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

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

/*-------------------------------------------------------------------------
 *
 *       FILE
 *              fe-misc.c
 *
 *       DESCRIPTION
 *               miscellaneous useful functions
 *
 * The communication routines here are analogous to the ones in
 * backend/libpq/pqcomm.c and backend/libpq/pqformat.c, but operate
 * in the considerably different environment of the frontend libpq.
 * In particular, we work with a bare nonblock-mode socket, rather than
 * a stdio stream, so that we can avoid unwanted blocking of the application.
 *
 * XXX: MOVE DEBUG PRINTOUT TO HIGHER LEVEL.  As is, block and restart
 * will cause repeat printouts.
 *
 * We must speak the same transmitted data representations as the backend
 * routines.
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *        src/interfaces/libpq/fe-misc.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres_fe.h"

#include <signal.h>
#include <time.h>

#ifdef WIN32
#include "win32.h"
#else
#include <unistd.h>
#include <sys/select.h>
#include <sys/time.h>
#endif

#ifdef HAVE_POLL_H
#include <poll.h>
#endif

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

static int      pqPutMsgBytes(const void *buf, size_t len, PGconn *conn);
static int      pqSendSome(PGconn *conn, int len);
static int      pqSocketCheck(PGconn *conn, int forRead, int forWrite,
                                                  pg_usec_time_t end_time);

/*
 * PQlibVersion: return the libpq version number
 */
int
PQlibVersion(void)
{
        return PG_VERSION_NUM;
}


/*
 * pqGetc: get 1 character from the connection
 *
 *      All these routines return 0 on success, EOF on error.
 *      Note that for the Get routines, EOF only means there is not enough
 *      data in the buffer, not that there is necessarily a hard error.
 */
int
pqGetc(char *result, PGconn *conn)
{
        if (conn->inCursor >= conn->inEnd)
                return EOF;

        *result = conn->inBuffer[conn->inCursor++];

        return 0;
}


/*
 * pqPutc: write 1 char to the current message
 */
int
pqPutc(char c, PGconn *conn)
{
        if (pqPutMsgBytes(&c, 1, conn))
                return EOF;

        return 0;
}


/*
 * pqGets[_append]:
 * get a null-terminated string from the connection,
 * and store it in an expansible PQExpBuffer.
 * If we run out of memory, all of the string is still read,
 * but the excess characters are silently discarded.
 */
static int
pqGets_internal(PQExpBuffer buf, PGconn *conn, bool resetbuffer)
{
        /* Copy conn data to locals for faster search loop */
        char       *inBuffer = conn->inBuffer;
        int                     inCursor = conn->inCursor;
        int                     inEnd = conn->inEnd;
        int                     slen;

        while (inCursor < inEnd && inBuffer[inCursor])
                inCursor++;

        if (inCursor >= inEnd)
                return EOF;

        slen = inCursor - conn->inCursor;

        if (resetbuffer)
                resetPQExpBuffer(buf);

        appendBinaryPQExpBuffer(buf, inBuffer + conn->inCursor, slen);

        conn->inCursor = ++inCursor;

        return 0;
}

int
pqGets(PQExpBuffer buf, PGconn *conn)
{
        return pqGets_internal(buf, conn, true);
}

int
pqGets_append(PQExpBuffer buf, PGconn *conn)
{
        return pqGets_internal(buf, conn, false);
}


/*
 * pqPuts: write a null-terminated string to the current message
 */
int
pqPuts(const char *s, PGconn *conn)
{
        if (pqPutMsgBytes(s, strlen(s) + 1, conn))
                return EOF;

        return 0;
}

/*
 * pqGetnchar:
 *      get a string of exactly len bytes in buffer s, no null termination
 */
int
pqGetnchar(char *s, size_t len, PGconn *conn)
{
        if (len > (size_t) (conn->inEnd - conn->inCursor))
                return EOF;

        memcpy(s, conn->inBuffer + conn->inCursor, len);
        /* no terminating null */

        conn->inCursor += len;

        return 0;
}

/*
 * pqSkipnchar:
 *      skip over len bytes in input buffer.
 *
 * Note: this is primarily useful for its debug output, which should
 * be exactly the same as for pqGetnchar.  We assume the data in question
 * will actually be used, but just isn't getting copied anywhere as yet.
 */
int
pqSkipnchar(size_t len, PGconn *conn)
{
        if (len > (size_t) (conn->inEnd - conn->inCursor))
                return EOF;

        conn->inCursor += len;

        return 0;
}

/*
 * pqPutnchar:
 *      write exactly len bytes to the current message
 */
int
pqPutnchar(const char *s, size_t len, PGconn *conn)
{
        if (pqPutMsgBytes(s, len, conn))
                return EOF;

