diff options
Diffstat (limited to 'hash-ll.h')
| -rw-r--r-- | hash-ll.h | 19 |
1 files changed, 19 insertions, 0 deletions
@@ -270,6 +270,25 @@ static inline void oid_set_algo(struct object_id *oid, const struct git_hash_alg oid->algo = hash_algo_by_ptr(algop); } +/* + * Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code + * for use in hash tables. Cryptographic hashes are supposed to have + * uniform distribution, so in contrast to `memhash()`, this just copies + * the first `sizeof(int)` bytes without shuffling any bits. Note that + * the results will be different on big-endian and little-endian + * platforms, so they should not be stored or transferred over the net. + */ +static inline unsigned int oidhash(const struct object_id *oid) +{ + /* + * Equivalent to 'return *(unsigned int *)oid->hash;', but safe on + * platforms that don't support unaligned reads. + */ + unsigned int hash; + memcpy(&hash, oid->hash, sizeof(hash)); + return hash; +} + const char *empty_tree_oid_hex(void); const char *empty_blob_oid_hex(void); |