When a CANCEL command is received, the player should drop all chunks
of the next song.  Added new funciton music_pipe_chop() which is used
for that.

Provide a debug function which asserts on the sample format of all
chunks.  Call this function in each iteration of the player main loop.

Each music chunk can now carry a tag object.  Decoder plugins which
support it (e.g. oggvorbis) may use this to inject decoded tags into
their output.

Add doxygen compatible comments.

The "volatile" keyword doesn't help here, because we have proper
memory barriers, but it disables some optimizations.  Remove it.

The name "num_chunks" expresses the meaning of the variable better.

Rename all variables and struct members.

Last music_pipe rename patch: renamed the global variable (singleton).

Replace all direct music_pipe struct accesses with wrapper functions.
The compiled machine code is the same, but this way, we can change
struct internals more easily.

.. and rename dc.audioFormat to dc.in_audio_format.  The music pipe
does not need to know the audio format, and its former "audioFormat"
property indicated the format of the most recently added chunk, which
might be confusing when you are reading the oldest chunks.

Rename all functions to the new prefix.

.. and rename ob_chunk to struct music_chunk.

No CamelCase in the file name.  The output_buffer struct is going to
be renamed to music_pipe.  There are so many buffer levels in MPD, and
calling this one "output buffer" is wrong, because it's not the last
buffer before the music reaches the output devices.

"LOG_H" is a macro which is also used by ffmpeg/log.h.  This is
ffmpeg's fault, because short macros should be reserved for
applications, but since it's always a good idea to choose prefixed
macro names, even for applications, we are going to do that in MPD.

The function ob_is_empty() is called very often.  It's worth it to
convert it to an inline function.

"bool" should be used in C99 programs for boolean values.

Typedefs shouldn't be used, use the bare struct names instead.

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

Get rid of CamelCase, and don't use a typedef, so we can
forward-declare it, and unclutter the include dependencies.

This releases several include file dependencies.  As a side effect,
"CHUNK_SIZE" isn't defined by decoder_api.h anymore, so we have to
define it directly in the plugins which need it.  It just isn't worth
it to add it to the decoder plugin API.

(Ab)use the decoder_command enumeration, which has nearly the same
values and the same meaning.

Since we moved all PCM conversions to decoder_data(), the attribute
convState isn't being used anymore by the OutputBuffer code.  Move it
to struct decoder.

OutputBuffer should be a more generic low-level library, without
dependencies to the other headers.  This patch adds the field
"notify", which is used to signal the player thread.  It is passed in
the constructor, and removes the need to compile with the decode.h
header.

Moved all of the player-waiting code to decoder_data(), to make
OutputBuffer more generic.

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

In lazy mode (previously the default), outputBuffer.c only wakes up
the player when it was previously empty.  That caused a deadlock when
the player was waiting for buffered_before_play, since the decoder
wouldn't wake up the player when buffered_before_play was reached.  In
non-lazy mode, always wake up the player when a new chunk was decoded.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7364 09075e82-0dd4-0310-85a5-a0d7c8717e4f

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

OutputBuffer.currentChunk contains redundant data: it is either -1
when there is no chunk which is currently being written, or it equals
"end".  If we always keep chunk[end] in a valid state, we can remove
OutputBuffer.currentChunk.

This patch may look a bit clumsy, especially flushOutputBuffer(), but
that will be fixed later with an major OutputBuffer API overhaul.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7339 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Try to only include headers which are really needed.  We should
particularly check all "headers including other headers".  The
long-term goal is to have a manageable, small API for plugins
(decoders, output) without so many mpd internals cluttering the
namespace.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7319 09075e82-0dd4-0310-85a5-a0d7c8717e4f

There is no danger that gcc will optimize access to OutputBufferChunk
properties, since decoder and player work in different chunk objects.
It is safe to remove "volatile" here.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7318 09075e82-0dd4-0310-85a5-a0d7c8717e4f

To do proper cleanup before exiting, we have to provide a destructor
for OutputBuffer.  One day, valgrind will not complain about memory
leaks!

git-svn-id: https://svn.musicpd.org/mpd/trunk@7315 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Don't be mean with integer sizes.  Although we will probably never
have more than 32k buffered chunks, we should use 32 bit integers for
addressing them.  We do not save very much (some of the saved space is
eaten by alignment anyway), but we save at least one assembler
instruction for converting short to int.

This change requires some more explicit casts, because gcc was less
picky when comparing short with a full int.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7313 09075e82-0dd4-0310-85a5-a0d7c8717e4f

First patch without camelCase ;)

output_buffer_skip() lets us eliminate advanceOutputBufferTo(), and
removes yet another external OutputBuffer struct access.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7312 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Try to make OutputBuffer self-contained, without depending on a global
variable.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7310 09075e82-0dd4-0310-85a5-a0d7c8717e4f

This is the first patch in a series which removes the shared memory,
and moves all the playerData objects into the normal libc heap.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7304 09075e82-0dd4-0310-85a5-a0d7c8717e4f

git-svn-id: https://svn.musicpd.org/mpd/trunk@7300 09075e82-0dd4-0310-85a5-a0d7c8717e4f

currentChunk is a global variable, which renders the whole output
buffer code non-reentrant.  Although this is not a real problem since
there is only one global output buffer currently, we should move it to
the OutputBuffer struct.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7284 09075e82-0dd4-0310-85a5-a0d7c8717e4f

Hiding OutputBuffer internals, yet again.  Two more assertions.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7274 09075e82-0dd4-0310-85a5-a0d7c8717e4f