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.

The previous patch on this topic was incomplete: it still added
data->chunk_length when calling flac_convert().  Remove this, too.

The inline function audio_format_sample_size() calculates how many
bytes each sample consumes.  This function already takes into account
that 24 bit samples are 4 bytes long, not 3.

Instead of letting ALSA block for us (and potentially allowing
something stupid on certain hardware or drivers), we do the
sleeping ourselves.  We calculate the sleep to be a fraction of
period_time to avoid oversleeping (and thus audible skipping).

Add information about the M4 macro dir ./m4/ to both configure.ac and
Makefile.am.

Potentially broken free() implementations don't like it

Use freeList() instead of free() to free all elements in
the list.

open(2) should only interrupt on "slow" devices, afaik...

[mk: still using fopen()]

Any pruned files will be noticed during update and pruned
from the live database, so this inefficient function can
go away and never come back.

A lot of the preparation was needed (and done in previous
months) in making update thread-safe, but here it is.

This was the first thing I made work inside a thread when I
started mpd-uclinux many years ago, and also the last thing I've
done in mainline mpd to work inside a thread, go figure.

Converted some more functions and their callers to enum update_return.

This way we avoid having to document -1, 0, 1

Pruning is very expensive and we won't need it in the future
anyways.  This brings startup back to previous speeds (before
songvec changes).

pthreads with our existing signal blocking/handling is broken,
for now just sleep a bit in the child to prevent the CHLD handler
from being called too early.  Also, improve error reporting when
handling SIGCHLD by storing the status to be called in the main
task (which can be logged, since we can't do logging inside the
sig handler).

Our linked-list implementation is wasteful and the
SongList isn't modified enough to benefit from being a linked
list.  So use a more compact array of song pointers which
saves ~200K on a library with ~9K songs (on x86-32).

It hasn't been used in many years

  commit 3a89afdd
  Author: Warren Dukes <warren.dukes@gmail.com>
  Date:   Sat Nov 20 20:28:32 2004 +0000

      remove --update-db option

      (SVN r2719)

LOC reduction and less noise makes things easier for
tired old folks to follow.

This allows us to avoid the nasty repetition in strncmp(foo,
bar, strlen(foo)).  We'll miss out on the compiler optimizing
strlen() into sizeof() - 1 for string literals for this; but we
don't use this it for performance-critical functions anyways...

Noticed-by: Courtney Cavin

This should save a few thousand ops.  Not worth it to malloc
for such a small (3-words on 32-bit ARM and x86) structures.
Signed-off-by: Eric Wong <normalperson@yhbt.net>

It is legal to call wakeup_main_task() from within the main thread,
e.g. from within a signal handler.  Remove the assertion.

Remove duplicated code.

The function decodeFirstFrame() allocates memory based on data from
the mp3 header.  This can make the buffer size allocation overflow, or
lead to a DoS attack with a very large buffer.  Cap this buffer at 8
million frames, which should really be enough for reasonable files.

The assertion on "!client_is_expired(client)" was wrong, because
writing the command response may cause the client to become expired.
Replace that assertion with a check.

A crafted mp4 file could cause an integer overflow in mp4_decode
function in src/inputPlugins/mp4_plugin.c.  mp4ff_num_samples()
function returns some tainted value. sizeof(float) * numSamples is an
integer overflow operation if numSamples is too huge, so xmalloc will
allocate a small memory region.  I constructe a mp4 file, and use
faad2 to open the file. mp4ff_num_samples() returns -1. So I think mpd
bears from the same problem.

Add a check to write_page() which checks if there is actually data.
Don't bother to call shout_send() if there is not.

The function is trivial, without a benefit.  Also don't initialize
buf.data[0], this is not a null terminated string.

Since the buffer size is known at compile time, we can save an
indirection by declaring it as a char array instead of a pointer.
That saves an extra allocation, and we can calculate with the
compile-time constant sizeof(data) instead of the attribute "max_len".

Declare both shout plugins "const", since they will never change, once
initialized at compile time.

Shout encoder plugins are known at compile time.  There is no reason
to use a complex data structure as "List" to manage them at runtime -
just put the pointers into a static array.

Don't typedef the structs at all.  It is easier to forward-declare
this way.

Don't typedef methods.  They are used exactly once, a few lines below.

[mk: moved this patch after "Refactor and cleanup of shout Ogg and MP3
audio outputs".  The original commit message follows, although it is
outdated:]

Creation of shout_mp3 audio output plugin. Basically I just copied the
existing shout plugin and replaced ogg with lame. Uses lame for mp3
encoding. Next step is to pull common functionality out of each shout
plugin and share it between them.

Configuration options for "shout_mp3" are the same as for "shout".

I've perhaps gone a bit overboard, but here's the current rundown:

Both Ogg and MP3 use the "shout" audio output plugin.  The shout audio
output plugin itself has two new plugins, one for the Ogg encoder,
and another for the MP3 (LAME) encoder.

Configuration for an Ogg stream doesn't change.  For an MP3 stream,
configuration is the same as Ogg, with two exceptions.  First, you must
specify the optional "encoding" parameter, which should be set to "mp3".
See mpd.conf(5) for more details.  Second, the "quality" parameter is
reversed for LAME, such that 1 is high quality for LAME, whereas 10 is
high quality for Ogg.

I've decomposed the code so that all libshout related operations
are done in audioOutput_shout.c, all Ogg specific functions are in
audioOutput_shout_ogg.c, and of course then all LAME specific functions
are handled in audioOutput_shout_mp3.c.

To develop encoder plugins for the shout audio output plugin, I basically
just mimicked the plugin system used for audio outputs.  This might be
overkill, but hopefully if anyone ever wants to support some other sort
of stream, like maybe AAC, FLAC, or WMA (hey it could happen), they will
hopefully be all set.

The Ogg encoder is slightly less optimal under this configuration.
It used to send shout data directly out of its ogg_page structures.  Now,
in the interest of encapsulation, it copies the data from its ogg_page
structures into a buffer provided by the shout audio output plugin (see
audioOutput_shout_ogg.c, line 77.)  I suspect the performance impact
is negligible.

As for metadata, I'm pretty sure they'll both work.  I wrote up a test
scaffold that would create a fake tag, and tell the plugin to send it
out to the stream every few seconds.  It seemed to work fine.  Of course,
if something does break, I'll be glad to fix it.

Lastly, I've renamed lots of things into snake_case, in keeping with
normalperson's wishes in that regard.

[mk: moved the MP3 patch after this one.  Splitted this patch into
several parts; the others were already applied before this one.  Fixed
a bunch GCC warnings and wrong whitespace modifications.  Made it
compile with mpd-mk by adapting to its prototypes]

Support sending metadata to a shout server using shout_metadata_new()
and shout_metadata_add().  The Ogg Vorbis encoder does not support
this currently.

[mk: this patch was separated from Eric's patch "Refactor and cleanup
of shout Ogg and MP3 audio outputs", I added a description]

Preparing the merge of Eric Wollesen's patch "Refactor and cleanup of
shout Ogg and MP3 audio outputs": we declare one of the struct types
here, to make the merge smoother.