/* grabbag - Convenience lib for various routines common to several tools

 * Copyright (C) 2002-2009  Josh Coalson

 * Copyright (C) 2011-2023  Xiph.Org Foundation

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 */

#ifdef HAVE_CONFIG_H

#  include <config.h>

#endif

#include <locale.h>

#include <math.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#if defined _MSC_VER || defined __MINGW32__

#include <io.h> /* for chmod() */

#endif

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

#include "FLAC/assert.h"

#include "FLAC/metadata.h"

#include "FLAC/stream_decoder.h"

#include "share/grabbag.h"

#include "share/replaygain_analysis.h"

#include "share/safe_str.h"

#ifdef local_min

#undef local_min

#endif

#define local_min(a,b) ((a)<(b)?(a):(b))

#ifdef local_max

#undef local_max

#endif

#define local_max(a,b) ((a)>(b)?(a):(b))

#ifdef abs32

#undef abs32

#endif

#define abs32(a) (((a)==INT32_MIN)?INT32_MAX:abs(a))

static const char *reference_format_ = "%s=%2.1f dB";

static const char *gain_format_ = "%s=%+2.2f dB";

static const char *peak_format_ = "%s=%1.8f";

static double album_peak_, title_peak_;

const uint32_t GRABBAG__REPLAYGAIN_MAX_TAG_SPACE_REQUIRED = 190;

/*

  FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 29 + 1 + 8 +

  FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 10 +

  FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 12 +

  FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 10 +

  FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN/8 + 21 + 1 + 12

*/

const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS = (const FLAC__byte * const)"REPLAYGAIN_REFERENCE_LOUDNESS";

const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN = (const FLAC__byte * const)"REPLAYGAIN_TRACK_GAIN";

const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK = (const FLAC__byte * const)"REPLAYGAIN_TRACK_PEAK";

const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN = (const FLAC__byte * const)"REPLAYGAIN_ALBUM_GAIN";

const FLAC__byte * const GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK = (const FLAC__byte * const)"REPLAYGAIN_ALBUM_PEAK";

static 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));

}

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

{

  FLAC__ASSERT(0 != filename);

  FLAC__ASSERT(0 != stats);

  (void)flac_chmod(filename, stats->st_mode);

}

static FLAC__bool append_tag_(FLAC__StreamMetadata *block, const char *format, const FLAC__byte *name, float value)

{

  char buffer[256];

  char *saved_locale;

  FLAC__StreamMetadata_VorbisComment_Entry entry;

  FLAC__ASSERT(0 != block);

  FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);

  FLAC__ASSERT(0 != format);

  FLAC__ASSERT(0 != name);

  buffer[sizeof(buffer)-1] = '\0';

  /*

   * We need to save the old locale and switch to "C" because the locale

   * influences the formatting of %f and we want it a certain way.

   */

  saved_locale = strdup(setlocale(LC_ALL, 0));

  if (0 == saved_locale)

    return false;

  setlocale(LC_ALL, "C");

  flac_snprintf(buffer, sizeof(buffer), format, name, value);

  setlocale(LC_ALL, saved_locale);

  free(saved_locale);

  entry.entry = (FLAC__byte *)buffer;

  entry.length = strlen(buffer);

  return FLAC__metadata_object_vorbiscomment_append_comment(block, entry, /*copy=*/true);

}

FLAC__bool grabbag__replaygain_is_valid_sample_frequency(uint32_t sample_frequency)

{

  return ValidGainFrequency( sample_frequency );

}

FLAC__bool grabbag__replaygain_init(uint32_t sample_frequency)

{

  title_peak_ = album_peak_ = 0.0;

  return InitGainAnalysis((long)sample_frequency) == INIT_GAIN_ANALYSIS_OK;

}

FLAC__bool grabbag__replaygain_analyze(const FLAC__int32 * const input[], FLAC__bool is_stereo, uint32_t bps, uint32_t samples)

{

  /* using a small buffer improves data locality; we'd like it to fit easily in the dcache */

  static flac_float_t lbuffer[2048], rbuffer[2048];

  static const uint32_t nbuffer = sizeof(lbuffer) / sizeof(lbuffer[0]);

  FLAC__int32 block_peak = 0, s;

  uint32_t i, j;

