Fix three PyChecker-detected gotchas.

[python/dscho.git] / Mac / tclmods / tclSelectNotify.c

/*
 * tclSelectNotify.c --
 *
 * Partial even handling, select only. This file is adapted from TclUnixNotify.c, and
 * meant as an add-in for Mac (and possibly Windows) environments where select *is* available.
 * TclMacNotify.c works together with this file.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * SCCS: @(#) tclUnixNotfy.c 1.42 97/07/02 20:55:44
 */

#if defined(__CFM68K__) && !defined(__USING_STATIC_LIBS__)
        #pragma import on
#endif

#include <unistd.h>

#if defined(__CFM68K__) && !defined(__USING_STATIC_LIBS__)
        #pragma import reset
#endif

#ifdef USE_GUSI
/* Move this include up otherwise tclPort.h tried to redefine signals */
#include <sys/signal.h>
#endif
#include "tclInt.h"
#include "tclPort.h"
#include <signal.h> 

#ifndef MASK_SIZE
#define MASK_SIZE howmany(FD_SETSIZE, NFDBITS)
#endif
#ifndef SELECT_MASK
#define SELECT_MASK fd_set
#endif

/* Prototype (too lazy to create new .h) */
int Tcl_PollSelectEvent(void);

/*
 * This structure is used to keep track of the notifier info for a 
 * a registered file.
 */

typedef struct FileHandler {
    int fd;
    int mask;                   /* Mask of desired events: TCL_READABLE,
                                 * etc. */
    int readyMask;              /* Mask of events that have been seen since the
                                 * last time file handlers were invoked for
                                 * this file. */
    Tcl_FileProc *proc;         /* Procedure to call, in the style of
                                 * Tcl_CreateFileHandler. */
    ClientData clientData;      /* Argument to pass to proc. */
    struct FileHandler *nextPtr;/* Next in list of all files we care about. */
} FileHandler;

/*
 * The following structure is what is added to the Tcl event queue when
 * file handlers are ready to fire.
 */

typedef struct FileHandlerEvent {
    Tcl_Event header;           /* Information that is standard for
                                 * all events. */
    int fd;                     /* File descriptor that is ready.  Used
                                 * to find the FileHandler structure for
                                 * the file (can't point directly to the
                                 * FileHandler structure because it could
                                 * go away while the event is queued). */
} FileHandlerEvent;

/*
 * The following static structure contains the state information for the
 * select based implementation of the Tcl notifier.
 */

static struct {
    FileHandler *firstFileHandlerPtr;
                                /* Pointer to head of file handler list. */
    fd_mask checkMasks[3*MASK_SIZE];
                                /* This array is used to build up the masks
                                 * to be used in the next call to select.
                                 * Bits are set in response to calls to
                                 * Tcl_CreateFileHandler. */
    fd_mask readyMasks[3*MASK_SIZE];
                                /* This array reflects the readable/writable
                                 * conditions that were found to exist by the
                                 * last call to select. */
    int numFdBits;              /* Number of valid bits in checkMasks
                                 * (one more than highest fd for which
                                 * Tcl_WatchFile has been called). */
} notifier;

/*
 * The following static indicates whether this module has been initialized.
 */

static int initialized = 0;

/*
 * Static routines defined in this file.
 */

static void             InitNotifier _ANSI_ARGS_((void));
static void             NotifierExitHandler _ANSI_ARGS_((
                            ClientData clientData));
static int              FileHandlerEventProc _ANSI_ARGS_((Tcl_Event *evPtr,
                            int flags));
\f
/*
 *----------------------------------------------------------------------
 *
 * InitNotifier --
 *
 *      Initializes the notifier state.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Creates a new exit handler.
 *
 *----------------------------------------------------------------------
 */

static void
InitNotifier()
{
    initialized = 1;
    memset(&notifier, 0, sizeof(notifier));
    Tcl_CreateExitHandler(NotifierExitHandler, NULL);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * NotifierExitHandler --
 *
 *      This function is called to cleanup the notifier state before
 *      Tcl is unloaded.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Destroys the notifier window.
 *
 *----------------------------------------------------------------------
 */

static void
NotifierExitHandler(clientData)
    ClientData clientData;              /* Not used. */
{
    initialized = 0;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_CreateFileHandler --
 *
 *      This procedure registers a file handler with the Xt notifier.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Creates a new file handler structure and registers one or more
 *      input procedures with Xt.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_CreateFileHandler(fd, mask, proc, clientData)
    int fd;                     /* Handle of stream to watch. */
    int mask;                   /* OR'ed combination of TCL_READABLE,
                                 * TCL_WRITABLE, and TCL_EXCEPTION:
                                 * indicates conditions under which
                                 * proc should be called. */
    Tcl_FileProc *proc;         /* Procedure to call for each
                                 * selected event. */
    ClientData clientData;      /* Arbitrary data to pass to proc. */
{
    FileHandler *filePtr;
    int index, bit;
    
