added ob_set_lazy()

src/decode.c

@@ -400,6 +400,8 @@ static void decodeParent(void)
 	/** the position of the first chunk in the next song */
 	int next = -1;
 
+	ob_set_lazy(0);
+
 	if (waitOnDecode(&decodeWaitedOn) < 0)
 		return;
 
@@ -421,9 +423,11 @@ static void decodeParent(void)
 				/* not enough decoded buffer space yet */
 				player_sleep();
 				continue;
-			} else
+			} else {
 				/* buffering is complete */
 				buffering = 0;
+				ob_set_lazy(1);
+			}
 		}
 
 		if (decodeWaitedOn) {
@@ -513,6 +517,7 @@ static void decodeParent(void)
 				}
 				nextChunk = ob_absolute(crossFadeChunks);
 				if (nextChunk >= 0) {
+					ob_set_lazy(1);
 					crossFade(beginChunk,
 						  ob_get_chunk(nextChunk),
 						  &(ob.audioFormat),
@@ -529,6 +534,7 @@ static void decodeParent(void)
 					} else {
 						/* wait for the
 						   decoder */
+						ob_set_lazy(0);
 						player_sleep();
 						continue;
 					}

src/outputBuffer.c

@@ -31,6 +31,7 @@ void ob_init(unsigned int size)
 	ob.size = size;
 	ob.begin = 0;
 	ob.end = 0;
+	ob.lazy = 0;
 	ob.chunks[0].chunkSize = 0;
 }
 
@@ -61,7 +62,7 @@ static inline unsigned successor(unsigned i)
  */
 static void output_buffer_expand(unsigned i)
 {
-	int was_empty = ob_is_empty();
+	int was_empty = !ob.lazy || ob_is_empty();
 
 	assert(i == (ob.end + 1) % ob.size);
 	assert(i != ob.end);
@@ -91,6 +92,11 @@ void ob_flush(void)
 	}
 }
 
+void ob_set_lazy(int lazy)
+{
+	ob.lazy = lazy;
+}
+
 int ob_is_empty(void)
 {
 	return ob.begin == ob.end;

src/outputBuffer.h

@@ -53,6 +53,10 @@ typedef struct _OutputBuffer {
 	/** the index after the last decoded chunk */
 	unsigned int volatile end;
 
+	/** non-zero if the player thread should only we woken up if
+	    the buffer becomes non-empty */
+	int lazy;
+
 	AudioFormat audioFormat;
 	ConvState convState;
 } OutputBuffer;
@@ -65,6 +69,14 @@ void ob_clear(void);
 
 void ob_flush(void);
 
+/**
+ * When a chunk is decoded, we wake up the player thread to tell him
+ * about it.  In "lazy" mode, we only wake him up when the buffer was
+ * previously empty, i.e. when the player thread has really been
+ * waiting for us.
+ */
+void ob_set_lazy(int lazy);
+
 /** is the buffer empty? */
 int ob_is_empty(void);