metadata.h

/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2001-2009  Josh Coalson
 * Copyright (C) 2011-2014  Xiph.Org Foundation
 *
 * 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
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef FLAC__METADATA_H
#define FLAC__METADATA_H

#include <sys/types.h> /* for off_t */
#include "export.h"
#include "callback.h"
#include "format.h"

/* --------------------------------------------------------------------
   (For an example of how all these routines are used, see the source
   code for the unit tests in src/test_libFLAC/metadata_*.c, or
   metaflac in src/metaflac/)
   ------------------------------------------------------------------*/

/** \file include/FLAC/metadata.h
 *
 *  \brief
 *  This module provides functions for creating and manipulating FLAC
 *  metadata blocks in memory, and three progressively more powerful
 *  interfaces for traversing and editing metadata in FLAC files.
 *
 *  See the detailed documentation for each interface in the
 *  \link flac_metadata metadata \endlink module.
 */

/** \defgroup flac_metadata FLAC/metadata.h: metadata interfaces
 *  \ingroup flac
 *
 *  \brief
 *  This module provides functions for creating and manipulating FLAC
 *  metadata blocks in memory, and three progressively more powerful
 *  interfaces for traversing and editing metadata in native FLAC files.
 *  Note that currently only the Chain interface (level 2) supports Ogg
 *  FLAC files, and it is read-only i.e. no writing back changed
 *  metadata to file.
 *
 *  There are three metadata interfaces of increasing complexity:
 *
 *  Level 0:
 *  Read-only access to the STREAMINFO, VORBIS_COMMENT, CUESHEET, and
 *  PICTURE blocks.
 *
 *  Level 1:
 *  Read-write access to all metadata blocks.  This level is write-
 *  efficient in most cases (more on this below), and uses less memory
 *  than level 2.
 *
 *  Level 2:
 *  Read-write access to all metadata blocks.  This level is write-
 *  efficient in all cases, but uses more memory since all metadata for
 *  the whole file is read into memory and manipulated before writing
 *  out again.
 *
 *  What do we mean by efficient?  Since FLAC metadata appears at the
 *  beginning of the file, when writing metadata back to a FLAC file
 *  it is possible to grow or shrink the metadata such that the entire
 *  file must be rewritten.  However, if the size remains the same during
 *  changes or PADDING blocks are utilized, only the metadata needs to be
 *  overwritten, which is much faster.
 *
 *  Efficient means the whole file is rewritten at most one time, and only
 *  when necessary.  Level 1 is not efficient only in the case that you
 *  cause more than one metadata block to grow or shrink beyond what can
 *  be accomodated by padding.  In this case you should probably use level
 *  2, which allows you to edit all the metadata for a file in memory and
 *  write it out all at once.
 *
 *  All levels know how to skip over and not disturb an ID3v2 tag at the
 *  front of the file.
 *
 *  All levels access files via their filenames.  In addition, level 2
 *  has additional alternative read and write functions that take an I/O
 *  handle and callbacks, for situations where access by filename is not
 *  possible.
 *
 *  In addition to the three interfaces, this module defines functions for
 *  creating and manipulating various metadata objects in memory.  As we see
 *  from the Format module, FLAC metadata blocks in memory are very primitive
 *  structures for storing information in an efficient way.  Reading
 *  information from the structures is easy but creating or modifying them
 *  directly is more complex.  The metadata object routines here facilitate
 *  this by taking care of the consistency and memory management drudgery.
 *
 *  Unless you will be using the level 1 or 2 interfaces to modify existing
 *  metadata however, you will not probably not need these.
 *
 *  From a dependency standpoint, none of the encoders or decoders require
 *  the metadata module.  This is so that embedded users can strip out the
 *  metadata module from libFLAC to reduce the size and complexity.
 */

#ifdef __cplusplus
extern "C" {
#endif


/** \defgroup flac_metadata_level0 FLAC/metadata.h: metadata level 0 interface
 *  \ingroup flac_metadata
 *
 *  \brief
 *  The level 0 interface consists of individual routines to read the
 *  STREAMINFO, VORBIS_COMMENT, CUESHEET, and PICTURE blocks, requiring
 *  only a filename.
 *
 *  They try to skip any ID3v2 tag at the head of the file.
 *
 * \{
 */

/** Read the STREAMINFO metadata block of the given FLAC file.  This function
 *  will try to skip any ID3v2 tag at the head of the file.
 *
 * \param filename    The path to the FLAC file to read.
 * \param streaminfo  A pointer to space for the STREAMINFO block.  Since
 *                    FLAC__StreamMetadata is a simple structure with no
 *                    memory allocation involved, you pass the address of
 *                    an existing structure.  It need not be initialized.
 * \assert
 *    \code filename != NULL \endcode
 *    \code streaminfo != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid STREAMINFO block was read from \a filename.  Returns
 *    \c false if there was a memory allocation error, a file decoder error,
 *    or the file contained no STREAMINFO block.  (A memory allocation error
 *    is possible because this function must set up a file decoder.)
 */
FLAC_API FLAC__bool FLAC__metadata_get_streaminfo(const char *filename, FLAC__StreamMetadata *streaminfo);

/** Read the VORBIS_COMMENT metadata block of the given FLAC file.  This
 *  function will try to skip any ID3v2 tag at the head of the file.
 *
 * \param filename    The path to the FLAC file to read.
 * \param tags        The address where the returned pointer will be
 *                    stored.  The \a tags object must be deleted by
 *                    the caller using FLAC__metadata_object_delete().
 * \assert
 *    \code filename != NULL \endcode
 *    \code tags != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid VORBIS_COMMENT block was read from \a filename,
 *    and \a *tags will be set to the address of the metadata structure.
 *    Returns \c false if there was a memory allocation error, a file
 *    decoder error, or the file contained no VORBIS_COMMENT block, and
 *    \a *tags will be set to \c NULL.
 */
FLAC_API FLAC__bool FLAC__metadata_get_tags(const char *filename, FLAC__StreamMetadata **tags);

/** Read the CUESHEET metadata block of the given FLAC file.  This
 *  function will try to skip any ID3v2 tag at the head of the file.
 *
 * \param filename    The path to the FLAC file to read.
 * \param cuesheet    The address where the returned pointer will be
 *                    stored.  The \a cuesheet object must be deleted by
 *                    the caller using FLAC__metadata_object_delete().
 * \assert
 *    \code filename != NULL \endcode
 *    \code cuesheet != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid CUESHEET block was read from \a filename,
 *    and \a *cuesheet will be set to the address of the metadata
 *    structure.  Returns \c false if there was a memory allocation
 *    error, a file decoder error, or the file contained no CUESHEET
 *    block, and \a *cuesheet will be set to \c NULL.
 */
FLAC_API FLAC__bool FLAC__metadata_get_cuesheet(const char *filename, FLAC__StreamMetadata **cuesheet);

/** Read a PICTURE metadata block of the given FLAC file.  This
 *  function will try to skip any ID3v2 tag at the head of the file.
 *  Since there can be more than one PICTURE block in a file, this
 *  function takes a number of parameters that act as constraints to
 *  the search.  The PICTURE block with the largest area matching all
 *  the constraints will be returned, or \a *picture will be set to
 *  \c NULL if there was no such block.
 *
 * \param filename    The path to the FLAC file to read.
 * \param picture     The address where the returned pointer will be
 *                    stored.  The \a picture object must be deleted by
 *                    the caller using FLAC__metadata_object_delete().
 * \param type        The desired picture type.  Use \c -1 to mean
 *                    "any type".
 * \param mime_type   The desired MIME type, e.g. "image/jpeg".  The
 *                    string will be matched exactly.  Use \c NULL to
 *                    mean "any MIME type".
 * \param description The desired description.  The string will be
 *                    matched exactly.  Use \c NULL to mean "any
 *                    description".
 * \param max_width   The maximum width in pixels desired.  Use
 *                    \c (unsigned)(-1) to mean "any width".
 * \param max_height  The maximum height in pixels desired.  Use
 *                    \c (unsigned)(-1) to mean "any height".
 * \param max_depth   The maximum color depth in bits-per-pixel desired.
 *                    Use \c (unsigned)(-1) to mean "any depth".
 * \param max_colors  The maximum number of colors desired.  Use
 *                    \c (unsigned)(-1) to mean "any number of colors".
 * \assert
 *    \code filename != NULL \endcode
 *    \code picture != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid PICTURE block was read from \a filename,
 *    and \a *picture will be set to the address of the metadata
 *    structure.  Returns \c false if there was a memory allocation
 *    error, a file decoder error, or the file contained no PICTURE
 *    block, and \a *picture will be set to \c NULL.
 */
FLAC_API FLAC__bool FLAC__metadata_get_picture(const char *filename, FLAC__StreamMetadata **picture, FLAC__StreamMetadata_Picture_Type type, const char *mime_type, const FLAC__byte *description, unsigned max_width, unsigned max_height, unsigned max_depth, unsigned max_colors);