    if (!initialized) {
        InitNotifier();
    }

    for (filePtr = notifier.firstFileHandlerPtr; filePtr != NULL;
            filePtr = filePtr->nextPtr) {
        if (filePtr->fd == fd) {
            break;
        }
    }
    if (filePtr == NULL) {
        filePtr = (FileHandler*) ckalloc(sizeof(FileHandler)); /* MLK */
        filePtr->fd = fd;
        filePtr->readyMask = 0;
        filePtr->nextPtr = notifier.firstFileHandlerPtr;
        notifier.firstFileHandlerPtr = filePtr;
    }
    filePtr->proc = proc;
    filePtr->clientData = clientData;
    filePtr->mask = mask;

    /*
     * Update the check masks for this file.
     */

    index = fd/(NBBY*sizeof(fd_mask));
    bit = 1 << (fd%(NBBY*sizeof(fd_mask)));
    if (mask & TCL_READABLE) {
        notifier.checkMasks[index] |= bit;
    } else {
        notifier.checkMasks[index] &= ~bit;
    } 
    if (mask & TCL_WRITABLE) {
        (notifier.checkMasks+MASK_SIZE)[index] |= bit;
    } else {
        (notifier.checkMasks+MASK_SIZE)[index] &= ~bit;
    }
    if (mask & TCL_EXCEPTION) {
        (notifier.checkMasks+2*(MASK_SIZE))[index] |= bit;
    } else {
        (notifier.checkMasks+2*(MASK_SIZE))[index] &= ~bit;
    }
    if (notifier.numFdBits <= fd) {
        notifier.numFdBits = fd+1;
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteFileHandler --
 *
 *      Cancel a previously-arranged callback arrangement for
 *      a file.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      If a callback was previously registered on file, remove it.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DeleteFileHandler(fd)
    int fd;             /* Stream id for which to remove callback procedure. */
{
    FileHandler *filePtr, *prevPtr;
    int index, bit, mask, i;

    if (!initialized) {
        InitNotifier();
    }

    /*
     * Find the entry for the given file (and return if there
     * isn't one).
     */

    for (prevPtr = NULL, filePtr = notifier.firstFileHandlerPtr; ;
            prevPtr = filePtr, filePtr = filePtr->nextPtr) {
        if (filePtr == NULL) {
            return;
        }
        if (filePtr->fd == fd) {
            break;
        }
    }

    /*
     * Update the check masks for this file.
     */

    index = fd/(NBBY*sizeof(fd_mask));
    bit = 1 << (fd%(NBBY*sizeof(fd_mask)));

    if (filePtr->mask & TCL_READABLE) {
        notifier.checkMasks[index] &= ~bit;
    }
    if (filePtr->mask & TCL_WRITABLE) {
        (notifier.checkMasks+MASK_SIZE)[index] &= ~bit;
    }
    if (filePtr->mask & TCL_EXCEPTION) {
        (notifier.checkMasks+2*(MASK_SIZE))[index] &= ~bit;
    }

    /*
     * Find current max fd.
     */

    if (fd+1 == notifier.numFdBits) {
        for (notifier.numFdBits = 0; index >= 0; index--) {
            mask = notifier.checkMasks[index]
                | (notifier.checkMasks+MASK_SIZE)[index]
                | (notifier.checkMasks+2*(MASK_SIZE))[index];
            if (mask) {
                for (i = (NBBY*sizeof(fd_mask)); i > 0; i--) {
                    if (mask & (1 << (i-1))) {
                        break;
                    }
                }
                notifier.numFdBits = index * (NBBY*sizeof(fd_mask)) + i;
                break;
            }
        }
    }

    /*
     * Clean up information in the callback record.
     */

    if (prevPtr == NULL) {
        notifier.firstFileHandlerPtr = filePtr->nextPtr;
    } else {
        prevPtr->nextPtr = filePtr->nextPtr;
    }
    ckfree((char *) filePtr);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * FileHandlerEventProc --
 *
 *      This procedure is called by Tcl_ServiceEvent when a file event
 *      reaches the front of the event queue.  This procedure is
 *      responsible for actually handling the event by invoking the
 *      callback for the file handler.
 *
 * Results:
 *      Returns 1 if the event was handled, meaning it should be removed
 *      from the queue.  Returns 0 if the event was not handled, meaning
 *      it should stay on the queue.  The only time the event isn't
 *      handled is if the TCL_FILE_EVENTS flag bit isn't set.
 *
 * Side effects:
 *      Whatever the file handler's callback procedure does.
 *
 *----------------------------------------------------------------------
 */

