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Merge branch 'np/lookup-object-hashing'

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Micro optimize hash function used in the object hash table.

* np/lookup-object-hashing:
  lookup_object: remove hashtable_index() and optimize hash_obj()
This commit is contained in:
Junio C Hamano
2013-09-20 12:30:49 -07:00
parent 08092082b7 9f36c9b7f7
commit 3fb9d685db
1 changed files with 10 additions and 12 deletions
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22
object.c
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@ -43,16 +43,17 @@ int type_from_string(const char *str)
die("invalid object type \"%s\"", str); die("invalid object type \"%s\"", str);
} }
static unsigned int hash_obj(struct object *obj, unsigned int n) static unsigned int hash_obj(const unsigned char *sha1, unsigned int n)
{ {
unsigned int hash; unsigned int hash;
memcpy(&hash, obj->sha1, sizeof(unsigned int)); memcpy(&hash, sha1, sizeof(unsigned int));
return hash % n; /* Assumes power-of-2 hash sizes in grow_object_hash */
return hash & (n - 1);
} }
static void insert_obj_hash(struct object *obj, struct object **hash, unsigned int size) static void insert_obj_hash(struct object *obj, struct object **hash, unsigned int size)
{ {
unsigned int j = hash_obj(obj, size); unsigned int j = hash_obj(obj->sha1, size);
while (hash[j]) { while (hash[j]) {
j++; j++;
@ -62,13 +63,6 @@ static void insert_obj_hash(struct object *obj, struct object **hash, unsigned i
hash[j] = obj; hash[j] = obj;
} }
static unsigned int hashtable_index(const unsigned char *sha1)
{
unsigned int i;
memcpy(&i, sha1, sizeof(unsigned int));
return i % obj_hash_size;
}
struct object *lookup_object(const unsigned char *sha1) struct object *lookup_object(const unsigned char *sha1)
{ {
unsigned int i, first; unsigned int i, first;
@ -77,7 +71,7 @@ struct object *lookup_object(const unsigned char *sha1)
if (!obj_hash) if (!obj_hash)
return NULL; return NULL;
first = i = hashtable_index(sha1); first = i = hash_obj(sha1, obj_hash_size);
while ((obj = obj_hash[i]) != NULL) { while ((obj = obj_hash[i]) != NULL) {
if (!hashcmp(sha1, obj->sha1)) if (!hashcmp(sha1, obj->sha1))
break; break;
@ -101,6 +95,10 @@ struct object *lookup_object(const unsigned char *sha1)
static void grow_object_hash(void) static void grow_object_hash(void)
{ {
int i; int i;
/*
* Note that this size must always be power-of-2 to match hash_obj
* above.
*/
int new_hash_size = obj_hash_size < 32 ? 32 : 2 * obj_hash_size; int new_hash_size = obj_hash_size < 32 ? 32 : 2 * obj_hash_size;
struct object **new_hash; struct object **new_hash;