/src/flac/src/libFLAC/metadata_iterators.c

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/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2001-2009  Josh Coalson
 * Copyright (C) 2011-2024  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
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

#include <sys/stat.h> /* for stat(), maybe chmod() */

#include "private/metadata.h"

#include "FLAC/assert.h"
#include "FLAC/stream_decoder.h"
#include "share/alloc.h"
#include "share/compat.h"
#include "share/macros.h"
#include "private/macros.h"
#include "private/memory.h"

/* Alias the first (in share/alloc.h) to the second (in src/libFLAC/memory.c). */
#define safe_malloc_mul_2op_ safe_malloc_mul_2op_p

/****************************************************************************
 *
 * Local function declarations
 *
 ***************************************************************************/

static void pack_uint32_(FLAC__uint32 val, FLAC__byte *b, uint32_t bytes);
static void pack_uint32_little_endian_(FLAC__uint32 val, FLAC__byte *b, uint32_t bytes);
static void pack_uint64_(FLAC__uint64 val, FLAC__byte *b, uint32_t bytes);
static FLAC__uint32 unpack_uint32_(FLAC__byte *b, uint32_t bytes);
static FLAC__uint32 unpack_uint32_little_endian_(FLAC__byte *b, uint32_t bytes);
static FLAC__uint64 unpack_uint64_(FLAC__byte *b, uint32_t bytes);

static FLAC__bool read_metadata_block_header_(FLAC__Metadata_SimpleIterator *iterator);
static FLAC__bool read_metadata_block_data_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block);
static FLAC__bool read_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__bool *is_last, FLAC__MetadataType *type, uint32_t *length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata *block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_StreamInfo *block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding *block, uint32_t block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application *block, uint32_t block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable *block, uint32_t block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry, uint32_t max_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_VorbisComment *block, uint32_t block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track *track);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet *block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture *block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Unknown *block, uint32_t block_length);

static FLAC__bool write_metadata_block_header_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block);
static FLAC__bool write_metadata_block_data_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block);
static FLAC__bool write_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block);
static FLAC__bool write_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block);
static FLAC__bool write_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_StreamInfo *block);
static FLAC__bool write_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Padding *block, uint32_t block_length);
static FLAC__bool write_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Application *block, uint32_t block_length);
static FLAC__bool write_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_SeekTable *block);
static FLAC__bool write_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_VorbisComment *block);
static FLAC__bool write_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_CueSheet *block);
static FLAC__bool write_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Picture *block);
static FLAC__bool write_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Unknown *block, uint32_t block_length);

static FLAC__bool write_metadata_block_stationary_(FLAC__Metadata_SimpleIterator *iterator, const FLAC__StreamMetadata *block);
static FLAC__bool write_metadata_block_stationary_with_padding_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, uint32_t padding_length, FLAC__bool padding_is_last);
static FLAC__bool rewrite_whole_file_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool append);

static void simple_iterator_push_(FLAC__Metadata_SimpleIterator *iterator);
static FLAC__bool simple_iterator_pop_(FLAC__Metadata_SimpleIterator *iterator);

static uint32_t seek_to_first_metadata_block_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb);
static uint32_t seek_to_first_metadata_block_(FILE *f);

static FLAC__bool simple_iterator_copy_file_prefix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, FLAC__bool append);
static FLAC__bool simple_iterator_copy_file_postfix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, int fixup_is_last_code, FLAC__off_t fixup_is_last_flag_offset, FLAC__bool backup);

static FLAC__bool copy_n_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status);
static FLAC__bool copy_n_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status);
static FLAC__bool copy_remaining_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__Metadata_SimpleIteratorStatus *status);
static FLAC__bool copy_remaining_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__Metadata_SimpleIteratorStatus *status);

static FLAC__bool open_tempfile_(const char *filename, const char *tempfile_path_prefix, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status);
static FLAC__bool transport_tempfile_(const char *filename, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status);
static void cleanup_tempfile_(FILE **tempfile, char **tempfilename);

static FLAC__bool get_file_stats_(const char *filename, struct flac_stat_s *stats);
static void set_file_stats_(const char *filename, struct flac_stat_s *stats);

static int fseek_wrapper_(FLAC__IOHandle handle, FLAC__int64 offset, int whence);
static FLAC__int64 ftell_wrapper_(FLAC__IOHandle handle);

static FLAC__Metadata_ChainStatus get_equivalent_status_(FLAC__Metadata_SimpleIteratorStatus status);


#ifdef FLAC__VALGRIND_TESTING
static size_t local__fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
{
  size_t ret = fwrite(ptr, size, nmemb, stream);
  if(!ferror(stream))
    fflush(stream);
  return ret;
}
#else
#define local__fwrite fwrite
#endif

/****************************************************************************
 *
 * Level 0 implementation
 *
 ***************************************************************************/

static FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data);
static void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data);
static void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data);

typedef struct {
  FLAC__bool got_error;
  FLAC__StreamMetadata *object;
} level0_client_data;

static FLAC__StreamMetadata *get_one_metadata_block_(const char *filename, FLAC__MetadataType type)
{
  level0_client_data cd;
  FLAC__StreamDecoder *decoder;
  FILE *file;
  FLAC__bool open_as_ogg = false;

  FLAC__ASSERT(0 != filename);

  cd.got_error = false;
  cd.object = 0;

  decoder = FLAC__stream_decoder_new();

  if(0 == decoder)
    return 0;

  FLAC__stream_decoder_set_md5_checking(decoder, false);
  FLAC__stream_decoder_set_metadata_ignore_all(decoder);
  FLAC__stream_decoder_set_metadata_respond(decoder, type);

  /* Try to open the file and determine whether it is Ogg */
  if(0 != (file = flac_fopen(filename, "rb"))) {
    FLAC__byte signature[4];
    if(fread(&signature, 1, 4, file) == 4) {
      if(memcmp(&signature,"OggS",4) == 0)
        open_as_ogg = true;
    }
    fclose(file);
  }

  if(!open_as_ogg) {
    if(FLAC__stream_decoder_init_file(decoder, filename, write_callback_, metadata_callback_, error_callback_, &cd) != FLAC__STREAM_DECODER_INIT_STATUS_OK || cd.got_error) {
      (void)FLAC__stream_decoder_finish(decoder);
      FLAC__stream_decoder_delete(decoder);
      return 0;
    }
  }
  else {
    if(FLAC__stream_decoder_init_ogg_file(decoder, filename, write_callback_, metadata_callback_, error_callback_, &cd) != FLAC__STREAM_DECODER_INIT_STATUS_OK || cd.got_error) {
      (void)FLAC__stream_decoder_finish(decoder);
      FLAC__stream_decoder_delete(decoder);
      return 0;
    }
  }

  if(!FLAC__stream_decoder_process_until_end_of_metadata(decoder) || cd.got_error) {
    (void)FLAC__stream_decoder_finish(decoder);
    FLAC__stream_decoder_delete(decoder);
    if(0 != cd.object)
      FLAC__metadata_object_delete(cd.object);
    return 0;
  }

  (void)FLAC__stream_decoder_finish(decoder);
  FLAC__stream_decoder_delete(decoder);

  return cd.object;
}

FLAC_API FLAC__bool FLAC__metadata_get_streaminfo(const char *filename, FLAC__StreamMetadata *streaminfo)
{
  FLAC__StreamMetadata *object;

  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != streaminfo);

  object = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_STREAMINFO);

  if (object) {
    /* can just copy the contents since STREAMINFO has no internal structure */
    *streaminfo = *object;
    FLAC__metadata_object_delete(object);
    return true;
  }
  else {
    return false;
  }
}

FLAC_API FLAC__bool FLAC__metadata_get_tags(const char *filename, FLAC__StreamMetadata **tags)
{
  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != tags);

  *tags = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_VORBIS_COMMENT);

  return 0 != *tags;
}

FLAC_API FLAC__bool FLAC__metadata_get_cuesheet(const char *filename, FLAC__StreamMetadata **cuesheet)
{
  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != cuesheet);

  *cuesheet = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_CUESHEET);

  return 0 != *cuesheet;
}

FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data)
{
  (void)decoder, (void)frame, (void)buffer, (void)client_data;

  return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
}

void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)
{
  level0_client_data *cd = (level0_client_data *)client_data;
  (void)decoder;

  /*
   * we assume we only get here when the one metadata block we were
   * looking for was passed to us
   */
  if(!cd->got_error && 0 == cd->object) {
    if(0 == (cd->object = FLAC__metadata_object_clone(metadata)))
      cd->got_error = true;
  }
}

void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
{
  level0_client_data *cd = (level0_client_data *)client_data;
  (void)decoder;

  if(status != FLAC__STREAM_DECODER_ERROR_STATUS_LOST_SYNC)
    cd->got_error = true;
}

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, uint32_t max_width, uint32_t max_height, uint32_t max_depth, uint32_t max_colors)
{
  FLAC__Metadata_SimpleIterator *it;
  FLAC__uint64 max_area_seen = 0;
  FLAC__uint64 max_depth_seen = 0;

  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != picture);

  *picture = 0;

  it = FLAC__metadata_simple_iterator_new();
  if(0 == it)
    return false;
  if(!FLAC__metadata_simple_iterator_init(it, filename, /*read_only=*/true, /*preserve_file_stats=*/true)) {
    FLAC__metadata_simple_iterator_delete(it);
    return false;
  }
  do {
    if(FLAC__metadata_simple_iterator_get_block_type(it) == FLAC__METADATA_TYPE_PICTURE) {
      FLAC__StreamMetadata *obj = FLAC__metadata_simple_iterator_get_block(it);
      if(0 != obj) {
        FLAC__uint64 area = (FLAC__uint64)obj->data.picture.width * (FLAC__uint64)obj->data.picture.height;

        /* check constraints */
        if(
          (type == (FLAC__StreamMetadata_Picture_Type)(-1) || type == obj->data.picture.type) &&
          (mime_type == 0 || !strcmp(mime_type, obj->data.picture.mime_type)) &&
          (description == 0 || !strcmp((const char *)description, (const char *)obj->data.picture.description)) &&
          obj->data.picture.width <= max_width &&
          obj->data.picture.height <= max_height &&
          obj->data.picture.depth <= max_depth &&
          obj->data.picture.colors <= max_colors &&
          (area > max_area_seen || (area == max_area_seen && obj->data.picture.depth > max_depth_seen))
        ) {
          if(*picture)
            FLAC__metadata_object_delete(*picture);
          *picture = obj;
          max_area_seen = area;
          max_depth_seen = obj->data.picture.depth;
        }
        else {
          FLAC__metadata_object_delete(obj);
        }
      }
      else
        break;
    }
  } while(FLAC__metadata_simple_iterator_next(it));

  FLAC__metadata_simple_iterator_delete(it);

  return (0 != *picture);
}


/****************************************************************************
 *
 * Level 1 implementation
 *
 ***************************************************************************/

#define SIMPLE_ITERATOR_MAX_PUSH_DEPTH (1+4)
/* 1 for initial offset, +4 for our own personal use */

struct FLAC__Metadata_SimpleIterator {
  FILE *file;
  char *filename, *tempfile_path_prefix;
  struct flac_stat_s stats;
  FLAC__bool has_stats;
  FLAC__bool is_writable;
  FLAC__Metadata_SimpleIteratorStatus status;
  FLAC__off_t offset[SIMPLE_ITERATOR_MAX_PUSH_DEPTH];
  FLAC__off_t first_offset; /* this is the offset to the STREAMINFO block */
  uint32_t depth;
  /* this is the metadata block header of the current block we are pointing to: */
  FLAC__bool is_last;
  FLAC__MetadataType type;
  uint32_t length;
};

FLAC_API const char * const FLAC__Metadata_SimpleIteratorStatusString[] = {
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR",
  "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR"
};


FLAC_API FLAC__Metadata_SimpleIterator *FLAC__metadata_simple_iterator_new(void)
{
  FLAC__Metadata_SimpleIterator *iterator = calloc(1, sizeof(FLAC__Metadata_SimpleIterator));

  if(0 != iterator) {
    iterator->file = 0;
    iterator->filename = 0;
    iterator->tempfile_path_prefix = 0;
    iterator->has_stats = false;
    iterator->is_writable = false;
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
    iterator->first_offset = iterator->offset[0] = -1;
    iterator->depth = 0;
  }

  return iterator;
}

static void simple_iterator_free_guts_(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);

  if(0 != iterator->file) {
    fclose(iterator->file);
    iterator->file = 0;
    if(iterator->has_stats)
      set_file_stats_(iterator->filename, &iterator->stats);
  }
  if(0 != iterator->filename) {
    free(iterator->filename);
    iterator->filename = 0;
  }
  if(0 != iterator->tempfile_path_prefix) {
    free(iterator->tempfile_path_prefix);
    iterator->tempfile_path_prefix = 0;
  }
}

