stream_decoder.h

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/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2000,2001,2002,2003,2004,2005  Josh Coalson
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the Xiph.org Foundation nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef FLAC__STREAM_DECODER_H
#define FLAC__STREAM_DECODER_H

#include "export.h"
#include "format.h"

#ifdef __cplusplus
extern "C" {
#endif


/** \file include/FLAC/stream_decoder.h
 *
 *  \brief
 *  This module contains the functions which implement the stream
 *  decoder.
 *
 *  See the detailed documentation in the
 *  \link flac_stream_decoder stream decoder \endlink module.
 */

/** \defgroup flac_decoder FLAC/ *_decoder.h: decoder interfaces
 *  \ingroup flac
 *
 *  \brief
 *  This module describes the three decoder layers provided by libFLAC.
 *
 * For decoding FLAC streams, libFLAC provides three layers of access.  The
 * lowest layer is non-seekable stream-level decoding, the next is seekable
 * stream-level decoding, and the highest layer is file-level decoding.  The
 * interfaces are described in the \link flac_stream_decoder stream decoder
 * \endlink, \link flac_seekable_stream_decoder seekable stream decoder
 * \endlink, and \link flac_file_decoder file decoder \endlink modules
 * respectively.  Typically you will choose the highest layer that your input
 * source will support.
 *
 * The stream decoder relies on callbacks for all input and output and has no
 * provisions for seeking.  The seekable stream decoder wraps the stream
 * decoder and exposes functions for seeking.  However, you must provide
 * extra callbacks for seek-related operations on your stream, like seek and
 * tell.  The file decoder wraps the seekable stream decoder and supplies
 * most of the callbacks internally, simplifying the processing of standard
 * files.
 */

/** \defgroup flac_stream_decoder FLAC/stream_decoder.h: stream decoder interface
 *  \ingroup flac_decoder
 *
 *  \brief
 *  This module contains the functions which implement the stream
 *  decoder.
 *
 * The basic usage of this decoder is as follows:
 * - The program creates an instance of a decoder using
 *   FLAC__stream_decoder_new().
 * - The program overrides the default settings and sets callbacks for
 *   reading, writing, error reporting, and metadata reporting using
 *   FLAC__stream_decoder_set_*() functions.
 * - The program initializes the instance to validate the settings and
 *   prepare for decoding using FLAC__stream_decoder_init().
 * - The program calls the FLAC__stream_decoder_process_*() functions
 *   to decode data, which subsequently calls the callbacks.
 * - The program finishes the decoding with FLAC__stream_decoder_finish(),
 *   which flushes the input and output and resets the decoder to the
 *   uninitialized state.
 * - The instance may be used again or deleted with
 *   FLAC__stream_decoder_delete().
 *
 * In more detail, the program will create a new instance by calling
 * FLAC__stream_decoder_new(), then call FLAC__stream_decoder_set_*()
 * functions to set the callbacks and client data, and call
 * FLAC__stream_decoder_init().  The required callbacks are:
 *
 * - Read callback - This function will be called when the decoder needs
 *   more input data.  The address of the buffer to be filled is supplied,
 *   along with the number of bytes the buffer can hold.  The callback may
 *   choose to supply less data and modify the byte count but must be careful
 *   not to overflow the buffer.  The callback then returns a status code
 *   chosen from FLAC__StreamDecoderReadStatus.
 * - Write callback - This function will be called when the decoder has
 *   decoded a single frame of data.  The decoder will pass the frame
 *   metadata as well as an array of pointers (one for each channel)
 *   pointing to the decoded audio.
 * - Metadata callback - This function will be called when the decoder has
 *   decoded a metadata block.  In a valid FLAC file there will always be
 *   one STREAMINFO block, followed by zero or more other metadata
 *   blocks.  These will be supplied by the decoder in the same order as
 *   they appear in the stream and always before the first audio frame
 *   (i.e. write callback).  The metadata block that is passed in must not
 *   be modified, and it doesn't live beyond the callback, so you should
 *   make a copy of it with FLAC__metadata_object_clone() if you will need
 *   it elsewhere.  Since metadata blocks can potentially be large, by
 *   default the decoder only calls the metadata callback for the STREAMINFO
 *   block; you can instruct the decoder to pass or filter other blocks with
 *   FLAC__stream_decoder_set_metadata_*() calls.
 * - Error callback - This function will be called whenever an error occurs
 *   during decoding.
 *
 * Once the decoder is initialized, your program will call one of several
 * functions to start the decoding process:
 *
 * - FLAC__stream_decoder_process_single() - Tells the decoder to process at
 *   most one metadata block or audio frame and return, calling either the
 *   metadata callback or write callback, respectively, once.  If the decoder
 *   loses sync it will return with only the error callback being called.
 * - FLAC__stream_decoder_process_until_end_of_metadata() - Tells the decoder
 *   to process the stream from the current location and stop upon reaching
 *   the first audio frame.  The user will get one metadata, write, or error
 *   callback per metadata block, audio frame, or sync error, respectively.
 * - FLAC__stream_decoder_process_until_end_of_stream() - Tells the decoder
 *   to process the stream from the current location until the read callback
 *   returns FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM or
 *   FLAC__STREAM_DECODER_READ_STATUS_ABORT.  The user will get one metadata,
 *   write, or error callback per metadata block, audio frame, or sync error,
 *   respectively.
 *
 * When the decoder has finished decoding (normally or through an abort),
 * the instance is finished by calling FLAC__stream_decoder_finish(), which
 * ensures the decoder is in the correct state and frees memory.  Then the
 * instance may be deleted with FLAC__stream_decoder_delete() or initialized
 * again to decode another stream.
 *
 * Note that the stream decoder has no real concept of stream position, it
 * just converts data.  To seek within a stream the callbacks have only to
 * flush the decoder using FLAC__stream_decoder_flush() and start feeding
 * data from the new position through the read callback.  The seekable
 * stream decoder does just this.
 *
 * The FLAC__stream_decoder_set_metadata_*() functions deserve special
 * attention.  By default, the decoder only calls the metadata_callback for
 * the STREAMINFO block.  These functions allow you to tell the decoder
 * explicitly which blocks to parse and return via the metadata_callback
 * and/or which to skip.  Use a FLAC__stream_decoder_set_metadata_respond_all(),
 * FLAC__stream_decoder_set_metadata_ignore() ... or FLAC__stream_decoder_set_metadata_ignore_all(),
 * FLAC__stream_decoder_set_metadata_respond() ... sequence to exactly specify which
 * blocks to return.  Remember that some metadata blocks can be big so
 * filtering out the ones you don't use can reduce the memory requirements
 * of the decoder.  Also note the special forms
 * FLAC__stream_decoder_set_metadata_respond_application(id) and
 * FLAC__stream_decoder_set_metadata_ignore_application(id) for filtering APPLICATION
 * blocks based on the application ID.
 *
 * STREAMINFO and SEEKTABLE blocks are always parsed and used internally, but
 * they still can legally be filtered from the metadata_callback.
 *
 * \note
 * The "set" functions may only be called when the decoder is in the
 * state FLAC__STREAM_DECODER_UNINITIALIZED, i.e. after
 * FLAC__stream_decoder_new() or FLAC__stream_decoder_finish(), but
 * before FLAC__stream_decoder_init().  If this is the case they will
 * return \c true, otherwise \c false.
 *
 * \note
 * FLAC__stream_decoder_finish() resets all settings to the constructor
 * defaults, including the callbacks.
 *
 * \{
 */