/* \} */


/** \defgroup flac_metadata_level1 FLAC/metadata.h: metadata level 1 interface
 *  \ingroup flac_metadata
 *
 * \brief
 * The level 1 interface provides read-write access to FLAC file metadata and
 * operates directly on the FLAC file.
 *
 * The general usage of this interface is:
 *
 * - Create an iterator using FLAC__metadata_simple_iterator_new()
 * - Attach it to a file using FLAC__metadata_simple_iterator_init() and check
 *   the exit code.  Call FLAC__metadata_simple_iterator_is_writable() to
 *   see if the file is writable, or only read access is allowed.
 * - Use FLAC__metadata_simple_iterator_next() and
 *   FLAC__metadata_simple_iterator_prev() to traverse the blocks.
 *   This is does not read the actual blocks themselves.
 *   FLAC__metadata_simple_iterator_next() is relatively fast.
 *   FLAC__metadata_simple_iterator_prev() is slower since it needs to search
 *   forward from the front of the file.
 * - Use FLAC__metadata_simple_iterator_get_block_type() or
 *   FLAC__metadata_simple_iterator_get_block() to access the actual data at
 *   the current iterator position.  The returned object is yours to modify
 *   and free.
 * - Use FLAC__metadata_simple_iterator_set_block() to write a modified block
 *   back.  You must have write permission to the original file.  Make sure to
 *   read the whole comment to FLAC__metadata_simple_iterator_set_block()
 *   below.
 * - Use FLAC__metadata_simple_iterator_insert_block_after() to add new blocks.
 *   Use the object creation functions from
 *   \link flac_metadata_object here \endlink to generate new objects.
 * - Use FLAC__metadata_simple_iterator_delete_block() to remove the block
 *   currently referred to by the iterator, or replace it with padding.
 * - Destroy the iterator with FLAC__metadata_simple_iterator_delete() when
 *   finished.
 *
 * \note
 * The FLAC file remains open the whole time between
 * FLAC__metadata_simple_iterator_init() and
 * FLAC__metadata_simple_iterator_delete(), so make sure you are not altering
 * the file during this time.
 *
 * \note
 * Do not modify the \a is_last, \a length, or \a type fields of returned
 * FLAC__StreamMetadata objects.  These are managed automatically.
 *
 * \note
 * If any of the modification functions
 * (FLAC__metadata_simple_iterator_set_block(),
 * FLAC__metadata_simple_iterator_delete_block(),
 * FLAC__metadata_simple_iterator_insert_block_after(), etc.) return \c false,
 * you should delete the iterator as it may no longer be valid.
 *
 * \{
 */

struct FLAC__Metadata_SimpleIterator;
/** The opaque structure definition for the level 1 iterator type.
 *  See the
 *  \link flac_metadata_level1 metadata level 1 module \endlink
 *  for a detailed description.
 */
typedef struct FLAC__Metadata_SimpleIterator FLAC__Metadata_SimpleIterator;

/** Status type for FLAC__Metadata_SimpleIterator.
 *
 *  The iterator's current status can be obtained by calling FLAC__metadata_simple_iterator_status().
 */
typedef enum {

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK = 0,
	/**< The iterator is in the normal OK state */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT,
	/**< The data passed into a function violated the function's usage criteria */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE,
	/**< The iterator could not open the target file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE,
	/**< The iterator could not find the FLAC signature at the start of the file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE,
	/**< The iterator tried to write to a file that was not writable */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA,
	/**< The iterator encountered input that does not conform to the FLAC metadata specification */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR,
	/**< The iterator encountered an error while reading the FLAC file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR,
	/**< The iterator encountered an error while seeking in the FLAC file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR,
	/**< The iterator encountered an error while writing the FLAC file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR,
	/**< The iterator encountered an error renaming the FLAC file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR,
	/**< The iterator encountered an error removing the temporary file */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR,
	/**< Memory allocation failed */

	FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR
	/**< The caller violated an assertion or an unexpected error occurred */

} FLAC__Metadata_SimpleIteratorStatus;

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


/** Create a new iterator instance.
 *
 * \retval FLAC__Metadata_SimpleIterator*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC_API FLAC__Metadata_SimpleIterator *FLAC__metadata_simple_iterator_new(void);

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

/** Get the current status of the iterator.  Call this after a function
 *  returns \c false to get the reason for the error.  Also resets the status
 *  to FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK.
 *
 * \param iterator  A pointer to an existing iterator.
 * \assert
 *    \code iterator != NULL \endcode
 * \retval FLAC__Metadata_SimpleIteratorStatus
 *    The current status of the iterator.
 */
FLAC_API FLAC__Metadata_SimpleIteratorStatus FLAC__metadata_simple_iterator_status(FLAC__Metadata_SimpleIterator *iterator);

/** Initialize the iterator to point to the first metadata block in the
 *  given FLAC file.
 *
 * \param iterator             A pointer to an existing iterator.
 * \param filename             The path to the FLAC file.
 * \param read_only            If \c true, the FLAC file will be opened
 *                             in read-only mode; if \c false, the FLAC
 *                             file will be opened for edit even if no
 *                             edits are performed.
 * \param preserve_file_stats  If \c true, the owner and modification
 *                             time will be preserved even if the FLAC
 *                             file is written to.
 * \assert
 *    \code iterator != NULL \endcode
 *    \code filename != NULL \endcode
 * \retval FLAC__bool
 *    \c false if a memory allocation error occurs, the file can't be
 *    opened, or another error occurs, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_init(FLAC__Metadata_SimpleIterator *iterator, const char *filename, FLAC__bool read_only, FLAC__bool preserve_file_stats);

/** Returns \c true if the FLAC file is writable.  If \c false, calls to
 *  FLAC__metadata_simple_iterator_set_block() and
 *  FLAC__metadata_simple_iterator_insert_block_after() will fail.
 *
 * \param iterator             A pointer to an existing iterator.
 * \assert
 *    \code iterator != NULL \endcode
 * \retval FLAC__bool
 *    See above.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_writable(const FLAC__Metadata_SimpleIterator *iterator);

/** Moves the iterator forward one metadata block, returning \c false if
 *  already at the end.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__bool
 *    \c false if already at the last metadata block of the chain, else
 *    \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_next(FLAC__Metadata_SimpleIterator *iterator);

/** Moves the iterator backward one metadata block, returning \c false if
 *  already at the beginning.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__bool
 *    \c false if already at the first metadata block of the chain, else
 *    \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_prev(FLAC__Metadata_SimpleIterator *iterator);

/** Returns a flag telling if the current metadata block is the last.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__bool
 *    \c true if the current metadata block is the last in the file,
 *    else \c false.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_last(const FLAC__Metadata_SimpleIterator *iterator);

/** Get the offset of the metadata block at the current position.  This
 *  avoids reading the actual block data which can save time for large
 *  blocks.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval off_t
 *    The offset of the metadata block at the current iterator position.
 *    This is the byte offset relative to the beginning of the file of
 *    the current metadata block's header.
 */
FLAC_API off_t FLAC__metadata_simple_iterator_get_block_offset(const FLAC__Metadata_SimpleIterator *iterator);

/** Get the type of the metadata block at the current position.  This
 *  avoids reading the actual block data which can save time for large
 *  blocks.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__MetadataType
 *    The type of the metadata block at the current iterator position.
 */
FLAC_API FLAC__MetadataType FLAC__metadata_simple_iterator_get_block_type(const FLAC__Metadata_SimpleIterator *iterator);

/** Get the length of the metadata block at the current position.  This
 *  avoids reading the actual block data which can save time for large
 *  blocks.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval unsigned
 *    The length of the metadata block at the current iterator position.
 *    The is same length as that in the
 *    <a href="http://xiph.org/flac/format.html#metadata_block_header">metadata block header</a>,
 *    i.e. the length of the metadata body that follows the header.
 */
FLAC_API unsigned FLAC__metadata_simple_iterator_get_block_length(const FLAC__Metadata_SimpleIterator *iterator);

/** Get the application ID of the \c APPLICATION block at the current
 *  position.  This avoids reading the actual block data which can save
 *  time for large blocks.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \param id        A pointer to a buffer of at least \c 4 bytes where
 *                  the ID will be stored.
 * \assert
 *    \code iterator != NULL \endcode
 *    \code id != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__bool
 *    \c true if the ID was successfully read, else \c false, in which
 *    case you should check FLAC__metadata_simple_iterator_status() to
 *    find out why.  If the status is
 *    \c FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT, then the
 *    current metadata block is not an \c APPLICATION block.  Otherwise
 *    if the status is
 *    \c FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR or
 *    \c FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR, an I/O error
 *    occurred and the iterator can no longer be used.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_get_application_id(FLAC__Metadata_SimpleIterator *iterator, FLAC__byte *id);

/** Get the metadata block at the current position.  You can modify the
 *  block but must use FLAC__metadata_simple_iterator_set_block() to
 *  write it back to the FLAC file.
 *
 *  You must call FLAC__metadata_object_delete() on the returned object
 *  when you are finished with it.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__StreamMetadata*
 *    The current metadata block, or \c NULL if there was a memory
 *    allocation error.
 */
FLAC_API FLAC__StreamMetadata *FLAC__metadata_simple_iterator_get_block(FLAC__Metadata_SimpleIterator *iterator);

