flac/include/FLAC/stream_decoder.h

/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2000,2001,2002  Josh Coalson
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 */

#ifndef FLAC__STREAM_DECODER_H
#define FLAC__STREAM_DECODER_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.  There will always be one STREAMINFO block
 *   per stream, 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_whole_stream() - Tells the decoder to
 *   start and continue processing the stream until the read callback
 *   returns FLAC__STREAM_DECODER_READ_END_OF_STREAM or
 *   FLAC__STREAM_DECODER_READ_ABORT.
 * - FLAC__stream_decoder_process_metadata() - Tells the decoder to start
 *   processing the stream and stop upon reaching the first audio frame.
 * - FLAC__stream_decoder_process_one_frame() - Tells the decoder to
 *   process one audio frame and return.  The decoder must have processed
 *   all metadata first before calling this function.
 * - FLAC__stream_decoder_process_remaining_frames() - Tells the decoder to
 *   process all remaining frames.  The decoder must have processed all
 *   metadata first but may also have processed frames with
 *   FLAC__stream_decoder_process_one_frame().
 *
 * 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.
 *
 * \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 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 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 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. */

	FLAC__STREAM_DECODER_ERROR_STATUS_BAD_HEADER,
	/**< The decoder encountered a corrupted frame header. */

	FLAC__STREAM_DECODER_ERROR_STATUS_FRAME_CRC_MISMATCH
	/**< The frame's data did not match the CRC in the footer. */

} FLAC__StreamDecoderErrorStatus;

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


/***********************************************************************
 *
 * class FLAC__StreamDecoder
 *
 ***********************************************************************/

struct FLAC__StreamDecoderProtected;
struct FLAC__StreamDecoderPrivate;
/** The opaque structure definition for the stream decoder type.
 *  See the \link flac_stream_decoder stream decoder module \endlink
 *  for a detailed description.
 */
typedef struct {
	struct FLAC__StreamDecoderProtected *protected_; /* avoid the C++ keyword 'protected' */
	struct FLAC__StreamDecoderPrivate *private_; /* avoid the C++ keyword 'private' */
} FLAC__StreamDecoder;


/***********************************************************************
 *
 * Class constructor/destructor
 *
 ***********************************************************************/

/** Create a new stream decoder instance.  The instance is created with
 *  default settings; see the individual FLAC__stream_decoder_set_*()
 *  functions for each setting's default.
 *
 * \retval FLAC__StreamDecoder*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC__StreamDecoder *FLAC__stream_decoder_new();

/** Free an decoder instance.  Deletes the object pointed to by \a decoder.
 *
 * \param decoder  A pointer to an existing decoder.
 * \assert
 *    \code decoder != NULL \endcode
 */
void FLAC__stream_decoder_delete(FLAC__StreamDecoder *);


/***********************************************************************
 *
 * Public class method prototypes
 *
 ***********************************************************************/

/** Set the read callback.
 *  The supplied 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.
 *
 * \note
 * The callback is mandatory and must be set before initialization.
 *
 * \default \c NULL
 * \param  decoder  An decoder instance to set.
 * \param  value    See above.
 * \assert
 *    \code decoder != NULL \endcode
 *    \code value != NULL \endcode
 * \retval FLAC__bool
 *    \c false if the decoder is already initialized, else \c true.
 */
FLAC__bool FLAC__stream_decoder_set_read_callback(FLAC__StreamDecoder *decoder, FLAC__StreamDecoderReadStatus (*value)(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], unsigned *bytes, void *client_data));

/** Set the write callback.
 *  The supplied 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.
 *
 * \note
 * The callback is mandatory and must be set before initialization.
 *
 * \default \c NULL
 * \param  decoder  An decoder instance to set.
 * \param  value    See above.
 * \assert
 *    \code decoder != NULL \endcode
 *    \code value != NULL \endcode
 * \retval FLAC__bool
 *    \c false if the decoder is already initialized, else \c true.
 */
FLAC__bool FLAC__stream_decoder_set_write_callback(FLAC__StreamDecoder *decoder, FLAC__StreamDecoderWriteStatus (*value)(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data));

/** Set the metadata callback.
 *  The supplied function will be called when the decoder has decoded a
 *  metadata block.  There will always be one STREAMINFO block per stream,
 *  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.
 *
 * \note
 * The callback is mandatory and must be set before initialization.
 *
 * \default \c NULL
 * \param  decoder  An decoder instance to set.
 * \param  value    See above.
 * \assert
 *    \code decoder != NULL \endcode
 *    \code value != NULL \endcode
 * \retval FLAC__bool
 *    \c false if the decoder is already initialized, else \c true.
 */
FLAC__bool FLAC__stream_decoder_set_metadata_callback(FLAC__StreamDecoder *decoder, void (*value)(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data));