  FLAC__ASSERT(bps >= FLAC__MIN_BITS_PER_SAMPLE && bps <= FLAC__MAX_BITS_PER_SAMPLE);

  FLAC__ASSERT(FLAC__MIN_BITS_PER_SAMPLE == 4 && FLAC__MAX_BITS_PER_SAMPLE == 32);

  if(bps == 16) {

    if(is_stereo) {

      j = 0;

      while(samples > 0) {

        const uint32_t n = local_min(samples, nbuffer);

        for(i = 0; i < n; i++, j++) {

          s = input[0][j];

          lbuffer[i] = (flac_float_t)s;

          s = abs(s);

          block_peak = local_max(block_peak, s);

          s = input[1][j];

          rbuffer[i] = (flac_float_t)s;

          s = abs(s);

          block_peak = local_max(block_peak, s);

        }

        samples -= n;

        if(AnalyzeSamples(lbuffer, rbuffer, n, 2) != GAIN_ANALYSIS_OK)

          return false;

      }

    }

    else {

      j = 0;

      while(samples > 0) {

        const uint32_t n = local_min(samples, nbuffer);

        for(i = 0; i < n; i++, j++) {

          s = input[0][j];

          lbuffer[i] = (flac_float_t)s;

          s = abs(s);

          block_peak = local_max(block_peak, s);

        }

        samples -= n;

        if(AnalyzeSamples(lbuffer, 0, n, 1) != GAIN_ANALYSIS_OK)

          return false;

      }

    }

  }

  else {

    const double scale = (

      (bps > 16)?

        (double)1. / (double)(1u << (bps - 16)) :

        (double)(1u << (16 - bps))

    );

    if(is_stereo) {

      j = 0;

      while(samples > 0) {

        const uint32_t n = local_min(samples, nbuffer);

        for(i = 0; i < n; i++, j++) {

          s = input[0][j];

          lbuffer[i] = (flac_float_t)(scale * (double)s);

          s = abs32(s);

          block_peak = local_max(block_peak, s);

          s = input[1][j];

          rbuffer[i] = (flac_float_t)(scale * (double)s);

          s = abs32(s);

          block_peak = local_max(block_peak, s);

        }

        samples -= n;

        if(AnalyzeSamples(lbuffer, rbuffer, n, 2) != GAIN_ANALYSIS_OK)

          return false;

      }

    }

    else {

      j = 0;

      while(samples > 0) {

        const uint32_t n = local_min(samples, nbuffer);

        for(i = 0; i < n; i++, j++) {

          s = input[0][j];

          lbuffer[i] = (flac_float_t)(scale * (double)s);

          s = abs32(s);

          block_peak = local_max(block_peak, s);

        }

        samples -= n;

        if(AnalyzeSamples(lbuffer, 0, n, 1) != GAIN_ANALYSIS_OK)

          return false;

      }

    }

  }

  {

    const double peak_scale = (double)(1u << (bps - 1));

    double peak = (double)block_peak / peak_scale;

    if(peak > title_peak_)

      title_peak_ = peak;

    if(peak > album_peak_)

      album_peak_ = peak;

  }

  return true;

}

void grabbag__replaygain_get_album(float *gain, float *peak)

{

  *gain = (float)GetAlbumGain();

  *peak = (float)album_peak_;

  album_peak_ = 0.0;

}

void grabbag__replaygain_get_title(float *gain, float *peak)

{

  *gain = (float)GetTitleGain();

  *peak = (float)title_peak_;

  title_peak_ = 0.0;

}

typedef struct {

  uint32_t channels;

  uint32_t bits_per_sample;

  uint32_t sample_rate;

  FLAC__bool error;

} DecoderInstance;

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

{

  DecoderInstance *instance = (DecoderInstance*)client_data;

  const uint32_t bits_per_sample = frame->header.bits_per_sample;

  const uint32_t channels = frame->header.channels;

  const uint32_t sample_rate = frame->header.sample_rate;

  const uint32_t samples = frame->header.blocksize;

  (void)decoder;

  if(

    !instance->error &&

    (channels == 2 || channels == 1) &&

    bits_per_sample == instance->bits_per_sample &&

    channels == instance->channels &&

    sample_rate == instance->sample_rate

  ) {

    instance->error = !grabbag__replaygain_analyze(buffer, channels==2, bits_per_sample, samples);

