While libsndfile doesn't like partial reads in the middle of a file
(see commit 95ac6071), it allows partial reads at the end of a file.
It doesn't pay attention to the file size when issuing a read.

Commit ecb67a1e (MPD 0.18.12) was a regression: previously,
partial reads at the end of a file were possible, but switching to
decoder_read_full() made this an error condition.  This way, a portion
at the end of each file was lost, leading to corruption with gapless
playback (https://github.com/MusicPlayerDaemon/MPD/issues/936).

This fix switches to the newly introduced function
decoder_read_much(), which does the same as the code before commit
ecb67a1e.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/936

Prepare for templated functions.

Bug #915 is about an I/O exception thrown where none was allowed,
leading to crash via std::terminate().  However, instead of catching
and logging the error inside the decoder plugin, it should be able to
propagate the I/O error to the MPD core, so MPD can avoid trying other
decoder plugins.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/915

Closes https://github.com/MusicPlayerDaemon/MPD/issues/867

Will be needed for End Trimming (RFC7845 4.4,
https://github.com/MusicPlayerDaemon/MPD/issues/867).

Fixes memory leak.  That's what we get for

Fixes the first part of
https://github.com/MusicPlayerDaemon/MPD/issues/867

Fixes regression from commit 69f09648

The WildMidi project added the pkg-config file in version 0.3.3, but
unfortunately, Debian still doesn't ship it 4 years later:

 https://bugs.debian.org/916631

However, for cross-compiling, the pkg-config file is very helpful.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/833

This reverts commit eb192137.

This is no longer necessary because we require FFmpeg 3.1 or newer
since MPD 0.21.2.

This fixes a deprecation warning because the implicit AVPacket copy
constructor copies the deprecated attribute `convergence_duration`.

Found with readability-uppercase-literal-suffix
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is the case with uClibc-ng currently.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry picked from commit 769cd0ee9f0cf8ceb026aa751b5d4a390bb5dbdc)
(changed define to match master)

Using libgme 0.6.2 on macOS, it appears that gme_info_t strings can be
empty, which creates weird track titles: (001/050)

This adds an additional check for an empty string.

Found with bugprone-suspicious-missing-comma
Signed-off-by: Rosen Penev <rosenp@gmail.com>

max_frames is size_t, not unsigned long. Fixes GCC warning.

When calling OggSeekFindEOS() from inside a OggVisitor callback, then
the #InputStream may be in the middle of an Ogg packet, and the newly
initialized #ogg_sync_state will not be able to load it without the
help of ogg_sync_pageseek().  By passing "synced=false" to
OggSeekFindEOS(), we force the use of ogg_sync_pageseek() even when
not actually seeking.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/719

Apparently, libmpcdec sets gain/peak variables to zero if they are not
present.  This clashes with our formula and results in bogus values
which cause noise during playback.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/640

The formula did not consider the channel count.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/639

Field 2 is called <released>, formerly used as <copyright>[1][2]. It is
formatted <year><space><company or author or group>, where <year> may be
<YYYY>, <YYY?>, <YY??> or <YYYY-YY>, for example "1987", "199?", "19??"
or "1985-87". The <company or author or group> may be for example Rob
Hubbard. A full field may be for example "1987 Rob Hubbard".

This change splits the <released> field at the first <space>, to retain
the <year> part.

The 51823 SID files in High Voltage SID Collection (HVSC) version 71
have the following distribution of dates:

    333 19??         11 1990-92       6 1995-99       2 2006-08
    827 198?         88 1990-93    2140 1996        530 2007
     32 1982         69 1990-94       9 1996-97      15 2007-08
      1 1982-83      49 1990-95       2 1996-98       2 2007-09
    255 1983       3467 1991          5 1996-99       1 2007-10
    677 1984         75 1991-92    1840 1997        430 2008
    775 1985         65 1991-93       4 1997-98      23 2008-09
      3 1985-86      10 1991-94    1276 1998          1 2008-12
     10 1985-87      35 1991-97       4 1998-99     631 2009
    943 1986       3320 1992        865 1999          1 2009-10
     12 1986-87      26 1992-93      24 200?        645 2010
      5 1986-89      59 1992-94     590 2000          1 2010-12
   2083 1987          1 1992-96       4 2000-01     538 2011
     31 1987-88    2996 1993        727 2001          1 2011-12
     44 1987-89      42 1993-94     875 2002        651 2012
   2510 1988         12 1993-95       2 2002-04     811 2013
    129 1988-89       2 1993-97     844 2003        790 2014
     91 1988-90    2737 1994          3 2003-05     740 2015
     58 1988-91      16 1994-95     842 2004        792 2016
   3466 1989         20 1994-96       2 2004-05     775 2017
     95 1989-90      17 1994-97     707 2005        638 2018
    150 1989-91    2271 1995          1 2005-06     284 2019
   1077 199?          2 1995-96       2 2005-07
   2834 1990          4 1995-97     785 2006
    119 1990-91       2 1995-98       6 2006-07

References:

[1] https://www.hvsc.c64.org/download/C64Music/DOCUMENTS/SID_file_format.txt
[2] https://hvsc.c64.org/info

High Voltage SID Collection (HVSC) metadata fields are encoded in
windows-1252, as described in DOCUMENTS/SID_file_format.txt:

https://www.hvsc.c64.org/download/C64Music/DOCUMENTS/SID_file_format.txt

If utf-8 transcoding fails, or the ICU library is unavailable, fall
back to plain ASCII and replace other characters with '?'.

The song length was previously undetermined.