        return 0;
}

/*
 * pqGetInt
 *      read a 2 or 4 byte integer and convert from network byte order
 *      to local byte order
 */
int
pqGetInt(int *result, size_t bytes, PGconn *conn)
{
        uint16          tmp2;
        uint32          tmp4;

        switch (bytes)
        {
                case 2:
                        if (conn->inCursor + 2 > conn->inEnd)
                                return EOF;
                        memcpy(&tmp2, conn->inBuffer + conn->inCursor, 2);
                        conn->inCursor += 2;
                        *result = (int) pg_ntoh16(tmp2);
                        break;
                case 4:
                        if (conn->inCursor + 4 > conn->inEnd)
                                return EOF;
                        memcpy(&tmp4, conn->inBuffer + conn->inCursor, 4);
                        conn->inCursor += 4;
                        *result = (int) pg_ntoh32(tmp4);
                        break;
                default:
                        pqInternalNotice(&conn->noticeHooks,
                                                         "integer of size %lu not supported by pqGetInt",
                                                         (unsigned long) bytes);
                        return EOF;
        }

        return 0;
}

/*
 * pqPutInt
 * write an integer of 2 or 4 bytes, converting from host byte order
 * to network byte order.
 */
int
pqPutInt(int value, size_t bytes, PGconn *conn)
{
        uint16          tmp2;
        uint32          tmp4;

        switch (bytes)
        {
                case 2:
                        tmp2 = pg_hton16((uint16) value);
                        if (pqPutMsgBytes((const char *) &tmp2, 2, conn))
                                return EOF;
                        break;
                case 4:
                        tmp4 = pg_hton32((uint32) value);
                        if (pqPutMsgBytes((const char *) &tmp4, 4, conn))
                                return EOF;
                        break;
                default:
                        pqInternalNotice(&conn->noticeHooks,
                                                         "integer of size %lu not supported by pqPutInt",
                                                         (unsigned long) bytes);
                        return EOF;
        }

        return 0;
}

/*
 * Make sure conn's output buffer can hold bytes_needed bytes (caller must
 * include already-stored data into the value!)
 *
 * Returns 0 on success, EOF if failed to enlarge buffer
 */
int
pqCheckOutBufferSpace(size_t bytes_needed, PGconn *conn)
{
        int                     newsize = conn->outBufSize;
        char       *newbuf;

        /* Quick exit if we have enough space */
        if (bytes_needed <= (size_t) newsize)
                return 0;

        /*
         * If we need to enlarge the buffer, we first try to double it in size; if
         * that doesn't work, enlarge in multiples of 8K.  This avoids thrashing
         * the malloc pool by repeated small enlargements.
         *
         * Note: tests for newsize > 0 are to catch integer overflow.
         */
        do
        {
                newsize *= 2;
        } while (newsize > 0 && bytes_needed > (size_t) newsize);

        if (newsize > 0 && bytes_needed <= (size_t) newsize)
        {
                newbuf = realloc(conn->outBuffer, newsize);
                if (newbuf)
                {
                        /* realloc succeeded */
                        conn->outBuffer = newbuf;
                        conn->outBufSize = newsize;
                        return 0;
                }
        }

        newsize = conn->outBufSize;
        do
        {
                newsize += 8192;
        } while (newsize > 0 && bytes_needed > (size_t) newsize);

        if (newsize > 0 && bytes_needed <= (size_t) newsize)
        {
                newbuf = realloc(conn->outBuffer, newsize);
                if (newbuf)
                {
                        /* realloc succeeded */
                        conn->outBuffer = newbuf;
                        conn->outBufSize = newsize;
                        return 0;
                }
        }

        /* realloc failed. Probably out of memory */
        appendPQExpBufferStr(&conn->errorMessage,
                                                 "cannot allocate memory for output buffer\n");
        return EOF;
}

/*
 * Make sure conn's input buffer can hold bytes_needed bytes (caller must
 * include already-stored data into the value!)
 *
 * Returns 0 on success, EOF if failed to enlarge buffer
 */
int
pqCheckInBufferSpace(size_t bytes_needed, PGconn *conn)
{
        int                     newsize = conn->inBufSize;
        char       *newbuf;

        /* Quick exit if we have enough space */
        if (bytes_needed <= (size_t) newsize)
                return 0;

        /*
         * Before concluding that we need to enlarge the buffer, left-justify
         * whatever is in it and recheck.  The caller's value of bytes_needed
         * includes any data to the left of inStart, but we can delete that in
         * preference to enlarging the buffer.  It's slightly ugly to have this
         * function do this, but it's better than making callers worry about it.
         */
        bytes_needed -= conn->inStart;

        if (conn->inStart < conn->inEnd)
        {
                if (conn->inStart > 0)
                {
                        memmove(conn->inBuffer, conn->inBuffer + conn->inStart,
                                        conn->inEnd - conn->inStart);
                        conn->inEnd -= conn->inStart;
                        conn->inCursor -= conn->inStart;
                        conn->inStart = 0;
                }
        }
        else
        {
                /* buffer is logically empty, reset it */
                conn->inStart = conn->inCursor = conn->inEnd = 0;
        }

