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/*
* Copyright 2003-2020 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 "OggDecoder.hxx"
#include "lib/xiph/OggFind.hxx"
#include "input/InputStream.hxx"
/**
* Load the end-of-stream packet and restore the previous file
* position.
*/
bool
OggDecoder::LoadEndPacket(ogg_packet &packet) const
{
if (!input_stream.CheapSeeking())
/* we do this for local files only, because seeking
around remote files is expensive and not worth the
trouble */
return false;
const auto old_offset = input_stream.GetOffset();
/* create temporary Ogg objects for seeking and parsing the
EOS packet */
bool result;
{
DecoderReader reader(client, input_stream);
OggSyncState sync2(reader);
OggStreamState stream2(GetSerialNo());
result = OggSeekFindEOS(sync2, stream2, packet,
input_stream);
}
/* restore the previous file position */
try {
input_stream.LockSeek(old_offset);
} catch (...) {
}
return result;
}
ogg_int64_t
OggDecoder::LoadEndGranulePos() const
{
ogg_packet packet;
if (!LoadEndPacket(packet))
return -1;
return packet.granulepos;
}
inline void
OggDecoder::SeekByte(offset_type offset)
{
input_stream.LockSeek(offset);
PostSeek(offset);
}
void
OggDecoder::SeekGranulePos(ogg_int64_t where_granulepos)
{
assert(IsSeekable());
/* binary search: interpolate the file offset where we expect
to find the given granule position, and repeat until we're
close enough */
static const ogg_int64_t MARGIN_BEFORE = 44100 / 3;
static const ogg_int64_t MARGIN_AFTER = 44100 / 10;
offset_type min_offset = 0, max_offset = input_stream.GetSize();
ogg_int64_t min_granule = 0, max_granule = end_granulepos;
while (true) {
const offset_type delta_offset = max_offset - min_offset;
const ogg_int64_t delta_granule = max_granule - min_granule;
const ogg_int64_t relative_granule = where_granulepos - min_granule;
const offset_type offset = min_offset + relative_granule * delta_offset
/ delta_granule;
SeekByte(offset);
const auto new_granule = ReadGranulepos();
if (new_granule < 0)
/* no granulepos here, which shouldn't happen
- we can't improve, so stop */
return;
if (new_granule > where_granulepos + MARGIN_AFTER) {
if (new_granule > max_granule)
/* something went wrong */
return;
if (max_granule == new_granule)
/* break out of the infinite loop, we
can't get any closer */
break;
/* reduce the max bounds and interpolate again */
max_granule = new_granule;
max_offset = GetStartOffset();
} else if (new_granule + MARGIN_BEFORE < where_granulepos) {
if (new_granule < min_granule)
/* something went wrong */
return;
if (min_granule == new_granule)
/* break out of the infinite loop, we
can't get any closer */
break;
/* increase the min bounds and interpolate
again */
min_granule = new_granule;
min_offset = GetStartOffset();
} else {
break;
}
}
/* go back to the last page start so OggVisitor can start
visiting from here (we have consumed a few pages
already) */
SeekByte(GetStartOffset());
}
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