(*
 * AVOptions
 * copyright (c) 2005 Michael Niedermayer <michaelni@gmx.at>
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * This is a part of Pascal porting of ffmpeg.
 * - Originally by Victor Zinetz for Delphi and Free Pascal on Windows.
 * - For Mac OS X, some modifications were made by The Creative CAT, denoted as CAT
 *   in the source codes.
 * - Changes and updates by the UltraStar Deluxe Team
 *
 * Conversion of libavutil/buffer.h
 * avutil version 54.7.100
 *
 *)

const
(**
 * Always treat the buffer as read-only, even when it has only one
 * reference.
 *)
  AV_BUFFER_FLAG_READONLY = (1 << 0);

type
(**
 * @defgroup lavu_buffer AVBuffer
 * @ingroup lavu_data
 *
 * @
 * AVBuffer is an API for reference-counted data buffers.
 *
 * There are two core objects in this API -- AVBuffer and AVBufferRef. AVBuffer
 * represents the data buffer itself; it is opaque and not meant to be accessed
 * by the caller directly, but only through AVBufferRef. However, the caller may
 * e.g. compare two AVBuffer pointers to check whether two different references
 * are describing the same data buffer. AVBufferRef represents a single
 * reference to an AVBuffer and it is the object that may be manipulated by the
 * caller directly.
 *
 * There are two functions provided for creating a new AVBuffer with a single
 * reference -- av_buffer_alloc() to just allocate a new buffer, and
 * av_buffer_create() to wrap an existing array in an AVBuffer. From an existing
 * reference, additional references may be created with av_buffer_ref().
 * Use av_buffer_unref() to free a reference (this will automatically free the
 * data once all the references are freed).
 *
 * The convention throughout this API and the rest of FFmpeg is such that the
 * buffer is considered writable if there exists only one reference to it (and
 * it has not been marked as read-only). The av_buffer_is_writable() function is
 * provided to check whether this is true and av_buffer_make_writable() will
 * automatically create a new writable buffer when necessary.
 * Of course nothing prevents the calling code from violating this convention,
 * however that is safe only when all the existing references are under its
 * control.
 *
 * @note Referencing and unreferencing the buffers is thread-safe and thus
 * may be done from multiple threads simultaneously without any need for
 * additional locking.
 *
 * @note Two different references to the same buffer can point to different
 * parts of the buffer (i.e. their AVBufferRef.data will not be equal).
 *)

(**
 * A reference counted buffer type. It is opaque and is meant to be used through
 * references (AVBufferRef).
 *)
  TAVBuffer = record
  end;

(**
 * A reference to a data buffer.
 *
 * The size of this struct is not a part of the public ABI and it is not meant
 * to be allocated directly.
 *)
  PPAVBufferRef = ^PAVBufferRef;
  PAVBufferRef = ^TAVBufferRef;
  TAVBufferRef = record
    buffer: TAVBuffer;
    (**
     * The data buffer. It is considered writable if and only if
     * this is the only reference to the buffer, in which case
     * av_buffer_is_writable() returns 1.
     *)
    data: PByte;
    (**
     * Size of data in bytes.
     *)
    size: cint;
  end;

  //callbacks used in the functions av_buffer_create and av_buffer_pool_init respectively
  TFree  = procedure(opaque: pointer; data: pbyte);
  TAlloc = function(size: cint): PAVBufferRef;

(**
 * The buffer pool. This structure is opaque and not meant to be accessed
 * directly. It is allocated with av_buffer_pool_init() and freed with
 * av_buffer_pool_uninit().
 *)
  PPAVBufferPool = ^PAVBufferPool;
  PAVBufferPool = ^TAVBufferPool;
  TAVBufferPool = record
  end;

(**
 * Allocate an AVBuffer of the given size using av_malloc().
 *
 * @return an AVBufferRef of given size or NULL when out of memory
 *)
function av_buffer_alloc(size: cint): PAVBufferRef;
  cdecl; external av__util;

(**
 * Same as av_buffer_alloc(), except the returned buffer will be initialized
 * to zero.
 *)
function av_buffer_allocz(size: cint): PAVBufferRef;
  cdecl; external av__util;

(**
 * Create an AVBuffer from an existing array.
 *
 * If this function is successful, data is owned by the AVBuffer. The caller may
 * only access data through the returned AVBufferRef and references derived from
 * it.
 * If this function fails, data is left untouched.
 * @param data   data array
 * @param size   size of data in bytes
 * @param free   a callback for freeing this buffer's data
 * @param opaque parameter to be got for processing or passed to free
 * @param flags  a combination of AV_BUFFER_FLAG_*
 *
 * @return an AVBufferRef referring to data on success, NULL on failure.
 *)

function av_buffer_create(data: PByte; size: cint;
                          free: TFree;
                          opaque: pointer; flags: cint): PAVBufferRef;
  cdecl; external av__util;