FLAC_API void FLAC__metadata_simple_iterator_delete(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);

  simple_iterator_free_guts_(iterator);
  free(iterator);
}

FLAC_API FLAC__Metadata_SimpleIteratorStatus FLAC__metadata_simple_iterator_status(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__Metadata_SimpleIteratorStatus status;

  FLAC__ASSERT(0 != iterator);

  status = iterator->status;
  iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
  return status;
}

static FLAC__bool simple_iterator_prime_input_(FLAC__Metadata_SimpleIterator *iterator, FLAC__bool read_only)
{
  uint32_t ret;

  FLAC__ASSERT(0 != iterator);

  if(read_only || 0 == (iterator->file = flac_fopen(iterator->filename, "r+b"))) {
    iterator->is_writable = false;
    if(read_only || errno == EACCES) {
      if(0 == (iterator->file = flac_fopen(iterator->filename, "rb"))) {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
        return false;
      }
    }
    else {
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
      return false;
    }
  }
  else {
    iterator->is_writable = true;
  }

  ret = seek_to_first_metadata_block_(iterator->file);
  switch(ret) {
    case 0:
      iterator->depth = 0;
      iterator->first_offset = iterator->offset[iterator->depth] = ftello(iterator->file);
      ret = read_metadata_block_header_(iterator);
      /* The first metadata block must be a streaminfo. If this is not the
       * case, the file is invalid and assumptions made elsewhere in the
       * code are invalid */
      if(iterator->type != FLAC__METADATA_TYPE_STREAMINFO) {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;
        return false;
      }
      return ret;
    case 1:
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
      return false;
    case 2:
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
      return false;
    case 3:
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE;
      return false;
    default:
      FLAC__ASSERT(0);
      return false;
  }
}

#if 0
@@@ If we decide to finish implementing this, put this comment back in metadata.h
/*
 * The 'tempfile_path_prefix' allows you to specify a directory where
 * tempfiles should go.  Remember that if your metadata edits cause the
 * FLAC file to grow, the entire file will have to be rewritten.  If
 * 'tempfile_path_prefix' is NULL, the temp file will be written in the
 * same directory as the original FLAC file.  This makes replacing the
 * original with the tempfile fast but requires extra space in the same
 * partition for the tempfile.  If space is a problem, you can pass a
 * directory name belonging to a different partition in
 * 'tempfile_path_prefix'.  Note that you should use the forward slash
 * '/' as the directory separator.  A trailing slash is not needed; it
 * will be added automatically.
 */
FLAC__bool FLAC__metadata_simple_iterator_init(FLAC__Metadata_SimpleIterator *iterator, const char *filename, FLAC__bool preserve_file_stats, const char *tempfile_path_prefix);
#endif

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)
{
  const char *tempfile_path_prefix = 0; /*@@@ search for comments near 'flac_rename(...)' for what it will take to finish implementing this */

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != filename);

  simple_iterator_free_guts_(iterator);

  if(!read_only && preserve_file_stats)
    iterator->has_stats = get_file_stats_(filename, &iterator->stats);

  if(0 == (iterator->filename = strdup(filename))) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
    return false;
  }
  if(0 != tempfile_path_prefix && 0 == (iterator->tempfile_path_prefix = strdup(tempfile_path_prefix))) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
    return false;
  }

  return simple_iterator_prime_input_(iterator, read_only);
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_writable(const FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);

  return iterator->is_writable;
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_next(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(iterator->is_last)
    return false;

  if(0 != fseeko(iterator->file, iterator->length, SEEK_CUR)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  iterator->offset[iterator->depth] = ftello(iterator->file);

  return read_metadata_block_header_(iterator);
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_prev(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__off_t this_offset;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(iterator->offset[iterator->depth] == iterator->first_offset)
    return false;

  if(0 != fseeko(iterator->file, iterator->first_offset, SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }
  this_offset = iterator->first_offset;
  if(!read_metadata_block_header_(iterator))
    return false;

  /* we ignore any error from ftello() and catch it in fseeko() */
  while(ftello(iterator->file) + (FLAC__off_t)iterator->length < iterator->offset[iterator->depth]) {
    if(0 != fseeko(iterator->file, iterator->length, SEEK_CUR)) {
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
      return false;
    }
    this_offset = ftello(iterator->file);
    if(!read_metadata_block_header_(iterator))
      return false;
  }

  iterator->offset[iterator->depth] = this_offset;

  return true;
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_last(const FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  return iterator->is_last;
}

/*@@@@add to tests*/
FLAC_API off_t FLAC__metadata_simple_iterator_get_block_offset(const FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  return (off_t)iterator->offset[iterator->depth];
}

FLAC_API FLAC__MetadataType FLAC__metadata_simple_iterator_get_block_type(const FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  return iterator->type;
}

/*@@@@add to tests*/
FLAC_API uint32_t FLAC__metadata_simple_iterator_get_block_length(const FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  return iterator->length;
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_get_application_id(FLAC__Metadata_SimpleIterator *iterator, FLAC__byte *id)
{
  const uint32_t id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(0 != id);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(iterator->type != FLAC__METADATA_TYPE_APPLICATION) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
    return false;
  }

  if(fread(id, 1, id_bytes, iterator->file) != id_bytes) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    return false;
  }

  /* back up */
  if(0 != fseeko(iterator->file, -((int)id_bytes), SEEK_CUR)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  return true;
}

FLAC_API FLAC__StreamMetadata *FLAC__metadata_simple_iterator_get_block(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__StreamMetadata *block = FLAC__metadata_object_new(iterator->type);

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(0 != block) {
    block->is_last = iterator->is_last;
    block->length = iterator->length;

    if(!read_metadata_block_data_(iterator, block)) {
      FLAC__metadata_object_delete(block);
      return 0;
    }

    /* back up to the beginning of the block data to stay consistent */
    if(0 != fseeko(iterator->file, iterator->offset[iterator->depth] + FLAC__STREAM_METADATA_HEADER_LENGTH, SEEK_SET)) {
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
      FLAC__metadata_object_delete(block);
      return 0;
    }
  }
  else
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  return block;
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_set_block(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool use_padding)
{
  FLAC__ASSERT_DECLARATION(FLAC__off_t debug_target_offset = iterator->offset[iterator->depth];)
  FLAC__bool ret;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(0 != block);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(!iterator->is_writable) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE;
    return false;
  }

  if(iterator->type == FLAC__METADATA_TYPE_STREAMINFO || block->type == FLAC__METADATA_TYPE_STREAMINFO) {
    if(iterator->type != block->type) {
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
      return false;
    }
  }

  block->is_last = iterator->is_last;

  if(iterator->length == block->length)
    return write_metadata_block_stationary_(iterator, block);
  else if(iterator->length > block->length) {
    if(use_padding && iterator->length >= FLAC__STREAM_METADATA_HEADER_LENGTH + block->length) {
      ret = write_metadata_block_stationary_with_padding_(iterator, block, iterator->length - FLAC__STREAM_METADATA_HEADER_LENGTH - block->length, block->is_last);
      FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
      FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
      return ret;
    }
    else {
      if((ret = rewrite_whole_file_(iterator, block, /*append=*/false))) {
        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
      }
      return ret;
    }
  }
  else /* iterator->length < block->length */ {
    uint32_t padding_leftover = 0;
    FLAC__bool padding_is_last = false;
    if(use_padding) {
      /* first see if we can even use padding */
      if(iterator->is_last) {
        use_padding = false;
      }
      else {
        const uint32_t extra_padding_bytes_required = block->length - iterator->length;
        simple_iterator_push_(iterator);
        if(!FLAC__metadata_simple_iterator_next(iterator)) {
          (void)simple_iterator_pop_(iterator);
          return false;
        }
        if(iterator->type != FLAC__METADATA_TYPE_PADDING) {
          use_padding = false;
        }
        else {
          if(FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length == extra_padding_bytes_required) {
            padding_leftover = 0;
            block->is_last = iterator->is_last;
          }
          else if(iterator->length < extra_padding_bytes_required)
            use_padding = false;
          else {
            padding_leftover = FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length - extra_padding_bytes_required;
            padding_is_last = iterator->is_last;
            block->is_last = false;
          }
        }
        if(!simple_iterator_pop_(iterator))
          return false;
      }
    }
    if(use_padding) {
      if(padding_leftover == 0) {
        ret = write_metadata_block_stationary_(iterator, block);
        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
        return ret;
      }
      else {
        FLAC__ASSERT(padding_leftover >= FLAC__STREAM_METADATA_HEADER_LENGTH);
        ret = write_metadata_block_stationary_with_padding_(iterator, block, padding_leftover - FLAC__STREAM_METADATA_HEADER_LENGTH, padding_is_last);
        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
        return ret;
      }
    }
    else {
      if((ret = rewrite_whole_file_(iterator, block, /*append=*/false))) {
        FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
        FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
      }
      return ret;
    }
  }
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_insert_block_after(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool use_padding)
{
  uint32_t padding_leftover = 0;
  FLAC__bool padding_is_last = false;

  FLAC__ASSERT_DECLARATION(FLAC__off_t debug_target_offset = iterator->offset[iterator->depth] + FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length;)
  FLAC__bool ret;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);
  FLAC__ASSERT(0 != block);
  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(!iterator->is_writable) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE;
    return false;
  }

  if(block->type == FLAC__METADATA_TYPE_STREAMINFO) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
    return false;
  }

  block->is_last = iterator->is_last;

  if(use_padding) {
    /* first see if we can even use padding */
    if(iterator->is_last) {
      use_padding = false;
    }
    else {
      simple_iterator_push_(iterator);
      if(!FLAC__metadata_simple_iterator_next(iterator)) {
        (void)simple_iterator_pop_(iterator);
        return false;
      }
      if(iterator->type != FLAC__METADATA_TYPE_PADDING) {
        use_padding = false;
      }
      else {
        if(iterator->length == block->length) {
          padding_leftover = 0;
          block->is_last = iterator->is_last;
        }
        else if(iterator->length < FLAC__STREAM_METADATA_HEADER_LENGTH + block->length)
          use_padding = false;
        else {
          padding_leftover = iterator->length - block->length;
          padding_is_last = iterator->is_last;
          block->is_last = false;
        }
      }
      if(!simple_iterator_pop_(iterator))
        return false;
    }
  }
  if(use_padding) {
    /* move to the next block, which is suitable padding */
    if(!FLAC__metadata_simple_iterator_next(iterator))
      return false;
    if(padding_leftover == 0) {
      ret = write_metadata_block_stationary_(iterator, block);
      FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
      FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
      return ret;
    }
    else {
      FLAC__ASSERT(padding_leftover >= FLAC__STREAM_METADATA_HEADER_LENGTH);
      ret = write_metadata_block_stationary_with_padding_(iterator, block, padding_leftover - FLAC__STREAM_METADATA_HEADER_LENGTH, padding_is_last);
      FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
      FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
      return ret;
    }
  }
  else {
    if((ret = rewrite_whole_file_(iterator, block, /*append=*/true))) {
      FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
      FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
    }
    return ret;
  }
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_delete_block(FLAC__Metadata_SimpleIterator *iterator, FLAC__bool use_padding)
{
  FLAC__ASSERT_DECLARATION(FLAC__off_t debug_target_offset = iterator->offset[iterator->depth];)
  FLAC__bool ret;

  FLAC__ASSERT(iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);

  if(!iterator->is_writable) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE;
    return false;
  }

  if(iterator->type == FLAC__METADATA_TYPE_STREAMINFO) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
    return false;
  }

  if(use_padding) {
    FLAC__StreamMetadata *padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING);
    if(0 == padding) {
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
      return false;
    }
    padding->length = iterator->length;
    if(!FLAC__metadata_simple_iterator_set_block(iterator, padding, false)) {
      FLAC__metadata_object_delete(padding);
      return false;
    }
    FLAC__metadata_object_delete(padding);
    if(!FLAC__metadata_simple_iterator_prev(iterator))
      return false;
    FLAC__ASSERT(iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length == debug_target_offset);
    FLAC__ASSERT(ftello(iterator->file) + (FLAC__off_t)iterator->length == debug_target_offset);
    return true;
  }
  else {
    if((ret = rewrite_whole_file_(iterator, 0, /*append=*/false))) {
      FLAC__ASSERT(iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length == debug_target_offset);
      FLAC__ASSERT(ftello(iterator->file) + (FLAC__off_t)iterator->length == debug_target_offset);
    }
    return ret;
  }
}



