/* Copyright (C) 2001-2004 Bart Massey and Jamey Sharp.

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 * 

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 * 

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN

 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 * 

 * Except as contained in this notice, the names of the authors or their

 * institutions shall not be used in advertising or otherwise to promote the

 * sale, use or other dealings in this Software without prior written

 * authorization from the authors.

 */

/* Stuff that reads stuff from the server. */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <assert.h>

#include <string.h>

#include <stdlib.h>

#include <unistd.h>

#include <stdio.h>

#include <errno.h>

#if USE_POLL

#include <poll.h>

#endif

#ifndef _WIN32

#include <sys/select.h>

#include <sys/socket.h>

#endif

#ifdef _WIN32

#include "xcb_windefs.h"

#endif /* _WIN32 */

#include "xcb.h"

#include "xcbext.h"

#include "xcbint.h"

#define XCB_ERROR 0

#define XCB_REPLY 1

#define XCB_XGE_EVENT 35

struct event_list {

    xcb_generic_event_t *event;

    struct event_list *next;

};

struct xcb_special_event {

    struct xcb_special_event *next;

    /* Match XGE events for the specific extension and event ID (the

     * first 32 bit word after evtype)

     */

    uint8_t     extension;

    uint32_t    eid;

    uint32_t    *stamp;

    struct event_list   *events;

    struct event_list   **events_tail;

    pthread_cond_t special_event_cond;

};

struct reply_list {

    void *reply;

    struct reply_list *next;

};

typedef struct pending_reply {

    uint64_t first_request;

    uint64_t last_request;

    enum workarounds workaround;

    int flags;

    struct pending_reply *next;

} pending_reply;

typedef struct reader_list {

    uint64_t request;

    pthread_cond_t *data;

    struct reader_list *next;

} reader_list;

typedef struct special_list {

    xcb_special_event_t *se;

    struct special_list *next;

} special_list;

static void remove_finished_readers(reader_list **prev_reader, uint64_t completed)

{

    while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, completed))

    {

        /* If you don't have what you're looking for now, you never

         * will. Wake up and leave me alone. */

        pthread_cond_signal((*prev_reader)->data);

        *prev_reader = (*prev_reader)->next;

    }

}

#if HAVE_SENDMSG

static int read_fds(xcb_connection_t *c, int *fds, int nfd)

{

    int *ifds = &c->in.in_fd.fd[c->in.in_fd.ifd];

    int infd = c->in.in_fd.nfd - c->in.in_fd.ifd;

    if (nfd > infd)

        return 0;

    memcpy(fds, ifds, nfd * sizeof (int));

    c->in.in_fd.ifd += nfd;

    return 1;

}

#endif

typedef struct xcb_ge_special_event_t {

    uint8_t  response_type; /**<  */

    uint8_t  extension; /**<  */

    uint16_t sequence; /**<  */

    uint32_t length; /**<  */

    uint16_t evtype; /**<  */

    uint8_t  pad0[2]; /**< */

    uint32_t eid; /**< */

    uint8_t  pad1[16]; /**<  */

} xcb_ge_special_event_t;

static int event_special(xcb_connection_t *c,

                         struct event_list *event)

{

    struct xcb_special_event *special_event;

    struct xcb_ge_special_event_t *ges = (void *) event->event;

    /* Special events are always XGE events */

    if ((ges->response_type & 0x7f) != XCB_XGE_EVENT)

        return 0;

    for (special_event = c->in.special_events;

         special_event;

         special_event = special_event->next)

    {

        if (ges->extension == special_event->extension &&

            ges->eid == special_event->eid)

        {

            *special_event->events_tail = event;

            special_event->events_tail = &event->next;

            if (special_event->stamp)

                ++(*special_event->stamp);

            pthread_cond_signal(&special_event->special_event_cond);

            return 1;

        }

    }

    return 0;

}

static int read_packet(xcb_connection_t *c)

