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/*

 * tclUnixNotify.c --

 *

 *      This file contains the implementation of the select-based

 *      Unix-specific notifier, which is the lowest-level part of the

 *      Tcl event loop.  This file works together with

 *      ../generic/tclNotify.c.

 *

 * 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.

 *

 * RCS: @(#) $Id: tclUnixNotfy.c,v 1.1.1.1 2002-01-16 10:25:37 markom Exp $

 */

#include "tclInt.h"

#include "tclPort.h"

#include <signal.h> 

/*

 * 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));

/*

 *----------------------------------------------------------------------

 *

 * 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);

}

/*

 *----------------------------------------------------------------------

 *

 * 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;

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_SetTimer --

 *

 *      This procedure sets the current notifier timer value.  This

 *      interface is not implemented in this notifier because we are

 *      always running inside of Tcl_DoOneEvent.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      None.

 *

 *----------------------------------------------------------------------

 */

void

Tcl_SetTimer(timePtr)

    Tcl_Time *timePtr;          /* Timeout value, may be NULL. */

{

    /*

     * The interval timer doesn't do anything in this implementation,

     * because the only event loop is via Tcl_DoOneEvent, which passes

     * timeout values to Tcl_WaitForEvent.

     */

}

/*

 *----------------------------------------------------------------------

 *

 * 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;

    }

}

/*

 *----------------------------------------------------------------------

 *

 * 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, i;

    unsigned long flags;

    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--) {

            flags = notifier.checkMasks[index]

                | (notifier.checkMasks+MASK_SIZE)[index]

                | (notifier.checkMasks+2*(MASK_SIZE))[index];

            if (flags) {

                for (i = (NBBY*sizeof(fd_mask)); i > 0; i--) {

                    if (flags & (((unsigned long)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);

}

/*

 *----------------------------------------------------------------------

 *

 * 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;

}

/*

 *----------------------------------------------------------------------

 *

 * Tcl_WaitForEvent --

 *

 *      This function is called by Tcl_DoOneEvent 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 the select would block forever, otherwise

 *      returns 0.

 *

 * Side effects:

 *      Queues file events that are detected by the select.

 *

 *----------------------------------------------------------------------

 */

int

Tcl_WaitForEvent(timePtr)

    Tcl_Time *timePtr;          /* Maximum block time, or NULL. */

{

    FileHandler *filePtr;

    FileHandlerEvent *fileEvPtr;

    struct timeval timeout, *timeoutPtr;

    int bit, index, mask, numFound;

    if (!initialized) {

        InitNotifier();

    }

    /*

     * Set up the timeout structure.  Note that if there are no events to

     * check for, we return with a negative result rather than blocking

     * forever.

     */

    if (timePtr) {

        timeout.tv_sec = timePtr->sec;

        timeout.tv_usec = timePtr->usec;

        timeoutPtr = &timeout;

    } else if (notifier.numFdBits == 0) {

        return -1;

    } else {

        timeoutPtr = NULL;

    }

    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));

    }

    /*

     * 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 0;

}