/****************************************************************************
 *
 * Level 2 implementation
 *
 ***************************************************************************/


typedef struct FLAC__Metadata_Node {
  FLAC__StreamMetadata *data;
  struct FLAC__Metadata_Node *prev, *next;
} FLAC__Metadata_Node;

struct FLAC__Metadata_Chain {
  char *filename; /* will be NULL if using callbacks */
  FLAC__bool is_ogg;
  FLAC__Metadata_Node *head;
  FLAC__Metadata_Node *tail;
  uint32_t nodes;
  FLAC__Metadata_ChainStatus status;
  FLAC__off_t first_offset, last_offset;
  /*
   * This is the length of the chain initially read from the FLAC file.
   * it is used to compare against the current length to decide whether
   * or not the whole file has to be rewritten.
   */
  FLAC__off_t initial_length;
  /* @@@ hacky, these are currently only needed by ogg reader */
  FLAC__IOHandle handle;
  FLAC__IOCallback_Read read_cb;
};

struct FLAC__Metadata_Iterator {
  FLAC__Metadata_Chain *chain;
  FLAC__Metadata_Node *current;
};

FLAC_API const char * const FLAC__Metadata_ChainStatusString[] = {
  "FLAC__METADATA_CHAIN_STATUS_OK",
  "FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT",
  "FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE",
  "FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE",
  "FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE",
  "FLAC__METADATA_CHAIN_STATUS_BAD_METADATA",
  "FLAC__METADATA_CHAIN_STATUS_READ_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR",
  "FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS",
  "FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH",
  "FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL"
};


static FLAC__Metadata_Node *node_new_(void)
{
  return calloc(1, sizeof(FLAC__Metadata_Node));
}

static void node_delete_(FLAC__Metadata_Node *node)
{
  FLAC__ASSERT(0 != node);
  if(0 != node->data)
    FLAC__metadata_object_delete(node->data);
  free(node);
}

static void chain_init_(FLAC__Metadata_Chain *chain)
{
  FLAC__ASSERT(0 != chain);

  chain->filename = 0;
  chain->is_ogg = false;
  chain->head = chain->tail = 0;
  chain->nodes = 0;
  chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
  chain->initial_length = 0;
  chain->read_cb = 0;
}

static void chain_clear_(FLAC__Metadata_Chain *chain)
{
  FLAC__Metadata_Node *node, *next;

  FLAC__ASSERT(0 != chain);

  for(node = chain->head; node; ) {
    next = node->next;
    node_delete_(node);
    node = next;
  }

  if(0 != chain->filename)
    free(chain->filename);

  chain_init_(chain);
}

static void chain_append_node_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
{
  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 != node);
  FLAC__ASSERT(0 != node->data);

  node->next = node->prev = 0;
  node->data->is_last = true;
  if(0 != chain->tail)
    chain->tail->data->is_last = false;

  if(0 == chain->head)
    chain->head = node;
  else {
    FLAC__ASSERT(0 != chain->tail);
    chain->tail->next = node;
    node->prev = chain->tail;
  }
  chain->tail = node;
  chain->nodes++;
}

static void chain_remove_node_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
{
  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 != node);

  if(node == chain->head)
    chain->head = node->next;
  else
    node->prev->next = node->next;

  if(node == chain->tail)
    chain->tail = node->prev;
  else
    node->next->prev = node->prev;

  if(0 != chain->tail)
    chain->tail->data->is_last = true;

  chain->nodes--;
}

static void chain_delete_node_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
{
  chain_remove_node_(chain, node);
  node_delete_(node);
}

static FLAC__off_t chain_calculate_length_(FLAC__Metadata_Chain *chain)
{
  const FLAC__Metadata_Node *node;
  FLAC__off_t length = 0;
  for(node = chain->head; node; node = node->next)
    length += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
  return length;
}

static void iterator_insert_node_(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Node *node)
{
  FLAC__ASSERT(0 != node);
  FLAC__ASSERT(0 != node->data);
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);
  FLAC__ASSERT(0 != iterator->chain);
  FLAC__ASSERT(0 != iterator->chain->head);
  FLAC__ASSERT(0 != iterator->chain->tail);

  node->data->is_last = false;

  node->prev = iterator->current->prev;
  node->next = iterator->current;

  if(0 == node->prev)
    iterator->chain->head = node;
  else
    node->prev->next = node;

  iterator->current->prev = node;

  iterator->chain->nodes++;
}

static void iterator_insert_node_after_(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Node *node)
{
  FLAC__ASSERT(0 != node);
  FLAC__ASSERT(0 != node->data);
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);
  FLAC__ASSERT(0 != iterator->chain);
  FLAC__ASSERT(0 != iterator->chain->head);
  FLAC__ASSERT(0 != iterator->chain->tail);

  iterator->current->data->is_last = false;

  node->prev = iterator->current;
  node->next = iterator->current->next;

  if(0 == node->next)
    iterator->chain->tail = node;
  else
    node->next->prev = node;

  node->prev->next = node;

  iterator->chain->tail->data->is_last = true;

  iterator->chain->nodes++;
}

/* return true iff node and node->next are both padding */
static FLAC__bool chain_merge_adjacent_padding_(FLAC__Metadata_Chain *chain, FLAC__Metadata_Node *node)
{
  if(node->data->type == FLAC__METADATA_TYPE_PADDING && 0 != node->next && node->next->data->type == FLAC__METADATA_TYPE_PADDING) {
    const uint32_t growth = FLAC__STREAM_METADATA_HEADER_LENGTH + node->next->data->length;
    node->data->length += growth; /* new block size can be greater than max metadata block size, but it'll be fixed later in chain_prepare_for_write_() */

    chain_delete_node_(chain, node->next);
    return true;
  }
  else
    return false;
}

#if defined(_MSC_VER)
// silence three MSVC warnings 'conversion from 'conversion from 'const __int64' to 'uint32_t', possible loss of data'
#pragma warning ( disable : 4244 )
#endif

/* Returns the new length of the chain, or 0 if there was an error. */
/* WATCHOUT: This can get called multiple times before a write, so
 * it should still work when this happens.
 */
/* WATCHOUT: Make sure to also update the logic in
 * FLAC__metadata_chain_check_if_tempfile_needed() if the logic here changes.
 */
static FLAC__off_t chain_prepare_for_write_(FLAC__Metadata_Chain *chain, FLAC__bool use_padding)
{
  FLAC__off_t current_length = chain_calculate_length_(chain);
  FLAC__Metadata_Node * i;

  /* Check all is_last settings on the blocks */
  for(i = chain->head; i->next != NULL; i = i->next)
    i->data->is_last = 0;
  chain->tail->data->is_last = 1;

  if(use_padding) {
    /* if the metadata shrank and the last block is padding, we just extend the last padding block */
    if(current_length < chain->initial_length && chain->tail->data->type == FLAC__METADATA_TYPE_PADDING) {
      const FLAC__off_t delta = chain->initial_length - current_length;
      chain->tail->data->length += delta;
      current_length += delta;
      FLAC__ASSERT(current_length == chain->initial_length);
    }
    /* if the metadata shrank more than 4 bytes then there's room to add another padding block */
    else if(current_length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH <= chain->initial_length) {
      FLAC__StreamMetadata *padding;
      FLAC__Metadata_Node *node;
      if(0 == (padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING))) {
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return 0;
      }
      padding->length = chain->initial_length - (FLAC__STREAM_METADATA_HEADER_LENGTH + current_length);
      if(0 == (node = node_new_())) {
        FLAC__metadata_object_delete(padding);
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return 0;
      }
      node->data = padding;
      chain_append_node_(chain, node);
      current_length = chain_calculate_length_(chain);
      FLAC__ASSERT(current_length == chain->initial_length);
    }
    /* if the metadata grew but the last block is padding, try cutting the padding to restore the original length so we don't have to rewrite the whole file */
    else if(current_length > chain->initial_length) {
      const FLAC__off_t delta = current_length - chain->initial_length;
      if(chain->tail->data->type == FLAC__METADATA_TYPE_PADDING) {
        /* if the delta is exactly the size of the last padding block, remove the padding block */
        if((FLAC__off_t)chain->tail->data->length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH == delta) {
          chain_delete_node_(chain, chain->tail);
          current_length = chain_calculate_length_(chain);
          FLAC__ASSERT(current_length == chain->initial_length);
        }
        /* if there is at least 'delta' bytes of padding, trim the padding down */
        else if((FLAC__off_t)chain->tail->data->length >= delta) {
          chain->tail->data->length -= delta;
          current_length -= delta;
          FLAC__ASSERT(current_length == chain->initial_length);
        }
      }
    }
  }

  /* check sizes of all metadata blocks; reduce padding size if necessary */
  {
    FLAC__Metadata_Node *node;
    for (node = chain->head; node; node = node->next) {
      if(node->data->length >= (1u << FLAC__STREAM_METADATA_LENGTH_LEN)) {
        if(node->data->type == FLAC__METADATA_TYPE_PADDING) {
          node->data->length = (1u << FLAC__STREAM_METADATA_LENGTH_LEN) - 1;
          current_length = chain_calculate_length_(chain);
        } else {
          chain->status = FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
          return 0;
        }
      }
    }
  }

  return current_length;
}

#if defined(_MSC_VER)
#pragma warning ( default : 4244 )
#endif

static FLAC__bool chain_read_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__IOCallback_Tell tell_cb)
{
  FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != chain);

  /* we assume we're already at the beginning of the file */

  switch(seek_to_first_metadata_block_cb_(handle, read_cb, seek_cb)) {
    case 0:
      break;
    case 1:
      chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
      return false;
    case 2:
      chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
      return false;
    case 3:
      chain->status = FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE;
      return false;
    default:
      FLAC__ASSERT(0);
      return false;
  }

  {
    FLAC__int64 pos = tell_cb(handle);
    if(pos < 0) {
      chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
      return false;
    }
    chain->first_offset = (FLAC__off_t)pos;
  }

  {
    FLAC__bool is_last;
    FLAC__MetadataType type;
    uint32_t length;

    do {
      node = node_new_();
      if(0 == node) {
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return false;
      }

      if(!read_metadata_block_header_cb_(handle, read_cb, &is_last, &type, &length)) {
        node_delete_(node);
        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
        return false;
      }

      node->data = FLAC__metadata_object_new(type);
      if(0 == node->data) {
        node_delete_(node);
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return false;
      }

      node->data->is_last = is_last;
      node->data->length = length;

      chain->status = get_equivalent_status_(read_metadata_block_data_cb_(handle, read_cb, seek_cb, node->data));
      if(chain->status != FLAC__METADATA_CHAIN_STATUS_OK) {
        node_delete_(node);
        return false;
      }
      chain_append_node_(chain, node);
    } while(!is_last);
  }

  {
    FLAC__int64 pos = tell_cb(handle);
    if(pos < 0) {
      chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
      return false;
    }
    chain->last_offset = (FLAC__off_t)pos;
  }

  if(chain->head->data->type != FLAC__METADATA_TYPE_STREAMINFO) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
    return false;
  }

  chain->initial_length = chain_calculate_length_(chain);

  return true;
}

static FLAC__StreamDecoderReadStatus chain_read_ogg_read_cb_(const FLAC__StreamDecoder *decoder, FLAC__byte buffer[], size_t *bytes, void *client_data)
{
  FLAC__Metadata_Chain *chain = (FLAC__Metadata_Chain*)client_data;
  (void)decoder;
  if(*bytes > 0 && chain->status == FLAC__METADATA_CHAIN_STATUS_OK) {
    *bytes = chain->read_cb(buffer, sizeof(FLAC__byte), *bytes, chain->handle);
    if(*bytes == 0)
      return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
    else
      return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
  }
  else
    return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
}

static FLAC__StreamDecoderWriteStatus chain_read_ogg_write_cb_(const FLAC__StreamDecoder *decoder, const FLAC__Frame *frame, const FLAC__int32 * const buffer[], void *client_data)
{
  (void)decoder, (void)frame, (void)buffer, (void)client_data;
  return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;
}

static void chain_read_ogg_metadata_cb_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)
{
  FLAC__Metadata_Chain *chain = (FLAC__Metadata_Chain*)client_data;
  FLAC__Metadata_Node *node;