{

    xcb_generic_reply_t genrep;

    uint64_t length = 32;

    uint64_t eventlength = 0; /* length after first 32 bytes for GenericEvents */

    int nfd = 0;         /* Number of file descriptors attached to the reply */

    uint64_t bufsize;

    void *buf;

    pending_reply *pend = 0;

    struct event_list *event;

    /* Wait for there to be enough data for us to read a whole packet */

    if(c->in.queue_len < length)

        return 0;

    /* Get the response type, length, and sequence number. */

    memcpy(&genrep, c->in.queue, sizeof(genrep));

    /* Compute 32-bit sequence number of this packet. */

    if((genrep.response_type & 0x7f) != XCB_KEYMAP_NOTIFY)

    {

        uint64_t lastread = c->in.request_read;

        c->in.request_read = (lastread & UINT64_C(0xffffffffffff0000)) | genrep.sequence;

        if(XCB_SEQUENCE_COMPARE(c->in.request_read, <, lastread))

            c->in.request_read += 0x10000;

        if(XCB_SEQUENCE_COMPARE(c->in.request_read, >, c->in.request_expected))

            c->in.request_expected = c->in.request_read;

        if(c->in.request_read != lastread)

        {

            if(c->in.current_reply)

            {

                _xcb_map_put(c->in.replies, lastread, c->in.current_reply);

                c->in.current_reply = 0;

                c->in.current_reply_tail = &c->in.current_reply;

            }

            c->in.request_completed = c->in.request_read - 1;

        }

        while(c->in.pending_replies &&

              c->in.pending_replies->workaround != WORKAROUND_EXTERNAL_SOCKET_OWNER &&

              XCB_SEQUENCE_COMPARE (c->in.pending_replies->last_request, <=, c->in.request_completed))

        {

            pending_reply *oldpend = c->in.pending_replies;

            c->in.pending_replies = oldpend->next;

            if(!oldpend->next)

                c->in.pending_replies_tail = &c->in.pending_replies;

            free(oldpend);

        }

        if(genrep.response_type == XCB_ERROR)

            c->in.request_completed = c->in.request_read;

        remove_finished_readers(&c->in.readers, c->in.request_completed);

    }

    if(genrep.response_type == XCB_ERROR || genrep.response_type == XCB_REPLY)

    {

        pend = c->in.pending_replies;

        if(pend &&

           !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&

             (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||

              XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))

            pend = 0;

    }

    /* For reply packets, check that the entire packet is available. */

    if(genrep.response_type == XCB_REPLY)

    {

        if(pend && pend->workaround == WORKAROUND_GLX_GET_FB_CONFIGS_BUG)

        {

            uint32_t *p = (uint32_t *) c->in.queue;

            genrep.length = p[2] * p[3] * 2;

        }

        length += genrep.length * 4;

        /* XXX a bit of a hack -- we "know" that all FD replys place

         * the number of fds in the pad0 byte */

        if (pend && pend->flags & XCB_REQUEST_REPLY_FDS)

            nfd = genrep.pad0;

    }

    /* XGE events may have sizes > 32 */

    if ((genrep.response_type & 0x7f) == XCB_XGE_EVENT)

        eventlength = genrep.length * 4;

    bufsize = length + eventlength + nfd * sizeof(int)  +

        (genrep.response_type == XCB_REPLY ? 0 : sizeof(uint32_t));

    if (bufsize < INT32_MAX)

        buf = malloc((size_t) bufsize);

    else

        buf = NULL;

    if(!buf)

    {

        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);

        return 0;

    }

    if(_xcb_in_read_block(c, buf, length) <= 0)

    {

        free(buf);

        return 0;

    }

    /* pull in XGE event data if available, append after event struct */

    if (eventlength)

    {

        if(_xcb_in_read_block(c, &((xcb_generic_event_t*)buf)[1], eventlength) <= 0)

        {

            free(buf);

            return 0;

        }

    }

#if HAVE_SENDMSG

    if (nfd)

    {

        if (!read_fds(c, (int *) &((char *) buf)[length], nfd))

        {

            free(buf);

            return 0;

        }

    }

#endif

    if(pend && (pend->flags & XCB_REQUEST_DISCARD_REPLY))

