xref: /xsrc/external/mit/libxcb/dist/src/xcb_out.c

/* 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 sends stuff to the server. */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#include "xcb.h"
#include "xcbext.h"
#include "xcbint.h"
#include "bigreq.h"

static inline void send_request(xcb_connection_t *c, int isvoid, enum workarounds workaround, int flags, struct iovec *vector, int count)
{
    if(c->has_error)
        return;

    ++c->out.request;
    if(!isvoid)
        c->in.request_expected = c->out.request;
    if(workaround != WORKAROUND_NONE || flags != 0)
        _xcb_in_expect_reply(c, c->out.request, workaround, flags);

    while(count && c->out.queue_len + vector[0].iov_len <= sizeof(c->out.queue))
    {
        memcpy(c->out.queue + c->out.queue_len, vector[0].iov_base, vector[0].iov_len);
        c->out.queue_len += vector[0].iov_len;
        vector[0].iov_base = (char *) vector[0].iov_base + vector[0].iov_len;
        vector[0].iov_len = 0;
        ++vector, --count;
    }
    if(!count)
        return;

    --vector, ++count;
    vector[0].iov_base = c->out.queue;
    vector[0].iov_len = c->out.queue_len;
    c->out.queue_len = 0;
    _xcb_out_send(c, vector, count);
}

static void send_sync(xcb_connection_t *c)
{
    static const union {
        struct {
            uint8_t major;
            uint8_t pad;
            uint16_t len;
        } fields;
        uint32_t packet;
    } sync_req = { { /* GetInputFocus */ 43, 0, 1 } };
    struct iovec vector[2];
    vector[1].iov_base = (char *) &sync_req;
    vector[1].iov_len = sizeof(sync_req);
    send_request(c, 0, WORKAROUND_NONE, XCB_REQUEST_DISCARD_REPLY, vector + 1, 1);
}

static void get_socket_back(xcb_connection_t *c)
{
    while(c->out.return_socket && c->out.socket_moving)
        pthread_cond_wait(&c->out.socket_cond, &c->iolock);
    if(!c->out.return_socket)
        return;

    c->out.socket_moving = 1;
    pthread_mutex_unlock(&c->iolock);
    c->out.return_socket(c->out.socket_closure);
    pthread_mutex_lock(&c->iolock);
    c->out.socket_moving = 0;

    pthread_cond_broadcast(&c->out.socket_cond);
    c->out.return_socket = 0;
    c->out.socket_closure = 0;
    _xcb_in_replies_done(c);
}

static void prepare_socket_request(xcb_connection_t *c)
{
    /* We're about to append data to out.queue, so we need to
     * atomically test for an external socket owner *and* some other
     * thread currently writing.
     *
     * If we have an external socket owner, we have to get the socket back
     * before we can use it again.
     *
     * If some other thread is writing to the socket, we assume it's
     * writing from out.queue, and so we can't stick data there.
     *
     * We satisfy this condition by first calling get_socket_back
     * (which may drop the lock, but will return when XCB owns the
     * socket again) and then checking for another writing thread and
     * escaping the loop if we're ready to go.
     */
    for (;;) {
        if(c->has_error)
            return;
        get_socket_back(c);
        if (!c->out.writing)
            break;
        pthread_cond_wait(&c->out.cond, &c->iolock);
    }
}

/* Public interface */

void xcb_prefetch_maximum_request_length(xcb_connection_t *c)
{
    if(c->has_error)
        return;
    pthread_mutex_lock(&c->out.reqlenlock);
    if(c->out.maximum_request_length_tag == LAZY_NONE)
    {
        const xcb_query_extension_reply_t *ext;
        ext = xcb_get_extension_data(c, &xcb_big_requests_id);
        if(ext && ext->present)
        {
            c->out.maximum_request_length_tag = LAZY_COOKIE;
            c->out.maximum_request_length.cookie = xcb_big_requests_enable(c);
        }
        else
        {
            c->out.maximum_request_length_tag = LAZY_FORCED;
            c->out.maximum_request_length.value = c->setup->maximum_request_length;
        }
    }
    pthread_mutex_unlock(&c->out.reqlenlock);
}

uint32_t xcb_get_maximum_request_length(xcb_connection_t *c)
{
    if(c->has_error)
        return 0;
    xcb_prefetch_maximum_request_length(c);
    pthread_mutex_lock(&c->out.reqlenlock);
    if(c->out.maximum_request_length_tag == LAZY_COOKIE)
    {
        xcb_big_requests_enable_reply_t *r = xcb_big_requests_enable_reply(c, c->out.maximum_request_length.cookie, 0);
        c->out.maximum_request_length_tag = LAZY_FORCED;
        if(r)
        {
            c->out.maximum_request_length.value = r->maximum_request_length;
            free(r);
        }
        else
            c->out.maximum_request_length.value = c->setup->maximum_request_length;
    }
    pthread_mutex_unlock(&c->out.reqlenlock);
    return c->out.maximum_request_length.value;
}