  }

  else {

    instance->error = true;

  }

  if(!instance->error)

    return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;

  else

    return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;

}

static void metadata_callback_(const FLAC__StreamDecoder *decoder, const FLAC__StreamMetadata *metadata, void *client_data)

{

  DecoderInstance *instance = (DecoderInstance*)client_data;

  (void)decoder;

  if(metadata->type == FLAC__METADATA_TYPE_STREAMINFO) {

    instance->bits_per_sample = metadata->data.stream_info.bits_per_sample;

    instance->channels = metadata->data.stream_info.channels;

    instance->sample_rate = metadata->data.stream_info.sample_rate;

    if(instance->channels != 1 && instance->channels != 2) {

      instance->error = true;

      return;

    }

    if(!grabbag__replaygain_is_valid_sample_frequency(instance->sample_rate)) {

      instance->error = true;

      return;

    }

  }

}

static void error_callback_(const FLAC__StreamDecoder *decoder, FLAC__StreamDecoderErrorStatus status, void *client_data)

{

  DecoderInstance *instance = (DecoderInstance*)client_data;

  (void)decoder, (void)status;

  instance->error = true;

}

const char *grabbag__replaygain_analyze_file(const char *filename, float *title_gain, float *title_peak)

{

  DecoderInstance instance;

  FLAC__StreamDecoder *decoder = FLAC__stream_decoder_new();

  if(0 == decoder)

    return "memory allocation error";

  instance.error = false;

  /* It does these three by default but lets be explicit: */

  FLAC__stream_decoder_set_md5_checking(decoder, false);

  FLAC__stream_decoder_set_metadata_ignore_all(decoder);

  FLAC__stream_decoder_set_metadata_respond(decoder, FLAC__METADATA_TYPE_STREAMINFO);

  if(FLAC__stream_decoder_init_file(decoder, filename, write_callback_, metadata_callback_, error_callback_, &instance) != FLAC__STREAM_DECODER_INIT_STATUS_OK) {

    FLAC__stream_decoder_delete(decoder);

    return "initializing decoder";

  }

  if(!FLAC__stream_decoder_process_until_end_of_stream(decoder) || instance.error) {

    FLAC__stream_decoder_delete(decoder);

    return "decoding file";

  }

  FLAC__stream_decoder_delete(decoder);

  grabbag__replaygain_get_title(title_gain, title_peak);

  return 0;

}

const char *grabbag__replaygain_store_to_vorbiscomment(FLAC__StreamMetadata *block, float album_gain, float album_peak, float title_gain, float title_peak)

{

  const char *error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_reference(block)))

    return error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_title(block, title_gain, title_peak)))

    return error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_album(block, album_gain, album_peak)))

    return error;

  return 0;

}

const char *grabbag__replaygain_store_to_vorbiscomment_reference(FLAC__StreamMetadata *block)

{

  FLAC__ASSERT(0 != block);

  FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);

  if(FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS) < 0)

    return "memory allocation error";

  if(!append_tag_(block, reference_format_, GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS, ReplayGainReferenceLoudness))

    return "memory allocation error";

  return 0;

}

const char *grabbag__replaygain_store_to_vorbiscomment_album(FLAC__StreamMetadata *block, float album_gain, float album_peak)

{

  FLAC__ASSERT(0 != block);

  FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);

  if(

    FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN) < 0 ||

    FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK) < 0

  )

    return "memory allocation error";

  if(

    !append_tag_(block, gain_format_, GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN, album_gain) ||

    !append_tag_(block, peak_format_, GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK, album_peak)

  )

    return "memory allocation error";

  return 0;

}

const char *grabbag__replaygain_store_to_vorbiscomment_title(FLAC__StreamMetadata *block, float title_gain, float title_peak)

{

  FLAC__ASSERT(0 != block);

  FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);

  if(

    FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN) < 0 ||

    FLAC__metadata_object_vorbiscomment_remove_entries_matching(block, (const char *)GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK) < 0

  )

    return "memory allocation error";

  if(

    !append_tag_(block, gain_format_, GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN, title_gain) ||

    !append_tag_(block, peak_format_, GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK, title_peak)

  )

    return "memory allocation error";

  return 0;

}

static const char *store_to_file_pre_(const char *filename, FLAC__Metadata_Chain **chain, FLAC__StreamMetadata **block)

