algorithm HASH, placing the result in the pre-allocated buffer OUT.
The required size of OUT depends on HASH, and is generally
GC_<HASH>_DIGEST_SIZE. For example, for GC_MD5 the output buffer
- must be 16 bytes. */
+ must be 16 bytes. The return value is 0 (GC_OK) on success, or
+ another Gc_rc error code. */
extern int
gc_hash_buffer (int hash, const void *in, size_t inlen, char *out);