/** Write a block back to the FLAC file.  This function tries to be
 *  as efficient as possible; how the block is actually written is
 *  shown by the following:
 *
 *  Existing block is a STREAMINFO block and the new block is a
 *  STREAMINFO block: the new block is written in place.  Make sure
 *  you know what you're doing when changing the values of a
 *  STREAMINFO block.
 *
 *  Existing block is a STREAMINFO block and the new block is a
 *  not a STREAMINFO block: this is an error since the first block
 *  must be a STREAMINFO block.  Returns \c false without altering the
 *  file.
 *
 *  Existing block is not a STREAMINFO block and the new block is a
 *  STREAMINFO block: this is an error since there may be only one
 *  STREAMINFO block.  Returns \c false without altering the file.
 *
 *  Existing block and new block are the same length: the existing
 *  block will be replaced by the new block, written in place.
 *
 *  Existing block is longer than new block: if use_padding is \c true,
 *  the existing block will be overwritten in place with the new
 *  block followed by a PADDING block, if possible, to make the total
 *  size the same as the existing block.  Remember that a padding
 *  block requires at least four bytes so if the difference in size
 *  between the new block and existing block is less than that, the
 *  entire file will have to be rewritten, using the new block's
 *  exact size.  If use_padding is \c false, the entire file will be
 *  rewritten, replacing the existing block by the new block.
 *
 *  Existing block is shorter than new block: if use_padding is \c true,
 *  the function will try and expand the new block into the following
 *  PADDING block, if it exists and doing so won't shrink the PADDING
 *  block to less than 4 bytes.  If there is no following PADDING
 *  block, or it will shrink to less than 4 bytes, or use_padding is
 *  \c false, the entire file is rewritten, replacing the existing block
 *  with the new block.  Note that in this case any following PADDING
 *  block is preserved as is.
 *
 *  After writing the block, the iterator will remain in the same
 *  place, i.e. pointing to the new block.
 *
 * \param iterator     A pointer to an existing initialized iterator.
 * \param block        The block to set.
 * \param use_padding  See above.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 *    \code block != NULL \endcode
 * \retval FLAC__bool
 *    \c true if successful, else \c false.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_set_block(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool use_padding);

/** This is similar to FLAC__metadata_simple_iterator_set_block()
 *  except that instead of writing over an existing block, it appends
 *  a block after the existing block.  \a use_padding is again used to
 *  tell the function to try an expand into following padding in an
 *  attempt to avoid rewriting the entire file.
 *
 *  This function will fail and return \c false if given a STREAMINFO
 *  block.
 *
 *  After writing the block, the iterator will be pointing to the
 *  new block.
 *
 * \param iterator     A pointer to an existing initialized iterator.
 * \param block        The block to set.
 * \param use_padding  See above.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 *    \code block != NULL \endcode
 * \retval FLAC__bool
 *    \c true if successful, else \c false.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_insert_block_after(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool use_padding);

/** Deletes the block at the current position.  This will cause the
 *  entire FLAC file to be rewritten, unless \a use_padding is \c true,
 *  in which case the block will be replaced by an equal-sized PADDING
 *  block.  The iterator will be left pointing to the block before the
 *  one just deleted.
 *
 *  You may not delete the STREAMINFO block.
 *
 * \param iterator     A pointer to an existing initialized iterator.
 * \param use_padding  See above.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_simple_iterator_init()
 * \retval FLAC__bool
 *    \c true if successful, else \c false.
 */
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_delete_block(FLAC__Metadata_SimpleIterator *iterator, FLAC__bool use_padding);

/* \} */


/** \defgroup flac_metadata_level2 FLAC/metadata.h: metadata level 2 interface
 *  \ingroup flac_metadata
 *
 * \brief
 * The level 2 interface provides read-write access to FLAC file metadata;
 * all metadata is read into memory, operated on in memory, and then written
 * to file, which is more efficient than level 1 when editing multiple blocks.
 *
 * Currently Ogg FLAC is supported for read only, via
 * FLAC__metadata_chain_read_ogg() but a subsequent
 * FLAC__metadata_chain_write() will fail.
 *
 * The general usage of this interface is:
 *
 * - Create a new chain using FLAC__metadata_chain_new().  A chain is a
 *   linked list of FLAC metadata blocks.
 * - Read all metadata into the the chain from a FLAC file using
 *   FLAC__metadata_chain_read() or FLAC__metadata_chain_read_ogg() and
 *   check the status.
 * - Optionally, consolidate the padding using
 *   FLAC__metadata_chain_merge_padding() or
 *   FLAC__metadata_chain_sort_padding().
 * - Create a new iterator using FLAC__metadata_iterator_new()
 * - Initialize the iterator to point to the first element in the chain
 *   using FLAC__metadata_iterator_init()
 * - Traverse the chain using FLAC__metadata_iterator_next and
 *   FLAC__metadata_iterator_prev().
 * - Get a block for reading or modification using
 *   FLAC__metadata_iterator_get_block().  The pointer to the object
 *   inside the chain is returned, so the block is yours to modify.
 *   Changes will be reflected in the FLAC file when you write the
 *   chain.  You can also add and delete blocks (see functions below).
 * - When done, write out the chain using FLAC__metadata_chain_write().
 *   Make sure to read the whole comment to the function below.
 * - Delete the chain using FLAC__metadata_chain_delete().
 *
 * \note
 * Even though the FLAC file is not open while the chain is being
 * manipulated, you must not alter the file externally during
 * this time.  The chain assumes the FLAC file will not change
 * between the time of FLAC__metadata_chain_read()/FLAC__metadata_chain_read_ogg()
 * and FLAC__metadata_chain_write().
 *
 * \note
 * Do not modify the is_last, length, or type fields of returned
 * FLAC__StreamMetadata objects.  These are managed automatically.
 *
 * \note
 * The metadata objects returned by FLAC__metadata_iterator_get_block()
 * are owned by the chain; do not FLAC__metadata_object_delete() them.
 * In the same way, blocks passed to FLAC__metadata_iterator_set_block()
 * become owned by the chain and they will be deleted when the chain is
 * deleted.
 *
 * \{
 */

struct FLAC__Metadata_Chain;
/** The opaque structure definition for the level 2 chain type.
 */
typedef struct FLAC__Metadata_Chain FLAC__Metadata_Chain;

struct FLAC__Metadata_Iterator;
/** The opaque structure definition for the level 2 iterator type.
 */
typedef struct FLAC__Metadata_Iterator FLAC__Metadata_Iterator;

typedef enum {
	FLAC__METADATA_CHAIN_STATUS_OK = 0,
	/**< The chain is in the normal OK state */

	FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT,
	/**< The data passed into a function violated the function's usage criteria */

	FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE,
	/**< The chain could not open the target file */

	FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE,
	/**< The chain could not find the FLAC signature at the start of the file */

	FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE,
	/**< The chain tried to write to a file that was not writable */

	FLAC__METADATA_CHAIN_STATUS_BAD_METADATA,
	/**< The chain encountered input that does not conform to the FLAC metadata specification */

	FLAC__METADATA_CHAIN_STATUS_READ_ERROR,
	/**< The chain encountered an error while reading the FLAC file */

	FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR,
	/**< The chain encountered an error while seeking in the FLAC file */

	FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR,
	/**< The chain encountered an error while writing the FLAC file */

	FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR,
	/**< The chain encountered an error renaming the FLAC file */

	FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR,
	/**< The chain encountered an error removing the temporary file */

	FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR,
	/**< Memory allocation failed */

	FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR,
	/**< The caller violated an assertion or an unexpected error occurred */

	FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS,
	/**< One or more of the required callbacks was NULL */

	FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH,
	/**< FLAC__metadata_chain_write() was called on a chain read by
	 *   FLAC__metadata_chain_read_with_callbacks()/FLAC__metadata_chain_read_ogg_with_callbacks(),
	 *   or
	 *   FLAC__metadata_chain_write_with_callbacks()/FLAC__metadata_chain_write_with_callbacks_and_tempfile()
	 *   was called on a chain read by
	 *   FLAC__metadata_chain_read()/FLAC__metadata_chain_read_ogg().
	 *   Matching read/write methods must always be used. */

	FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL
	/**< FLAC__metadata_chain_write_with_callbacks() was called when the
	 *   chain write requires a tempfile; use
	 *   FLAC__metadata_chain_write_with_callbacks_and_tempfile() instead.
	 *   Or, FLAC__metadata_chain_write_with_callbacks_and_tempfile() was
	 *   called when the chain write does not require a tempfile; use
	 *   FLAC__metadata_chain_write_with_callbacks() instead.
	 *   Always check FLAC__metadata_chain_check_if_tempfile_needed()
	 *   before writing via callbacks. */

} FLAC__Metadata_ChainStatus;

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

/*********** FLAC__Metadata_Chain ***********/

/** Create a new chain instance.
 *
 * \retval FLAC__Metadata_Chain*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC_API FLAC__Metadata_Chain *FLAC__metadata_chain_new(void);

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

/** Get the current status of the chain.  Call this after a function
 *  returns \c false to get the reason for the error.  Also resets the
 *  status to FLAC__METADATA_CHAIN_STATUS_OK.
 *
 * \param chain    A pointer to an existing chain.
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__Metadata_ChainStatus
 *    The current status of the chain.
 */
FLAC_API FLAC__Metadata_ChainStatus FLAC__metadata_chain_status(FLAC__Metadata_Chain *chain);

/** Read all metadata from a FLAC file into the chain.
 *
 * \param chain    A pointer to an existing chain.
 * \param filename The path to the FLAC file to read.
 * \assert
 *    \code chain != NULL \endcode
 *    \code filename != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid list of metadata blocks was read from
 *    \a filename, else \c false.  On failure, check the status with
 *    FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_read(FLAC__Metadata_Chain *chain, const char *filename);

/** Read all metadata from an Ogg FLAC file into the chain.
 *
 * \note Ogg FLAC metadata data writing is not supported yet and
 * FLAC__metadata_chain_write() will fail.
 *
 * \param chain    A pointer to an existing chain.
 * \param filename The path to the Ogg FLAC file to read.
 * \assert
 *    \code chain != NULL \endcode
 *    \code filename != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid list of metadata blocks was read from
 *    \a filename, else \c false.  On failure, check the status with
 *    FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg(FLAC__Metadata_Chain *chain, const char *filename);