{

  FLAC__Metadata_Iterator *iterator;

  const char *error;

  FLAC__bool found_vc_block = false;

  if(0 == (*chain = FLAC__metadata_chain_new()))

    return "memory allocation error";

  if(!FLAC__metadata_chain_read(*chain, filename)) {

    error = FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(*chain)];

    FLAC__metadata_chain_delete(*chain);

    return error;

  }

  if(0 == (iterator = FLAC__metadata_iterator_new())) {

    FLAC__metadata_chain_delete(*chain);

    return "memory allocation error";

  }

  FLAC__metadata_iterator_init(iterator, *chain);

  do {

    *block = FLAC__metadata_iterator_get_block(iterator);

    if((*block)->type == FLAC__METADATA_TYPE_VORBIS_COMMENT)

      found_vc_block = true;

  } while(!found_vc_block && FLAC__metadata_iterator_next(iterator));

  if(!found_vc_block) {

    /* create a new block */

    *block = FLAC__metadata_object_new(FLAC__METADATA_TYPE_VORBIS_COMMENT);

    if(0 == *block) {

      FLAC__metadata_chain_delete(*chain);

      FLAC__metadata_iterator_delete(iterator);

      return "memory allocation error";

    }

    while(FLAC__metadata_iterator_next(iterator))

      ;

    if(!FLAC__metadata_iterator_insert_block_after(iterator, *block)) {

      error = FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(*chain)];

      FLAC__metadata_chain_delete(*chain);

      FLAC__metadata_iterator_delete(iterator);

      return error;

    }

    /* iterator is left pointing to new block */

    FLAC__ASSERT(FLAC__metadata_iterator_get_block(iterator) == *block);

  }

  FLAC__metadata_iterator_delete(iterator);

  FLAC__ASSERT(0 != *block);

  FLAC__ASSERT((*block)->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);

  return 0;

}

static const char *store_to_file_post_(const char *filename, FLAC__Metadata_Chain *chain, FLAC__bool preserve_modtime)

{

  struct flac_stat_s stats;

  const FLAC__bool have_stats = get_file_stats_(filename, &stats);

  (void)grabbag__file_change_stats(filename, /*read_only=*/false);

  FLAC__metadata_chain_sort_padding(chain);

  if(!FLAC__metadata_chain_write(chain, /*use_padding=*/true, preserve_modtime)) {

    const char *error;

    error = FLAC__Metadata_ChainStatusString[FLAC__metadata_chain_status(chain)];

    FLAC__metadata_chain_delete(chain);

    return error;

  }

  FLAC__metadata_chain_delete(chain);

  if(have_stats)

    set_file_stats_(filename, &stats);

  return 0;

}

const char *grabbag__replaygain_store_to_file(const char *filename, float album_gain, float album_peak, float title_gain, float title_peak, FLAC__bool preserve_modtime)

{

  FLAC__Metadata_Chain *chain;

  FLAC__StreamMetadata *block = NULL;

  const char *error;

  if(0 != (error = store_to_file_pre_(filename, &chain, &block)))

    return error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment(block, album_gain, album_peak, title_gain, title_peak))) {

    FLAC__metadata_chain_delete(chain);

    return error;

  }

  if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))

    return error;

  return 0;

}

const char *grabbag__replaygain_store_to_file_reference(const char *filename, FLAC__bool preserve_modtime)

{

  FLAC__Metadata_Chain *chain;

  FLAC__StreamMetadata *block = NULL;

  const char *error;

  if(0 != (error = store_to_file_pre_(filename, &chain, &block)))

    return error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_reference(block))) {

    FLAC__metadata_chain_delete(chain);

    return error;

  }

  if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))

    return error;

  return 0;

}

const char *grabbag__replaygain_store_to_file_album(const char *filename, float album_gain, float album_peak, FLAC__bool preserve_modtime)

{

  FLAC__Metadata_Chain *chain;

  FLAC__StreamMetadata *block = NULL;

  const char *error;

  if(0 != (error = store_to_file_pre_(filename, &chain, &block)))

    return error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_album(block, album_gain, album_peak))) {

    FLAC__metadata_chain_delete(chain);

    return error;

  }

  if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))

    return error;

  return 0;

