, to_length,
                                                                 conn->std_strings,
                                                                 (conn->sversion >= 90000));
}

unsigned char *
PQescapeBytea(const unsigned char *from, size_t from_length, size_t *to_length)
{
        return PQescapeByteaInternal(NULL, from, from_length, to_length,
                                                                 static_std_strings,
                                                                 false /* can't use hex */ );
}


#define ISFIRSTOCTDIGIT(CH) ((CH) >= '0' && (CH) <= '3')
#define ISOCTDIGIT(CH) ((CH) >= '0' && (CH) <= '7')
#define OCTVAL(CH) ((CH) - '0')

/*
 *              PQunescapeBytea - converts the null terminated string representation
 *              of a bytea, strtext, into binary, filling a buffer. It returns a
 *              pointer to the buffer (or NULL on error), and the size of the
 *              buffer in retbuflen. The pointer may subsequently be used as an
 *              argument to the function PQfreemem.
 *
 *              The following transformations are made:
 *              \\       == ASCII 92 == \
 *              \ooo == a byte whose value = ooo (ooo is an octal number)
 *              \x       == x (x is any character not matched by the above transformations)
 */
unsigned char *
PQunescapeBytea(const unsigned char *strtext, size_t *retbuflen)
{
        size_t          strtextlen,
                                buflen;
        unsigned char *buffer,
                           *tmpbuf;
        size_t          i,
                                j;

        if (strtext == NULL)
                return NULL;

        strtextlen = strlen((const char *) strtext);

        if (strtext[0] == '\\' && strtext[1] == 'x')
        {
                const unsigned char *s;
                unsigned char *p;

                buflen = (strtextlen - 2) / 2;
                /* Avoid unportable malloc(0) */
                buffer = (unsigned char *) malloc(buflen > 0 ? buflen : 1);
                if (buffer == NULL)
                        return NULL;

                s = strtext + 2;
                p = buffer;
                while (*s)
                {
                        char            v1,
                                                v2;

                        /*
                         * Bad input is silently ignored.  Note that this includes
                         * whitespace between hex pairs, which is allowed by byteain.
                         */
                        v1 = get_hex(*s++);
                        if (!*s || v1 == (char) -1)
                                continue;
                        v2 = get_hex(*s++);
                        if (v2 != (char) -1)
                                *p++ = (v1 << 4) | v2;
                }

                buflen = p - buffer;
        }
        else
        {
                /*
                 * Length of input is max length of output, but add one to avoid
                 * unportable malloc(0) if input is zero-length.
                 */
                buffer = (unsigned char *) malloc(strtextlen + 1);
                if (buffer == NULL)
                        return NULL;

                for (i = j = 0; i < strtextlen;)
                {
                        switch (strtext[i])
                        {
                                case '\\':
                                        i++;
                                        if (strtext[i] == '\\')
                                                buffer[j++] = strtext[i++];
                                        else
                                        {
                                                if ((ISFIRSTOCTDIGIT(strtext[i])) &&
                                                        (ISOCTDIGIT(strtext[i + 1])) &&
                                                        (ISOCTDIGIT(strtext[i + 2])))
                                                {
                                                        int                     byte;

                                                        byte = OCTVAL(strtext[i++]);
                                                        byte = (byte << 3) + OCTVAL(strtext[i++]);
                                                        byte = (byte << 3) + OCTVAL(strtext[i++]);
                                                        buffer[j++] = byte;
                                                }
                                        }

                                        /*
                                         * Note: if we see '\' followed by something that isn't a
                                         * recognized escape sequence, we loop around having done
                                         * nothing except advance i.  Therefore the something will
                                         * be emitted as ordinary data on the next cycle. Corner
                                         * case: '\' at end of string will just be discarded.
                                         */
                                        break;

                                default:
                                        buffer[j++] = strtext[i++];
                                        break;
                        }
                }
                buflen = j;                             /* buflen is the length of the dequoted data */
        }

        /* Shrink the buffer to be no larger than necessary */
        /* +1 avoids unportable behavior when buflen==0 */
        tmpbuf = realloc(buffer, buflen + 1);

        /* It would only be a very brain-dead realloc that could fail, but... */
        if (!tmpbuf)
        {
                free(buffer);
                return NULL;
        }

        *retbuflen = buflen;
        return tmpbuf;
}