static void close_fds(int *fds, unsigned int num_fds)
{
    for (unsigned int index = 0; index < num_fds; index++)
        close(fds[index]);
}

static void send_fds(xcb_connection_t *c, int *fds, unsigned int num_fds)
{
#if HAVE_SENDMSG
    /* Calling _xcb_out_flush_to() can drop the iolock and wait on a condition
     * variable if another thread is currently writing (c->out.writing > 0).
     * This call waits for writers to be done and thus _xcb_out_flush_to() will
     * do the work itself (in which case we are a writer and
     * prepare_socket_request() will wait for us to be done if another threads
     * tries to send fds, too). Thanks to this, we can atomically write out FDs.
     */
    prepare_socket_request(c);

    while (num_fds > 0) {
        while (c->out.out_fd.nfd == XCB_MAX_PASS_FD && !c->has_error) {
            /* XXX: if c->out.writing > 0, this releases the iolock and
             * potentially allows other threads to interfere with their own fds.
             */
            _xcb_out_flush_to(c, c->out.request);

            if (c->out.out_fd.nfd == XCB_MAX_PASS_FD) {
                /* We need some request to send FDs with */
                _xcb_out_send_sync(c);
            }
        }
        if (c->has_error)
            break;

        c->out.out_fd.fd[c->out.out_fd.nfd++] = fds[0];
        fds++;
        num_fds--;
    }
#endif
    close_fds(fds, num_fds);
}

uint64_t xcb_send_request_with_fds64(xcb_connection_t *c, int flags, struct iovec *vector,
                const xcb_protocol_request_t *req, unsigned int num_fds, int *fds)
{
    uint64_t request;
    uint32_t prefix[2];
    int veclen = req->count;
    enum workarounds workaround = WORKAROUND_NONE;

    if(c->has_error) {
        close_fds(fds, num_fds);
        return 0;
    }

    assert(c != 0);
    assert(vector != 0);
    assert(req->count > 0);

    if(!(flags & XCB_REQUEST_RAW))
    {
        static const char pad[3];
        unsigned int i;
        uint16_t shortlen = 0;
        size_t longlen = 0;
        assert(vector[0].iov_len >= 4);
        /* set the major opcode, and the minor opcode for extensions */
        if(req->ext)
        {
            const xcb_query_extension_reply_t *extension = xcb_get_extension_data(c, req->ext);
            if(!(extension && extension->present))
            {
                close_fds(fds, num_fds);
                _xcb_conn_shutdown(c, XCB_CONN_CLOSED_EXT_NOTSUPPORTED);
                return 0;
            }
            ((uint8_t *) vector[0].iov_base)[0] = extension->major_opcode;
            ((uint8_t *) vector[0].iov_base)[1] = req->opcode;
        }
        else
            ((uint8_t *) vector[0].iov_base)[0] = req->opcode;

        /* put together the length field, possibly using BIGREQUESTS */
        for(i = 0; i < req->count; ++i)
        {
            longlen += vector[i].iov_len;
            if(!vector[i].iov_base)
            {
                vector[i].iov_base = (char *) pad;
                assert(vector[i].iov_len <= sizeof(pad));
            }
        }
        assert((longlen & 3) == 0);
        longlen >>= 2;

        if(longlen <= c->setup->maximum_request_length)
        {
            /* we don't need BIGREQUESTS. */
            shortlen = longlen;
            longlen = 0;
        }
        else if(longlen > xcb_get_maximum_request_length(c))
        {
            close_fds(fds, num_fds);
            _xcb_conn_shutdown(c, XCB_CONN_CLOSED_REQ_LEN_EXCEED);
            return 0; /* server can't take this; maybe need BIGREQUESTS? */
        }

        /* set the length field. */
        ((uint16_t *) vector[0].iov_base)[1] = shortlen;
        if(!shortlen)
        {
            prefix[0] = ((uint32_t *) vector[0].iov_base)[0];
            prefix[1] = ++longlen;
            vector[0].iov_base = (uint32_t *) vector[0].iov_base + 1;
            vector[0].iov_len -= sizeof(uint32_t);
            --vector, ++veclen;
            vector[0].iov_base = prefix;
            vector[0].iov_len = sizeof(prefix);
        }
    }
    flags &= ~XCB_REQUEST_RAW;

    /* do we need to work around the X server bug described in glx.xml? */
    /* XXX: GetFBConfigs won't use BIG-REQUESTS in any sane
     * configuration, but that should be handled here anyway. */
    if(req->ext && !req->isvoid && !strcmp(req->ext->name, "GLX") &&
            ((req->opcode == 17 && ((uint32_t *) vector[0].iov_base)[1] == 0x10004) ||
             req->opcode == 21))
        workaround = WORKAROUND_GLX_GET_FB_CONFIGS_BUG;

    /* get a sequence number and arrange for delivery. */
    pthread_mutex_lock(&c->iolock);

    /* send FDs before establishing a good request number, because this might
     * call send_sync(), too
     */
    send_fds(c, fds, num_fds);

    prepare_socket_request(c);

