libavutil/container_fifo.h

   1 /*
   2  * This file is part of FFmpeg.
   3  *
   4  * FFmpeg is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * FFmpeg is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with FFmpeg; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #ifndef AVUTIL_CONTAINER_FIFO_H
  20 #define AVUTIL_CONTAINER_FIFO_H
  21
  22 #include <stddef.h>
  23
  24 /**
  25  * AVContainerFifo is a FIFO for "containers" - dynamically allocated reusable
  26  * structs (e.g. AVFrame or AVPacket). AVContainerFifo uses an internal pool of
  27  * such containers to avoid allocating and freeing them repeatedly.
  28  */
  29 typedef struct AVContainerFifo AVContainerFifo;
  30
  31 enum AVContainerFifoFlags {
  32     /**
  33      * Signal to av_container_fifo_write() that it should make a new reference
  34      * to data in src rather than consume its contents.
  35      *
  36      * @note you must handle this flag manually in your own fifo_transfer()
  37      *       callback
  38      */
  39     AV_CONTAINER_FIFO_FLAG_REF  = (1 << 0),
  40
  41     /**
  42      * This and all higher bits in flags may be set to any value by the caller
  43      * and are guaranteed to be passed through to the fifo_transfer() callback
  44      * and not be interpreted by AVContainerFifo code.
  45      */
  46     AV_CONTAINER_FIFO_FLAG_USER = (1 << 16),
  47 };
  48
  49 /**
  50  * Allocate a new AVContainerFifo for the container type defined by provided
  51  * callbacks.
  52  *
  53  * @param opaque user data that will be passed to the callbacks provided to this
  54  *               function
  55  * @param container_alloc allocate a new container instance and return a pointer
  56  *                        to it, or NULL on failure
  57  * @param container_reset reset the provided container instance to a clean state
  58  * @param container_free free the provided container instance
  59  * @param fifo_transfer Transfer the contents of container src to dst.
  60  * @param flags currently unused
  61  *
  62  * @return newly allocated AVContainerFifo, or NULL on failure
  63  */
  64 AVContainerFifo*
  65 av_container_fifo_alloc(void *opaque,
  66                         void* (*container_alloc)(void *opaque),
  67                         void  (*container_reset)(void *opaque, void *obj),
  68                         void  (*container_free) (void *opaque, void *obj),
  69                         int   (*fifo_transfer)  (void *opaque, void *dst, void *src, unsigned flags),
  70                         unsigned flags);
  71
  72 /**
  73  * Allocate an AVContainerFifo instance for AVFrames.
  74  *
  75  * @param flags currently unused
  76  */
  77 AVContainerFifo *av_container_fifo_alloc_avframe(unsigned flags);
  78
  79 /**
  80  * Free a AVContainerFifo and everything in it.
  81  */
  82 void av_container_fifo_free(AVContainerFifo **cf);
  83
  84 /**
  85  * Write the contents of obj to the FIFO.
  86  *
  87  * The fifo_transfer() callback previously provided to av_container_fifo_alloc()
  88  * will be called with obj as src in order to perform the actual transfer.
  89  */
  90 int av_container_fifo_write(AVContainerFifo *cf, void *obj, unsigned flags);
  91
  92 /**
  93  * Read the next available object from the FIFO into obj.
  94  *
  95  * The fifo_read() callback previously provided to av_container_fifo_alloc()
  96  * will be called with obj as dst in order to perform the actual transfer.
  97  */
  98 int av_container_fifo_read(AVContainerFifo *cf, void *obj, unsigned flags);
  99
 100 /**
 101  * Access objects stored in the FIFO without retrieving them. The
 102  * fifo_transfer() callback will NOT be invoked and the FIFO state will not be
 103  * modified.
 104  *
 105  * @param pobj Pointer to the object stored in the FIFO will be written here on
 106  *             success. The object remains owned by the FIFO and the caller may
 107  *             only access it as long as the FIFO is not modified.
 108  * @param offset Position of the object to retrieve - 0 is the next item that
 109  *               would be read, 1 the one after, etc. Must be smaller than
 110  *               av_container_fifo_can_read().
 111  *
 112  * @retval 0 success, a pointer was written into pobj
 113  * @retval AVERROR(EINVAL) invalid offset value
 114  */
 115 int av_container_fifo_peek(AVContainerFifo *cf, void **pobj, size_t offset);
 116
 117 /**
 118  * Discard the specified number of elements from the FIFO.
 119  *
 120  * @param nb_elems number of elements to discard, MUST NOT be larger than
 121  *                 av_fifo_can_read(f)
 122  */
 123 void av_container_fifo_drain(AVContainerFifo *cf, size_t nb_elems);
 124
 125 /**
 126  * @return number of objects available for reading
 127  */
 128 size_t av_container_fifo_can_read(const AVContainerFifo *cf);
 129
 130 #endif // AVCODEC_CONTAINER_FIFO_H