        /* Recheck whether we have enough space */
        if (bytes_needed <= (size_t) newsize)
                return 0;

        /*
         * If we need to enlarge the buffer, we first try to double it in size; if
         * that doesn't work, enlarge in multiples of 8K.  This avoids thrashing
         * the malloc pool by repeated small enlargements.
         *
         * Note: tests for newsize > 0 are to catch integer overflow.
         */
        do
        {
                newsize *= 2;
        } while (newsize > 0 && bytes_needed > (size_t) newsize);

        if (newsize > 0 && bytes_needed <= (size_t) newsize)
        {
                newbuf = realloc(conn->inBuffer, newsize);
                if (newbuf)
                {
                        /* realloc succeeded */
                        conn->inBuffer = newbuf;
                        conn->inBufSize = newsize;
                        return 0;
                }
        }

        newsize = conn->inBufSize;
        do
        {
                newsize += 8192;
        } while (newsize > 0 && bytes_needed > (size_t) newsize);

        if (newsize > 0 && bytes_needed <= (size_t) newsize)
        {
                newbuf = realloc(conn->inBuffer, newsize);
                if (newbuf)
                {
                        /* realloc succeeded */
                        conn->inBuffer = newbuf;
                        conn->inBufSize = newsize;
                        return 0;
                }
        }

        /* realloc failed. Probably out of memory */
        appendPQExpBufferStr(&conn->errorMessage,
                                                 "cannot allocate memory for input buffer\n");
        return EOF;
}

/*
 * pqParseDone: after a server-to-client message has successfully
 * been parsed, advance conn->inStart to account for it.
 */
void
pqParseDone(PGconn *conn, int newInStart)
{
        /* trace server-to-client message */
        if (conn->Pfdebug)
                pqTraceOutputMessage(conn, conn->inBuffer + conn->inStart, false);

        /* Mark message as done */
        conn->inStart = newInStart;
}

/*
 * pqPutMsgStart: begin construction of a message to the server
 *
 * msg_type is the message type byte, or 0 for a message without type byte
 * (only startup messages have no type byte)
 *
 * Returns 0 on success, EOF on error
 *
 * The idea here is that we construct the message in conn->outBuffer,
 * beginning just past any data already in outBuffer (ie, at
 * outBuffer+outCount).  We enlarge the buffer as needed to hold the message.
 * When the message is complete, we fill in the length word (if needed) and
 * then advance outCount past the message, making it eligible to send.
 *
 * The state variable conn->outMsgStart points to the incomplete message's
 * length word: it is either outCount or outCount+1 depending on whether
 * there is a type byte.  The state variable conn->outMsgEnd is the end of
 * the data collected so far.
 */
int
pqPutMsgStart(char msg_type, PGconn *conn)
{
        int                     lenPos;
        int                     endPos;

        /* allow room for message type byte */
        if (msg_type)
                endPos = conn->outCount + 1;
        else
                endPos = conn->outCount;

        /* do we want a length word? */
        lenPos = endPos;
        /* allow room for message length */
        endPos += 4;

        /* make sure there is room for message header */
        if (pqCheckOutBufferSpace(endPos, conn))
                return EOF;
        /* okay, save the message type byte if any */
        if (msg_type)
                conn->outBuffer[conn->outCount] = msg_type;
        /* set up the message pointers */
        conn->outMsgStart = lenPos;
        conn->outMsgEnd = endPos;
        /* length word, if needed, will be filled in by pqPutMsgEnd */

        return 0;
}

/*
 * pqPutMsgBytes: add bytes to a partially-constructed message
 *
 * Returns 0 on success, EOF on error
 */
static int
pqPutMsgBytes(const void *buf, size_t len, PGconn *conn)
{
        /* make sure there is room for it */
        if (pqCheckOutBufferSpace(conn->outMsgEnd + len, conn))
                return EOF;
        /* okay, save the data */
        memcpy(conn->outBuffer + conn->outMsgEnd, buf, len);
        conn->outMsgEnd += len;
        /* no Pfdebug call here, caller should do it */
        return 0;
}

/*
 * pqPutMsgEnd: finish constructing a message and possibly send it
 *
 * Returns 0 on success, EOF on error
 *
 * We don't actually send anything here unless we've accumulated at least
 * 8K worth of data (the typical size of a pipe buffer on Unix systems).
 * This avoids sending small partial packets.  The caller must use pqFlush
 * when it's important to flush all the data out to the server.
 */
int
pqPutMsgEnd(PGconn *conn)
{
        /* Fill in length word if needed */
        if (conn->outMsgStart >= 0)
        {
                uint32          msgLen = conn->outMsgEnd - conn->outMsgStart;

                msgLen = pg_hton32(msgLen);
                memcpy(conn->outBuffer + conn->outMsgStart, &msgLen, 4);
        }

