Document get_*_buffer()

Originally committed as revision 12548 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avio.h

@@ -260,7 +260,19 @@ char *url_fgets(ByteIOContext *s, char *buf, int buf_size);
 
 void put_flush_packet(ByteIOContext *s);
 
+
+/**
+ * Reads size bytes from ByteIOContext into buf.
+ * @returns number of bytes read or AVERROR
+ */
 int get_buffer(ByteIOContext *s, unsigned char *buf, int size);
+
+/**
+ * Reads size bytes from ByteIOContext into buf.
+ * This reads at most 1 packet. If thats not enough fewer bytes will be
+ * returned.
+ * @returns number of bytes read or AVERROR
+ */
 int get_partial_buffer(ByteIOContext *s, unsigned char *buf, int size);
 
 /** @note return 0 if EOF, so you cannot use it if EOF handling is