added outputBufferShift()

Hiding OutputBuffer internals, yet again.  Two more assertions.

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

src/decode.c

@@ -557,10 +557,7 @@ static void decodeParent(PlayerControl * pc, DecoderControl * dc, OutputBuffer *
 				break;
 			pc->totalPlayTime +=
 				sizeToTime * beginChunk->chunkSize;
-			if ((unsigned)cb->begin + 1 >= buffered_chunks) {
-				cb->begin = 0;
-			} else
-				cb->begin++;
+			outputBufferShift(cb);
 			player_wakeup_decoder_nb();
 		} else if (!outputBufferEmpty(cb) && cb->begin == next) {
 			/* at the beginning of a new song */

src/outputBuffer.c

@@ -56,6 +56,16 @@ int outputBufferEmpty(const OutputBuffer * cb)
 	return cb->begin == cb->end;
 }
 
+void outputBufferShift(OutputBuffer * cb)
+{
+	assert(cb->begin != cb->end);
+	assert(cb->begin < buffered_chunks);
+
+	++cb->begin;
+	if (cb->begin >= buffered_chunks)
+		cb->begin = 0;
+}
+
 unsigned int outputBufferRelative(const OutputBuffer * cb, unsigned i)
 {
 	if (i >= cb->begin)

src/outputBuffer.h

@@ -65,6 +65,8 @@ void flushOutputBuffer(OutputBuffer * cb);
 /** is the buffer empty? */
 int outputBufferEmpty(const OutputBuffer * cb);
 
+void outputBufferShift(OutputBuffer * cb);
+
 /**
  * what is the position of the specified chunk number, relative to
  * the first chunk in use?