        /* trace client-to-server message */
        if (conn->Pfdebug)
        {
                if (conn->outCount < conn->outMsgStart)
                        pqTraceOutputMessage(conn, conn->outBuffer + conn->outCount, true);
                else
                        pqTraceOutputNoTypeByteMessage(conn,
                                                                                   conn->outBuffer + conn->outMsgStart);
        }

        /* Make message eligible to send */
        conn->outCount = conn->outMsgEnd;

        if (conn->outCount >= 8192)
        {
                int                     toSend = conn->outCount - (conn->outCount % 8192);

                if (pqSendSome(conn, toSend) < 0)
                        return EOF;
                /* in nonblock mode, don't complain if unable to send it all */
        }

        return 0;
}

/* ----------
 * pqReadData: read more data, if any is available
 * Possible return values:
 *       1: successfully loaded at least one more byte
 *       0: no data is presently available, but no error detected
 *      -1: error detected (including EOF = connection closure);
 *              conn->errorMessage set
 * NOTE: callers must not assume that pointers or indexes into conn->inBuffer
 * remain valid across this call!
 * ----------
 */
int
pqReadData(PGconn *conn)
{
        int                     someread = 0;
        int                     nread;

        if (conn->sock == PGINVALID_SOCKET)
        {
                libpq_append_conn_error(conn, "connection not open");
                return -1;
        }

        /* Left-justify any data in the buffer to make room */
        if (conn->inStart < conn->inEnd)
        {
                if (conn->inStart > 0)
                {
                        memmove(conn->inBuffer, conn->inBuffer + conn->inStart,
                                        conn->inEnd - conn->inStart);
                        conn->inEnd -= conn->inStart;
                        conn->inCursor -= conn->inStart;
                        conn->inStart = 0;
                }
        }
        else
        {
                /* buffer is logically empty, reset it */
                conn->inStart = conn->inCursor = conn->inEnd = 0;
        }

        /*
         * If the buffer is fairly full, enlarge it. We need to be able to enlarge
         * the buffer in case a single message exceeds the initial buffer size. We
         * enlarge before filling the buffer entirely so as to avoid asking the
         * kernel for a partial packet. The magic constant here should be large
         * enough for a TCP packet or Unix pipe bufferload.  8K is the usual pipe
         * buffer size, so...
         */
        if (conn->inBufSize - conn->inEnd < 8192)
        {
                if (pqCheckInBufferSpace(conn->inEnd + (size_t) 8192, conn))
                {
                        /*
                         * We don't insist that the enlarge worked, but we need some room
                         */
                        if (conn->inBufSize - conn->inEnd < 100)
                                return -1;              /* errorMessage already set */
                }
        }

        /* OK, try to read some data */
retry3:
        nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
                                                  conn->inBufSize - conn->inEnd);
        if (nread < 0)
        {
                switch (SOCK_ERRNO)
                {
                        case EINTR:
                                goto retry3;

                                /* Some systems return EAGAIN/EWOULDBLOCK for no data */
#ifdef EAGAIN
                        case EAGAIN:
                                return someread;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
                        case EWOULDBLOCK:
                                return someread;
#endif

                                /* We might get ECONNRESET etc here if connection failed */
                        case ALL_CONNECTION_FAILURE_ERRNOS:
                                goto definitelyFailed;

                        default:
                                /* pqsecure_read set the error message for us */
                                return -1;
                }
        }
        if (nread > 0)
        {
                conn->inEnd += nread;

                /*
                 * Hack to deal with the fact that some kernels will only give us back
                 * 1 packet per recv() call, even if we asked for more and there is
                 * more available.  If it looks like we are reading a long message,
                 * loop back to recv() again immediately, until we run out of data or
                 * buffer space.  Without this, the block-and-restart behavior of
                 * libpq's higher levels leads to O(N^2) performance on long messages.
                 *
                 * Since we left-justified the data above, conn->inEnd gives the
                 * amount of data already read in the current message.  We consider
                 * the message "long" once we have acquired 32k ...
                 */
                if (conn->inEnd > 32768 &&
                        (conn->inBufSize - conn->inEnd) >= 8192)
                {
                        someread = 1;
                        goto retry3;
                }
                return 1;
        }

        if (someread)
                return 1;                               /* got a zero read after successful tries */