  (void)decoder;

  node = node_new_();
  if(0 == node) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
    return;
  }

  node->data = FLAC__metadata_object_clone(metadata);
  if(0 == node->data) {
    node_delete_(node);
    chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
    return;
  }

  chain_append_node_(chain, node);
}

static void chain_read_ogg_error_cb_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)
{
  FLAC__Metadata_Chain *chain = (FLAC__Metadata_Chain*)client_data;
  (void)decoder, (void)status;
  chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
}

static FLAC__bool chain_read_ogg_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb)
{
  FLAC__StreamDecoder *decoder;

  FLAC__ASSERT(0 != chain);

  /* we assume we're already at the beginning of the file */

  chain->handle = handle;
  chain->read_cb = read_cb;
  if(0 == (decoder = FLAC__stream_decoder_new())) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
    return false;
  }
  FLAC__stream_decoder_set_metadata_respond_all(decoder);
  if(FLAC__stream_decoder_init_ogg_stream(decoder, chain_read_ogg_read_cb_, /*seek_callback=*/0, /*tell_callback=*/0, /*length_callback=*/0, /*eof_callback=*/0, chain_read_ogg_write_cb_, chain_read_ogg_metadata_cb_, chain_read_ogg_error_cb_, chain) != FLAC__STREAM_DECODER_INIT_STATUS_OK) {
    FLAC__stream_decoder_delete(decoder);
    chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
    return false;
  }

  chain->first_offset = 0; /*@@@ wrong; will need to be set correctly to implement metadata writing for Ogg FLAC */

  if(!FLAC__stream_decoder_process_until_end_of_metadata(decoder))
    chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
  if(chain->status != FLAC__METADATA_CHAIN_STATUS_OK) {
    FLAC__stream_decoder_delete(decoder);
    return false;
  }

  FLAC__stream_decoder_delete(decoder);

  chain->last_offset = 0; /*@@@ wrong; will need to be set correctly to implement metadata writing for Ogg FLAC */

  chain->initial_length = chain_calculate_length_(chain);

  if(chain->initial_length == 0 || chain->head->data->type != FLAC__METADATA_TYPE_STREAMINFO) {
    /* Ogg FLAC file must have at least streaminfo and vorbis comment */
    chain->status = FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
    return false;
  }

  return true;
}

static FLAC__bool chain_rewrite_metadata_in_place_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, FLAC__IOCallback_Seek seek_cb)
{
  FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 != chain->head);

  if(0 != seek_cb(handle, chain->first_offset, SEEK_SET)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
    return false;
  }

  for(node = chain->head; node; node = node->next) {
    if(!write_metadata_block_header_cb_(handle, write_cb, node->data)) {
      chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
      return false;
    }
    if(!write_metadata_block_data_cb_(handle, write_cb, node->data)) {
      chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
      return false;
    }
  }

  /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/

  chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
  return true;
}

static FLAC__bool chain_rewrite_metadata_in_place_(FLAC__Metadata_Chain *chain)
{
  FILE *file;
  FLAC__bool ret;

  FLAC__ASSERT(0 != chain->filename);

  if(0 == (file = flac_fopen(chain->filename, "r+b"))) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
    return false;
  }

  /* chain_rewrite_metadata_in_place_cb_() sets chain->status for us */
  ret = chain_rewrite_metadata_in_place_cb_(chain, (FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, fseek_wrapper_);

  fclose(file);

  return ret;
}

static FLAC__bool chain_rewrite_file_(FLAC__Metadata_Chain *chain, const char *tempfile_path_prefix)
{
  FILE *f, *tempfile = NULL;
  char *tempfilename;
  FLAC__Metadata_SimpleIteratorStatus status;
  const FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 != chain->filename);
  FLAC__ASSERT(0 != chain->head);

  /* copy the file prefix (data up to first metadata block */
  if(0 == (f = flac_fopen(chain->filename, "rb"))) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
    return false;
  }
  if(!open_tempfile_(chain->filename, tempfile_path_prefix, &tempfile, &tempfilename, &status)) {
    chain->status = get_equivalent_status_(status);
    goto err;
  }
  if(!copy_n_bytes_from_file_(f, tempfile, chain->first_offset, &status)) {
    chain->status = get_equivalent_status_(status);
    goto err;
  }

  /* write the metadata */
  for(node = chain->head; node; node = node->next) {
    if(!write_metadata_block_header_(tempfile, &status, node->data)) {
      chain->status = get_equivalent_status_(status);
      goto err;
    }
    if(!write_metadata_block_data_(tempfile, &status, node->data)) {
      chain->status = get_equivalent_status_(status);
      goto err;
    }
  }
  /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/

  /* copy the file postfix (everything after the metadata) */
  if(0 != fseeko(f, chain->last_offset, SEEK_SET)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
    goto err;
  }
  if(!copy_remaining_bytes_from_file_(f, tempfile, &status)) {
    chain->status = get_equivalent_status_(status);
    goto err;
  }

  /* move the tempfile on top of the original */
  (void)fclose(f);
  if(!transport_tempfile_(chain->filename, &tempfile, &tempfilename, &status))
    return false;

  return true;

err:
  (void)fclose(f);
  cleanup_tempfile_(&tempfile, &tempfilename);
  return false;
}

/* assumes 'handle' is already at beginning of file */
static FLAC__bool chain_rewrite_file_cb_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb)
{
  FLAC__Metadata_SimpleIteratorStatus status;
  const FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 == chain->filename);
  FLAC__ASSERT(0 != chain->head);

  /* copy the file prefix (data up to first metadata block */
  if(!copy_n_bytes_from_file_cb_(handle, read_cb, temp_handle, temp_write_cb, chain->first_offset, &status)) {
    chain->status = get_equivalent_status_(status);
    return false;
  }

  /* write the metadata */
  for(node = chain->head; node; node = node->next) {
    if(!write_metadata_block_header_cb_(temp_handle, temp_write_cb, node->data)) {
      chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
      return false;
    }
    if(!write_metadata_block_data_cb_(temp_handle, temp_write_cb, node->data)) {
      chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
      return false;
    }
  }
  /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/

  /* copy the file postfix (everything after the metadata) */
  if(0 != seek_cb(handle, chain->last_offset, SEEK_SET)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
    return false;
  }
  if(!copy_remaining_bytes_from_file_cb_(handle, read_cb, eof_cb, temp_handle, temp_write_cb, &status)) {
    chain->status = get_equivalent_status_(status);
    return false;
  }

  return true;
}

FLAC_API FLAC__Metadata_Chain *FLAC__metadata_chain_new(void)
{
  FLAC__Metadata_Chain *chain = calloc(1, sizeof(FLAC__Metadata_Chain));

  if(0 != chain)
    chain_init_(chain);

  return chain;
}

FLAC_API void FLAC__metadata_chain_delete(FLAC__Metadata_Chain *chain)
{
  FLAC__ASSERT(0 != chain);

  chain_clear_(chain);

  free(chain);
}

FLAC_API FLAC__Metadata_ChainStatus FLAC__metadata_chain_status(FLAC__Metadata_Chain *chain)
{
  FLAC__Metadata_ChainStatus status;

  FLAC__ASSERT(0 != chain);

  status = chain->status;
  chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
  return status;
}

static FLAC__bool chain_read_(FLAC__Metadata_Chain *chain, const char *filename, FLAC__bool is_ogg)
{
  FILE *file;
  FLAC__bool ret;

  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 != filename);

  chain_clear_(chain);

  if(0 == (chain->filename = strdup(filename))) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
    return false;
  }

  chain->is_ogg = is_ogg;

  if(0 == (file = flac_fopen(filename, "rb"))) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
    return false;
  }

  /* the function also sets chain->status for us */
  ret = is_ogg?
    chain_read_ogg_cb_(chain, file, (FLAC__IOCallback_Read)fread) :
    chain_read_cb_(chain, file, (FLAC__IOCallback_Read)fread, fseek_wrapper_, ftell_wrapper_)
  ;

  fclose(file);

  return ret;
}

FLAC_API FLAC__bool FLAC__metadata_chain_read(FLAC__Metadata_Chain *chain, const char *filename)
{
  return chain_read_(chain, filename, /*is_ogg=*/false);
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg(FLAC__Metadata_Chain *chain, const char *filename)
{
  return chain_read_(chain, filename, /*is_ogg=*/true);
}

static FLAC__bool chain_read_with_callbacks_(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks, FLAC__bool is_ogg)
{
  FLAC__bool ret;

  FLAC__ASSERT(0 != chain);

  chain_clear_(chain);

  if (0 == callbacks.read || 0 == callbacks.seek || 0 == callbacks.tell) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
    return false;
  }

  chain->is_ogg = is_ogg;

  /* rewind */
  if(0 != callbacks.seek(handle, 0, SEEK_SET)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
    return false;
  }

  /* the function also sets chain->status for us */
  ret = is_ogg?
    chain_read_ogg_cb_(chain, handle, callbacks.read) :
    chain_read_cb_(chain, handle, callbacks.read, callbacks.seek, callbacks.tell)
  ;

  return ret;
}

FLAC_API FLAC__bool FLAC__metadata_chain_read_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
{
  return chain_read_with_callbacks_(chain, handle, callbacks, /*is_ogg=*/false);
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
{
  return chain_read_with_callbacks_(chain, handle, callbacks, /*is_ogg=*/true);
}

typedef enum {
  LBS_NONE = 0,
  LBS_SIZE_CHANGED,
  LBS_BLOCK_ADDED,
  LBS_BLOCK_REMOVED
} LastBlockState;

#if defined(_MSC_VER)
// silence three MSVC warnings 'conversion from 'conversion from 'const __int64' to 'uint32_t', possible loss of data'
#pragma warning ( disable : 4244 )
#endif

FLAC_API FLAC__bool FLAC__metadata_chain_check_if_tempfile_needed(FLAC__Metadata_Chain *chain, FLAC__bool use_padding)
{
  /* This does all the same checks that are in chain_prepare_for_write_()
   * but doesn't actually alter the chain.  Make sure to update the logic
   * here if chain_prepare_for_write_() changes.
   */
  FLAC__off_t current_length;
  LastBlockState lbs_state = LBS_NONE;
  uint32_t lbs_size = 0;

  FLAC__ASSERT(0 != chain);

  current_length = chain_calculate_length_(chain);

  if(use_padding) {
    const FLAC__Metadata_Node * const node = chain->tail;
    /* if the metadata shrank and the last block is padding, we just extend the last padding block */
    if(current_length < chain->initial_length && node->data->type == FLAC__METADATA_TYPE_PADDING) {
      lbs_state = LBS_SIZE_CHANGED;
      lbs_size = node->data->length + (chain->initial_length - current_length);
    }
    /* if the metadata shrank more than 4 bytes then there's room to add another padding block */
    else if(current_length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH <= chain->initial_length) {
      lbs_state = LBS_BLOCK_ADDED;
      lbs_size = chain->initial_length - (current_length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
    }
    /* if the metadata grew but the last block is padding, try cutting the padding to restore the original length so we don't have to rewrite the whole file */
    else if(current_length > chain->initial_length) {
      const FLAC__off_t delta = current_length - chain->initial_length;
      if(node->data->type == FLAC__METADATA_TYPE_PADDING) {
        /* if the delta is exactly the size of the last padding block, remove the padding block */
        if((FLAC__off_t)node->data->length + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH == delta) {
          lbs_state = LBS_BLOCK_REMOVED;
          lbs_size = 0;
        }
        /* if there is at least 'delta' bytes of padding, trim the padding down */
        else if((FLAC__off_t)node->data->length >= delta) {
          lbs_state = LBS_SIZE_CHANGED;
          lbs_size = node->data->length - delta;
        }
      }
    }
  }

  current_length = 0;
  /* check sizes of all metadata blocks; reduce padding size if necessary */
  {
    const FLAC__Metadata_Node *node;
    for(node = chain->head; node; node = node->next) {
      uint32_t block_len = node->data->length;
      if(node == chain->tail) {
        if(lbs_state == LBS_BLOCK_REMOVED)
          continue;
        else if(lbs_state == LBS_SIZE_CHANGED)
          block_len = lbs_size;
      }
      if(block_len >= (1u << FLAC__STREAM_METADATA_LENGTH_LEN)) {
        if(node->data->type == FLAC__METADATA_TYPE_PADDING)
          block_len = (1u << FLAC__STREAM_METADATA_LENGTH_LEN) - 1;
        else
          return false /* the return value doesn't matter */;
      }
      current_length += (FLAC__STREAM_METADATA_HEADER_LENGTH + block_len);
    }

    if(lbs_state == LBS_BLOCK_ADDED) {
      /* test added padding block */
      uint32_t block_len = lbs_size;
      if(block_len >= (1u << FLAC__STREAM_METADATA_LENGTH_LEN))
        block_len = (1u << FLAC__STREAM_METADATA_LENGTH_LEN) - 1;
      current_length += (FLAC__STREAM_METADATA_HEADER_LENGTH + block_len);
    }
  }

  return (current_length != chain->initial_length);
}

#if defined(_MSC_VER)
#pragma warning ( default : 4244 )
#endif

FLAC_API FLAC__bool FLAC__metadata_chain_write(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__bool preserve_file_stats)
{
  struct flac_stat_s stats;
  const char *tempfile_path_prefix = 0;
  FLAC__off_t current_length;