/** Read all metadata from a FLAC stream into the chain via I/O callbacks.
 *
 *  The \a handle need only be open for reading, but must be seekable.
 *  The equivalent minimum stdio fopen() file mode is \c "r" (or \c "rb"
 *  for Windows).
 *
 * \param chain    A pointer to an existing chain.
 * \param handle   The I/O handle of the FLAC stream to read.  The
 *                 handle will NOT be closed after the metadata is read;
 *                 that is the duty of the caller.
 * \param callbacks
 *                 A set of callbacks to use for I/O.  The mandatory
 *                 callbacks are \a read, \a seek, and \a tell.
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid list of metadata blocks was read from
 *    \a handle, else \c false.  On failure, check the status with
 *    FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_read_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks);

/** Read all metadata from an Ogg FLAC stream into the chain via I/O callbacks.
 *
 *  The \a handle need only be open for reading, but must be seekable.
 *  The equivalent minimum stdio fopen() file mode is \c "r" (or \c "rb"
 *  for Windows).
 *
 * \note Ogg FLAC metadata data writing is not supported yet and
 * FLAC__metadata_chain_write() will fail.
 *
 * \param chain    A pointer to an existing chain.
 * \param handle   The I/O handle of the Ogg FLAC stream to read.  The
 *                 handle will NOT be closed after the metadata is read;
 *                 that is the duty of the caller.
 * \param callbacks
 *                 A set of callbacks to use for I/O.  The mandatory
 *                 callbacks are \a read, \a seek, and \a tell.
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__bool
 *    \c true if a valid list of metadata blocks was read from
 *    \a handle, else \c false.  On failure, check the status with
 *    FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks);

/** Checks if writing the given chain would require the use of a
 *  temporary file, or if it could be written in place.
 *
 *  Under certain conditions, padding can be utilized so that writing
 *  edited metadata back to the FLAC file does not require rewriting the
 *  entire file.  If rewriting is required, then a temporary workfile is
 *  required.  When writing metadata using callbacks, you must check
 *  this function to know whether to call
 *  FLAC__metadata_chain_write_with_callbacks() or
 *  FLAC__metadata_chain_write_with_callbacks_and_tempfile().  When
 *  writing with FLAC__metadata_chain_write(), the temporary file is
 *  handled internally.
 *
 * \param chain    A pointer to an existing chain.
 * \param use_padding
 *                 Whether or not padding will be allowed to be used
 *                 during the write.  The value of \a use_padding given
 *                 here must match the value later passed to
 *                 FLAC__metadata_chain_write_with_callbacks() or
 *                 FLAC__metadata_chain_write_with_callbacks_with_tempfile().
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__bool
 *    \c true if writing the current chain would require a tempfile, or
 *    \c false if metadata can be written in place.
 */
FLAC_API FLAC__bool FLAC__metadata_chain_check_if_tempfile_needed(FLAC__Metadata_Chain *chain, FLAC__bool use_padding);

/** Write all metadata out to the FLAC file.  This function tries to be as
 *  efficient as possible; how the metadata is actually written is shown by
 *  the following:
 *
 *  If the current chain is the same size as the existing metadata, the new
 *  data is written in place.
 *
 *  If the current chain is longer than the existing metadata, and
 *  \a use_padding is \c true, and the last block is a PADDING block of
 *  sufficient length, the function will truncate the final padding block
 *  so that the overall size of the metadata is the same as the existing
 *  metadata, and then just rewrite the metadata.  Otherwise, if not all of
 *  the above conditions are met, the entire FLAC file must be rewritten.
 *  If you want to use padding this way it is a good idea to call
 *  FLAC__metadata_chain_sort_padding() first so that you have the maximum
 *  amount of padding to work with, unless you need to preserve ordering
 *  of the PADDING blocks for some reason.
 *
 *  If the current chain is shorter than the existing metadata, and
 *  \a use_padding is \c true, and the final block is a PADDING block, the padding
 *  is extended to make the overall size the same as the existing data.  If
 *  \a use_padding is \c true and the last block is not a PADDING block, a new
 *  PADDING block is added to the end of the new data to make it the same
 *  size as the existing data (if possible, see the note to
 *  FLAC__metadata_simple_iterator_set_block() about the four byte limit)
 *  and the new data is written in place.  If none of the above apply or
 *  \a use_padding is \c false, the entire FLAC file is rewritten.
 *
 *  If \a preserve_file_stats is \c true, the owner and modification time will
 *  be preserved even if the FLAC file is written.
 *
 *  For this write function to be used, the chain must have been read with
 *  FLAC__metadata_chain_read()/FLAC__metadata_chain_read_ogg(), not
 *  FLAC__metadata_chain_read_with_callbacks()/FLAC__metadata_chain_read_ogg_with_callbacks().
 *
 * \param chain               A pointer to an existing chain.
 * \param use_padding         See above.
 * \param preserve_file_stats See above.
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__bool
 *    \c true if the write succeeded, else \c false.  On failure,
 *    check the status with FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_write(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__bool preserve_file_stats);

/** Write all metadata out to a FLAC stream via callbacks.
 *
 *  (See FLAC__metadata_chain_write() for the details on how padding is
 *  used to write metadata in place if possible.)
 *
 *  The \a handle must be open for updating and be seekable.  The
 *  equivalent minimum stdio fopen() file mode is \c "r+" (or \c "r+b"
 *  for Windows).
 *
 *  For this write function to be used, the chain must have been read with
 *  FLAC__metadata_chain_read_with_callbacks()/FLAC__metadata_chain_read_ogg_with_callbacks(),
 *  not FLAC__metadata_chain_read()/FLAC__metadata_chain_read_ogg().
 *  Also, FLAC__metadata_chain_check_if_tempfile_needed() must have returned
 *  \c false.
 *
 * \param chain        A pointer to an existing chain.
 * \param use_padding  See FLAC__metadata_chain_write()
 * \param handle       The I/O handle of the FLAC stream to write.  The
 *                     handle will NOT be closed after the metadata is
 *                     written; that is the duty of the caller.
 * \param callbacks    A set of callbacks to use for I/O.  The mandatory
 *                     callbacks are \a write and \a seek.
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__bool
 *    \c true if the write succeeded, else \c false.  On failure,
 *    check the status with FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks);

/** Write all metadata out to a FLAC stream via callbacks.
 *
 *  (See FLAC__metadata_chain_write() for the details on how padding is
 *  used to write metadata in place if possible.)
 *
 *  This version of the write-with-callbacks function must be used when
 *  FLAC__metadata_chain_check_if_tempfile_needed() returns true.  In
 *  this function, you must supply an I/O handle corresponding to the
 *  FLAC file to edit, and a temporary handle to which the new FLAC
 *  file will be written.  It is the caller's job to move this temporary
 *  FLAC file on top of the original FLAC file to complete the metadata
 *  edit.
 *
 *  The \a handle must be open for reading and be seekable.  The
 *  equivalent minimum stdio fopen() file mode is \c "r" (or \c "rb"
 *  for Windows).
 *
 *  The \a temp_handle must be open for writing.  The
 *  equivalent minimum stdio fopen() file mode is \c "w" (or \c "wb"
 *  for Windows).  It should be an empty stream, or at least positioned
 *  at the start-of-file (in which case it is the caller's duty to
 *  truncate it on return).
 *
 *  For this write function to be used, the chain must have been read with
 *  FLAC__metadata_chain_read_with_callbacks()/FLAC__metadata_chain_read_ogg_with_callbacks(),
 *  not FLAC__metadata_chain_read()/FLAC__metadata_chain_read_ogg().
 *  Also, FLAC__metadata_chain_check_if_tempfile_needed() must have returned
 *  \c true.
 *
 * \param chain        A pointer to an existing chain.
 * \param use_padding  See FLAC__metadata_chain_write()
 * \param handle       The I/O handle of the original FLAC stream to read.
 *                     The handle will NOT be closed after the metadata is
 *                     written; that is the duty of the caller.
 * \param callbacks    A set of callbacks to use for I/O on \a handle.
 *                     The mandatory callbacks are \a read, \a seek, and
 *                     \a eof.
 * \param temp_handle  The I/O handle of the FLAC stream to write.  The
 *                     handle will NOT be closed after the metadata is
 *                     written; that is the duty of the caller.
 * \param temp_callbacks
 *                     A set of callbacks to use for I/O on temp_handle.
 *                     The only mandatory callback is \a write.
 * \assert
 *    \code chain != NULL \endcode
 * \retval FLAC__bool
 *    \c true if the write succeeded, else \c false.  On failure,
 *    check the status with FLAC__metadata_chain_status().
 */
FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks_and_tempfile(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks, FLAC__IOHandle temp_handle, FLAC__IOCallbacks temp_callbacks);

/** Merge adjacent PADDING blocks into a single block.
 *
 * \note This function does not write to the FLAC file, it only
 * modifies the chain.
 *
 * \warning Any iterator on the current chain will become invalid after this
 * call.  You should delete the iterator and get a new one.
 *
 * \param chain               A pointer to an existing chain.
 * \assert
 *    \code chain != NULL \endcode
 */
FLAC_API void FLAC__metadata_chain_merge_padding(FLAC__Metadata_Chain *chain);

/** This function will move all PADDING blocks to the end on the metadata,
 *  then merge them into a single block.
 *
 * \note This function does not write to the FLAC file, it only
 * modifies the chain.
 *
 * \warning Any iterator on the current chain will become invalid after this
 * call.  You should delete the iterator and get a new one.
 *
 * \param chain  A pointer to an existing chain.
 * \assert
 *    \code chain != NULL \endcode
 */
FLAC_API void FLAC__metadata_chain_sort_padding(FLAC__Metadata_Chain *chain);