        /*
         * A return value of 0 could mean just that no data is now available, or
         * it could mean EOF --- that is, the server has closed the connection.
         * Since we have the socket in nonblock mode, the only way to tell the
         * difference is to see if select() is saying that the file is ready.
         * Grumble.  Fortunately, we don't expect this path to be taken much,
         * since in normal practice we should not be trying to read data unless
         * the file selected for reading already.
         *
         * In SSL mode it's even worse: SSL_read() could say WANT_READ and then
         * data could arrive before we make the pqReadReady() test, but the second
         * SSL_read() could still say WANT_READ because the data received was not
         * a complete SSL record.  So we must play dumb and assume there is more
         * data, relying on the SSL layer to detect true EOF.
         */

#ifdef USE_SSL
        if (conn->ssl_in_use)
                return 0;
#endif

        switch (pqReadReady(conn))
        {
                case 0:
                        /* definitely no data available */
                        return 0;
                case 1:
                        /* ready for read */
                        break;
                default:
                        /* we override pqReadReady's message with something more useful */
                        goto definitelyEOF;
        }

        /*
         * Still not sure that it's EOF, because some data could have just
         * arrived.
         */
retry4:
        nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
                                                  conn->inBufSize - conn->inEnd);
        if (nread < 0)
        {
                switch (SOCK_ERRNO)
                {
                        case EINTR:
                                goto retry4;

                                /* Some systems return EAGAIN/EWOULDBLOCK for no data */
#ifdef EAGAIN
                        case EAGAIN:
                                return 0;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
                        case EWOULDBLOCK:
                                return 0;
#endif

                                /* We might get ECONNRESET etc here if connection failed */
                        case ALL_CONNECTION_FAILURE_ERRNOS:
                                goto definitelyFailed;

                        default:
                                /* pqsecure_read set the error message for us */
                                return -1;
                }
        }
        if (nread > 0)
        {
                conn->inEnd += nread;
                return 1;
        }

        /*
         * OK, we are getting a zero read even though select() says ready. This
         * means the connection has been closed.  Cope.
         */
definitelyEOF:
        libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
                                                        "\tThis probably means the server terminated abnormally\n"
                                                        "\tbefore or while processing the request.");

        /* Come here if lower-level code already set a suitable errorMessage */
definitelyFailed:
        /* Do *not* drop any already-read data; caller still wants it */
        pqDropConnection(conn, false);
        conn->status = CONNECTION_BAD;  /* No more connection to backend */
        return -1;
}

/*
 * pqSendSome: send data waiting in the output buffer.
 *
 * len is how much to try to send (typically equal to outCount, but may
 * be less).
 *
 * Return 0 on success, -1 on failure and 1 when not all data could be sent
 * because the socket would block and the connection is non-blocking.
 *
 * Note that this is also responsible for consuming data from the socket
 * (putting it in conn->inBuffer) in any situation where we can't send
 * all the specified data immediately.
 *
 * If a socket-level write failure occurs, conn->write_failed is set and the
 * error message is saved in conn->write_err_msg, but we clear the output
 * buffer and return zero anyway; this is because callers should soldier on
 * until we have read what we can from the server and checked for an error
 * message.  write_err_msg should be reported only when we are unable to
 * obtain a server error first.  Much of that behavior is implemented at
 * lower levels, but this function deals with some edge cases.
 */
static int
pqSendSome(PGconn *conn, int len)
{
        char       *ptr = conn->outBuffer;
        int                     remaining = conn->outCount;
        int                     result = 0;

        /*
         * If we already had a write failure, we will never again try to send data
         * on that connection.  Even if the kernel would let us, we've probably
         * lost message boundary sync with the server.  conn->write_failed
         * therefore persists until the connection is reset, and we just discard
         * all data presented to be written.  However, as long as we still have a
         * valid socket, we should continue to absorb data from the backend, so
         * that we can collect any final error messages.
         */
        if (conn->write_failed)
        {
                /* conn->write_err_msg should be set up already */
                conn->outCount = 0;
                /* Absorb input data if any, and detect socket closure */
                if (conn->sock != PGINVALID_SOCKET)
                {
                        if (pqReadData(conn) < 0)
                                return -1;
                }
                return 0;
        }

        if (conn->sock == PGINVALID_SOCKET)
        {
                conn->write_failed = true;
                /* Store error message in conn->write_err_msg, if possible */
                /* (strdup failure is OK, we'll cope later) */
                conn->write_err_msg = strdup(libpq_gettext("connection not open\n"));
                /* Discard queued data; no chance it'll ever be sent */
                conn->outCount = 0;
                return 0;
        }

        /* while there's still data to send */
        while (len > 0)
        {
                int                     sent;

#ifndef WIN32
                sent = pqsecure_write(conn, ptr, len);
#else

                /*
                 * Windows can fail on large sends, per KB article Q201213. The
                 * failure-point appears to be different in different versions of
                 * Windows, but 64k should always be safe.
                 */
                sent = pqsecure_write(conn, ptr, Min(len, 65536));
#endif

                if (sent < 0)
                {
                        /* Anything except EAGAIN/EWOULDBLOCK/EINTR is trouble */
                        switch (SOCK_ERRNO)
                        {
#ifdef EAGAIN
                                case EAGAIN:
                                        break;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
                                case EWOULDBLOCK:
                                        break;
#endif
                                case EINTR:
                                        continue;

