repack: move `pack_geometry` struct to the stack

[thirdparty/git.git] / hash-ll.h

diff --git a/hash-ll.h b/hash-ll.h
index 80509251370523029710e2e691b832e601be939f..8d7973769fda4fb68f83e24b219c3473bbd32171 100644 (file)
--- a/hash-ll.h
+++ b/hash-ll.h
@@ -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);