    {

        free(buf);

        return 1;

    }

    if(genrep.response_type != XCB_REPLY)

        ((xcb_generic_event_t *) buf)->full_sequence = c->in.request_read;

    /* reply, or checked error */

    if( genrep.response_type == XCB_REPLY ||

       (genrep.response_type == XCB_ERROR && pend && (pend->flags & XCB_REQUEST_CHECKED)))

    {

        struct reply_list *cur = malloc(sizeof(struct reply_list));

        if(!cur)

        {

            _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);

            free(buf);

            return 0;

        }

        cur->reply = buf;

        cur->next = 0;

        *c->in.current_reply_tail = cur;

        c->in.current_reply_tail = &cur->next;

        if(c->in.readers && c->in.readers->request == c->in.request_read)

            pthread_cond_signal(c->in.readers->data);

        return 1;

    }

    /* event, or unchecked error */

    event = malloc(sizeof(struct event_list));

    if(!event)

    {

        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);

        free(buf);

        return 0;

    }

    event->event = buf;

    event->next = 0;

    if (!event_special(c, event)) {

        *c->in.events_tail = event;

        c->in.events_tail = &event->next;

        pthread_cond_signal(&c->in.event_cond);

    }

    return 1; /* I have something for you... */

}

static xcb_generic_event_t *get_event(xcb_connection_t *c)

{

    struct event_list *cur = c->in.events;

    xcb_generic_event_t *ret;

    if(!c->in.events)

        return 0;

    ret = cur->event;

    c->in.events = cur->next;

    if(!cur->next)

        c->in.events_tail = &c->in.events;

    free(cur);

    return ret;

}

static void free_reply_list(struct reply_list *head)

{

    while(head)

    {

        struct reply_list *cur = head;

        head = cur->next;

        free(cur->reply);

        free(cur);

    }

}

static int read_block(const int fd, void *buf, const ssize_t len)

{

    int done = 0;

    while(done < len)

    {

        int ret = recv(fd, ((char *) buf) + done, len - done, 0);

        if(ret > 0)

            done += ret;

#ifndef _WIN32

        if(ret < 0 && errno == EAGAIN)

#else

        if(ret == SOCKET_ERROR && WSAGetLastError() == WSAEWOULDBLOCK)

#endif /* !_Win32 */

        {

#if USE_POLL

            struct pollfd pfd;

            pfd.fd = fd;

            pfd.events = POLLIN;

            pfd.revents = 0;

            do {

                ret = poll(&pfd, 1, -1);

            } while (ret == -1 && errno == EINTR);

#else

            fd_set fds;

            FD_ZERO(&fds);

            FD_SET(fd, &fds);

            /* Initializing errno here makes sure that for Win32 this loop will execute only once */

            errno = 0;

            do {

                ret = select(fd + 1, &fds, 0, 0, 0);

            } while (ret == -1 && errno == EINTR);

#endif /* USE_POLL */

        }

        if(ret <= 0)

            return ret;

    }

    return len;

}

static int poll_for_reply(xcb_connection_t *c, uint64_t request, void **reply, xcb_generic_error_t **error)

{

    struct reply_list *head;

    /* If an error occurred when issuing the request, fail immediately. */

    if(!request)

        head = 0;

    /* We've read requests past the one we want, so if it has replies we have

     * them all and they're in the replies map. */

    else if(XCB_SEQUENCE_COMPARE(request, <, c->in.request_read))

    {

        head = _xcb_map_remove(c->in.replies, request);

        if(head && head->next)

            _xcb_map_put(c->in.replies, request, head->next);

    }

    /* We're currently processing the responses to the request we want, and we

     * have a reply ready to return. So just return it without blocking. */

    else if(request == c->in.request_read && c->in.current_reply)

    {

        head = c->in.current_reply;

        c->in.current_reply = head->next;

        if(!head->next)

            c->in.current_reply_tail = &c->in.current_reply;

    }

    /* We know this request can't have any more replies, and we've already

     * established it doesn't have a reply now. Don't bother blocking. */

    else if(request == c->in.request_completed)

        head = 0;