/*********** FLAC__Metadata_Iterator ***********/

/** Create a new iterator instance.
 *
 * \retval FLAC__Metadata_Iterator*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC_API FLAC__Metadata_Iterator *FLAC__metadata_iterator_new(void);

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

/** Initialize the iterator to point to the first metadata block in the
 *  given chain.
 *
 * \param iterator  A pointer to an existing iterator.
 * \param chain     A pointer to an existing and initialized (read) chain.
 * \assert
 *    \code iterator != NULL \endcode
 *    \code chain != NULL \endcode
 */
FLAC_API void FLAC__metadata_iterator_init(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Chain *chain);

/** Moves the iterator forward one metadata block, returning \c false if
 *  already at the end.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__bool
 *    \c false if already at the last metadata block of the chain, else
 *    \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_iterator_next(FLAC__Metadata_Iterator *iterator);

/** Moves the iterator backward one metadata block, returning \c false if
 *  already at the beginning.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__bool
 *    \c false if already at the first metadata block of the chain, else
 *    \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_iterator_prev(FLAC__Metadata_Iterator *iterator);

/** Get the type of the metadata block at the current position.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__MetadataType
 *    The type of the metadata block at the current iterator position.
 */
FLAC_API FLAC__MetadataType FLAC__metadata_iterator_get_block_type(const FLAC__Metadata_Iterator *iterator);

/** Get the metadata block at the current position.  You can modify
 *  the block in place but must write the chain before the changes
 *  are reflected to the FLAC file.  You do not need to call
 *  FLAC__metadata_iterator_set_block() to reflect the changes;
 *  the pointer returned by FLAC__metadata_iterator_get_block()
 *  points directly into the chain.
 *
 * \warning
 * Do not call FLAC__metadata_object_delete() on the returned object;
 * to delete a block use FLAC__metadata_iterator_delete_block().
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__StreamMetadata*
 *    The current metadata block.
 */
FLAC_API FLAC__StreamMetadata *FLAC__metadata_iterator_get_block(FLAC__Metadata_Iterator *iterator);

/** Set the metadata block at the current position, replacing the existing
 *  block.  The new block passed in becomes owned by the chain and it will be
 *  deleted when the chain is deleted.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \param block     A pointer to a metadata block.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 *    \code block != NULL \endcode
 * \retval FLAC__bool
 *    \c false if the conditions in the above description are not met, or
 *    a memory allocation error occurs, otherwise \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_iterator_set_block(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block);

/** Removes the current block from the chain.  If \a replace_with_padding is
 *  \c true, the block will instead be replaced with a padding block of equal
 *  size.  You can not delete the STREAMINFO block.  The iterator will be
 *  left pointing to the block before the one just "deleted", even if
 *  \a replace_with_padding is \c true.
 *
 * \param iterator              A pointer to an existing initialized iterator.
 * \param replace_with_padding  See above.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__bool
 *    \c false if the conditions in the above description are not met,
 *    otherwise \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_iterator_delete_block(FLAC__Metadata_Iterator *iterator, FLAC__bool replace_with_padding);

/** Insert a new block before the current block.  You cannot insert a block
 *  before the first STREAMINFO block.  You cannot insert a STREAMINFO block
 *  as there can be only one, the one that already exists at the head when you
 *  read in a chain.  The chain takes ownership of the new block and it will be
 *  deleted when the chain is deleted.  The iterator will be left pointing to
 *  the new block.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \param block     A pointer to a metadata block to insert.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__bool
 *    \c false if the conditions in the above description are not met, or
 *    a memory allocation error occurs, otherwise \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_before(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block);

/** Insert a new block after the current block.  You cannot insert a STREAMINFO
 *  block as there can be only one, the one that already exists at the head when
 *  you read in a chain.  The chain takes ownership of the new block and it will
 *  be deleted when the chain is deleted.  The iterator will be left pointing to
 *  the new block.
 *
 * \param iterator  A pointer to an existing initialized iterator.
 * \param block     A pointer to a metadata block to insert.
 * \assert
 *    \code iterator != NULL \endcode
 *    \a iterator has been successfully initialized with
 *    FLAC__metadata_iterator_init()
 * \retval FLAC__bool
 *    \c false if the conditions in the above description are not met, or
 *    a memory allocation error occurs, otherwise \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_after(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block);

/* \} */


/** \defgroup flac_metadata_object FLAC/metadata.h: metadata object methods
 *  \ingroup flac_metadata
 *
 * \brief
 * This module contains methods for manipulating FLAC metadata objects.
 *
 * Since many are variable length we have to be careful about the memory
 * management.  We decree that all pointers to data in the object are
 * owned by the object and memory-managed by the object.
 *
 * Use the FLAC__metadata_object_new() and FLAC__metadata_object_delete()
 * functions to create all instances.  When using the
 * FLAC__metadata_object_set_*() functions to set pointers to data, set
 * \a copy to \c true to have the function make it's own copy of the data, or
 * to \c false to give the object ownership of your data.  In the latter case
 * your pointer must be freeable by free() and will be free()d when the object
 * is FLAC__metadata_object_delete()d.  It is legal to pass a null pointer as
 * the data pointer to a FLAC__metadata_object_set_*() function as long as
 * the length argument is 0 and the \a copy argument is \c false.
 *
 * The FLAC__metadata_object_new() and FLAC__metadata_object_clone() function
 * will return \c NULL in the case of a memory allocation error, otherwise a new
 * object.  The FLAC__metadata_object_set_*() functions return \c false in the
 * case of a memory allocation error.
 *
 * We don't have the convenience of C++ here, so note that the library relies
 * on you to keep the types straight.  In other words, if you pass, for
 * example, a FLAC__StreamMetadata* that represents a STREAMINFO block to
 * FLAC__metadata_object_application_set_data(), you will get an assertion
 * failure.
 *
 * For convenience the FLAC__metadata_object_vorbiscomment_*() functions
 * maintain a trailing NUL on each Vorbis comment entry.  This is not counted
 * toward the length or stored in the stream, but it can make working with plain
 * comments (those that don't contain embedded-NULs in the value) easier.
 * Entries passed into these functions have trailing NULs added if missing, and
 * returned entries are guaranteed to have a trailing NUL.
 *
 * The FLAC__metadata_object_vorbiscomment_*() functions that take a Vorbis
 * comment entry/name/value will first validate that it complies with the Vorbis
 * comment specification and return false if it does not.
 *
 * There is no need to recalculate the length field on metadata blocks you
 * have modified.  They will be calculated automatically before they  are
 * written back to a file.
 *
 * \{
 */


/** Create a new metadata object instance of the given type.
 *
 *  The object will be "empty"; i.e. values and data pointers will be \c 0,
 *  with the exception of FLAC__METADATA_TYPE_VORBIS_COMMENT, which will have
 *  the vendor string set (but zero comments).
 *
 *  Do not pass in a value greater than or equal to
 *  \a FLAC__METADATA_TYPE_UNDEFINED unless you really know what you're
 *  doing.
 *
 * \param type  Type of object to create
 * \retval FLAC__StreamMetadata*
 *    \c NULL if there was an error allocating memory or the type code is
 *    greater than FLAC__MAX_METADATA_TYPE_CODE, else the new instance.
 */
FLAC_API FLAC__StreamMetadata *FLAC__metadata_object_new(FLAC__MetadataType type);

/** Create a copy of an existing metadata object.
 *
 *  The copy is a "deep" copy, i.e. dynamically allocated data within the
 *  object is also copied.  The caller takes ownership of the new block and
 *  is responsible for freeing it with FLAC__metadata_object_delete().
 *
 * \param object  Pointer to object to copy.
 * \assert
 *    \code object != NULL \endcode
 * \retval FLAC__StreamMetadata*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC_API FLAC__StreamMetadata *FLAC__metadata_object_clone(const FLAC__StreamMetadata *object);

/** Free a metadata object.  Deletes the object pointed to by \a object.
 *
 *  The delete is a "deep" delete, i.e. dynamically allocated data within the
 *  object is also deleted.
 *
 * \param object  A pointer to an existing object.
 * \assert
 *    \code object != NULL \endcode
 */
FLAC_API void FLAC__metadata_object_delete(FLAC__StreamMetadata *object);

/** Compares two metadata objects.
 *
 *  The compare is "deep", i.e. dynamically allocated data within the
 *  object is also compared.
 *
 * \param block1  A pointer to an existing object.
 * \param block2  A pointer to an existing object.
 * \assert
 *    \code block1 != NULL \endcode
 *    \code block2 != NULL \endcode
 * \retval FLAC__bool
 *    \c true if objects are identical, else \c false.
 */
FLAC_API FLAC__bool FLAC__metadata_object_is_equal(const FLAC__StreamMetadata *block1, const FLAC__StreamMetadata *block2);

/** Sets the application data of an APPLICATION block.
 *
 *  If \a copy is \c true, a copy of the data is stored; otherwise, the object
 *  takes ownership of the pointer.  The existing data will be freed if this
 *  function is successful, otherwise the original data will remain if \a copy
 *  is \c true and malloc() fails.
 *
 * \note It is safe to pass a const pointer to \a data if \a copy is \c true.
 *
 * \param object  A pointer to an existing APPLICATION object.
 * \param data    A pointer to the data to set.
 * \param length  The length of \a data in bytes.
 * \param copy    See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_APPLICATION \endcode
 *    \code (data != NULL && length > 0) ||
 * (data == NULL && length == 0 && copy == false) \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_application_set_data(FLAC__StreamMetadata *object, FLAC__byte *data, unsigned length, FLAC__bool copy);