    /* send GetInputFocus (sync_req) when 64k-2 requests have been sent without
     * a reply.
     * Also send sync_req (could use NoOp) at 32-bit wrap to avoid having
     * applications see sequence 0 as that is used to indicate
     * an error in sending the request
     */

    while ((req->isvoid && c->out.request == c->in.request_expected + (1 << 16) - 2) ||
           (unsigned int) (c->out.request + 1) == 0)
    {
        send_sync(c);
        prepare_socket_request(c);
    }

    send_request(c, req->isvoid, workaround, flags, vector, veclen);
    request = c->has_error ? 0 : c->out.request;
    pthread_mutex_unlock(&c->iolock);
    return request;
}

/* request number are actually uint64_t internally but keep API compat with unsigned int */
unsigned int xcb_send_request_with_fds(xcb_connection_t *c, int flags, struct iovec *vector,
        const xcb_protocol_request_t *req, unsigned int num_fds, int *fds)
{
    return xcb_send_request_with_fds64(c, flags, vector, req, num_fds, fds);
}

uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *req)
{
    return xcb_send_request_with_fds64(c, flags, vector, req, 0, NULL);
}

/* request number are actually uint64_t internally but keep API compat with unsigned int */
unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *req)
{
    return xcb_send_request64(c, flags, vector, req);
}

void
xcb_send_fd(xcb_connection_t *c, int fd)
{
    int fds[1] = { fd };

    if (c->has_error) {
        close(fd);
        return;
    }
    pthread_mutex_lock(&c->iolock);
    send_fds(c, &fds[0], 1);
    pthread_mutex_unlock(&c->iolock);
}

int xcb_take_socket(xcb_connection_t *c, void (*return_socket)(void *closure), void *closure, int flags, uint64_t *sent)
{
    int ret;
    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);
    get_socket_back(c);

    /* _xcb_out_flush may drop the iolock allowing other threads to
     * write requests, so keep flushing until we're done
     */
    do
        ret = _xcb_out_flush_to(c, c->out.request);
    while (ret && c->out.request != c->out.request_written);
    if(ret)
    {
        c->out.return_socket = return_socket;
        c->out.socket_closure = closure;
        if(flags) {
            /* c->out.request + 1 will be the first request sent by the external
             * socket owner. If the socket is returned before this request is sent
             * it will be detected in _xcb_in_replies_done and this pending_reply
             * will be discarded.
             */
            _xcb_in_expect_reply(c, c->out.request + 1, WORKAROUND_EXTERNAL_SOCKET_OWNER, flags);
        }
        assert(c->out.request == c->out.request_written);
        *sent = c->out.request;
    }
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

int xcb_writev(xcb_connection_t *c, struct iovec *vector, int count, uint64_t requests)
{
    int ret;
    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);
    c->out.request += requests;
    ret = _xcb_out_send(c, vector, count);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

int xcb_flush(xcb_connection_t *c)
{
    int ret;
    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);
    ret = _xcb_out_flush_to(c, c->out.request);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

/* Private interface */

int _xcb_out_init(_xcb_out *out)
{
    if(pthread_cond_init(&out->socket_cond, 0))
        return 0;
    out->return_socket = 0;
    out->socket_closure = 0;
    out->socket_moving = 0;

    if(pthread_cond_init(&out->cond, 0))
        return 0;
    out->writing = 0;

    out->queue_len = 0;

    out->request = 0;
    out->request_written = 0;

    if(pthread_mutex_init(&out->reqlenlock, 0))
        return 0;
    out->maximum_request_length_tag = LAZY_NONE;

    return 1;
}

void _xcb_out_destroy(_xcb_out *out)
{
    pthread_cond_destroy(&out->cond);
    pthread_mutex_destroy(&out->reqlenlock);
}

int _xcb_out_send(xcb_connection_t *c, struct iovec *vector, int count)
{
    int ret = 1;
    while(ret && count)
        ret = _xcb_conn_wait(c, &c->out.cond, &vector, &count);
    c->out.request_written = c->out.request;
    pthread_cond_broadcast(&c->out.cond);
    _xcb_in_wake_up_next_reader(c);
    return ret;
}

void _xcb_out_send_sync(xcb_connection_t *c)
{
    prepare_socket_request(c);
    send_sync(c);
}

int _xcb_out_flush_to(xcb_connection_t *c, uint64_t request)
{
    assert(XCB_SEQUENCE_COMPARE(request, <=, c->out.request));
    if(XCB_SEQUENCE_COMPARE(c->out.request_written, >=, request))
        return 1;
    if(c->out.queue_len)
    {
        struct iovec vec;
        vec.iov_base = c->out.queue;
        vec.iov_len = c->out.queue_len;
        c->out.queue_len = 0;
        return _xcb_out_send(c, &vec, 1);
    }
    while(c->out.writing)
        pthread_cond_wait(&c->out.cond, &c->iolock);
    assert(XCB_SEQUENCE_COMPARE(c->out.request_written, >=, request));
    return 1;
}