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-rw-r--r--libavformat/avio.h47
1 files changed, 47 insertions, 0 deletions
diff --git a/libavformat/avio.h b/libavformat/avio.h
index 06dd7f5ef8..abe13b2719 100644
--- a/libavformat/avio.h
+++ b/libavformat/avio.h
@@ -122,6 +122,53 @@ typedef struct AVIOContext {
* to any av_opt_* functions in that case.
*/
const AVClass *av_class;
+
+ /*
+ * The following shows the relationship between buffer, buf_ptr, buf_end, buf_size,
+ * and pos, when reading and when writing (since AVIOContext is used for both):
+ *
+ **********************************************************************************
+ * READING
+ **********************************************************************************
+ *
+ * | buffer_size |
+ * |---------------------------------------|
+ * | |
+ *
+ * buffer buf_ptr buf_end
+ * +---------------+-----------------------+
+ * |/ / / / / / / /|/ / / / / / /| |
+ * read buffer: |/ / consumed / | to be read /| |
+ * |/ / / / / / / /|/ / / / / / /| |
+ * +---------------+-----------------------+
+ *
+ * pos
+ * +-------------------------------------------+-----------------+
+ * input file: | | |
+ * +-------------------------------------------+-----------------+
+ *
+ *
+ **********************************************************************************
+ * WRITING
+ **********************************************************************************
+ *
+ * | buffer_size |
+ * |-------------------------------|
+ * | |
+ *
+ * buffer buf_ptr buf_end
+ * +-------------------+-----------+
+ * |/ / / / / / / / / /| |
+ * write buffer: | / to be flushed / | |
+ * |/ / / / / / / / / /| |
+ * +-------------------+-----------+
+ *
+ * pos
+ * +--------------------------+-----------------------------------+
+ * output file: | | |
+ * +--------------------------+-----------------------------------+
+ *
+ */
unsigned char *buffer; /**< Start of the buffer. */
int buffer_size; /**< Maximum buffer size */
unsigned char *buf_ptr; /**< Current position in the buffer */