static int
FileHandlerEventProc(evPtr, flags)
    Tcl_Event *evPtr;           /* Event to service. */
    int flags;                  /* Flags that indicate what events to
                                 * handle, such as TCL_FILE_EVENTS. */
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr = (FileHandlerEvent *) evPtr;
    int mask;

    if (!(flags & TCL_FILE_EVENTS)) {
        return 0;
    }

    /*
     * Search through the file handlers to find the one whose handle matches
     * the event.  We do this rather than keeping a pointer to the file
     * handler directly in the event, so that the handler can be deleted
     * while the event is queued without leaving a dangling pointer.
     */

    for (filePtr = notifier.firstFileHandlerPtr; filePtr != NULL;
            filePtr = filePtr->nextPtr) {
        if (filePtr->fd != fileEvPtr->fd) {
            continue;
        }

        /*
         * The code is tricky for two reasons:
         * 1. The file handler's desired events could have changed
         *    since the time when the event was queued, so AND the
         *    ready mask with the desired mask.
         * 2. The file could have been closed and re-opened since
         *    the time when the event was queued.  This is why the
         *    ready mask is stored in the file handler rather than
         *    the queued event:  it will be zeroed when a new
         *    file handler is created for the newly opened file.
         */

        mask = filePtr->readyMask & filePtr->mask;
        filePtr->readyMask = 0;
        if (mask != 0) {
            (*filePtr->proc)(filePtr->clientData, mask);
        }
        break;
    }
    return 1;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_PollSelectEvent --
 *
 *      This function is called by Tcl_WaitForEvent to wait for new
 *      events on the message queue.  If the block time is 0, then
 *      Tcl_WaitForEvent just polls without blocking.
 *
 * Results:
 *      Returns 1 if any event handled, 0 otherwise.
 *
 * Side effects:
 *      Queues file events that are detected by the select.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_PollSelectEvent(void)
{
    FileHandler *filePtr;
    FileHandlerEvent *fileEvPtr;
    struct timeval timeout, *timeoutPtr;
    int bit, index, mask, numFound;

    if (!initialized) {
        InitNotifier();
    }

    /*
     * Set up the timeout structure. 
     */

    timeout.tv_sec = 0;
    timeout.tv_usec = 0;
    timeoutPtr = &timeout;

    memcpy((VOID *) notifier.readyMasks, (VOID *) notifier.checkMasks,
            3*MASK_SIZE*sizeof(fd_mask));
    numFound = select(notifier.numFdBits,
            (SELECT_MASK *) &notifier.readyMasks[0],
            (SELECT_MASK *) &notifier.readyMasks[MASK_SIZE],
            (SELECT_MASK *) &notifier.readyMasks[2*MASK_SIZE], timeoutPtr);

    /*
     * Some systems don't clear the masks after an error, so
     * we have to do it here.
     */

    if (numFound == -1) {
        memset((VOID *) notifier.readyMasks, 0, 3*MASK_SIZE*sizeof(fd_mask));
    }
    
    /*
     * Return if nothing to do.
     */
    if ( numFound == 0 )
        return 0;

    /*
     * Queue all detected file events before returning.
     */

    for (filePtr = notifier.firstFileHandlerPtr;
            (filePtr != NULL) && (numFound > 0);
            filePtr = filePtr->nextPtr) {
        index = filePtr->fd / (NBBY*sizeof(fd_mask));
        bit = 1 << (filePtr->fd % (NBBY*sizeof(fd_mask)));
        mask = 0;

        if (notifier.readyMasks[index] & bit) {
            mask |= TCL_READABLE;
        }
        if ((notifier.readyMasks+MASK_SIZE)[index] & bit) {
            mask |= TCL_WRITABLE;
        }
        if ((notifier.readyMasks+2*(MASK_SIZE))[index] & bit) {
            mask |= TCL_EXCEPTION;
        }

        if (!mask) {
            continue;
        } else {
            numFound--;
        }

        /*
         * Don't bother to queue an event if the mask was previously
         * non-zero since an event must still be on the queue.
         */

        if (filePtr->readyMask == 0) {
            fileEvPtr = (FileHandlerEvent *) ckalloc(
                sizeof(FileHandlerEvent));
            fileEvPtr->header.proc = FileHandlerEventProc;
            fileEvPtr->fd = filePtr->fd;
            Tcl_QueueEvent((Tcl_Event *) fileEvPtr, TCL_QUEUE_TAIL);
        }
        filePtr->readyMask = mask;
    }
    return 1;
}