                                default:
                                        /* Discard queued data; no chance it'll ever be sent */
                                        conn->outCount = 0;

                                        /* Absorb input data if any, and detect socket closure */
                                        if (conn->sock != PGINVALID_SOCKET)
                                        {
                                                if (pqReadData(conn) < 0)
                                                        return -1;
                                        }

                                        /*
                                         * Lower-level code should already have filled
                                         * conn->write_err_msg (and set conn->write_failed) or
                                         * conn->errorMessage.  In the former case, we pretend
                                         * there's no problem; the write_failed condition will be
                                         * dealt with later.  Otherwise, report the error now.
                                         */
                                        if (conn->write_failed)
                                                return 0;
                                        else
                                                return -1;
                        }
                }
                else
                {
                        ptr += sent;
                        len -= sent;
                        remaining -= sent;
                }

                if (len > 0)
                {
                        /*
                         * We didn't send it all, wait till we can send more.
                         *
                         * There are scenarios in which we can't send data because the
                         * communications channel is full, but we cannot expect the server
                         * to clear the channel eventually because it's blocked trying to
                         * send data to us.  (This can happen when we are sending a large
                         * amount of COPY data, and the server has generated lots of
                         * NOTICE responses.)  To avoid a deadlock situation, we must be
                         * prepared to accept and buffer incoming data before we try
                         * again.  Furthermore, it is possible that such incoming data
                         * might not arrive until after we've gone to sleep.  Therefore,
                         * we wait for either read ready or write ready.
                         *
                         * In non-blocking mode, we don't wait here directly, but return 1
                         * to indicate that data is still pending.  The caller should wait
                         * for both read and write ready conditions, and call
                         * PQconsumeInput() on read ready, but just in case it doesn't, we
                         * call pqReadData() ourselves before returning.  That's not
                         * enough if the data has not arrived yet, but it's the best we
                         * can do, and works pretty well in practice.  (The documentation
                         * used to say that you only need to wait for write-ready, so
                         * there are still plenty of applications like that out there.)
                         *
                         * Note that errors here don't result in write_failed becoming
                         * set.
                         */
                        if (pqReadData(conn) < 0)
                        {
                                result = -1;    /* error message already set up */
                                break;
                        }

                        if (pqIsnonblocking(conn))
                        {
                                result = 1;
                                break;
                        }

                        if (pqWait(true, true, conn))
                        {
                                result = -1;
                                break;
                        }
                }
        }

        /* shift the remaining contents of the buffer */
        if (remaining > 0)
                memmove(conn->outBuffer, ptr, remaining);
        conn->outCount = remaining;

        return result;
}


/*
 * pqFlush: send any data waiting in the output buffer
 *
 * Return 0 on success, -1 on failure and 1 when not all data could be sent
 * because the socket would block and the connection is non-blocking.
 * (See pqSendSome comments about how failure should be handled.)
 */
int
pqFlush(PGconn *conn)
{
        if (conn->outCount > 0)
        {
                if (conn->Pfdebug)
                        fflush(conn->Pfdebug);

                return pqSendSome(conn, conn->outCount);
        }

        return 0;
}


/*
 * pqWait: wait until we can read or write the connection socket
 *
 * JAB: If SSL enabled and used and forRead, buffered bytes short-circuit the
 * call to select().
 *
 * We also stop waiting and return if the kernel flags an exception condition
 * on the socket.  The actual error condition will be detected and reported
 * when the caller tries to read or write the socket.
 */
int
pqWait(int forRead, int forWrite, PGconn *conn)
{
        return pqWaitTimed(forRead, forWrite, conn, -1);
}

/*
 * pqWaitTimed: wait, but not past end_time.
 *
 * Returns -1 on failure, 0 if the socket is readable/writable, 1 if it timed out.
 *
 * The timeout is specified by end_time, which is the int64 number of
 * microseconds since the Unix epoch (that is, time_t times 1 million).
 * Timeout is infinite if end_time is -1.  Timeout is immediate (no blocking)
 * if end_time is 0 (or indeed, any time before now).
 */
int
pqWaitTimed(int forRead, int forWrite, PGconn *conn, pg_usec_time_t end_time)
{
        int                     result;

        result = pqSocketCheck(conn, forRead, forWrite, end_time);

        if (result < 0)
                return -1;                              /* errorMessage is already set */

        if (result == 0)
        {
                libpq_append_conn_error(conn, "timeout expired");
                return 1;
        }

        return 0;
}

/*
 * pqReadReady: is select() saying the file is ready to read?
 * Returns -1 on failure, 0 if not ready, 1 if ready.
 */
int
pqReadReady(PGconn *conn)
{
        return pqSocketCheck(conn, 1, 0, 0);
}