    /* We may have more replies on the way for this request: block until we're

     * sure. */

    else

        return 0;

    if(error)

        *error = 0;

    *reply = 0;

    if(head)

    {

        if(((xcb_generic_reply_t *) head->reply)->response_type == XCB_ERROR)

        {

            if(error)

                *error = head->reply;

            else

                free(head->reply);

        }

        else

            *reply = head->reply;

        free(head);

    }

    return 1;

}

static void insert_reader(reader_list **prev_reader, reader_list *reader, uint64_t request, pthread_cond_t *cond)

{

    while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, request))

        prev_reader = &(*prev_reader)->next;

    reader->request = request;

    reader->data = cond;

    reader->next = *prev_reader;

    *prev_reader = reader;

}

static void remove_reader(reader_list **prev_reader, reader_list *reader)

{

    while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, reader->request))

        if(*prev_reader == reader)

        {

            *prev_reader = (*prev_reader)->next;

            break;

        }

}

static void insert_special(special_list **prev_special, special_list *special, xcb_special_event_t *se)

{

    special->se = se;

    special->next = *prev_special;

    *prev_special = special;

}

static void remove_special(special_list **prev_special, special_list *special)

{

    while(*prev_special)

    {

        if(*prev_special == special)

        {

            *prev_special = (*prev_special)->next;

            break;

        }

        prev_special = &(*prev_special)->next;

    }

}

static void *wait_for_reply(xcb_connection_t *c, uint64_t request, xcb_generic_error_t **e)

{

    void *ret = 0;

    /* If this request has not been written yet, write it. */

    if(c->out.return_socket || _xcb_out_flush_to(c, request))

    {

        pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

        reader_list reader;

        insert_reader(&c->in.readers, &reader, request, &cond;;

        while(!poll_for_reply(c, request, &ret, e))

            if(!_xcb_conn_wait(c, &cond, 0, 0))

                break;

        remove_reader(&c->in.readers, &reader);

        pthread_cond_destroy(&cond;;

    }

    _xcb_in_wake_up_next_reader(c);

    return ret;

}

static uint64_t widen(xcb_connection_t *c, unsigned int request)

{

    uint64_t widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;

    if(widened_request > c->out.request)

        widened_request -= UINT64_C(1) << 32;

    return widened_request;

}

/* Public interface */

void *xcb_wait_for_reply(xcb_connection_t *c, unsigned int request, xcb_generic_error_t **e)

{

    void *ret;

    if(e)

        *e = 0;

    if(c->has_error)

        return 0;

    pthread_mutex_lock(&c->iolock);

    ret = wait_for_reply(c, widen(c, request), e);

    pthread_mutex_unlock(&c->iolock);

    return ret;

}

void *xcb_wait_for_reply64(xcb_connection_t *c, uint64_t request, xcb_generic_error_t **e)

{

    void *ret;

    if(e)

        *e = 0;

    if(c->has_error)

        return 0;

    pthread_mutex_lock(&c->iolock);

    ret = wait_for_reply(c, request, e);

    pthread_mutex_unlock(&c->iolock);

    return ret;

}

int *xcb_get_reply_fds(xcb_connection_t *c, void *reply, size_t reply_size)

{

    return (int *) (&((char *) reply)[reply_size]);

}

static void insert_pending_discard(xcb_connection_t *c, pending_reply **prev_next, uint64_t seq)

{

    pending_reply *pend;

    pend = malloc(sizeof(*pend));

    if(!pend)

    {

        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);

        return;

    }

    pend->first_request = seq;

    pend->last_request = seq;

    pend->workaround = 0;

    pend->flags = XCB_REQUEST_DISCARD_REPLY;

    pend->next = *prev_next;

    *prev_next = pend;

    if(!pend->next)

        c->in.pending_replies_tail = &pend->next;

}

static void discard_reply(xcb_connection_t *c, uint64_t request)

{

    void *reply;

    pending_reply **prev_pend;