(**
 * Default free callback, which calls av_free() on the buffer data.
 * This function is meant to be passed to av_buffer_create(), not called
 * directly.
 *)
procedure av_buffer_default_free(opaque: pointer; data: pbyte);
  cdecl; external av__util;

(**
 * Create a new reference to an AVBuffer.
 *
 * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on
 * failure.
 *)
function av_buffer_ref(buf: PAVBufferRef): PAVBufferRef;
  cdecl; external av__util;

(**
 * Free a given reference and automatically free the buffer if there are no more
 * references to it.
 *
 * @param buf the reference to be freed. The pointer is set to NULL on return.
 *)
procedure av_buffer_unref(buf: PPAVBufferRef);
  cdecl; external av__util;

(**
 * @return 1 if the caller may write to the data referred to by buf (which is
 * true if and only if buf is the only reference to the underlying AVBuffer).
 * Return 0 otherwise.
 * A positive answer is valid until av_buffer_ref() is called on buf.
 *)
function av_buffer_is_writable(buf: {const} PAVBufferRef): cint;
  cdecl; external av__util;

(**
 * @return the opaque parameter set by av_buffer_create.
 *)
procedure av_buffer_get_opaque(buf: {const} PAVBufferRef);
  cdecl; external av__util;

function av_buffer_get_ref_count(buf: {const} PAVBufferRef): cint;
  cdecl; external av__util;

(**
 * Create a writable reference from a given buffer reference, avoiding data copy
 * if possible.
 *
 * @param buf buffer reference to make writable. On success, buf is either left
 *            untouched, or it is unreferenced and a new writable AVBufferRef is
 *            written in its place. On failure, buf is left untouched.
 * @return 0 on success, a negative AVERROR on failure.
 *)
function av_buffer_make_writable(buf: PPAVBufferRef): cint;
  cdecl; external av__util;

(**
 * Reallocate a given buffer.
 *
 * @param buf  a buffer reference to reallocate. On success, buf will be
 *             unreferenced and a new reference with the required size will be
 *             written in its place. On failure buf will be left untouched. *buf
 *             may be NULL, then a new buffer is allocated.
 * @param size required new buffer size.
 * @return 0 on success, a negative AVERROR on failure.
 *
 * @note the buffer is actually reallocated with av_realloc() only if it was
 * initially allocated through av_buffer_realloc(NULL) and there is only one
 * reference to it (i.e. the one passed to this function). In all other cases
 * a new buffer is allocated and the data is copied.
 *)
function av_buffer_realloc(buf: PPAVBufferRef; size: cint): cint;
  cdecl; external av__util;

(**
 * @defgroup lavu_bufferpool AVBufferPool
 * @ingroup lavu_data
 *
 * @
 * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers.
 *
 * Frequently allocating and freeing large buffers may be slow. AVBufferPool is
 * meant to solve this in cases when the caller needs a set of buffers of the
 * same size (the most obvious use case being buffers for raw video or audio
 * frames).
 *
 * At the beginning, the user must call av_buffer_pool_init() to create the
 * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to
 * get a reference to a new buffer, similar to av_buffer_alloc(). This new
 * reference works in all aspects the same way as the one created by
 * av_buffer_alloc(). However, when the last reference to this buffer is
 * unreferenced, it is returned to the pool instead of being freed and will be
 * reused for subsequent av_buffer_pool_get() calls.
 *
 * When the caller is done with the pool and no longer needs to allocate any new
 * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable.
 * Once all the buffers are released, it will automatically be freed.
 *
 * Allocating and releasing buffers with this API is thread-safe as long as
 * either the default alloc callback is used, or the user-supplied one is
 * thread-safe.
 *)

(**
 * Allocate and initialize a buffer pool.
 *
 * @param size size of each buffer in this pool
 * @param alloc a function that will be used to allocate new buffers when the
 * pool is empty. May be NULL, then the default allocator will be used
 * (av_buffer_alloc()).
 * @return newly created buffer pool on success, NULL on error.
 *)
function av_buffer_pool_init(size: cint; alloc: TAlloc): PAVBufferRef;
  cdecl; external av__util;

(**
 * Mark the pool as being available for freeing. It will actually be freed only
 * once all the allocated buffers associated with the pool are released. Thus it
 * is safe to call this function while some of the allocated buffers are still
 * in use.
 *
 * @param pool pointer to the pool to be freed. It will be set to NULL.
 * @see av_buffer_pool_can_uninit()
 *)
procedure av_buffer_pool_uninit(pool: PPAVBufferPool);
  cdecl; external av__util;

(**
 * Allocate a new AVBuffer, reusing an old buffer from the pool when available.
 * This function may be called simultaneously from multiple threads.
 *
 * @return a reference to the new buffer on success, NULL on error.
 *)
function av_buffer_pool_get(pool: PAVBufferPool): PAVBufferRef;
  cdecl; external av__util;