This patch allows mpd to recognise the albumartist tag in the way
foobar2000 and others write it to files.

Splitted flac_copy_vorbis_comment() into flac_copy_comment() and
flac_copy_comment().

Simplify flac_copy_vorbis_comment() by moving the comment
identification code out.

Free the tag object when it turns out to be empty.  This simplifies
several functions and APIs.

Renamed types, functions, variables.

Use GLib's G_GNUC_UNUSED instead of gcc.h's mpd_unused.

Having an array instead of individual variables allows the use of the
replay_gain_mode enum as an array index.

Renamed functions and variables.

Don't pass the "seekable" flag with every decoder_data() invocation.
Since that flag won't change within the file, it is enough to pass it
to decoder_initialized() once per file.

Everybody should use struct input_stream.

These plugins are not input plugins, they are decoder plugins.  No
CamelCase in the directory name.

Don't compile the sources of disabled decoder plugins at all, and
don't attempt to register these.

The last bit of CamelCase in audio_format.h.  Additionally, rename a
bunch of local variables.

Do full C99 integer type conversion in all modules which were not
touched by Eric's merged patch.

chunk_length can be converted to a local variable, because it is
always reset to 0 after it was used.

Since flacSendChunk() is a trivial function and is only used in one
location, move the code there.  The advantage is that calling
decoder_data() directly returns the decoder_command value, so we can
eliminate one decoder_get_command() call.

Support for bit rates except 16 bits (and 8 bits on little endian) has
always been broken.  Since we added optimized functions for 8, 16,
24/32 bits, we can remove the generic flac_convert() function.
Instead of removing it, convert it to a wrapper function for
flac_convert_*().

Same optimization for 8 and 32 bit files, like the previous patch for
16 bit.  Along the way, this patch adds 24 bit FLAC support!

flac_convert_16() runs a lot faster than the generic (and quite buggy)
function flac_convert().  flac_convert_16() is only used for
non-stereo files, since there is already flac_convert_stereo16().

By mistake, I casted the sample value to uint16_t, which is wrong.
This patch simplifies the code by using a int16_t pointer instead of
casting to int16_t* every time.

There is still a lot of duplicated code in flac_plugin.c and
oggflac_plugin.c.  Move code from flac_plugin.c to _flac_common.c, and
use the new function flac_common_write() also in oggflac_plugin.c,
porting lots of optimizations over to it.

Getting rid of CamelCase; not having typedefs also allows us to
forward-declare the structures.

Another big patch which hides internal mpd APIs from decoder plugins:
decoder plugins regularly poll dc->command; expose it with a
decoder_api.h function.

InputPlugin is the API which is implemented by a decoder plugin.  This
belongs to the public API/ABI, so move it to decoder_api.h.  It will
later be renamed to something like "decoder_plugin".

Similar to the previous patch: pass total_time instead of manipulating
dc->totalTime directly.

dc->audioFormat is set once by the decoder plugins before invoking
decoder_initialized(); hide dc->audioFormat and let the decoder pass
an AudioFormat pointer to decoder_initialized().

The decoder struct should later be made opaque to the decoder plugin,
because maintaining a stable struct ABI is quite difficult.  The ABI
should only consist of a small number of stable functions.

Much of the existing code queries all three variables sequentially.
Since only one of them can be set at a time, this can be optimized and
unified by merging all of them into one enum variable.  Later, the
"command" checks can be expressed in a "switch" statement.

Include only headers which are really required.  This speeds up
compilation and helps detect cross-layer accesses.

Also enable -Wunused-parameter - this forces us to add the gcc
"unused" attribute to a lot of parameters (mostly library callback
functions), but it's worth it during code refactorizations.

We had functions names varied between
outputBufferFoo, fooOutputBuffer, and output_buffer_foo

That was too confusing for my little brain to handle.
And the global variable was somehow named 'cb' instead of
the more obvious 'ob'...

git-svn-id: https://svn.musicpd.org/mpd/trunk@7355 09075e82-0dd4-0310-85a5-a0d7c8717e4f

All of our main singleton data structures are implicitly shared,
so there's no reason to keep passing them around and around in
the stack and making our internal API harder to deal with.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7354 09075e82-0dd4-0310-85a5-a0d7c8717e4f

This at least makes the argument list to a lot of our plugin
functions shorter and removes a good amount of line nois^W^Wcode,
hopefully making things easier to read and follow.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7353 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Tools like "sparse" check for missing downcasts, since implicit cast
may be dangerous.  Although that does not change the compiler result,
it may make the code more readable (IMHO), because you always see when
there may be data cut off.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7196 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Signed-off-by: Eric Wong <normalperson@yhbt.net>

git-svn-id: https://svn.musicpd.org/mpd/trunk@7143 09075e82-0dd4-0310-85a5-a0d7c8717e4f

This will make refactoring features easier, especially now that
pthreads support and larger refactorings are on the horizon.

Hopefully, this will make porting to other platforms (even
non-UNIX-like ones for masochists) easier, too.

os_compat.h will house all the #includes for system headers
considered to be the "core" of MPD.  Headers for optional
features will be left to individual source files.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7130 09075e82-0dd4-0310-85a5-a0d7c8717e4f

git-svn-id: https://svn.musicpd.org/mpd/trunk@5834 09075e82-0dd4-0310-85a5-a0d7c8717e4f