+/**
+ * Calculate the Adler32 checksum of a buffer.
+ *
+ * Passing the return value to a subsequent av_adler32_update() call
+ * allows the checksum of multiple buffers to be calculated as though
+ * they were concatenated.
+ *
+ * @param adler initial checksum value
+ * @param buf pointer to input buffer
+ * @param len size of input buffer
+ * @return updated checksum
+ */