- * Decompress data previously compressed by @lizard_compress().
- * Input is taken from @in. @buf is used to store the output.
- * You need to provide the length of the uncompressed data in @expected_length.
+ * This one acts much like @lizard_decompress(). The difference is it
+ * checks the data to be of correct length (therefore it will not
+ * crash on invalid data).
+ *
+ * It decompresses data provided by @in. The @buf is used to get the
+ * memory for output (you get one by @lizard_alloc()).
+ *
+ * The pointer to decompressed data is returned. To free it, free the
+ * buffer by @lizard_free().
+ *
+ * In the case of error, NULL is returned. In that case, `errno` is
+ * set either to `EINVAL` (expected_length does not match) or to
+ * `EFAULT` (a segfault has been caught while decompressing -- it
+ * probably means expected_length was set way too low). Both cases
+ * suggest either wrongly computed length or data corruption.