/** Set the error callback.
 *  The supplied function will be called whenever an error occurs during
 *  decoding.
 *
 * \note
 * The callback is mandatory and must be set before initialization.
 *
 * \default \c NULL
 * \param  decoder  An decoder instance to set.
 * \param  value    See above.
 * \assert
 *    \code decoder != NULL \endcode
 *    \code value != NULL \endcode
 * \retval FLAC__bool
 *    \c false if the decoder is already initialized, else \c true.
 */
FLAC__bool FLAC__stream_decoder_set_error_callback(FLAC__StreamDecoder *decoder, void (*value)(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data));

/** Set the client data to be passed back to callbacks.
 *  This value will be supplied to callbacks in their \a client_data
 *  argument.
 *
 * \default \c NULL
 * \param  decoder  An decoder instance to set.
 * \param  value    See above.
 * \assert
 *    \code decoder != NULL \endcode
 * \retval FLAC__bool
 *    \c false if the decoder is already initialized, else \c true.
 */
FLAC__bool FLAC__stream_decoder_set_client_data(FLAC__StreamDecoder *decoder, void *value);

/*
 * These 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 _respond_all(), _ignore() ...
 * or _ignore_all(), _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 _respond/_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 here.
 */
/*
 *          metadata_respond/ignore        By default, only the STREAMINFO block is returned via metadata_callback()
 */
FLAC__bool FLAC__stream_decoder_set_metadata_respond(FLAC__StreamDecoder *decoder, FLAC__MetadataType type);
FLAC__bool FLAC__stream_decoder_set_metadata_respond_application(FLAC__StreamDecoder *decoder, const FLAC__byte id[4]);
FLAC__bool FLAC__stream_decoder_set_metadata_respond_all(FLAC__StreamDecoder *decoder);
FLAC__bool FLAC__stream_decoder_set_metadata_ignore(FLAC__StreamDecoder *decoder, FLAC__MetadataType type);
FLAC__bool FLAC__stream_decoder_set_metadata_ignore_application(FLAC__StreamDecoder *decoder, const FLAC__byte id[4]);
FLAC__bool FLAC__stream_decoder_set_metadata_ignore_all(FLAC__StreamDecoder *decoder);

/*
 * Methods to return the current stream decoder state, number
 * of channels, channel assignment, bits-per-sample, sample
 * rate in Hz, and blocksize in samples.  All but the decoder
 * state will only be valid after decoding has started.
 */
FLAC__StreamDecoderState FLAC__stream_decoder_get_state(const FLAC__StreamDecoder *decoder);
unsigned FLAC__stream_decoder_get_channels(const FLAC__StreamDecoder *decoder);
FLAC__ChannelAssignment FLAC__stream_decoder_get_channel_assignment(const FLAC__StreamDecoder *decoder);
unsigned FLAC__stream_decoder_get_bits_per_sample(const FLAC__StreamDecoder *decoder);
unsigned FLAC__stream_decoder_get_sample_rate(const FLAC__StreamDecoder *decoder);
unsigned FLAC__stream_decoder_get_blocksize(const FLAC__StreamDecoder *decoder);

/*
 * Initialize the instance; should be called after construction and
 * 'set' calls but before any of the 'process' calls.  Will set and
 * return the decoder state, which will be
 * FLAC__STREAM_DECODER_SEARCH_FOR_METADATA if initialization
 * succeeded.
 */
FLAC__StreamDecoderState FLAC__stream_decoder_init(FLAC__StreamDecoder *decoder);

/*
 * Flush the decoding buffer, release resources, and return the decoder
 * state to FLAC__STREAM_DECODER_UNINITIALIZED.
 */
void FLAC__stream_decoder_finish(FLAC__StreamDecoder *decoder);

/*
 * state control methods
 */
FLAC__bool FLAC__stream_decoder_flush(FLAC__StreamDecoder *decoder);
FLAC__bool FLAC__stream_decoder_reset(FLAC__StreamDecoder *decoder);

/*
 * Methods for decoding the data
 */
FLAC__bool FLAC__stream_decoder_process_whole_stream(FLAC__StreamDecoder *decoder);
FLAC__bool FLAC__stream_decoder_process_metadata(FLAC__StreamDecoder *decoder);
FLAC__bool FLAC__stream_decoder_process_one_frame(FLAC__StreamDecoder *decoder);
FLAC__bool FLAC__stream_decoder_process_remaining_frames(FLAC__StreamDecoder *decoder);

/* \} */

#ifdef __cplusplus
}
#endif

#endif