/** Resize the seekpoint array.
 *
 *  If the size shrinks, elements will truncated; if it grows, new placeholder
 *  points will be added to the end.
 *
 * \param object          A pointer to an existing SEEKTABLE object.
 * \param new_num_points  The desired length of the array; may be \c 0.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 *    \code (object->data.seek_table.points == NULL && object->data.seek_table.num_points == 0) ||
 * (object->data.seek_table.points != NULL && object->data.seek_table.num_points > 0) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation error, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_resize_points(FLAC__StreamMetadata *object, unsigned new_num_points);

/** Set a seekpoint in a seektable.
 *
 * \param object     A pointer to an existing SEEKTABLE object.
 * \param point_num  Index into seekpoint array to set.
 * \param point      The point to set.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 *    \code object->data.seek_table.num_points > point_num \endcode
 */
FLAC_API void FLAC__metadata_object_seektable_set_point(FLAC__StreamMetadata *object, unsigned point_num, FLAC__StreamMetadata_SeekPoint point);

/** Insert a seekpoint into a seektable.
 *
 * \param object     A pointer to an existing SEEKTABLE object.
 * \param point_num  Index into seekpoint array to set.
 * \param point      The point to set.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 *    \code object->data.seek_table.num_points >= point_num \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation error, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_insert_point(FLAC__StreamMetadata *object, unsigned point_num, FLAC__StreamMetadata_SeekPoint point);

/** Delete a seekpoint from a seektable.
 *
 * \param object     A pointer to an existing SEEKTABLE object.
 * \param point_num  Index into seekpoint array to set.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 *    \code object->data.seek_table.num_points > point_num \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation error, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_delete_point(FLAC__StreamMetadata *object, unsigned point_num);

/** Check a seektable to see if it conforms to the FLAC specification.
 *  See the format specification for limits on the contents of the
 *  seektable.
 *
 * \param object  A pointer to an existing SEEKTABLE object.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 * \retval FLAC__bool
 *    \c false if seek table is illegal, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_is_legal(const FLAC__StreamMetadata *object);

/** Append a number of placeholder points to the end of a seek table.
 *
 * \note
 * As with the other ..._seektable_template_... functions, you should
 * call FLAC__metadata_object_seektable_template_sort() when finished
 * to make the seek table legal.
 *
 * \param object  A pointer to an existing SEEKTABLE object.
 * \param num     The number of placeholder points to append.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_template_append_placeholders(FLAC__StreamMetadata *object, unsigned num);

/** Append a specific seek point template to the end of a seek table.
 *
 * \note
 * As with the other ..._seektable_template_... functions, you should
 * call FLAC__metadata_object_seektable_template_sort() when finished
 * to make the seek table legal.
 *
 * \param object  A pointer to an existing SEEKTABLE object.
 * \param sample_number  The sample number of the seek point template.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_template_append_point(FLAC__StreamMetadata *object, FLAC__uint64 sample_number);

/** Append specific seek point templates to the end of a seek table.
 *
 * \note
 * As with the other ..._seektable_template_... functions, you should
 * call FLAC__metadata_object_seektable_template_sort() when finished
 * to make the seek table legal.
 *
 * \param object  A pointer to an existing SEEKTABLE object.
 * \param sample_numbers  An array of sample numbers for the seek points.
 * \param num     The number of seek point templates to append.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_template_append_points(FLAC__StreamMetadata *object, FLAC__uint64 sample_numbers[], unsigned num);

/** Append a set of evenly-spaced seek point templates to the end of a
 *  seek table.
 *
 * \note
 * As with the other ..._seektable_template_... functions, you should
 * call FLAC__metadata_object_seektable_template_sort() when finished
 * to make the seek table legal.
 *
 * \param object  A pointer to an existing SEEKTABLE object.
 * \param num     The number of placeholder points to append.
 * \param total_samples  The total number of samples to be encoded;
 *                       the seekpoints will be spaced approximately
 *                       \a total_samples / \a num samples apart.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 *    \code total_samples > 0 \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_template_append_spaced_points(FLAC__StreamMetadata *object, unsigned num, FLAC__uint64 total_samples);

/** Append a set of evenly-spaced seek point templates to the end of a
 *  seek table.
 *
 * \note
 * As with the other ..._seektable_template_... functions, you should
 * call FLAC__metadata_object_seektable_template_sort() when finished
 * to make the seek table legal.
 *
 * \param object  A pointer to an existing SEEKTABLE object.
 * \param samples The number of samples apart to space the placeholder
 *                points.  The first point will be at sample \c 0, the
 *                second at sample \a samples, then 2*\a samples, and
 *                so on.  As long as \a samples and \a total_samples
 *                are greater than \c 0, there will always be at least
 *                one seekpoint at sample \c 0.
 * \param total_samples  The total number of samples to be encoded;
 *                       the seekpoints will be spaced
 *                       \a samples samples apart.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 *    \code samples > 0 \endcode
 *    \code total_samples > 0 \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_template_append_spaced_points_by_samples(FLAC__StreamMetadata *object, unsigned samples, FLAC__uint64 total_samples);

/** Sort a seek table's seek points according to the format specification,
 *  removing duplicates.
 *
 * \param object   A pointer to a seek table to be sorted.
 * \param compact  If \c false, behaves like FLAC__format_seektable_sort().
 *                 If \c true, duplicates are deleted and the seek table is
 *                 shrunk appropriately; the number of placeholder points
 *                 present in the seek table will be the same after the call
 *                 as before.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_SEEKTABLE \endcode
 * \retval FLAC__bool
 *    \c false if realloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_seektable_template_sort(FLAC__StreamMetadata *object, FLAC__bool compact);

/** Sets the vendor string in a VORBIS_COMMENT block.
 *
 *  For convenience, a trailing NUL is added to the entry if it doesn't have
 *  one already.
 *
 *  If \a copy is \c true, a copy of the entry is stored; otherwise, the object
 *  takes ownership of the \c entry.entry pointer.
 *
 *  \note If this function returns \c false, the caller still owns the
 *  pointer.
 *
 * \param object  A pointer to an existing VORBIS_COMMENT object.
 * \param entry   The entry to set the vendor string to.
 * \param copy    See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code (entry.entry != NULL && entry.length > 0) ||
 * (entry.entry == NULL && entry.length == 0) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails or \a entry does not comply with the
 *    Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_set_vendor_string(FLAC__StreamMetadata *object, FLAC__StreamMetadata_VorbisComment_Entry entry, FLAC__bool copy);

/** Resize the comment array.
 *
 *  If the size shrinks, elements will truncated; if it grows, new empty
 *  fields will be added to the end.
 *
 * \param object            A pointer to an existing VORBIS_COMMENT object.
 * \param new_num_comments  The desired length of the array; may be \c 0.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code (object->data.vorbis_comment.comments == NULL && object->data.vorbis_comment.num_comments == 0) ||
 * (object->data.vorbis_comment.comments != NULL && object->data.vorbis_comment.num_comments > 0) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_resize_comments(FLAC__StreamMetadata *object, unsigned new_num_comments);

/** Sets a comment in a VORBIS_COMMENT block.
 *
 *  For convenience, a trailing NUL is added to the entry if it doesn't have
 *  one already.
 *
 *  If \a copy is \c true, a copy of the entry is stored; otherwise, the object
 *  takes ownership of the \c entry.entry pointer.
 *
 *  \note If this function returns \c false, the caller still owns the
 *  pointer.
 *
 * \param object       A pointer to an existing VORBIS_COMMENT object.
 * \param comment_num  Index into comment array to set.
 * \param entry        The entry to set the comment to.
 * \param copy         See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code comment_num < object->data.vorbis_comment.num_comments \endcode
 *    \code (entry.entry != NULL && entry.length > 0) ||
 * (entry.entry == NULL && entry.length == 0) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails or \a entry does not comply with the
 *    Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_set_comment(FLAC__StreamMetadata *object, unsigned comment_num, FLAC__StreamMetadata_VorbisComment_Entry entry, FLAC__bool copy);

/** Insert a comment in a VORBIS_COMMENT block at the given index.
 *
 *  For convenience, a trailing NUL is added to the entry if it doesn't have
 *  one already.
 *
 *  If \a copy is \c true, a copy of the entry is stored; otherwise, the object
 *  takes ownership of the \c entry.entry pointer.
 *
 *  \note If this function returns \c false, the caller still owns the
 *  pointer.
 *
 * \param object       A pointer to an existing VORBIS_COMMENT object.
 * \param comment_num  The index at which to insert the comment.  The comments
 *                     at and after \a comment_num move right one position.
 *                     To append a comment to the end, set \a comment_num to
 *                     \c object->data.vorbis_comment.num_comments .
 * \param entry        The comment to insert.
 * \param copy         See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code object->data.vorbis_comment.num_comments >= comment_num \endcode
 *    \code (entry.entry != NULL && entry.length > 0) ||
 * (entry.entry == NULL && entry.length == 0 && copy == false) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails or \a entry does not comply with the
 *    Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_insert_comment(FLAC__StreamMetadata *object, unsigned comment_num, FLAC__StreamMetadata_VorbisComment_Entry entry, FLAC__bool copy);