/*
 * pqWriteReady: is select() saying the file is ready to write?
 * Returns -1 on failure, 0 if not ready, 1 if ready.
 */
int
pqWriteReady(PGconn *conn)
{
        return pqSocketCheck(conn, 0, 1, 0);
}

/*
 * Checks a socket, using poll or select, for data to be read, written,
 * or both.  Returns >0 if one or more conditions are met, 0 if it timed
 * out, -1 if an error occurred.
 *
 * If SSL is in use, the SSL buffer is checked prior to checking the socket
 * for read data directly.
 */
static int
pqSocketCheck(PGconn *conn, int forRead, int forWrite, pg_usec_time_t end_time)
{
        int                     result;

        if (!conn)
                return -1;
        if (conn->sock == PGINVALID_SOCKET)
        {
                libpq_append_conn_error(conn, "invalid socket");
                return -1;
        }

#ifdef USE_SSL
        /* Check for SSL library buffering read bytes */
        if (forRead && conn->ssl_in_use && pgtls_read_pending(conn))
        {
                /* short-circuit the select */
                return 1;
        }
#endif

        /* We will retry as long as we get EINTR */
        do
                result = PQsocketPoll(conn->sock, forRead, forWrite, end_time);
        while (result < 0 && SOCK_ERRNO == EINTR);

        if (result < 0)
        {
                char            sebuf[PG_STRERROR_R_BUFLEN];

                libpq_append_conn_error(conn, "%s() failed: %s", "select",
                                                                SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
        }

        return result;
}


/*
 * Check a file descriptor for read and/or write data, possibly waiting.
 * If neither forRead nor forWrite are set, immediately return a timeout
 * condition (without waiting).  Return >0 if condition is met, 0
 * if a timeout occurred, -1 if an error or interrupt occurred.
 *
 * The timeout is specified by end_time, which is the int64 number of
 * microseconds since the Unix epoch (that is, time_t times 1 million).
 * Timeout is infinite if end_time is -1.  Timeout is immediate (no blocking)
 * if end_time is 0 (or indeed, any time before now).
 */
int
PQsocketPoll(int sock, int forRead, int forWrite, pg_usec_time_t end_time)
{
        /* We use poll(2) if available, otherwise select(2) */
#ifdef HAVE_POLL
        struct pollfd input_fd;
        int                     timeout_ms;

        if (!forRead && !forWrite)
                return 0;

        input_fd.fd = sock;
        input_fd.events = POLLERR;
        input_fd.revents = 0;

        if (forRead)
                input_fd.events |= POLLIN;
        if (forWrite)
                input_fd.events |= POLLOUT;

        /* Compute appropriate timeout interval */
        if (end_time == -1)
                timeout_ms = -1;
        else if (end_time == 0)
                timeout_ms = 0;
        else
        {
                pg_usec_time_t now = PQgetCurrentTimeUSec();

                if (end_time > now)
                        timeout_ms = (end_time - now) / 1000;
                else
                        timeout_ms = 0;
        }

        return poll(&input_fd, 1, timeout_ms);
#else                                                   /* !HAVE_POLL */

        fd_set          input_mask;
        fd_set          output_mask;
        fd_set          except_mask;
        struct timeval timeout;
        struct timeval *ptr_timeout;

        if (!forRead && !forWrite)
                return 0;

        FD_ZERO(&input_mask);
        FD_ZERO(&output_mask);
        FD_ZERO(&except_mask);
        if (forRead)
                FD_SET(sock, &input_mask);

        if (forWrite)
                FD_SET(sock, &output_mask);
        FD_SET(sock, &except_mask);

        /* Compute appropriate timeout interval */
        if (end_time == -1)
                ptr_timeout = NULL;
        else if (end_time == 0)
        {
                timeout.tv_sec = 0;
                timeout.tv_usec = 0;
                ptr_timeout = &timeout;
        }
        else
        {
                pg_usec_time_t now = PQgetCurrentTimeUSec();

                if (end_time > now)
                {
                        timeout.tv_sec = (end_time - now) / 1000000;
                        timeout.tv_usec = (end_time - now) % 1000000;
                }
                else
                {
                        timeout.tv_sec = 0;
                        timeout.tv_usec = 0;
                }
                ptr_timeout = &timeout;
        }

        return select(sock + 1, &input_mask, &output_mask,
                                  &except_mask, ptr_timeout);
#endif                                                  /* HAVE_POLL */
}

/*
 * PQgetCurrentTimeUSec: get current time with microsecond precision
 *
 * This provides a platform-independent way of producing a reference
 * value for PQsocketPoll's timeout parameter.
 */
pg_usec_time_t
PQgetCurrentTimeUSec(void)
{
        struct timeval tval;

        gettimeofday(&tval, NULL);
        return (pg_usec_time_t) tval.tv_sec * 1000000 + tval.tv_usec;
}


