Commit 79b23663 added the field `skip`
to support unaligned reads, but set the `offset` field to a wrong
value.  This resulted in miscalculation of `remaining`, causing
an assertion failure.

The fix is to assign `offset` the correct value, but consider the
`skip` value in the assertion.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1067

After a Seek() to an odd offset, some data needs to be skipped from
the start of the block, and reading right into the given buffer
doesn't work.

Skip the beginning of a sector if the last seek was odd, and clear the
buffer on seek.

Skip the beginning of a sector if the last seek was odd, and clear the
buffer on seek.

Oh the horror!  This plugin cannot possibly ever have worked.  It was
broken from the start, when it was added in commit 37796699 nearly
twelve (!) years ago.

The plugin would always read at sector boundaries, so it could only
ever work at multiples of 2 kB.

Don't silently return 0 when there is no more data, because this may
crash the caller.  And flush output even if input EOF has been reached.

Sometimes, zzip_file_read() returns 0 even though the end of the file
was not reached.  This causes assertion failures in
DecoderBridge::Read().

Closes https://github.com/MusicPlayerDaemon/MPD/issues/935

This eliminates a tiny amount of overhead because the compiler can
choose how to pass the parameter.

Some more `-Wpedantic` fixups.

This makes ccache more efficient when recompiling with different
plugins.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Introduced in C++17. It replaces gcc's warn_unused_result.

Found with modernize-use-nodiscard.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Aparently, libcdio sometimes returns empty filenames, causing MPD
crashes.  This shouldn't really happen, and I consider this a libcdio
bug - but if it happens, people blame MPD, so let's add a check.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/776

Found with performance-unnecessary-value-param
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-pass-by-value
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-redundant-void-arg
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-override
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Most importantly, this commit translates ZZIP_ENOENT to
std::system_error(ENOENT) so IsFileNotFound() returns true and
find_stream_art() can suppress the log line.

This can be used for other purposes as well.