  FLAC__ASSERT(0 != chain);

  if (chain->is_ogg) { /* cannot write back to Ogg FLAC yet */
    chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
    return false;
  }

  if (0 == chain->filename) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
    return false;
  }

  current_length = chain_prepare_for_write_(chain, use_padding);

  /* a return value of 0 means there was an error; chain->status is already set */
  if (0 == current_length)
    return false;

  if(preserve_file_stats)
    get_file_stats_(chain->filename, &stats);

  if(current_length == chain->initial_length) {
    if(!chain_rewrite_metadata_in_place_(chain))
      return false;
  }
  else {
    if(!chain_rewrite_file_(chain, tempfile_path_prefix))
      return false;

    /* recompute lengths and offsets */
    {
      const FLAC__Metadata_Node *node;
      chain->initial_length = current_length;
      chain->last_offset = chain->first_offset;
      for(node = chain->head; node; node = node->next)
        chain->last_offset += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
    }
  }

  if(preserve_file_stats)
    set_file_stats_(chain->filename, &stats);

  return true;
}

FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks(FLAC__Metadata_Chain *chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
{
  FLAC__off_t current_length;

  FLAC__ASSERT(0 != chain);

  if (chain->is_ogg) { /* cannot write back to Ogg FLAC yet */
    chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
    return false;
  }

  if (0 != chain->filename) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
    return false;
  }

  if (0 == callbacks.write || 0 == callbacks.seek) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
    return false;
  }

  if (FLAC__metadata_chain_check_if_tempfile_needed(chain, use_padding)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL;
    return false;
  }

  current_length = chain_prepare_for_write_(chain, use_padding);

  /* a return value of 0 means there was an error; chain->status is already set */
  if (0 == current_length)
    return false;

  FLAC__ASSERT(current_length == chain->initial_length);

  return chain_rewrite_metadata_in_place_cb_(chain, handle, callbacks.write, callbacks.seek);
}

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)
{
  FLAC__off_t current_length;

  FLAC__ASSERT(0 != chain);

  if (chain->is_ogg) { /* cannot write back to Ogg FLAC yet */
    chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
    return false;
  }

  if (0 != chain->filename) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
    return false;
  }

  if (0 == callbacks.read || 0 == callbacks.seek || 0 == callbacks.eof) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
    return false;
  }
  if (0 == temp_callbacks.write) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
    return false;
  }

  if (!FLAC__metadata_chain_check_if_tempfile_needed(chain, use_padding)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL;
    return false;
  }

  current_length = chain_prepare_for_write_(chain, use_padding);

  /* a return value of 0 means there was an error; chain->status is already set */
  if (0 == current_length)
    return false;

  FLAC__ASSERT(current_length != chain->initial_length);

  /* rewind */
  if(0 != callbacks.seek(handle, 0, SEEK_SET)) {
    chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
    return false;
  }

  if(!chain_rewrite_file_cb_(chain, handle, callbacks.read, callbacks.seek, callbacks.eof, temp_handle, temp_callbacks.write))
    return false;

  /* recompute lengths and offsets */
  {
    const FLAC__Metadata_Node *node;
    chain->initial_length = current_length;
    chain->last_offset = chain->first_offset;
    for(node = chain->head; node; node = node->next)
      chain->last_offset += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
  }

  return true;
}

FLAC_API void FLAC__metadata_chain_merge_padding(FLAC__Metadata_Chain *chain)
{
  FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != chain);

  for(node = chain->head; node; ) {
    if(!chain_merge_adjacent_padding_(chain, node))
      node = node->next;
  }
}

FLAC_API void FLAC__metadata_chain_sort_padding(FLAC__Metadata_Chain *chain)
{
  FLAC__Metadata_Node *node, *save;
  uint32_t i;

  FLAC__ASSERT(0 != chain);

  /*
   * Don't try and be too smart... this simple algo is good enough for
   * the small number of nodes that we deal with.
   */
  for(i = 0, node = chain->head; i < chain->nodes; i++) {
    if(node->data->type == FLAC__METADATA_TYPE_PADDING) {
      save = node->next;
      chain_remove_node_(chain, node);
      chain_append_node_(chain, node);
      node = save;
    }
    else {
      node = node->next;
    }
  }

  FLAC__metadata_chain_merge_padding(chain);
}


FLAC_API FLAC__Metadata_Iterator *FLAC__metadata_iterator_new(void)
{
  FLAC__Metadata_Iterator *iterator = calloc(1, sizeof(FLAC__Metadata_Iterator));

  /* calloc() implies:
    iterator->current = 0;
    iterator->chain = 0;
  */

  return iterator;
}

FLAC_API void FLAC__metadata_iterator_delete(FLAC__Metadata_Iterator *iterator)
{
  FLAC__ASSERT(0 != iterator);

  free(iterator);
}

FLAC_API void FLAC__metadata_iterator_init(FLAC__Metadata_Iterator *iterator, FLAC__Metadata_Chain *chain)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != chain);
  FLAC__ASSERT(0 != chain->head);

  iterator->chain = chain;
  iterator->current = chain->head;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_next(FLAC__Metadata_Iterator *iterator)
{
  FLAC__ASSERT(0 != iterator);

  if(0 == iterator->current || 0 == iterator->current->next)
    return false;

  iterator->current = iterator->current->next;
  return true;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_prev(FLAC__Metadata_Iterator *iterator)
{
  FLAC__ASSERT(0 != iterator);

  if(0 == iterator->current || 0 == iterator->current->prev)
    return false;

  iterator->current = iterator->current->prev;
  return true;
}

FLAC_API FLAC__MetadataType FLAC__metadata_iterator_get_block_type(const FLAC__Metadata_Iterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);
  FLAC__ASSERT(0 != iterator->current->data);

  return iterator->current->data->type;
}

FLAC_API FLAC__StreamMetadata *FLAC__metadata_iterator_get_block(FLAC__Metadata_Iterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);

  return iterator->current->data;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_set_block(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != block);
  return FLAC__metadata_iterator_delete_block(iterator, false) && FLAC__metadata_iterator_insert_block_after(iterator, block);
}

FLAC_API FLAC__bool FLAC__metadata_iterator_delete_block(FLAC__Metadata_Iterator *iterator, FLAC__bool replace_with_padding)
{
  FLAC__Metadata_Node *save;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);

  if(0 == iterator->current->prev) {
    FLAC__ASSERT(iterator->current->data->type == FLAC__METADATA_TYPE_STREAMINFO);
    return false;
  }

  save = iterator->current->prev;

  if(replace_with_padding) {
    FLAC__metadata_object_delete_data(iterator->current->data);
    iterator->current->data->type = FLAC__METADATA_TYPE_PADDING;
  }
  else {
    chain_delete_node_(iterator->chain, iterator->current);
  }

  iterator->current = save;
  return true;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_before(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block)
{
  FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);
  FLAC__ASSERT(0 != block);

  if(block->type == FLAC__METADATA_TYPE_STREAMINFO)
    return false;

  if(0 == iterator->current->prev) {
    FLAC__ASSERT(iterator->current->data->type == FLAC__METADATA_TYPE_STREAMINFO);
    return false;
  }

  if(0 == (node = node_new_()))
    return false;

  node->data = block;
  iterator_insert_node_(iterator, node);
  iterator->current = node;
  return true;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_after(FLAC__Metadata_Iterator *iterator, FLAC__StreamMetadata *block)
{
  FLAC__Metadata_Node *node;

  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->current);
  FLAC__ASSERT(0 != block);

  if(block->type == FLAC__METADATA_TYPE_STREAMINFO)
    return false;

  if(0 == (node = node_new_()))
    return false;

  node->data = block;
  iterator_insert_node_after_(iterator, node);
  iterator->current = node;
  return true;
}


/****************************************************************************
 *
 * Local function definitions
 *
 ***************************************************************************/

void pack_uint32_(FLAC__uint32 val, FLAC__byte *b, uint32_t bytes)
{
  uint32_t i;

  b += bytes;

  for(i = 0; i < bytes; i++) {
    *(--b) = (FLAC__byte)(val & 0xff);
    val >>= 8;
  }
}

void pack_uint32_little_endian_(FLAC__uint32 val, FLAC__byte *b, uint32_t bytes)
{
  uint32_t i;

  for(i = 0; i < bytes; i++) {
    *(b++) = (FLAC__byte)(val & 0xff);
    val >>= 8;
  }
}

void pack_uint64_(FLAC__uint64 val, FLAC__byte *b, uint32_t bytes)
{
  uint32_t i;

  b += bytes;

  for(i = 0; i < bytes; i++) {
    *(--b) = (FLAC__byte)(val & 0xff);
    val >>= 8;
  }
}

FLAC__uint32 unpack_uint32_(FLAC__byte *b, uint32_t bytes)
{
  FLAC__uint32 ret = 0;
  uint32_t i;

  for(i = 0; i < bytes; i++)
    ret = (ret << 8) | (FLAC__uint32)(*b++);

  return ret;
}

FLAC__uint32 unpack_uint32_little_endian_(FLAC__byte *b, uint32_t bytes)
{
  FLAC__uint32 ret = 0;
  uint32_t i;

  b += bytes;

  for(i = 0; i < bytes; i++)
    ret = (ret << 8) | (FLAC__uint32)(*--b);

  return ret;
}

FLAC__uint64 unpack_uint64_(FLAC__byte *b, uint32_t bytes)
{
  FLAC__uint64 ret = 0;
  uint32_t i;

  for(i = 0; i < bytes; i++)
    ret = (ret << 8) | (FLAC__uint64)(*b++);

  return ret;
}

FLAC__bool read_metadata_block_header_(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);

  if(!read_metadata_block_header_cb_((FLAC__IOHandle)iterator->file, (FLAC__IOCallback_Read)fread, &iterator->is_last, &iterator->type, &iterator->length)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    return false;
  }

  return true;
}

FLAC__bool read_metadata_block_data_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block)
{
  FLAC__ASSERT(0 != iterator);
  FLAC__ASSERT(0 != iterator->file);

  iterator->status = read_metadata_block_data_cb_((FLAC__IOHandle)iterator->file, (FLAC__IOCallback_Read)fread, fseek_wrapper_, block);

  return (iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);
}

FLAC__bool read_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__bool *is_last, FLAC__MetadataType *type, uint32_t *length)
{
  FLAC__byte raw_header[FLAC__STREAM_METADATA_HEADER_LENGTH];

  if(read_cb(raw_header, 1, FLAC__STREAM_METADATA_HEADER_LENGTH, handle) != FLAC__STREAM_METADATA_HEADER_LENGTH)
    return false;

  *is_last = raw_header[0] & 0x80? true : false;
  *type = (FLAC__MetadataType)(raw_header[0] & 0x7f);
  *length = unpack_uint32_(raw_header + 1, 3);

