music_chunk: added music_chunk_write(), music_chunk_expand()

Moved some code from music_pipe_write() and music_pipe_expand().  Only
music_chunk.c should access the music_chunk internals.

src/chunk.c

@@ -17,8 +17,11 @@
  */
 
 #include "chunk.h"
+#include "audio_format.h"
 #include "tag.h"
 
+#include <assert.h>
+
 void
 music_chunk_init(struct music_chunk *chunk)
 {
@@ -32,3 +35,42 @@ music_chunk_free(struct music_chunk *chunk)
 	if (chunk->tag != NULL)
 		tag_free(chunk->tag);
 }
+
+void *
+music_chunk_write(struct music_chunk *chunk,
+		  const struct audio_format *audio_format,
+		  float data_time, uint16_t bit_rate,
+		  size_t *max_length_r)
+{
+	const size_t frame_size = audio_format_frame_size(audio_format);
+	size_t num_frames;
+
+	if (chunk->length == 0) {
+		/* if the chunk is empty, nobody has set bitRate and
+		   times yet */
+
+		chunk->bit_rate = bit_rate;
+		chunk->times = data_time;
+	}
+
+	num_frames = (sizeof(chunk->data) - chunk->length) / frame_size;
+	if (num_frames == 0)
+		return NULL;
+
+	*max_length_r = num_frames * frame_size;
+	return chunk->data + chunk->length;
+}
+
+bool
+music_chunk_expand(struct music_chunk *chunk,
+		   const struct audio_format *audio_format, size_t length)
+{
+	const size_t frame_size = audio_format_frame_size(audio_format);
+
+	assert(chunk != NULL);
+	assert(chunk->length + length <= sizeof(chunk->data));
+
+	chunk->length += length;
+
+	return chunk->length + frame_size > sizeof(chunk->data);
+}

src/chunk.h

@@ -19,13 +19,17 @@
 #ifndef MPD_CHUNK_H
 #define MPD_CHUNK_H
 
+#include <stdbool.h>
 #include <stdint.h>
+#include <stddef.h>
 
 enum {
 	/* pick 1020 since its devisible for 8,16,24, and 32-bit audio */
 	CHUNK_SIZE = 1020,
 };
 
+struct audio_format;
+
 /**
  * A chunk of music data.  Its format is defined by the
  * music_pipe_append() caller.
@@ -58,4 +62,36 @@ music_chunk_init(struct music_chunk *chunk);
 void
 music_chunk_free(struct music_chunk *chunk);
 
+/**
+ * Prepares appending to the music chunk.  Returns a buffer where you
+ * may write into.  After you are finished, call music_chunk_expand().
+ *
+ * @param chunk the music_chunk object
+ * @param audio_format the audio format for the appended data; must
+ * stay the same for the life cycle of this chunk
+ * @param data_time the time within the song
+ * @param bit_rate the current bit rate of the source file
+ * @param max_length_r the maximum write length is returned here
+ * @return a writable buffer, or NULL if the chunk is full
+ */
+void *
+music_chunk_write(struct music_chunk *chunk,
+		  const struct audio_format *audio_format,
+		  float data_time, uint16_t bit_rate,
+		  size_t *max_length_r);
+
+/**
+ * Increases the length of the chunk after the caller has written to
+ * the buffer returned by music_chunk_write().
+ *
+ * @param chunk the music_chunk object
+ * @param audio_format the audio format for the appended data; must
+ * stay the same for the life cycle of this chunk
+ * @param length the number of bytes which were appended
+ * @return true if the chunk is full
+ */
+bool
+music_chunk_expand(struct music_chunk *chunk,
+		   const struct audio_format *audio_format, size_t length);
+
 #endif

src/pipe.c

@@ -201,23 +201,13 @@ music_pipe_write(const struct audio_format *audio_format,
 {
 	const size_t frame_size = audio_format_frame_size(audio_format);
 	struct music_chunk *chunk;
-	size_t num_frames;
 
 	chunk = tail_chunk(frame_size);
 	if (chunk == NULL)
 		return NULL;
 
-	if (chunk->length == 0) {
-		/* if the chunk is empty, nobody has set bitRate and
-		   times yet */
-
-		chunk->bit_rate = bit_rate;
-		chunk->times = data_time;
-	}
-
-	num_frames = (sizeof(chunk->data) - chunk->length) / frame_size;
-	*max_length_r = num_frames * frame_size;
-	return chunk->data + chunk->length;
+	return music_chunk_write(chunk, audio_format, data_time, bit_rate,
+				 max_length_r);
 }
 
 void
@@ -225,17 +215,16 @@ music_pipe_expand(const struct audio_format *audio_format, size_t length)
 {
 	const size_t frame_size = audio_format_frame_size(audio_format);
 	struct music_chunk *chunk;
+	bool full;
 
 	/* no partial frames allowed */
 	assert(length % frame_size == 0);
 
 	chunk = tail_chunk(frame_size);
 	assert(chunk != NULL);
-	assert(chunk->length + length <= sizeof(chunk->data));
 
-	chunk->length += length;
-
-	if (chunk->length + frame_size > sizeof(chunk->data))
+	full = music_chunk_expand(chunk, audio_format, length);
+	if (full)
 		music_pipe_flush();
 }