fftools: add a multistream thread-safe queue

It is similar to AVThreadMessageQueue, but supports multiple streams,
each with its own EOF state.

fftools/Makefile

@@ -16,6 +16,7 @@ OBJS-ffmpeg +=                  \
     fftools/ffmpeg_opt.o        \
     fftools/objpool.o           \
     fftools/sync_queue.o        \
+    fftools/thread_queue.o      \
 
 define DOFFTOOL
 OBJS-$(1) += fftools/cmdutils.o fftools/opt_common.o fftools/$(1).o $(OBJS-$(1)-yes)

fftools/thread_queue.c

@@ -0,0 +1,245 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include "libavutil/avassert.h"
+#include "libavutil/error.h"
+#include "libavutil/fifo.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/mem.h"
+#include "libavutil/thread.h"
+
+#include "objpool.h"
+#include "thread_queue.h"
+
+enum {
+    FINISHED_SEND = (1 << 0),
+    FINISHED_RECV = (1 << 1),
+};
+
+typedef struct FifoElem {
+    void        *obj;
+    unsigned int stream_idx;
+} FifoElem;
+
+struct ThreadQueue {
+    int              *finished;
+    unsigned int    nb_streams;
+
+    AVFifo  *fifo;
+
+    ObjPool *obj_pool;
+    void   (*obj_move)(void *dst, void *src);
+
+    pthread_mutex_t lock;
+    pthread_cond_t  cond;
+};
+
+void tq_free(ThreadQueue **ptq)
+{
+    ThreadQueue *tq = *ptq;
+
+    if (!tq)
+        return;
+
+    if (tq->fifo) {
+        FifoElem elem;
+        while (av_fifo_read(tq->fifo, &elem, 1) >= 0)
+            objpool_release(tq->obj_pool, &elem.obj);
+    }
+    av_fifo_freep2(&tq->fifo);
+
+    objpool_free(&tq->obj_pool);
+
+    av_freep(&tq->finished);
+
+    pthread_cond_destroy(&tq->cond);
+    pthread_mutex_destroy(&tq->lock);
+
+    av_freep(ptq);
+}
+
+ThreadQueue *tq_alloc(unsigned int nb_streams, size_t queue_size,
+                      ObjPool *obj_pool, void (*obj_move)(void *dst, void *src))
+{
+    ThreadQueue *tq;
+    int ret;
+
+    tq = av_mallocz(sizeof(*tq));
+    if (!tq)
+        return NULL;
+
+    ret = pthread_cond_init(&tq->cond, NULL);
+    if (ret) {
+        av_freep(&tq);
+        return NULL;
+    }
+
+    ret = pthread_mutex_init(&tq->lock, NULL);
+    if (ret) {
+        pthread_cond_destroy(&tq->cond);
+        av_freep(&tq);
+        return NULL;
+    }
+
+    tq->finished = av_calloc(nb_streams, sizeof(*tq->finished));
+    if (!tq->finished)
+        goto fail;
+    tq->nb_streams = nb_streams;
+
+    tq->fifo = av_fifo_alloc2(queue_size, sizeof(FifoElem), 0);
+    if (!tq->fifo)
+        goto fail;
+
+    tq->obj_pool = obj_pool;
+    tq->obj_move = obj_move;
+
+    return tq;
+fail:
+    tq_free(&tq);
+    return NULL;
+}
+
+int tq_send(ThreadQueue *tq, unsigned int stream_idx, void *data)
+{
+    int *finished;
+    int ret;
+
+    av_assert0(stream_idx < tq->nb_streams);
+    finished = &tq->finished[stream_idx];
+
+    pthread_mutex_lock(&tq->lock);
+
+    if (*finished & FINISHED_SEND) {
+        ret = AVERROR(EINVAL);
+        goto finish;
+    }
+
+    while (!(*finished & FINISHED_RECV) && !av_fifo_can_write(tq->fifo))
+        pthread_cond_wait(&tq->cond, &tq->lock);
+
+    if (*finished & FINISHED_RECV) {
+        ret = AVERROR_EOF;
+        *finished |= FINISHED_SEND;
+    } else {
+        FifoElem elem = { .stream_idx = stream_idx };
+
+        ret = objpool_get(tq->obj_pool, &elem.obj);
+        if (ret < 0)
+            goto finish;
+
+        tq->obj_move(elem.obj, data);
+
+        ret = av_fifo_write(tq->fifo, &elem, 1);
+        av_assert0(ret >= 0);
+        pthread_cond_broadcast(&tq->cond);
+    }
+
+finish:
+    pthread_mutex_unlock(&tq->lock);
+
+    return ret;
+}
+
+static int receive_locked(ThreadQueue *tq, int *stream_idx,
+                          void *data)
+{
+    FifoElem elem;
+    unsigned int nb_finished = 0;
+
+    if (av_fifo_read(tq->fifo, &elem, 1) >= 0) {
+        tq->obj_move(data, elem.obj);
+        objpool_release(tq->obj_pool, &elem.obj);
+        *stream_idx = elem.stream_idx;
+        return 0;
+    }
+
+    for (unsigned int i = 0; i < tq->nb_streams; i++) {
+        if (!(tq->finished[i] & FINISHED_SEND))
+            continue;
+
+        /* return EOF to the consumer at most once for each stream */
+        if (!(tq->finished[i] & FINISHED_RECV)) {
+            tq->finished[i] |= FINISHED_RECV;
+            *stream_idx   = i;
+            return AVERROR_EOF;
+        }
+
+        nb_finished++;
+    }
+
+    return nb_finished == tq->nb_streams ? AVERROR_EOF : AVERROR(EAGAIN);
+}
+
+int tq_receive(ThreadQueue *tq, int *stream_idx, void *data)
+{
+    int ret;
+
+    *stream_idx = -1;
+
+    pthread_mutex_lock(&tq->lock);
+
+    while (1) {
+        ret = receive_locked(tq, stream_idx, data);
+        if (ret == AVERROR(EAGAIN)) {
+            pthread_cond_wait(&tq->cond, &tq->lock);
+            continue;
+        }
+
+        break;
+    }
+
+    if (ret == 0)
+        pthread_cond_broadcast(&tq->cond);
+
+    pthread_mutex_unlock(&tq->lock);
+
+    return ret;
+}
+
+void tq_send_finish(ThreadQueue *tq, unsigned int stream_idx)
+{
+    av_assert0(stream_idx < tq->nb_streams);
+
+    pthread_mutex_lock(&tq->lock);
+
+    /* mark the stream as send-finished;
+     * next time the consumer thread tries to read this stream it will get
+     * an EOF and recv-finished flag will be set */
+    tq->finished[stream_idx] |= FINISHED_SEND;
+    pthread_cond_broadcast(&tq->cond);
+
+    pthread_mutex_unlock(&tq->lock);
+}
+
+void tq_receive_finish(ThreadQueue *tq, unsigned int stream_idx)
+{
+    av_assert0(stream_idx < tq->nb_streams);
+
+    pthread_mutex_lock(&tq->lock);
+
+    /* mark the stream as recv-finished;
+     * next time the producer thread tries to send for this stream, it will
+     * get an EOF and send-finished flag will be set */
+    tq->finished[stream_idx] |= FINISHED_RECV;
+    pthread_cond_broadcast(&tq->cond);
+
+    pthread_mutex_unlock(&tq->lock);
+}

