150 lines
3.9 KiB
C++
150 lines
3.9 KiB
C++
/*
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* Copyright 2003-2020 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "OggDecoder.hxx"
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#include "lib/xiph/OggFind.hxx"
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#include "input/InputStream.hxx"
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/**
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* Load the end-of-stream packet and restore the previous file
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* position.
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*/
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bool
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OggDecoder::LoadEndPacket(ogg_packet &packet) const
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{
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if (!input_stream.CheapSeeking())
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/* we do this for local files only, because seeking
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around remote files is expensive and not worth the
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trouble */
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return false;
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const auto old_offset = input_stream.GetOffset();
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/* create temporary Ogg objects for seeking and parsing the
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EOS packet */
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bool result;
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{
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DecoderReader reader(client, input_stream);
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OggSyncState sync2(reader);
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OggStreamState stream2(GetSerialNo());
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/* passing synced=false because we're inside an
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OggVisitor callback, and our InputStream may be in
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the middle of an Ogg packet */
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result = OggSeekFindEOS(sync2, stream2, packet,
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input_stream, false);
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}
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/* restore the previous file position */
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try {
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input_stream.LockSeek(old_offset);
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} catch (...) {
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}
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return result;
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}
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ogg_int64_t
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OggDecoder::LoadEndGranulePos() const
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{
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ogg_packet packet;
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if (!LoadEndPacket(packet))
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return -1;
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return packet.granulepos;
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}
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inline void
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OggDecoder::SeekByte(offset_type offset)
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{
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input_stream.LockSeek(offset);
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PostSeek(offset);
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}
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void
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OggDecoder::SeekGranulePos(ogg_int64_t where_granulepos)
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{
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assert(IsSeekable());
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/* binary search: interpolate the file offset where we expect
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to find the given granule position, and repeat until we're
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close enough */
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static const ogg_int64_t MARGIN_BEFORE = 44100 / 3;
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static const ogg_int64_t MARGIN_AFTER = 44100 / 10;
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offset_type min_offset = 0, max_offset = input_stream.GetSize();
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ogg_int64_t min_granule = 0, max_granule = end_granulepos;
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while (true) {
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const offset_type delta_offset = max_offset - min_offset;
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const ogg_int64_t delta_granule = max_granule - min_granule;
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const ogg_int64_t relative_granule = where_granulepos - min_granule;
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const offset_type offset = min_offset + relative_granule * delta_offset
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/ delta_granule;
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SeekByte(offset);
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const auto new_granule = ReadGranulepos();
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if (new_granule < 0)
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/* no granulepos here, which shouldn't happen
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- we can't improve, so stop */
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return;
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if (new_granule > where_granulepos + MARGIN_AFTER) {
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if (new_granule > max_granule)
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/* something went wrong */
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return;
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if (max_granule == new_granule)
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/* break out of the infinite loop, we
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can't get any closer */
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break;
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/* reduce the max bounds and interpolate again */
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max_granule = new_granule;
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max_offset = GetStartOffset();
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} else if (new_granule + MARGIN_BEFORE < where_granulepos) {
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if (new_granule < min_granule)
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/* something went wrong */
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return;
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if (min_granule == new_granule)
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/* break out of the infinite loop, we
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can't get any closer */
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break;
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/* increase the min bounds and interpolate
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again */
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min_granule = new_granule;
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min_offset = GetStartOffset();
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} else {
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break;
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}
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}
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/* go back to the last page start so OggVisitor can start
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visiting from here (we have consumed a few pages
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already) */
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SeekByte(GetStartOffset());
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}
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