  /* Note that we don't check:
   *    if(iterator->type >= FLAC__METADATA_TYPE_UNDEFINED)
   * we just will read in an opaque block
   */

  return true;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata *block)
{
  switch(block->type) {
    case FLAC__METADATA_TYPE_STREAMINFO:
      return read_metadata_block_data_streaminfo_cb_(handle, read_cb, &block->data.stream_info);
    case FLAC__METADATA_TYPE_PADDING:
      return read_metadata_block_data_padding_cb_(handle, seek_cb, &block->data.padding, block->length);
    case FLAC__METADATA_TYPE_APPLICATION:
      return read_metadata_block_data_application_cb_(handle, read_cb, &block->data.application, block->length);
    case FLAC__METADATA_TYPE_SEEKTABLE:
      return read_metadata_block_data_seektable_cb_(handle, read_cb, &block->data.seek_table, block->length);
    case FLAC__METADATA_TYPE_VORBIS_COMMENT:
      return read_metadata_block_data_vorbis_comment_cb_(handle, read_cb, seek_cb, &block->data.vorbis_comment, block->length);
    case FLAC__METADATA_TYPE_CUESHEET:
      return read_metadata_block_data_cuesheet_cb_(handle, read_cb, &block->data.cue_sheet);
    case FLAC__METADATA_TYPE_PICTURE:
      return read_metadata_block_data_picture_cb_(handle, read_cb, &block->data.picture);
    default:
      return read_metadata_block_data_unknown_cb_(handle, read_cb, &block->data.unknown, block->length);
  }
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_StreamInfo *block)
{
  FLAC__byte buffer[FLAC__STREAM_METADATA_STREAMINFO_LENGTH], *b;

  if(read_cb(buffer, 1, FLAC__STREAM_METADATA_STREAMINFO_LENGTH, handle) != FLAC__STREAM_METADATA_STREAMINFO_LENGTH)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

  b = buffer;

  /* we are using hardcoded numbers for simplicity but we should
   * probably eventually write a bit-level unpacker and use the
   * _STREAMINFO_ constants.
   */
  block->min_blocksize = unpack_uint32_(b, 2); b += 2;
  block->max_blocksize = unpack_uint32_(b, 2); b += 2;
  block->min_framesize = unpack_uint32_(b, 3); b += 3;
  block->max_framesize = unpack_uint32_(b, 3); b += 3;
  block->sample_rate = (unpack_uint32_(b, 2) << 4) | ((uint32_t)(b[2] & 0xf0) >> 4);
  block->channels = (uint32_t)((b[2] & 0x0e) >> 1) + 1;
  block->bits_per_sample = ((((uint32_t)(b[2] & 0x01)) << 4) | (((uint32_t)(b[3] & 0xf0)) >> 4)) + 1;
  block->total_samples = (((FLAC__uint64)(b[3] & 0x0f)) << 32) | unpack_uint64_(b+4, 4);
  memcpy(block->md5sum, b+8, 16);

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding *block, uint32_t block_length)
{
  (void)block; /* nothing to do; we don't care about reading the padding bytes */

  if(0 != seek_cb(handle, block_length, SEEK_CUR))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application *block, uint32_t block_length)
{
  const uint32_t id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;

  if(read_cb(block->id, 1, id_bytes, handle) != id_bytes)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

  if(block_length < id_bytes)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

  block_length -= id_bytes;

  if(block_length == 0) {
    block->data = 0;
  }
  else {
    if(0 == (block->data = malloc(block_length)))
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    if(read_cb(block->data, 1, block_length, handle) != block_length)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  }

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable *block, uint32_t block_length)
{
  uint32_t i;
  FLAC__byte buffer[FLAC__STREAM_METADATA_SEEKPOINT_LENGTH];

  if(block_length % FLAC__STREAM_METADATA_SEEKPOINT_LENGTH != 0)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;

  block->num_points = block_length / FLAC__STREAM_METADATA_SEEKPOINT_LENGTH;

  if(block->num_points == 0)
    block->points = 0;
  else if(0 == (block->points = safe_malloc_mul_2op_p(block->num_points, /*times*/sizeof(FLAC__StreamMetadata_SeekPoint))))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  for(i = 0; i < block->num_points; i++) {
    if(read_cb(buffer, 1, FLAC__STREAM_METADATA_SEEKPOINT_LENGTH, handle) != FLAC__STREAM_METADATA_SEEKPOINT_LENGTH)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    /* some MAGIC NUMBERs here */
    block->points[i].sample_number = unpack_uint64_(buffer, 8);
    block->points[i].stream_offset = unpack_uint64_(buffer+8, 8);
    block->points[i].frame_samples = unpack_uint32_(buffer+16, 2);
  }

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry *entry, uint32_t max_length)
{
  const uint32_t entry_length_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
  FLAC__byte buffer[4]; /* magic number is asserted below */

  FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8 == sizeof(buffer));

  if(max_length < entry_length_len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;

  max_length -= entry_length_len;
  if(read_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  entry->length = unpack_uint32_little_endian_(buffer, entry_length_len);
  if(max_length < entry->length) {
    entry->length = 0;
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;
  }

  if(0 != entry->entry)
    free(entry->entry);

  if(0 == (entry->entry = safe_malloc_add_2op_(entry->length, /*+*/1)))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  if(entry->length > 0 && read_cb(entry->entry, 1, entry->length, handle) != entry->length)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

  entry->entry[entry->length] = '\0';

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_VorbisComment *block, uint32_t block_length)
{
  uint32_t i;
  FLAC__Metadata_SimpleIteratorStatus status;
  const uint32_t num_comments_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8;
  FLAC__byte buffer[4]; /* magic number is asserted below */

  FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8 == sizeof(buffer));

  status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, &(block->vendor_string), block_length);
  if(block_length >= 4)
    block_length -= 4;
  if(status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA)
    goto skip;
  else if(status != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
    return status;
  block_length -= block->vendor_string.length;

  if(block_length < num_comments_len) goto skip; else block_length -= num_comments_len;
  if(read_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->num_comments = unpack_uint32_little_endian_(buffer, num_comments_len);

  if(block->num_comments == 0) {
    block->comments = 0;
  }
  else if(block->num_comments > (block_length >> 2)) { /* each comment needs at least 4 byte */
    block->num_comments = 0;
    status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;
    goto skip;
  }
  else if(0 == (block->comments = calloc(block->num_comments, sizeof(FLAC__StreamMetadata_VorbisComment_Entry)))) {
    block->num_comments = 0;
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
  }

  for(i = 0; i < block->num_comments; i++) {
    status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, block->comments + i, block_length);
    if(block_length >= 4) block_length -= 4;
    if(status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA) {
      block->num_comments = i;
      goto skip;
    }
    else if(status != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK) return status;
    block_length -= block->comments[i].length;
  }

  skip:
  if(block_length > 0) {
    /* bad metadata */
    if(0 != seek_cb(handle, block_length, SEEK_CUR))
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
  }

  return status;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track *track)
{
  uint32_t i, len;
  FLAC__byte buffer[32]; /* asserted below that this is big enough */

  FLAC__ASSERT(sizeof(buffer) >= sizeof(FLAC__uint64));
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8);

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  track->offset = unpack_uint64_(buffer, len);

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  track->number = (FLAC__byte)unpack_uint32_(buffer, len);

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN / 8;
  if(read_cb(track->isrc, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

  FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) % 8 == 0);
  len = (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN == 1);
  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN == 1);
  track->type = buffer[0] >> 7;
  track->pre_emphasis = (buffer[0] >> 6) & 1;

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  track->num_indices = (FLAC__byte)unpack_uint32_(buffer, len);

  if(track->num_indices == 0) {
    track->indices = 0;
  }
  else if(0 == (track->indices = calloc(track->num_indices, sizeof(FLAC__StreamMetadata_CueSheet_Index))))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  for(i = 0; i < track->num_indices; i++) {
    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN / 8;
    if(read_cb(buffer, 1, len, handle) != len)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    track->indices[i].offset = unpack_uint64_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN / 8;
    if(read_cb(buffer, 1, len, handle) != len)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    track->indices[i].number = (FLAC__byte)unpack_uint32_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8;
    if(read_cb(buffer, 1, len, handle) != len)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  }

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet *block)
{
  uint32_t i, len;
  FLAC__Metadata_SimpleIteratorStatus status;
  FLAC__byte buffer[1024]; /* MSVC needs a constant expression so we put a magic number and assert */

  FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN)/8 <= sizeof(buffer));
  FLAC__ASSERT(sizeof(FLAC__uint64) <= sizeof(buffer));

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN / 8;
  if(read_cb(block->media_catalog_number, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->lead_in = unpack_uint64_(buffer, len);

  FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) % 8 == 0);
  len = (FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->is_cd = buffer[0]&0x80? true : false;

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->num_tracks = unpack_uint32_(buffer, len);

  if(block->num_tracks == 0) {
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;
  }
  else if(0 == (block->tracks = calloc(block->num_tracks, sizeof(FLAC__StreamMetadata_CueSheet_Track))))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  for(i = 0; i < block->num_tracks; i++) {
    if(FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = read_metadata_block_data_cuesheet_track_cb_(handle, read_cb, block->tracks + i)))
      return status;
  }

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cstring_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__byte **data, FLAC__uint32 *length, FLAC__uint32 length_len)
{
  FLAC__byte buffer[sizeof(FLAC__uint32)];

  FLAC__ASSERT(0 != data);
  FLAC__ASSERT(length_len%8 == 0);

  length_len /= 8; /* convert to bytes */

  FLAC__ASSERT(sizeof(buffer) >= length_len);

  if(read_cb(buffer, 1, length_len, handle) != length_len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  *length = unpack_uint32_(buffer, length_len);

  if(*length > (1u << FLAC__STREAM_METADATA_LENGTH_LEN)) /* data cannot be larger than FLAC metadata block */
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA;

  if(0 != *data)
    free(*data);

  if(0 == (*data = safe_malloc_add_2op_(*length, /*+*/1)))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  if(*length > 0) {
    if(read_cb(*data, 1, *length, handle) != *length)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  }

  (*data)[*length] = '\0';

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture *block)
{
  FLAC__Metadata_SimpleIteratorStatus status;
  FLAC__byte buffer[4]; /* asserted below that this is big enough */
  FLAC__uint32 len;

  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_TYPE_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_COLORS_LEN/8);

  FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_TYPE_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_PICTURE_TYPE_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->type = (FLAC__StreamMetadata_Picture_Type)unpack_uint32_(buffer, len);

  if((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, (FLAC__byte**)(&(block->mime_type)), &len, FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
    return status;

  if((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, &(block->description), &len, FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
    return status;

  FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->width = unpack_uint32_(buffer, len);

  FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->height = unpack_uint32_(buffer, len);

  FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->depth = unpack_uint32_(buffer, len);

  FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_COLORS_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_PICTURE_COLORS_LEN / 8;
  if(read_cb(buffer, 1, len, handle) != len)
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  block->colors = unpack_uint32_(buffer, len);

  /* for convenience we use read_metadata_block_data_picture_cstring_cb_() even though it adds an extra terminating NUL we don't use */
  if((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, &(block->data), &(block->data_length), FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
    return status;

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Unknown *block, uint32_t block_length)
{
  if(block_length == 0) {
    block->data = 0;
  }
  else {
    if(0 == (block->data = malloc(block_length)))
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    if(read_cb(block->data, 1, block_length, handle) != block_length)
      return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
  }

  return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__bool write_metadata_block_header_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block)
{
  FLAC__ASSERT(0 != file);
  FLAC__ASSERT(0 != status);

  if(!write_metadata_block_header_cb_((FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, block)) {
    *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
    return false;
  }

  return true;
}

FLAC__bool write_metadata_block_data_(FILE *file, FLAC__Metadata_SimpleIteratorStatus *status, const FLAC__StreamMetadata *block)
{
  FLAC__ASSERT(0 != file);
  FLAC__ASSERT(0 != status);

  if (write_metadata_block_data_cb_((FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, block)) {
    *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
    return true;
  }
  else {
    *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
    return false;
  }
}

FLAC__bool write_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block)
{
  FLAC__byte buffer[FLAC__STREAM_METADATA_HEADER_LENGTH];