}

const char *grabbag__replaygain_store_to_file_title(const char *filename, float title_gain, float title_peak, FLAC__bool preserve_modtime)

{

  FLAC__Metadata_Chain *chain;

  FLAC__StreamMetadata *block = NULL;

  const char *error;

  if(0 != (error = store_to_file_pre_(filename, &chain, &block)))

    return error;

  if(0 != (error = grabbag__replaygain_store_to_vorbiscomment_title(block, title_gain, title_peak))) {

    FLAC__metadata_chain_delete(chain);

    return error;

  }

  if(0 != (error = store_to_file_post_(filename, chain, preserve_modtime)))

    return error;

  return 0;

}

static FLAC__bool parse_double_(const FLAC__StreamMetadata_VorbisComment_Entry *entry, double *val)

{

  char s[32], *end;

  const char *p, *q;

  double v;

  FLAC__ASSERT(0 != entry);

  FLAC__ASSERT(0 != val);

  p = (const char *)entry->entry;

  q = strchr(p, '=');

  if(0 == q)

    return false;

  q++;

  safe_strncpy(s, q, local_min(sizeof(s), (size_t) (entry->length - (q-p))));

  v = strtod(s, &end);

  if(end == s)

    return false;

  *val = v;

  return true;

}

FLAC__bool grabbag__replaygain_load_from_vorbiscomment(const FLAC__StreamMetadata *block, FLAC__bool album_mode, FLAC__bool strict, double *reference, double *gain, double *peak)

{

  int reference_offset, gain_offset, peak_offset;

  char *saved_locale;

  FLAC__bool res = true;

  FLAC__ASSERT(0 != block);

  FLAC__ASSERT(0 != reference);

  FLAC__ASSERT(0 != gain);

  FLAC__ASSERT(0 != peak);

  FLAC__ASSERT(block->type == FLAC__METADATA_TYPE_VORBIS_COMMENT);

  /* Default to current level until overridden by a detected tag; this

   * will always be true until we change replaygain_analysis.c

   */

  *reference = ReplayGainReferenceLoudness;

  /*

   * We need to save the old locale and switch to "C" because the locale

   * influences the behaviour of strtod and we want it a certain way.

   */

  saved_locale = strdup(setlocale(LC_ALL, 0));

  if (0 == saved_locale)

    return false;

  setlocale(LC_ALL, "C");

  if(0 <= (reference_offset = FLAC__metadata_object_vorbiscomment_find_entry_from(block, /*offset=*/0, (const char *)GRABBAG__REPLAYGAIN_TAG_REFERENCE_LOUDNESS)))

    (void)parse_double_(block->data.vorbis_comment.comments + reference_offset, reference);

  if(0 > (gain_offset = FLAC__metadata_object_vorbiscomment_find_entry_from(block, /*offset=*/0, (const char *)(album_mode? GRABBAG__REPLAYGAIN_TAG_ALBUM_GAIN : GRABBAG__REPLAYGAIN_TAG_TITLE_GAIN))))

    res = false;

  if(0 > (peak_offset = FLAC__metadata_object_vorbiscomment_find_entry_from(block, /*offset=*/0, (const char *)(album_mode? GRABBAG__REPLAYGAIN_TAG_ALBUM_PEAK : GRABBAG__REPLAYGAIN_TAG_TITLE_PEAK))))

    res = false;

  if(res && !parse_double_(block->data.vorbis_comment.comments + gain_offset, gain))

    res = false;

  if(res && !parse_double_(block->data.vorbis_comment.comments + peak_offset, peak))

    res = false;

  if(res && *peak < 0.0)

    res = false;

  setlocale(LC_ALL, saved_locale);

  free(saved_locale);

  /* something failed; retry with strict */

  if (!res && !strict)

    res = grabbag__replaygain_load_from_vorbiscomment(block, !album_mode, /*strict=*/true, reference, gain, peak);

  return res;

}

double grabbag__replaygain_compute_scale_factor(double peak, double gain, double preamp, FLAC__bool prevent_clipping)

{

  double scale;

  FLAC__ASSERT(peak >= 0.0);

  gain += preamp;

  scale = (float) pow(10.0, gain * 0.05);

  if(prevent_clipping && peak > 0.0) {

    const double max_scale = (float)(1.0 / peak);

    if(scale > max_scale)

      scale = max_scale;

  }

  return scale;

}