/** Appends a comment to a VORBIS_COMMENT block.
 *
 *  For convenience, a trailing NUL is added to the entry if it doesn't have
 *  one already.
 *
 *  If \a copy is \c true, a copy of the entry is stored; otherwise, the object
 *  takes ownership of the \c entry.entry pointer.
 *
 *  \note If this function returns \c false, the caller still owns the
 *  pointer.
 *
 * \param object       A pointer to an existing VORBIS_COMMENT object.
 * \param entry        The comment to insert.
 * \param copy         See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code (entry.entry != NULL && entry.length > 0) ||
 * (entry.entry == NULL && entry.length == 0 && copy == false) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails or \a entry does not comply with the
 *    Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_append_comment(FLAC__StreamMetadata *object, FLAC__StreamMetadata_VorbisComment_Entry entry, FLAC__bool copy);

/** Replaces comments in a VORBIS_COMMENT block with a new one.
 *
 *  For convenience, a trailing NUL is added to the entry if it doesn't have
 *  one already.
 *
 *  Depending on the the value of \a all, either all or just the first comment
 *  whose field name(s) match the given entry's name will be replaced by the
 *  given entry.  If no comments match, \a entry will simply be appended.
 *
 *  If \a copy is \c true, a copy of the entry is stored; otherwise, the object
 *  takes ownership of the \c entry.entry pointer.
 *
 *  \note If this function returns \c false, the caller still owns the
 *  pointer.
 *
 * \param object       A pointer to an existing VORBIS_COMMENT object.
 * \param entry        The comment to insert.
 * \param all          If \c true, all comments whose field name matches
 *                     \a entry's field name will be removed, and \a entry will
 *                     be inserted at the position of the first matching
 *                     comment.  If \c false, only the first comment whose
 *                     field name matches \a entry's field name will be
 *                     replaced with \a entry.
 * \param copy         See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code (entry.entry != NULL && entry.length > 0) ||
 * (entry.entry == NULL && entry.length == 0 && copy == false) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails or \a entry does not comply with the
 *    Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_replace_comment(FLAC__StreamMetadata *object, FLAC__StreamMetadata_VorbisComment_Entry entry, FLAC__bool all, FLAC__bool copy);

/** Delete a comment in a VORBIS_COMMENT block at the given index.
 *
 * \param object       A pointer to an existing VORBIS_COMMENT object.
 * \param comment_num  The index of the comment to delete.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code object->data.vorbis_comment.num_comments > comment_num \endcode
 * \retval FLAC__bool
 *    \c false if realloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_delete_comment(FLAC__StreamMetadata *object, unsigned comment_num);

/** Creates a Vorbis comment entry from NUL-terminated name and value strings.
 *
 *  On return, the filled-in \a entry->entry pointer will point to malloc()ed
 *  memory and shall be owned by the caller.  For convenience the entry will
 *  have a terminating NUL.
 *
 * \param entry              A pointer to a Vorbis comment entry.  The entry's
 *                           \c entry pointer should not point to allocated
 *                           memory as it will be overwritten.
 * \param field_name         The field name in ASCII, \c NUL terminated.
 * \param field_value        The field value in UTF-8, \c NUL terminated.
 * \assert
 *    \code entry != NULL \endcode
 *    \code field_name != NULL \endcode
 *    \code field_value != NULL \endcode
 * \retval FLAC__bool
 *    \c false if malloc() fails, or if \a field_name or \a field_value does
 *    not comply with the Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_entry_from_name_value_pair(FLAC__StreamMetadata_VorbisComment_Entry *entry, const char *field_name, const char *field_value);

/** Splits a Vorbis comment entry into NUL-terminated name and value strings.
 *
 *  The returned pointers to name and value will be allocated by malloc()
 *  and shall be owned by the caller.
 *
 * \param entry              An existing Vorbis comment entry.
 * \param field_name         The address of where the returned pointer to the
 *                           field name will be stored.
 * \param field_value        The address of where the returned pointer to the
 *                           field value will be stored.
 * \assert
 *    \code (entry.entry != NULL && entry.length > 0) \endcode
 *    \code memchr(entry.entry, '=', entry.length) != NULL \endcode
 *    \code field_name != NULL \endcode
 *    \code field_value != NULL \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation fails or \a entry does not comply with the
 *    Vorbis comment specification, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_entry_to_name_value_pair(const FLAC__StreamMetadata_VorbisComment_Entry entry, char **field_name, char **field_value);

/** Check if the given Vorbis comment entry's field name matches the given
 *  field name.
 *
 * \param entry              An existing Vorbis comment entry.
 * \param field_name         The field name to check.
 * \param field_name_length  The length of \a field_name, not including the
 *                           terminating \c NUL.
 * \assert
 *    \code (entry.entry != NULL && entry.length > 0) \endcode
 * \retval FLAC__bool
 *    \c true if the field names match, else \c false
 */
FLAC_API FLAC__bool FLAC__metadata_object_vorbiscomment_entry_matches(const FLAC__StreamMetadata_VorbisComment_Entry entry, const char *field_name, unsigned field_name_length);

/** Find a Vorbis comment with the given field name.
 *
 *  The search begins at entry number \a offset; use an offset of 0 to
 *  search from the beginning of the comment array.
 *
 * \param object      A pointer to an existing VORBIS_COMMENT object.
 * \param offset      The offset into the comment array from where to start
 *                    the search.
 * \param field_name  The field name of the comment to find.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 *    \code field_name != NULL \endcode
 * \retval int
 *    The offset in the comment array of the first comment whose field
 *    name matches \a field_name, or \c -1 if no match was found.
 */
FLAC_API int FLAC__metadata_object_vorbiscomment_find_entry_from(const FLAC__StreamMetadata *object, unsigned offset, const char *field_name);

/** Remove first Vorbis comment matching the given field name.
 *
 * \param object      A pointer to an existing VORBIS_COMMENT object.
 * \param field_name  The field name of comment to delete.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 * \retval int
 *    \c -1 for memory allocation error, \c 0 for no matching entries,
 *    \c 1 for one matching entry deleted.
 */
FLAC_API int FLAC__metadata_object_vorbiscomment_remove_entry_matching(FLAC__StreamMetadata *object, const char *field_name);

/** Remove all Vorbis comments matching the given field name.
 *
 * \param object      A pointer to an existing VORBIS_COMMENT object.
 * \param field_name  The field name of comments to delete.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_VORBIS_COMMENT \endcode
 * \retval int
 *    \c -1 for memory allocation error, \c 0 for no matching entries,
 *    else the number of matching entries deleted.
 */
FLAC_API int FLAC__metadata_object_vorbiscomment_remove_entries_matching(FLAC__StreamMetadata *object, const char *field_name);

/** Create a new CUESHEET track instance.
 *
 *  The object will be "empty"; i.e. values and data pointers will be \c 0.
 *
 * \retval FLAC__StreamMetadata_CueSheet_Track*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC_API FLAC__StreamMetadata_CueSheet_Track *FLAC__metadata_object_cuesheet_track_new(void);

/** Create a copy of an existing CUESHEET track object.
 *
 *  The copy is a "deep" copy, i.e. dynamically allocated data within the
 *  object is also copied.  The caller takes ownership of the new object and
 *  is responsible for freeing it with
 *  FLAC__metadata_object_cuesheet_track_delete().
 *
 * \param object  Pointer to object to copy.
 * \assert
 *    \code object != NULL \endcode
 * \retval FLAC__StreamMetadata_CueSheet_Track*
 *    \c NULL if there was an error allocating memory, else the new instance.
 */
FLAC_API FLAC__StreamMetadata_CueSheet_Track *FLAC__metadata_object_cuesheet_track_clone(const FLAC__StreamMetadata_CueSheet_Track *object);

/** Delete a CUESHEET track object
 *
 * \param object       A pointer to an existing CUESHEET track object.
 * \assert
 *    \code object != NULL \endcode
 */
FLAC_API void FLAC__metadata_object_cuesheet_track_delete(FLAC__StreamMetadata_CueSheet_Track *object);

/** Resize a track's index point array.
 *
 *  If the size shrinks, elements will truncated; if it grows, new blank
 *  indices will be added to the end.
 *
 * \param object           A pointer to an existing CUESHEET object.
 * \param track_num        The index of the track to modify.  NOTE: this is not
 *                         necessarily the same as the track's \a number field.
 * \param new_num_indices  The desired length of the array; may be \c 0.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks > track_num \endcode
 *    \code (object->data.cue_sheet.tracks[track_num].indices == NULL && object->data.cue_sheet.tracks[track_num].num_indices == 0) ||
 * (object->data.cue_sheet.tracks[track_num].indices != NULL && object->data.cue_sheet.tracks[track_num].num_indices > 0) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation error, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_track_resize_indices(FLAC__StreamMetadata *object, unsigned track_num, unsigned new_num_indices);

/** Insert an index point in a CUESHEET track at the given index.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    The index of the track to modify.  NOTE: this is not
 *                     necessarily the same as the track's \a number field.
 * \param index_num    The index into the track's index array at which to
 *                     insert the index point.  NOTE: this is not necessarily
 *                     the same as the index point's \a number field.  The
 *                     indices at and after \a index_num move right one
 *                     position.  To append an index point to the end, set
 *                     \a index_num to
 *                     \c object->data.cue_sheet.tracks[track_num].num_indices .
 * \param index        The index point to insert.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks > track_num \endcode
 *    \code object->data.cue_sheet.tracks[track_num].num_indices >= index_num \endcode
 * \retval FLAC__bool
 *    \c false if realloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_track_insert_index(FLAC__StreamMetadata *object, unsigned track_num, unsigned index_num, FLAC__StreamMetadata_CueSheet_Index index);