  FLAC__ASSERT(block->length < (1u << FLAC__STREAM_METADATA_LENGTH_LEN));
  /* double protection */
  if(block->length >= (1u << FLAC__STREAM_METADATA_LENGTH_LEN))
    return false;

  buffer[0] = (block->is_last? 0x80 : 0) | (FLAC__byte)block->type;
  pack_uint32_(block->length, buffer + 1, 3);

  if(write_cb(buffer, 1, FLAC__STREAM_METADATA_HEADER_LENGTH, handle) != FLAC__STREAM_METADATA_HEADER_LENGTH)
    return false;

  return true;
}

FLAC__bool write_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata *block)
{
  FLAC__ASSERT(0 != block);

  switch(block->type) {
    case FLAC__METADATA_TYPE_STREAMINFO:
      return write_metadata_block_data_streaminfo_cb_(handle, write_cb, &block->data.stream_info);
    case FLAC__METADATA_TYPE_PADDING:
      return write_metadata_block_data_padding_cb_(handle, write_cb, &block->data.padding, block->length);
    case FLAC__METADATA_TYPE_APPLICATION:
      return write_metadata_block_data_application_cb_(handle, write_cb, &block->data.application, block->length);
    case FLAC__METADATA_TYPE_SEEKTABLE:
      return write_metadata_block_data_seektable_cb_(handle, write_cb, &block->data.seek_table);
    case FLAC__METADATA_TYPE_VORBIS_COMMENT:
      return write_metadata_block_data_vorbis_comment_cb_(handle, write_cb, &block->data.vorbis_comment);
    case FLAC__METADATA_TYPE_CUESHEET:
      return write_metadata_block_data_cuesheet_cb_(handle, write_cb, &block->data.cue_sheet);
    case FLAC__METADATA_TYPE_PICTURE:
      return write_metadata_block_data_picture_cb_(handle, write_cb, &block->data.picture);
    default:
      return write_metadata_block_data_unknown_cb_(handle, write_cb, &block->data.unknown, block->length);
  }
}

FLAC__bool write_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_StreamInfo *block)
{
  FLAC__byte buffer[FLAC__STREAM_METADATA_STREAMINFO_LENGTH];
  const uint32_t channels1 = block->channels - 1;
  const uint32_t bps1 = block->bits_per_sample - 1;

  /* we are using hardcoded numbers for simplicity but we should
   * probably eventually write a bit-level packer and use the
   * _STREAMINFO_ constants.
   */
  pack_uint32_(block->min_blocksize, buffer, 2);
  pack_uint32_(block->max_blocksize, buffer+2, 2);
  pack_uint32_(block->min_framesize, buffer+4, 3);
  pack_uint32_(block->max_framesize, buffer+7, 3);
  buffer[10] = (block->sample_rate >> 12) & 0xff;
  buffer[11] = (block->sample_rate >> 4) & 0xff;
  buffer[12] = ((block->sample_rate & 0x0f) << 4) | (channels1 << 1) | (bps1 >> 4);
  buffer[13] = (FLAC__byte)(((bps1 & 0x0f) << 4) | ((block->total_samples >> 32) & 0x0f));
  pack_uint32_((FLAC__uint32)block->total_samples, buffer+14, 4);
  memcpy(buffer+18, block->md5sum, 16);

  if(write_cb(buffer, 1, FLAC__STREAM_METADATA_STREAMINFO_LENGTH, handle) != FLAC__STREAM_METADATA_STREAMINFO_LENGTH)
    return false;

  return true;
}

FLAC__bool write_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Padding *block, uint32_t block_length)
{
  uint32_t i, n = block_length;
  FLAC__byte buffer[1024];

  (void)block;

  memset(buffer, 0, 1024);

  for(i = 0; i < n/1024; i++)
    if(write_cb(buffer, 1, 1024, handle) != 1024)
      return false;

  n %= 1024;

  if(write_cb(buffer, 1, n, handle) != n)
    return false;

  return true;
}

FLAC__bool write_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Application *block, uint32_t block_length)
{
  const uint32_t id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;

  if(write_cb(block->id, 1, id_bytes, handle) != id_bytes)
    return false;

  block_length -= id_bytes;

  if(write_cb(block->data, 1, block_length, handle) != block_length)
    return false;

  return true;
}

FLAC__bool write_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_SeekTable *block)
{
  uint32_t i;
  FLAC__byte buffer[FLAC__STREAM_METADATA_SEEKPOINT_LENGTH];

  for(i = 0; i < block->num_points; i++) {
    /* some MAGIC NUMBERs here */
    pack_uint64_(block->points[i].sample_number, buffer, 8);
    pack_uint64_(block->points[i].stream_offset, buffer+8, 8);
    pack_uint32_(block->points[i].frame_samples, buffer+16, 2);
    if(write_cb(buffer, 1, FLAC__STREAM_METADATA_SEEKPOINT_LENGTH, handle) != FLAC__STREAM_METADATA_SEEKPOINT_LENGTH)
      return false;
  }

  return true;
}

FLAC__bool write_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_VorbisComment *block)
{
  uint32_t i;
  const uint32_t entry_length_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
  const uint32_t num_comments_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8;
  FLAC__byte buffer[4]; /* magic number is asserted below */

  FLAC__ASSERT(flac_max(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN, FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN) / 8 == sizeof(buffer));

  pack_uint32_little_endian_(block->vendor_string.length, buffer, entry_length_len);
  if(write_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
    return false;
  if(write_cb(block->vendor_string.entry, 1, block->vendor_string.length, handle) != block->vendor_string.length)
    return false;

  pack_uint32_little_endian_(block->num_comments, buffer, num_comments_len);
  if(write_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
    return false;

  for(i = 0; i < block->num_comments; i++) {
    pack_uint32_little_endian_(block->comments[i].length, buffer, entry_length_len);
    if(write_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
      return false;
    if(write_cb(block->comments[i].entry, 1, block->comments[i].length, handle) != block->comments[i].length)
      return false;
  }

  return true;
}

FLAC__bool write_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_CueSheet *block)
{
  uint32_t i, j, len;
  FLAC__byte buffer[1024]; /* asserted below that this is big enough */

  FLAC__ASSERT(sizeof(buffer) >= sizeof(FLAC__uint64));
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN)/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN/8);

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN / 8;
  if(write_cb(block->media_catalog_number, 1, len, handle) != len)
    return false;

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN / 8;
  pack_uint64_(block->lead_in, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) % 8 == 0);
  len = (FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8;
  memset(buffer, 0, len);
  if(block->is_cd)
    buffer[0] |= 0x80;
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN % 8 == 0);
  len = FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN / 8;
  pack_uint32_(block->num_tracks, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  for(i = 0; i < block->num_tracks; i++) {
    FLAC__StreamMetadata_CueSheet_Track *track = block->tracks + i;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN / 8;
    pack_uint64_(track->offset, buffer, len);
    if(write_cb(buffer, 1, len, handle) != len)
      return false;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN / 8;
    pack_uint32_(track->number, buffer, len);
    if(write_cb(buffer, 1, len, handle) != len)
      return false;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN / 8;
    if(write_cb(track->isrc, 1, len, handle) != len)
      return false;

    FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) % 8 == 0);
    len = (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8;
    memset(buffer, 0, len);
    buffer[0] = (track->type << 7) | (track->pre_emphasis << 6);
    if(write_cb(buffer, 1, len, handle) != len)
      return false;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN / 8;
    pack_uint32_(track->num_indices, buffer, len);
    if(write_cb(buffer, 1, len, handle) != len)
      return false;

    for(j = 0; j < track->num_indices; j++) {
      FLAC__StreamMetadata_CueSheet_Index *indx = track->indices + j;

      FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN % 8 == 0);
      len = FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN / 8;
      pack_uint64_(indx->offset, buffer, len);
      if(write_cb(buffer, 1, len, handle) != len)
        return false;

      FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN % 8 == 0);
      len = FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN / 8;
      pack_uint32_(indx->number, buffer, len);
      if(write_cb(buffer, 1, len, handle) != len)
        return false;

      FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN % 8 == 0);
      len = FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8;
      memset(buffer, 0, len);
      if(write_cb(buffer, 1, len, handle) != len)
        return false;
    }
  }

  return true;
}

FLAC__bool write_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Picture *block)
{
  uint32_t len;
  size_t slen;
  FLAC__byte buffer[4]; /* magic number is asserted below */

  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_TYPE_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_COLORS_LEN%8);
  FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN%8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_TYPE_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_COLORS_LEN/8);
  FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN/8);

  len = FLAC__STREAM_METADATA_PICTURE_TYPE_LEN/8;
  pack_uint32_(block->type, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN/8;
  slen = strlen(block->mime_type);
  pack_uint32_(slen, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;
  if(write_cb(block->mime_type, 1, slen, handle) != slen)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN/8;
  slen = strlen((const char *)block->description);
  pack_uint32_(slen, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;
  if(write_cb(block->description, 1, slen, handle) != slen)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN/8;
  pack_uint32_(block->width, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN/8;
  pack_uint32_(block->height, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN/8;
  pack_uint32_(block->depth, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_COLORS_LEN/8;
  pack_uint32_(block->colors, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;

  len = FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN/8;
  pack_uint32_(block->data_length, buffer, len);
  if(write_cb(buffer, 1, len, handle) != len)
    return false;
  if(write_cb(block->data, 1, block->data_length, handle) != block->data_length)
    return false;

  return true;
}

FLAC__bool write_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Unknown *block, uint32_t block_length)
{
  if(write_cb(block->data, 1, block_length, handle) != block_length)
    return false;

  return true;
}

FLAC__bool write_metadata_block_stationary_(FLAC__Metadata_SimpleIterator *iterator, const FLAC__StreamMetadata *block)
{
  if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  if(!write_metadata_block_header_(iterator->file, &iterator->status, block))
    return false;

  if(!write_metadata_block_data_(iterator->file, &iterator->status, block))
    return false;

  if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  return read_metadata_block_header_(iterator);
}

FLAC__bool write_metadata_block_stationary_with_padding_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, uint32_t padding_length, FLAC__bool padding_is_last)
{
  FLAC__StreamMetadata *padding;

  if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  block->is_last = false;

  if(!write_metadata_block_header_(iterator->file, &iterator->status, block))
    return false;

  if(!write_metadata_block_data_(iterator->file, &iterator->status, block))
    return false;

  if(0 == (padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING)))
    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

  padding->is_last = padding_is_last;
  padding->length = padding_length;

  if(!write_metadata_block_header_(iterator->file, &iterator->status, padding)) {
    FLAC__metadata_object_delete(padding);
    return false;
  }

  if(!write_metadata_block_data_(iterator->file, &iterator->status, padding)) {
    FLAC__metadata_object_delete(padding);
    return false;
  }

  FLAC__metadata_object_delete(padding);

  if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  return read_metadata_block_header_(iterator);
}

FLAC__bool rewrite_whole_file_(FLAC__Metadata_SimpleIterator *iterator, FLAC__StreamMetadata *block, FLAC__bool append)
{
  FILE *tempfile = NULL;
  char *tempfilename = NULL;
  int fixup_is_last_code = 0; /* 0 => no need to change any is_last flags */
  FLAC__off_t fixup_is_last_flag_offset = -1;

  FLAC__ASSERT(0 != block || append == false);

  if(iterator->is_last) {
    if(append) {
      fixup_is_last_code = 1; /* 1 => clear the is_last flag at the following offset */
      fixup_is_last_flag_offset = iterator->offset[iterator->depth];
    }
    else if(0 == block) {
      simple_iterator_push_(iterator);
      if(!FLAC__metadata_simple_iterator_prev(iterator)) {
        (void)simple_iterator_pop_(iterator);
        return false;
      }
      fixup_is_last_code = -1; /* -1 => set the is_last the flag at the following offset */
      fixup_is_last_flag_offset = iterator->offset[iterator->depth];
      if(!simple_iterator_pop_(iterator))
        return false;
    }
  }

  if(!simple_iterator_copy_file_prefix_(iterator, &tempfile, &tempfilename, append))
    return false;

  if(0 != block) {
    if(!write_metadata_block_header_(tempfile, &iterator->status, block)) {
      cleanup_tempfile_(&tempfile, &tempfilename);
      return false;
    }

    if(!write_metadata_block_data_(tempfile, &iterator->status, block)) {
      cleanup_tempfile_(&tempfile, &tempfilename);
      return false;
    }
  }

  if(!simple_iterator_copy_file_postfix_(iterator, &tempfile, &tempfilename, fixup_is_last_code, fixup_is_last_flag_offset, block==0))
    return false;

  if(append)
    return FLAC__metadata_simple_iterator_next(iterator);

  return true;
}

void simple_iterator_push_(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(iterator->depth+1 < SIMPLE_ITERATOR_MAX_PUSH_DEPTH);
  iterator->offset[iterator->depth+1] = iterator->offset[iterator->depth];
  iterator->depth++;
}

