fftools: add a multistream thread-safe queue

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

1 files changed, 81 insertions, 0 deletions

diff --git a/fftools/thread_queue.h b/fftools/thread_queue.h
new file mode 100644
index 0000000000..0cc8c71ebd
--- /dev/null
+++ b/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