/*
 * A couple of "miscellaneous" multibyte related functions. They used
 * to be in fe-print.c but that file is doomed.
 */

/*
 * Returns the byte length of the character beginning at s, using the
 * specified encoding.
 *
 * Caution: when dealing with text that is not certainly valid in the
 * specified encoding, the result may exceed the actual remaining
 * string length.  Callers that are not prepared to deal with that
 * should use PQmblenBounded() instead.
 */
int
PQmblen(const char *s, int encoding)
{
        return pg_encoding_mblen(encoding, s);
}

/*
 * Returns the byte length of the character beginning at s, using the
 * specified encoding; but not more than the distance to end of string.
 */
int
PQmblenBounded(const char *s, int encoding)
{
        return strnlen(s, pg_encoding_mblen(encoding, s));
}

/*
 * Returns the display length of the character beginning at s, using the
 * specified encoding.
 */
int
PQdsplen(const char *s, int encoding)
{
        return pg_encoding_dsplen(encoding, s);
}

/*
 * Get encoding id from environment variable PGCLIENTENCODING.
 */
int
PQenv2encoding(void)
{
        char       *str;
        int                     encoding = PG_SQL_ASCII;

        str = getenv("PGCLIENTENCODING");
        if (str && *str != '\0')
        {
                encoding = pg_char_to_encoding(str);
                if (encoding < 0)
                        encoding = PG_SQL_ASCII;
        }
        return encoding;
}


#ifdef ENABLE_NLS

static void
libpq_binddomain(void)
{
        /*
         * At least on Windows, there are gettext implementations that fail if
         * multiple threads call bindtextdomain() concurrently.  Use a mutex and
         * flag variable to ensure that we call it just once per process.  It is
         * not known that similar bugs exist on non-Windows platforms, but we
         * might as well do it the same way everywhere.
         */
        static volatile bool already_bound = false;
        static pthread_mutex_t binddomain_mutex = PTHREAD_MUTEX_INITIALIZER;

        if (!already_bound)
        {
                /* bindtextdomain() does not preserve errno */
#ifdef WIN32
                int                     save_errno = GetLastError();
#else
                int                     save_errno = errno;
#endif

                (void) pthread_mutex_lock(&binddomain_mutex);

                if (!already_bound)
                {
                        const char *ldir;

                        /*
                         * No relocatable lookup here because the calling executable could
                         * be anywhere
                         */
                        ldir = getenv("PGLOCALEDIR");
                        if (!ldir)
                                ldir = LOCALEDIR;
                        bindtextdomain(PG_TEXTDOMAIN("libpq"), ldir);
                        already_bound = true;
                }

                (void) pthread_mutex_unlock(&binddomain_mutex);

#ifdef WIN32
                SetLastError(save_errno);
#else
                errno = save_errno;
#endif
        }
}

char *
libpq_gettext(const char *msgid)
{
        libpq_binddomain();
        return dgettext(PG_TEXTDOMAIN("libpq"), msgid);
}

char *
libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
{
        libpq_binddomain();
        return dngettext(PG_TEXTDOMAIN("libpq"), msgid, msgid_plural, n);
}

#endif                                                  /* ENABLE_NLS */


/*
 * Append a formatted string to the given buffer, after translating it.  A
 * newline is automatically appended; the format should not end with a
 * newline.
 */
void
libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
{
        int                     save_errno = errno;
        bool            done;
        va_list         args;

        Assert(fmt[strlen(fmt) - 1] != '\n');

        if (PQExpBufferBroken(errorMessage))
                return;                                 /* already failed */

        /* Loop in case we have to retry after enlarging the buffer. */
        do
        {
                errno = save_errno;
                va_start(args, fmt);
                done = appendPQExpBufferVA(errorMessage, libpq_gettext(fmt), args);
                va_end(args);
        } while (!done);

        appendPQExpBufferChar(errorMessage, '\n');
}

/*
 * Append a formatted string to the error message buffer of the given
 * connection, after translating it.  A newline is automatically appended; the
 * format should not end with a newline.
 */
void
libpq_append_conn_error(PGconn *conn, const char *fmt,...)
{
        int                     save_errno = errno;
        bool            done;
        va_list         args;

        Assert(fmt[strlen(fmt) - 1] != '\n');

        if (PQExpBufferBroken(&conn->errorMessage))
                return;                                 /* already failed */

        /* Loop in case we have to retry after enlarging the buffer. */
        do
        {
                errno = save_errno;
                va_start(args, fmt);
                done = appendPQExpBufferVA(&conn->errorMessage, libpq_gettext(fmt), args);
                va_end(args);
        } while (!done);

        appendPQExpBufferChar(&conn->errorMessage, '\n');
}