    /* Free any replies or errors that we've already read. Stop if

     * xcb_wait_for_reply would block or we've run out of replies. */

    while(poll_for_reply(c, request, &reply, 0) && reply)

        free(reply);

    /* If we've proven there are no more responses coming, we're done. */

    if(XCB_SEQUENCE_COMPARE(request, <=, c->in.request_completed))

        return;

    /* Walk the list of pending requests. Mark the first match for deletion. */

    for(prev_pend = &c->in.pending_replies; *prev_pend; prev_pend = &(*prev_pend)->next)

    {

        if(XCB_SEQUENCE_COMPARE((*prev_pend)->first_request, >, request))

            break;

        if((*prev_pend)->first_request == request)

        {

            /* Pending reply found. Mark for discard: */

            (*prev_pend)->flags |= XCB_REQUEST_DISCARD_REPLY;

            return;

        }

    }

    /* Pending reply not found (likely due to _unchecked request). Create one: */

    insert_pending_discard(c, prev_pend, request);

}

void xcb_discard_reply(xcb_connection_t *c, unsigned int sequence)

{

    if(c->has_error)

        return;

    /* If an error occurred when issuing the request, fail immediately. */

    if(!sequence)

        return;

    pthread_mutex_lock(&c->iolock);

    discard_reply(c, widen(c, sequence));

    pthread_mutex_unlock(&c->iolock);

}

void xcb_discard_reply64(xcb_connection_t *c, uint64_t sequence)

{

    if(c->has_error)

        return;

    /* If an error occurred when issuing the request, fail immediately. */

    if(!sequence)

        return;

    pthread_mutex_lock(&c->iolock);

    discard_reply(c, sequence);

    pthread_mutex_unlock(&c->iolock);

}

int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)

{

    int ret;

    if(c->has_error)

    {

        *reply = 0;

        if(error)

            *error = 0;

        return 1; /* would not block */

    }

    assert(reply != 0);

    pthread_mutex_lock(&c->iolock);

    ret = poll_for_reply(c, widen(c, request), reply, error);

    if(!ret && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */

        ret = poll_for_reply(c, widen(c, request), reply, error);

    pthread_mutex_unlock(&c->iolock);

    return ret;

}

int xcb_poll_for_reply64(xcb_connection_t *c, uint64_t request, void **reply, xcb_generic_error_t **error)

{

    int ret;

    if(c->has_error)

    {

        *reply = 0;

        if(error)

            *error = 0;

        return 1; /* would not block */

    }

    assert(reply != 0);

    pthread_mutex_lock(&c->iolock);

    ret = poll_for_reply(c, request, reply, error);

    if(!ret && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */

        ret = poll_for_reply(c, request, reply, error);

    pthread_mutex_unlock(&c->iolock);

    return ret;

}

xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c)

{

    xcb_generic_event_t *ret;

    if(c->has_error)

        return 0;

    pthread_mutex_lock(&c->iolock);

    /* get_event returns 0 on empty list. */

    while(!(ret = get_event(c)))

        if(!_xcb_conn_wait(c, &c->in.event_cond, 0, 0))

            break;

    _xcb_in_wake_up_next_reader(c);

    pthread_mutex_unlock(&c->iolock);

    return ret;

}

static xcb_generic_event_t *poll_for_next_event(xcb_connection_t *c, int queued)

{

    xcb_generic_event_t *ret = 0;

    if(!c->has_error)

    {

        pthread_mutex_lock(&c->iolock);

        /* FIXME: follow X meets Z architecture changes. */

        ret = get_event(c);

        if(!ret && !queued && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */

            ret = get_event(c);

        pthread_mutex_unlock(&c->iolock);

    }

    return ret;

}

xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)

{

    return poll_for_next_event(c, 0);

}

xcb_generic_event_t *xcb_poll_for_queued_event(xcb_connection_t *c)

{

    return poll_for_next_event(c, 1);

}

xcb_generic_error_t *xcb_request_check(xcb_connection_t *c, xcb_void_cookie_t cookie)

