mpd/src/decoder/plugins/FlacMetadata.cxx

/*
 * Copyright (C) 2003-2014 The Music Player Daemon Project
 * http://www.musicpd.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"
#include "FlacMetadata.hxx"
#include "XiphTags.hxx"
#include "MixRampInfo.hxx"
#include "tag/TagHandler.hxx"
#include "tag/TagTable.hxx"
#include "tag/TagBuilder.hxx"
#include "tag/Tag.hxx"
#include "tag/VorbisComment.hxx"
#include "ReplayGainInfo.hxx"
#include "util/ASCII.hxx"
#include "util/SplitString.hxx"

#include <string.h>

static const char *
vorbis_comment_value(const FLAC__StreamMetadata *block,
		     const char *name)
{
	int offset =
		FLAC__metadata_object_vorbiscomment_find_entry_from(block, 0,
								    name);
	if (offset < 0)
		return nullptr;

	size_t name_length = strlen(name);

	const FLAC__StreamMetadata_VorbisComment_Entry &vc =
		block->data.vorbis_comment.comments[offset];
	const char *comment = (const char *)vc.entry;

	/* 1 is for '=' */
	return comment + name_length + 1;
}

static bool
flac_find_float_comment(const FLAC__StreamMetadata *block,
			const char *cmnt, float *fl)
{
	const char *value = vorbis_comment_value(block, cmnt);
	if (value == nullptr)
		return false;

	*fl = (float)atof(value);
	return true;
}

bool
flac_parse_replay_gain(ReplayGainInfo &rgi,
		       const FLAC__StreamMetadata *block)
{
	rgi.Clear();

	bool found = false;
	if (flac_find_float_comment(block, "replaygain_album_gain",
				    &rgi.tuples[REPLAY_GAIN_ALBUM].gain))
		found = true;
	if (flac_find_float_comment(block, "replaygain_album_peak",
				    &rgi.tuples[REPLAY_GAIN_ALBUM].peak))
		found = true;
	if (flac_find_float_comment(block, "replaygain_track_gain",
				    &rgi.tuples[REPLAY_GAIN_TRACK].gain))
		found = true;
	if (flac_find_float_comment(block, "replaygain_track_peak",
				    &rgi.tuples[REPLAY_GAIN_TRACK].peak))
		found = true;

	return found;
}

gcc_pure
static std::string
flac_find_string_comment(const FLAC__StreamMetadata *block, const char *cmnt)
{
	const char *value = vorbis_comment_value(block, cmnt);
	if (value == nullptr)
		return std::string();

	return std::string(value);
}

MixRampInfo
flac_parse_mixramp(const FLAC__StreamMetadata *block)
{
	MixRampInfo mix_ramp;
	mix_ramp.SetStart(flac_find_string_comment(block, "mixramp_start"));
	mix_ramp.SetEnd(flac_find_string_comment(block, "mixramp_end"));
	return mix_ramp;
}

/**
 * Checks if the specified name matches the entry's name, and if yes,
 * returns the comment value;
 */
static const char *
flac_comment_value(const FLAC__StreamMetadata_VorbisComment_Entry *entry,
		   const char *name)
{
	return vorbis_comment_value((const char *)entry->entry, name);
}

/**
 * Check if the comment's name equals the passed name, and if so, copy
 * the comment value into the tag.
 */
static bool
flac_copy_comment(const FLAC__StreamMetadata_VorbisComment_Entry *entry,
		  const char *name, TagType tag_type,
		  const struct tag_handler *handler, void *handler_ctx)
{
	const char *value = flac_comment_value(entry, name);
	if (value != nullptr) {
		tag_handler_invoke_tag(handler, handler_ctx, tag_type, value);
		return true;
	}

	return false;
}

static void
flac_scan_comment(const FLAC__StreamMetadata_VorbisComment_Entry *entry,
		  const struct tag_handler *handler, void *handler_ctx)
{
	if (handler->pair != nullptr) {
		const char *comment = (const char *)entry->entry;
		const SplitString split(comment, '=');
		if (split.IsDefined() && !split.IsEmpty())
			tag_handler_invoke_pair(handler, handler_ctx,
						split.GetFirst(),
						split.GetSecond());
	}

	for (const struct tag_table *i = xiph_tags; i->name != nullptr; ++i)
		if (flac_copy_comment(entry, i->name, i->type,
				      handler, handler_ctx))
			return;

	for (unsigned i = 0; i < TAG_NUM_OF_ITEM_TYPES; ++i)
		if (flac_copy_comment(entry,
				      tag_item_names[i], (TagType)i,
				      handler, handler_ctx))
			return;
}

static void
flac_scan_comments(const FLAC__StreamMetadata_VorbisComment *comment,
		   const struct tag_handler *handler, void *handler_ctx)
{
	for (unsigned i = 0; i < comment->num_comments; ++i)
		flac_scan_comment(&comment->comments[i],
				  handler, handler_ctx);
}

gcc_pure
static inline SongTime
flac_duration(const FLAC__StreamMetadata_StreamInfo *stream_info)
{
	assert(stream_info->sample_rate > 0);

	return SongTime::FromScale<uint64_t>(stream_info->total_samples,
					     stream_info->sample_rate);
}

void
flac_scan_metadata(const FLAC__StreamMetadata *block,
		   const struct tag_handler *handler, void *handler_ctx)
{
	switch (block->type) {
	case FLAC__METADATA_TYPE_VORBIS_COMMENT:
		flac_scan_comments(&block->data.vorbis_comment,
				   handler, handler_ctx);
		break;

	case FLAC__METADATA_TYPE_STREAMINFO:
		if (block->data.stream_info.sample_rate > 0)
			tag_handler_invoke_duration(handler, handler_ctx,
						    flac_duration(&block->data.stream_info));
		break;

	default:
		break;
	}
}

Tag
flac_vorbis_comments_to_tag(const FLAC__StreamMetadata_VorbisComment *comment)
{
	TagBuilder tag_builder;
	flac_scan_comments(comment, &add_tag_handler, &tag_builder);
	return tag_builder.Commit();
}

void
FlacMetadataChain::Scan(const struct tag_handler *handler, void *handler_ctx)
{
	FLACMetadataIterator iterator(*this);

	do {
		FLAC__StreamMetadata *block = iterator.GetBlock();
		if (block == nullptr)
			break;

		flac_scan_metadata(block, handler, handler_ctx);
	} while (iterator.Next());
}