/** State values for a FLAC__StreamDecoder
 *
 *  The decoder's state can be obtained by calling FLAC__stream_decoder_get_state().
 */
typedef enum {

	FLAC__STREAM_DECODER_SEARCH_FOR_METADATA = 0,
	/**< The decoder is ready to search for metadata. */

	FLAC__STREAM_DECODER_READ_METADATA,
	/**< The decoder is ready to or is in the process of reading metadata. */

	FLAC__STREAM_DECODER_SEARCH_FOR_FRAME_SYNC,
	/**< The decoder is ready to or is in the process of searching for the frame sync code. */

	FLAC__STREAM_DECODER_READ_FRAME,
	/**< The decoder is ready to or is in the process of reading a frame. */

	FLAC__STREAM_DECODER_END_OF_STREAM,
	/**< The decoder has reached the end of the stream. */

	FLAC__STREAM_DECODER_ABORTED,
	/**< The decoder was aborted by the read callback. */

	FLAC__STREAM_DECODER_UNPARSEABLE_STREAM,
	/**< The decoder encountered reserved fields in use in the stream. */

	FLAC__STREAM_DECODER_MEMORY_ALLOCATION_ERROR,
	/**< An error occurred allocating memory. */

	FLAC__STREAM_DECODER_ALREADY_INITIALIZED,
	/**< FLAC__stream_decoder_init() was called when the decoder was
	 * already initialized, usually because
	 * FLAC__stream_decoder_finish() was not called.
	 */

	FLAC__STREAM_DECODER_INVALID_CALLBACK,
	/**< FLAC__stream_decoder_init() was called without all callbacks being set. */

	FLAC__STREAM_DECODER_UNINITIALIZED
	/**< The decoder is in the uninitialized state. */

} FLAC__StreamDecoderState;

/** Maps a FLAC__StreamDecoderState to a C string.
 *
 *  Using a FLAC__StreamDecoderState as the index to this array
 *  will give the string equivalent.  The contents should not be modified.
 */
extern FLAC_API const char * const FLAC__StreamDecoderStateString[];


/** Return values for the FLAC__StreamDecoder read callback.
 */
typedef enum {

	FLAC__STREAM_DECODER_READ_STATUS_CONTINUE,
	/**< The read was OK and decoding can continue. */

	FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM,
	/**< The read was attempted at the end of the stream. */

	FLAC__STREAM_DECODER_READ_STATUS_ABORT
	/**< An unrecoverable error occurred.  The decoder will return from the process call. */

} FLAC__StreamDecoderReadStatus;

/** Maps a FLAC__StreamDecoderReadStatus to a C string.
 *
 *  Using a FLAC__StreamDecoderReadStatus as the index to this array
 *  will give the string equivalent.  The contents should not be modified.
 */
extern FLAC_API const char * const FLAC__StreamDecoderReadStatusString[];


/** Return values for the FLAC__StreamDecoder write callback.
 */
typedef enum {

	FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE,
	/**< The write was OK and decoding can continue. */

	FLAC__STREAM_DECODER_WRITE_STATUS_ABORT
	/**< An unrecoverable error occurred.  The decoder will return from the process call. */

} FLAC__StreamDecoderWriteStatus;

/** Maps a FLAC__StreamDecoderWriteStatus to a C string.
 *
 *  Using a FLAC__StreamDecoderWriteStatus as the index to this array
 *  will give the string equivalent.  The contents should not be modified.
 */
extern FLAC_API const char * const FLAC__StreamDecoderWriteStatusString[];


/** Possible values passed in to the FLAC__StreamDecoder error callback.
 */
typedef enum {

	FLAC__STREAM_DECODER_ERROR_STATUS_LOST_SYNC,
	/**< An error in the stream caused the decoder to lose synchronization. */