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/* the Music Player Daemon (MPD)
* Copyright (C) 2003-2007 by Warren Dukes (warren.dukes@gmail.com)
* This project's homepage is: http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "metadata_pipe.h"
#include "ringbuf.h"
#include "decode.h"
#include "os_compat.h"
#include "log.h"
#include "outputBuffer.h"
#include "gcc.h"
/* These are defined in outputBuffer_accessors.h, cleanup is needed */
mpd_uint8 ob_get_decoder_sequence(void);
mpd_uint8 ob_get_player_sequence(void);
static struct ringbuf *mp;
/* Each one of these is a packet inside the metadata pipe */
struct tag_container {
float metadata_time;
mpd_uint8 seq; /* ob.seq_decoder at time of metadata_pipe_send() */
MpdTag *tag; /* our payload */
};
/*
* We have two readers even though ringbuf was designed for one (locklessly),
* so we will use a lock to allow readers to safely read. Writing is only
* done from one thread, so it will never block or clobber.
*/
static pthread_mutex_t read_lock = PTHREAD_MUTEX_INITIALIZER;
static MpdTag *current_tag; /* requires read_lock for both r/w access */
static void metadata_pipe_finish(void)
{
ringbuf_free(mp);
if (current_tag)
freeMpdTag(current_tag);
}
void init_metadata_pipe(void)
{
mp = ringbuf_create(sizeof(struct tag_container) * 16);
atexit(metadata_pipe_finish);
}
void metadata_pipe_send(MpdTag *tag, float metadata_time)
{
struct tag_container tc;
size_t written;
assert(pthread_equal(pthread_self(), dc.thread));
if (mpd_unlikely(ringbuf_write_space(mp)
< sizeof(struct tag_container))) {
DEBUG("metadata_pipe: insufficient buffer space, dropping\n");
freeMpdTag(tag);
return;
}
tc.tag = tag;
tc.metadata_time = metadata_time;
tc.seq = ob_get_decoder_sequence();
written = ringbuf_write(mp, &tc, sizeof(struct tag_container));
assert(written == sizeof(struct tag_container));
}
MpdTag * metadata_pipe_recv(void)
{
struct tag_container tc;
size_t r;
static const size_t mpd_uint8_max = 255; /* XXX CLEANUP */
mpd_uint8 expect_seq = ob_get_player_sequence();
unsigned long current_time = ob_get_elapsed_time();
MpdTag *tag = NULL;
if (pthread_mutex_trylock(&read_lock) == EBUSY)
return NULL;
retry:
if (!(r = ringbuf_peek(mp, &tc, sizeof(struct tag_container))))
goto out;
assert(r == sizeof(struct tag_container));
assert(tc.tag);
if (expect_seq == tc.seq) {
if (current_time < tc.metadata_time)
goto out; /* not ready for tag yet */
if (mpdTagsAreEqual(tc.tag, current_tag)) {
freeMpdTag(tc.tag);
ringbuf_read_advance(mp, sizeof(struct tag_container));
goto out; /* nothing changed, don't bother */
}
tag = mpdTagDup(tc.tag);
if (current_tag)
freeMpdTag(current_tag);
current_tag = tc.tag;
ringbuf_read_advance(mp, sizeof(struct tag_container));
} else if (expect_seq > tc.seq ||
(!expect_seq && tc.seq == mpd_uint8_max)) {
DEBUG("metadata_pipe: reader is ahead of writer\n");
freeMpdTag(tc.tag);
ringbuf_read_advance(mp, sizeof(struct tag_container));
goto retry; /* read and skip packets */
} else {
DEBUG("metadata_pipe: writer is ahead of reader\n");
/* not ready for tag yet */
}
out:
pthread_mutex_unlock(&read_lock);
return tag;
}
MpdTag *metadata_pipe_current(void)
{
MpdTag *tag;
assert(! pthread_equal(pthread_self(), dc.thread));
if (pthread_mutex_trylock(&read_lock) == EBUSY)
return NULL;
tag = current_tag ? mpdTagDup(current_tag) : NULL;
pthread_mutex_unlock(&read_lock);
return tag;
}
void metadata_pipe_clear(void)
{
struct tag_container tc;
size_t r;
pthread_mutex_lock(&read_lock);
while ((r = ringbuf_read(mp, &tc, sizeof(struct tag_container)))) {
assert(r == sizeof(struct tag_container));
freeMpdTag(tc.tag);
}
if (current_tag) {
freeMpdTag(current_tag);
current_tag = NULL;
}
pthread_mutex_unlock(&read_lock);
}
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