fftools/thread_queue.h

@@ -0,0 +1,81 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef FFTOOLS_THREAD_QUEUE_H
+#define FFTOOLS_THREAD_QUEUE_H
+
+#include <string.h>
+
+#include "objpool.h"
+
+typedef struct ThreadQueue ThreadQueue;
+
+/**
+ * Allocate a queue for sending data between threads.
+ *
+ * @param nb_streams number of streams for which a distinct EOF state is
+ *                   maintained
+ * @param queue_size number of items that can be stored in the queue without
+ *                   blocking
+ * @param obj_pool object pool that will be used to allocate items stored in the
+ *                 queue; the pool becomes owned by the queue
+ * @param callback that moves the contents between two data pointers
+ */
+ThreadQueue *tq_alloc(unsigned int nb_streams, size_t queue_size,
+                      ObjPool *obj_pool, void (*obj_move)(void *dst, void *src));
+void         tq_free(ThreadQueue **tq);
+
+/**
+ * Send an item for the given stream to the queue.
+ *
+ * @param data the item to send, its contents will be moved using the callback
+ *             provided to tq_alloc(); on failure the item will be left
+ *             untouched
+ * @return
+ * - 0 the item was successfully sent
+ * - AVERROR(ENOMEM) could not allocate an item for writing to the FIFO
+ * - AVERROR(EINVAL) the sending side has previously been marked as finished
+ * - AVERROR_EOF the receiving side has marked the given stream as finished
+ */
+int tq_send(ThreadQueue *tq, unsigned int stream_idx, void *data);
+/**
+ * Mark the given stream finished from the sending side.
+ */
+void tq_send_finish(ThreadQueue *tq, unsigned int stream_idx);
+
+/**
+ * Read the next item from the queue.
+ *
+ * @param stream_idx the index of the stream that was processed or -1 will be
+ *                   written here
+ * @param data the data item will be written here on success using the
+ *             callback provided to tq_alloc()
+ * @return
+ * - 0 a data item was successfully read; *stream_idx contains a non-negative
+ *   stream index
+ * - AVERROR_EOF When *stream_idx is non-negative, this signals that the sending
+ *   side has marked the given stream as finished. This will happen at most once
+ *   for each stream. When *stream_idx is -1, all streams are done.
+ */
+int tq_receive(ThreadQueue *tq, int *stream_idx, void *data);
+/**
+ * Mark the given stream finished from the receiving side.
+ */
+void tq_receive_finish(ThreadQueue *tq, unsigned int stream_idx);
+
+#endif // FFTOOLS_THREAD_QUEUE_H