/** Insert a blank index point in a CUESHEET track at the given index.
 *
 *  A blank index point is one in which all field values are zero.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    The index of the track to modify.  NOTE: this is not
 *                     necessarily the same as the track's \a number field.
 * \param index_num    The index into the track's index array at which to
 *                     insert the index point.  NOTE: this is not necessarily
 *                     the same as the index point's \a number field.  The
 *                     indices at and after \a index_num move right one
 *                     position.  To append an index point to the end, set
 *                     \a index_num to
 *                     \c object->data.cue_sheet.tracks[track_num].num_indices .
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks > track_num \endcode
 *    \code object->data.cue_sheet.tracks[track_num].num_indices >= index_num \endcode
 * \retval FLAC__bool
 *    \c false if realloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_track_insert_blank_index(FLAC__StreamMetadata *object, unsigned track_num, unsigned index_num);

/** Delete an index point in a CUESHEET track at the given index.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    The index into the track array of the track to
 *                     modify.  NOTE: this is not necessarily the same
 *                     as the track's \a number field.
 * \param index_num    The index into the track's index array of the index
 *                     to delete.  NOTE: this is not necessarily the same
 *                     as the index's \a number field.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks > track_num \endcode
 *    \code object->data.cue_sheet.tracks[track_num].num_indices > index_num \endcode
 * \retval FLAC__bool
 *    \c false if realloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_track_delete_index(FLAC__StreamMetadata *object, unsigned track_num, unsigned index_num);

/** Resize the track array.
 *
 *  If the size shrinks, elements will truncated; if it grows, new blank
 *  tracks will be added to the end.
 *
 * \param object            A pointer to an existing CUESHEET object.
 * \param new_num_tracks    The desired length of the array; may be \c 0.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code (object->data.cue_sheet.tracks == NULL && object->data.cue_sheet.num_tracks == 0) ||
 * (object->data.cue_sheet.tracks != NULL && object->data.cue_sheet.num_tracks > 0) \endcode
 * \retval FLAC__bool
 *    \c false if memory allocation error, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_resize_tracks(FLAC__StreamMetadata *object, unsigned new_num_tracks);

/** Sets a track in a CUESHEET block.
 *
 *  If \a copy is \c true, a copy of the track is stored; otherwise, the object
 *  takes ownership of the \a track pointer.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    Index into track array to set.  NOTE: this is not
 *                     necessarily the same as the track's \a number field.
 * \param track        The track to set the track to.  You may safely pass in
 *                     a const pointer if \a copy is \c true.
 * \param copy         See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code track_num < object->data.cue_sheet.num_tracks \endcode
 *    \code (track->indices != NULL && track->num_indices > 0) ||
 * (track->indices == NULL && track->num_indices == 0) \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_set_track(FLAC__StreamMetadata *object, unsigned track_num, FLAC__StreamMetadata_CueSheet_Track *track, FLAC__bool copy);

/** Insert a track in a CUESHEET block at the given index.
 *
 *  If \a copy is \c true, a copy of the track is stored; otherwise, the object
 *  takes ownership of the \a track pointer.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    The index at which to insert the track.  NOTE: this
 *                     is not necessarily the same as the track's \a number
 *                     field.  The tracks at and after \a track_num move right
 *                     one position.  To append a track to the end, set
 *                     \a track_num to \c object->data.cue_sheet.num_tracks .
 * \param track        The track to insert.  You may safely pass in a const
 *                     pointer if \a copy is \c true.
 * \param copy         See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks >= track_num \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_insert_track(FLAC__StreamMetadata *object, unsigned track_num, FLAC__StreamMetadata_CueSheet_Track *track, FLAC__bool copy);

/** Insert a blank track in a CUESHEET block at the given index.
 *
 *  A blank track is one in which all field values are zero.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    The index at which to insert the track.  NOTE: this
 *                     is not necessarily the same as the track's \a number
 *                     field.  The tracks at and after \a track_num move right
 *                     one position.  To append a track to the end, set
 *                     \a track_num to \c object->data.cue_sheet.num_tracks .
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks >= track_num \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_insert_blank_track(FLAC__StreamMetadata *object, unsigned track_num);

/** Delete a track in a CUESHEET block at the given index.
 *
 * \param object       A pointer to an existing CUESHEET object.
 * \param track_num    The index into the track array of the track to
 *                     delete.  NOTE: this is not necessarily the same
 *                     as the track's \a number field.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 *    \code object->data.cue_sheet.num_tracks > track_num \endcode
 * \retval FLAC__bool
 *    \c false if realloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_delete_track(FLAC__StreamMetadata *object, unsigned track_num);

/** Check a cue sheet to see if it conforms to the FLAC specification.
 *  See the format specification for limits on the contents of the
 *  cue sheet.
 *
 * \param object     A pointer to an existing CUESHEET object.
 * \param check_cd_da_subset  If \c true, check CUESHEET against more
 *                   stringent requirements for a CD-DA (audio) disc.
 * \param violation  Address of a pointer to a string.  If there is a
 *                   violation, a pointer to a string explanation of the
 *                   violation will be returned here. \a violation may be
 *                   \c NULL if you don't need the returned string.  Do not
 *                   free the returned string; it will always point to static
 *                   data.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 * \retval FLAC__bool
 *    \c false if cue sheet is illegal, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_cuesheet_is_legal(const FLAC__StreamMetadata *object, FLAC__bool check_cd_da_subset, const char **violation);

/** Calculate and return the CDDB/freedb ID for a cue sheet.  The function
 *  assumes the cue sheet corresponds to a CD; the result is undefined
 *  if the cuesheet's is_cd bit is not set.
 *
 * \param object     A pointer to an existing CUESHEET object.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_CUESHEET \endcode
 * \retval FLAC__uint32
 *    The unsigned integer representation of the CDDB/freedb ID
 */
FLAC_API FLAC__uint32 FLAC__metadata_object_cuesheet_calculate_cddb_id(const FLAC__StreamMetadata *object);

/** Sets the MIME type of a PICTURE block.
 *
 *  If \a copy is \c true, a copy of the string is stored; otherwise, the object
 *  takes ownership of the pointer.  The existing string will be freed if this
 *  function is successful, otherwise the original string will remain if \a copy
 *  is \c true and malloc() fails.
 *
 * \note It is safe to pass a const pointer to \a mime_type if \a copy is \c true.
 *
 * \param object      A pointer to an existing PICTURE object.
 * \param mime_type   A pointer to the MIME type string.  The string must be
 *                    ASCII characters 0x20-0x7e, NUL-terminated.  No validation
 *                    is done.
 * \param copy        See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_PICTURE \endcode
 *    \code (mime_type != NULL) \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_picture_set_mime_type(FLAC__StreamMetadata *object, char *mime_type, FLAC__bool copy);

/** Sets the description of a PICTURE block.
 *
 *  If \a copy is \c true, a copy of the string is stored; otherwise, the object
 *  takes ownership of the pointer.  The existing string will be freed if this
 *  function is successful, otherwise the original string will remain if \a copy
 *  is \c true and malloc() fails.
 *
 * \note It is safe to pass a const pointer to \a description if \a copy is \c true.
 *
 * \param object      A pointer to an existing PICTURE object.
 * \param description A pointer to the description string.  The string must be
 *                    valid UTF-8, NUL-terminated.  No validation is done.
 * \param copy        See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_PICTURE \endcode
 *    \code (description != NULL) \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_picture_set_description(FLAC__StreamMetadata *object, FLAC__byte *description, FLAC__bool copy);

/** Sets the picture data of a PICTURE block.
 *
 *  If \a copy is \c true, a copy of the data is stored; otherwise, the object
 *  takes ownership of the pointer.  Also sets the \a data_length field of the
 *  metadata object to what is passed in as the \a length parameter.  The
 *  existing data will be freed if this function is successful, otherwise the
 *  original data and data_length will remain if \a copy is \c true and
 *  malloc() fails.
 *
 * \note It is safe to pass a const pointer to \a data if \a copy is \c true.
 *
 * \param object  A pointer to an existing PICTURE object.
 * \param data    A pointer to the data to set.
 * \param length  The length of \a data in bytes.
 * \param copy    See above.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_PICTURE \endcode
 *    \code (data != NULL && length > 0) ||
 * (data == NULL && length == 0 && copy == false) \endcode
 * \retval FLAC__bool
 *    \c false if \a copy is \c true and malloc() fails, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_picture_set_data(FLAC__StreamMetadata *object, FLAC__byte *data, FLAC__uint32 length, FLAC__bool copy);

/** Check a PICTURE block to see if it conforms to the FLAC specification.
 *  See the format specification for limits on the contents of the
 *  PICTURE block.
 *
 * \param object     A pointer to existing PICTURE block to be checked.
 * \param violation  Address of a pointer to a string.  If there is a
 *                   violation, a pointer to a string explanation of the
 *                   violation will be returned here. \a violation may be
 *                   \c NULL if you don't need the returned string.  Do not
 *                   free the returned string; it will always point to static
 *                   data.
 * \assert
 *    \code object != NULL \endcode
 *    \code object->type == FLAC__METADATA_TYPE_PICTURE \endcode
 * \retval FLAC__bool
 *    \c false if PICTURE block is illegal, else \c true.
 */
FLAC_API FLAC__bool FLAC__metadata_object_picture_is_legal(const FLAC__StreamMetadata *object, const char **violation);

/* \} */

#ifdef __cplusplus
}
#endif

#endif