FLAC__bool simple_iterator_pop_(FLAC__Metadata_SimpleIterator *iterator)
{
  FLAC__ASSERT(iterator->depth > 0);
  iterator->depth--;
  if(0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }

  return read_metadata_block_header_(iterator);
}

/* return meanings:
 * 0: ok
 * 1: read error
 * 2: seek error
 * 3: not a FLAC file
 */
uint32_t seek_to_first_metadata_block_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb)
{
  FLAC__byte buffer[4];
  size_t n;
  uint32_t i;

  FLAC__ASSERT(FLAC__STREAM_SYNC_LENGTH == sizeof(buffer));

  /* skip any id3v2 tag */
  errno = 0;
  n = read_cb(buffer, 1, 4, handle);
  if(errno)
    return 1;
  else if(n != 4)
    return 3;
  else if(0 == memcmp(buffer, "ID3", 3)) {
    uint32_t tag_length = 0;

    /* skip to the tag length */
    if(seek_cb(handle, 2, SEEK_CUR) < 0)
      return 2;

    /* read the length */
    for(i = 0; i < 4; i++) {
      if(read_cb(buffer, 1, 1, handle) < 1 || buffer[0] & 0x80)
        return 1;
      tag_length <<= 7;
      tag_length |= (buffer[0] & 0x7f);
    }

    /* skip the rest of the tag */
    if(seek_cb(handle, tag_length, SEEK_CUR) < 0)
      return 2;

    /* read the stream sync code */
    errno = 0;
    n = read_cb(buffer, 1, 4, handle);
    if(errno)
      return 1;
    else if(n != 4)
      return 3;
  }

  /* check for the fLaC signature */
  if(0 == memcmp(FLAC__STREAM_SYNC_STRING, buffer, FLAC__STREAM_SYNC_LENGTH))
    return 0;
  else
    return 3;
}

uint32_t seek_to_first_metadata_block_(FILE *f)
{
  return seek_to_first_metadata_block_cb_((FLAC__IOHandle)f, (FLAC__IOCallback_Read)fread, fseek_wrapper_);
}

FLAC__bool simple_iterator_copy_file_prefix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, FLAC__bool append)
{
  const FLAC__off_t offset_end = append? iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length : iterator->offset[iterator->depth];

  if(0 != fseeko(iterator->file, 0, SEEK_SET)) {
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }
  if(!open_tempfile_(iterator->filename, iterator->tempfile_path_prefix, tempfile, tempfilename, &iterator->status)) {
    cleanup_tempfile_(tempfile, tempfilename);
    return false;
  }
  if(!copy_n_bytes_from_file_(iterator->file, *tempfile, offset_end, &iterator->status)) {
    cleanup_tempfile_(tempfile, tempfilename);
    return false;
  }

  return true;
}

FLAC__bool simple_iterator_copy_file_postfix_(FLAC__Metadata_SimpleIterator *iterator, FILE **tempfile, char **tempfilename, int fixup_is_last_code, FLAC__off_t fixup_is_last_flag_offset, FLAC__bool backup)
{
  FLAC__off_t save_offset = iterator->offset[iterator->depth];
  FLAC__ASSERT(0 != *tempfile);

  if(0 != fseeko(iterator->file, save_offset + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length, SEEK_SET)) {
    cleanup_tempfile_(tempfile, tempfilename);
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
    return false;
  }
  if(!copy_remaining_bytes_from_file_(iterator->file, *tempfile, &iterator->status)) {
    cleanup_tempfile_(tempfile, tempfilename);
    return false;
  }

  if(fixup_is_last_code != 0) {
    /*
     * if code == 1, it means a block was appended to the end so
     *   we have to clear the is_last flag of the previous block
     * if code == -1, it means the last block was deleted so
     *   we have to set the is_last flag of the previous block
     */
    /* MAGIC NUMBERs here; we know the is_last flag is the high bit of the byte at this location */
    FLAC__byte x;
    if(0 != fseeko(*tempfile, fixup_is_last_flag_offset, SEEK_SET)) {
      cleanup_tempfile_(tempfile, tempfilename);
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
      return false;
    }
    if(fread(&x, 1, 1, *tempfile) != 1) {
      cleanup_tempfile_(tempfile, tempfilename);
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
      return false;
    }
    if(fixup_is_last_code > 0) {
      FLAC__ASSERT(x & 0x80);
      x &= 0x7f;
    }
    else {
      FLAC__ASSERT(!(x & 0x80));
      x |= 0x80;
    }
    if(0 != fseeko(*tempfile, fixup_is_last_flag_offset, SEEK_SET)) {
      cleanup_tempfile_(tempfile, tempfilename);
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
      return false;
    }
    if(local__fwrite(&x, 1, 1, *tempfile) != 1) {
      cleanup_tempfile_(tempfile, tempfilename);
      iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
      return false;
    }
  }

  (void)fclose(iterator->file);

  if(!transport_tempfile_(iterator->filename, tempfile, tempfilename, &iterator->status))
    return false;

  if(iterator->has_stats)
    set_file_stats_(iterator->filename, &iterator->stats);

  if(!simple_iterator_prime_input_(iterator, !iterator->is_writable))
    return false;
  if(backup) {
    while(iterator->offset[iterator->depth] + (FLAC__off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (FLAC__off_t)iterator->length < save_offset)
      if(!FLAC__metadata_simple_iterator_next(iterator))
        return false;
    return true;
  }
  else {
    /* move the iterator to it's original block faster by faking a push, then doing a pop_ */
    FLAC__ASSERT(iterator->depth == 0);
    iterator->offset[0] = save_offset;
    iterator->depth++;
    return simple_iterator_pop_(iterator);
  }
}

FLAC__bool copy_n_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status)
{
  FLAC__byte buffer[8192];
  size_t n;

  FLAC__ASSERT(bytes >= 0);
  while(bytes > 0) {
    n = flac_min(sizeof(buffer), (size_t)bytes);
    if(fread(buffer, 1, n, file) != n) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
      return false;
    }
    if(local__fwrite(buffer, 1, n, tempfile) != n) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
      return false;
    }
    bytes -= n;
  }

  return true;
}

FLAC__bool copy_n_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__off_t bytes, FLAC__Metadata_SimpleIteratorStatus *status)
{
  FLAC__byte buffer[8192];
  size_t n;

  FLAC__ASSERT(bytes >= 0);
  while(bytes > 0) {
    n = flac_min(sizeof(buffer), (size_t)bytes);
    if(read_cb(buffer, 1, n, handle) != n) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
      return false;
    }
    if(temp_write_cb(buffer, 1, n, temp_handle) != n) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
      return false;
    }
    bytes -= n;
  }

  return true;
}

FLAC__bool copy_remaining_bytes_from_file_(FILE *file, FILE *tempfile, FLAC__Metadata_SimpleIteratorStatus *status)
{
  FLAC__byte buffer[8192];
  size_t n;

  while(!feof(file)) {
    n = fread(buffer, 1, sizeof(buffer), file);
    if(n == 0 && !feof(file)) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
      return false;
    }
    if(n > 0 && local__fwrite(buffer, 1, n, tempfile) != n) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
      return false;
    }
  }

  return true;
}

FLAC__bool copy_remaining_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__Metadata_SimpleIteratorStatus *status)
{
  FLAC__byte buffer[8192];
  size_t n;

  while(!eof_cb(handle)) {
    n = read_cb(buffer, 1, sizeof(buffer), handle);
    if(n == 0 && !eof_cb(handle)) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
      return false;
    }
    if(n > 0 && temp_write_cb(buffer, 1, n, temp_handle) != n) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
      return false;
    }
  }

  return true;
}

static int
local_snprintf(char *str, size_t size, const char *fmt, ...)
{
  va_list va;
  int rc;

#if defined _MSC_VER
  if (size == 0)
    return 1024;
#endif

  va_start (va, fmt);

#if defined _MSC_VER
  rc = vsnprintf_s (str, size, _TRUNCATE, fmt, va);
  if (rc < 0)
    rc = size - 1;
#elif defined __MINGW32__
  rc = __mingw_vsnprintf (str, size, fmt, va);
#else
  rc = vsnprintf (str, size, fmt, va);
#endif
  va_end (va);

  return rc;
}

FLAC__bool open_tempfile_(const char *filename, const char *tempfile_path_prefix, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status)
{
  static const char *tempfile_suffix = ".metadata_edit";
  if(0 == tempfile_path_prefix) {
    size_t dest_len = strlen(filename) + strlen(tempfile_suffix) + 1;
    if(0 == (*tempfilename = safe_malloc_(dest_len))) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
      return false;
    }
    local_snprintf(*tempfilename, dest_len, "%s%s", filename, tempfile_suffix);
  }
  else {
    const char *p = strrchr(filename, '/');
    size_t dest_len;
    if(0 == p)
      p = filename;
    else
      p++;

    dest_len = strlen(tempfile_path_prefix) + strlen(p) + strlen(tempfile_suffix) + 2;

    if(0 == (*tempfilename = safe_malloc_(dest_len))) {
      *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
      return false;
    }
    local_snprintf(*tempfilename, dest_len, "%s/%s%s", tempfile_path_prefix, p, tempfile_suffix);
  }

  if(0 == (*tempfile = flac_fopen(*tempfilename, "w+b"))) {
    *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
    return false;
  }

  return true;
}

FLAC__bool transport_tempfile_(const char *filename, FILE **tempfile, char **tempfilename, FLAC__Metadata_SimpleIteratorStatus *status)
{
  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != tempfile);
  FLAC__ASSERT(0 != *tempfile);
  FLAC__ASSERT(0 != tempfilename);
  FLAC__ASSERT(0 != *tempfilename);
  FLAC__ASSERT(0 != status);

  (void)fclose(*tempfile);
  *tempfile = 0;

#if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__ || defined __EMX__
  /* on some flavors of windows, flac_rename() will fail if the destination already exists */
  if(flac_unlink(filename) < 0) {
    cleanup_tempfile_(tempfile, tempfilename);
    *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR;
    return false;
  }
#endif

  /*@@@ to fully support the tempfile_path_prefix we need to update this piece to actually copy across filesystems instead of just flac_rename(): */
  if(0 != flac_rename(*tempfilename, filename)) {
    cleanup_tempfile_(tempfile, tempfilename);
    *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR;
    return false;
  }

  cleanup_tempfile_(tempfile, tempfilename);

  return true;
}

void cleanup_tempfile_(FILE **tempfile, char **tempfilename)
{
  if(0 != *tempfile) {
    (void)fclose(*tempfile);
    *tempfile = 0;
  }

  if(0 != *tempfilename) {
    (void)flac_unlink(*tempfilename);
    free(*tempfilename);
    *tempfilename = 0;
  }
}

FLAC__bool get_file_stats_(const char *filename, struct flac_stat_s *stats)
{
  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != stats);
  return (0 == flac_stat(filename, stats));
}

void set_file_stats_(const char *filename, struct flac_stat_s *stats)
{
#if defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE >= 200809L) && !defined(_WIN32)
  struct timespec srctime[2] = {};
  srctime[0].tv_sec = stats->st_atime;
  srctime[1].tv_sec = stats->st_mtime;
#else
  struct utimbuf srctime;
  srctime.actime = stats->st_atime;
  srctime.modtime = stats->st_mtime;
#endif

  FLAC__ASSERT(0 != filename);
  FLAC__ASSERT(0 != stats);

  (void)flac_chmod(filename, stats->st_mode);
  (void)flac_utime(filename, &srctime);
#if !defined _MSC_VER && !defined __BORLANDC__ && !defined __MINGW32__
  FLAC_CHECK_RETURN(chown(filename, stats->st_uid, -1));
  FLAC_CHECK_RETURN(chown(filename, -1, stats->st_gid));
#endif
}

int fseek_wrapper_(FLAC__IOHandle handle, FLAC__int64 offset, int whence)
{
  return fseeko((FILE*)handle, (FLAC__off_t)offset, whence);
}

FLAC__int64 ftell_wrapper_(FLAC__IOHandle handle)
{
  return ftello((FILE*)handle);
}

FLAC__Metadata_ChainStatus get_equivalent_status_(FLAC__Metadata_SimpleIteratorStatus status)
{
  switch(status) {
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK:
      return FLAC__METADATA_CHAIN_STATUS_OK;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT:
      return FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE:
      return FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE:
      return FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE:
      return FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA:
      return FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR:
      return FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR:
      return FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR:
      return FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR:
      return FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR:
      return FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR:
      return FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
    case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR:
    default:
      return FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
  }
}

Coverage Report

Created: 2024-07-23 06:08