add method availableOutputBuffer()

The method availableOutputBuffer() calculates how many chunks are in
use.  This simplifies code which needs this information, and it can
run without knowing OutputBuffer internals.  The function knows how to
calculate this when begin>end; this might have been a bug in
decodeParent(), which does not.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7250 09075e82-0dd4-0310-85a5-a0d7c8717e4f

3 files changed, 12 insertions, 2 deletions

diff --git a/src/decode.c b/src/decode.c
index a07d61843..520485383 100644
--- a/src/decode.c
+++ b/src/decode.c
@@ -425,8 +425,7 @@ static void decodeParent(PlayerControl * pc, DecoderControl * dc, OutputBuffer *
 	pc->play = 0;
 	wakeup_main_task();
 
-	while ((unsigned)cb->end - cb->begin < bbp &&
-	       cb->end != buffered_chunks - 1 &&
+	while (availableOutputBuffer(cb) < bbp &&
 	       dc->state != DECODE_STATE_STOP) {
 		processDecodeInput();
 		player_sleep();
diff --git a/src/outputBuffer.c b/src/outputBuffer.c
index d15a947e3..f5a6dbf51 100644
--- a/src/outputBuffer.c
+++ b/src/outputBuffer.c
@@ -57,6 +57,14 @@ void flushOutputBuffer(OutputBuffer * cb)
 	}
 }
 
+unsigned availableOutputBuffer(const OutputBuffer * cb)
+{
+	if (cb->end >= cb->begin)
+		return cb->end - cb->begin;
+	else
+		return cb->end + buffered_chunks - cb->begin;
+}
+
 /**
  * Return the tail chunk has room for additional data.  If there is no
  * room in the queue, this function blocks until the player thread has
diff --git a/src/outputBuffer.h b/src/outputBuffer.h
index 4d480e08a..08124dffa 100644
--- a/src/outputBuffer.h
+++ b/src/outputBuffer.h
@@ -55,6 +55,9 @@ void clearOutputBuffer(OutputBuffer * cb);
 
 void flushOutputBuffer(OutputBuffer * cb);
 
+/** determine the number of decoded chunks */
+unsigned availableOutputBuffer(const OutputBuffer * cb);
+
 /* we send inStream for buffering the inputStream while waiting to
    send the next chunk */
 int sendDataToOutputBuffer(OutputBuffer * cb,