{

    uint64_t request;

    xcb_generic_error_t *ret = 0;

    void *reply;

    if(c->has_error)

        return 0;

    pthread_mutex_lock(&c->iolock);

    request = widen(c, cookie.sequence);

    if(XCB_SEQUENCE_COMPARE(request, >=, c->in.request_expected)

       && XCB_SEQUENCE_COMPARE(request, >, c->in.request_completed))

    {

        _xcb_out_send_sync(c);

        _xcb_out_flush_to(c, c->out.request);

    }

    reply = wait_for_reply(c, request, &ret;;

    assert(!reply);

    pthread_mutex_unlock(&c->iolock);

    return ret;

}

static xcb_generic_event_t *get_special_event(xcb_connection_t *c,

                                              xcb_special_event_t *se)

{

    xcb_generic_event_t *event = NULL;

    struct event_list *events;

    if ((events = se->events) != NULL) {

        event = events->event;

        if (!(se->events = events->next))

            se->events_tail = &se->events;

        free (events);

    }

    return event;

}

xcb_generic_event_t *xcb_poll_for_special_event(xcb_connection_t *c,

                                                xcb_special_event_t *se)

{

    xcb_generic_event_t *event;

    if(c->has_error)

        return 0;

    pthread_mutex_lock(&c->iolock);

    event = get_special_event(c, se);

    if(!event && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */

        event = get_special_event(c, se);

    pthread_mutex_unlock(&c->iolock);

    return event;

}

xcb_generic_event_t *xcb_wait_for_special_event(xcb_connection_t *c,

                                                xcb_special_event_t *se)

{

    special_list special;

    xcb_generic_event_t *event;

    if(c->has_error)

        return 0;

    pthread_mutex_lock(&c->iolock);

    insert_special(&c->in.special_waiters, &special, se);

    /* get_special_event returns 0 on empty list. */

    while(!(event = get_special_event(c, se)))

        if(!_xcb_conn_wait(c, &se->special_event_cond, 0, 0))

            break;

    remove_special(&c->in.special_waiters, &special);

    _xcb_in_wake_up_next_reader(c);

    pthread_mutex_unlock(&c->iolock);

    return event;

}

xcb_special_event_t *

xcb_register_for_special_xge(xcb_connection_t *c,

                             xcb_extension_t *ext,

                             uint32_t eid,

                             uint32_t *stamp)

{

    xcb_special_event_t *se;

    const xcb_query_extension_reply_t   *ext_reply;

    if(c->has_error)

        return NULL;

    ext_reply = xcb_get_extension_data(c, ext);

    if (!ext_reply)

        return NULL;

    pthread_mutex_lock(&c->iolock);

    for (se = c->in.special_events; se; se = se->next) {

        if (se->extension == ext_reply->major_opcode &&

            se->eid == eid) {

            pthread_mutex_unlock(&c->iolock);

            return NULL;

        }

    }

    se = calloc(1, sizeof(xcb_special_event_t));

    if (!se) {

        pthread_mutex_unlock(&c->iolock);

        return NULL;

    }

    se->extension = ext_reply->major_opcode;

    se->eid = eid;

    se->events = NULL;

    se->events_tail = &se->events;

    se->stamp = stamp;

    pthread_cond_init(&se->special_event_cond, 0);

    se->next = c->in.special_events;

    c->in.special_events = se;

    pthread_mutex_unlock(&c->iolock);

    return se;

}

void

xcb_unregister_for_special_event(xcb_connection_t *c,

                                 xcb_special_event_t *se)

{

    xcb_special_event_t *s, **prev;

    struct event_list   *events, *next;

    if (!se)

        return;

    if (c->has_error)

        return;

    pthread_mutex_lock(&c->iolock);

    for (prev = &c->in.special_events; (s = *prev) != NULL; prev = &(s->next)) {

        if (s == se) {

            *prev = se->next;

            for (events = se->events; events; events = next) {

                next = events->next;

                free (events->event);

                free (events);

            }

            pthread_cond_destroy(&se->special_event_cond);

            free (se);

            break;

        }

    }

    pthread_mutex_unlock(&c->iolock);

}

/* Private interface */