git/decorate.c
Kevin Bracey 83f0412f3f decorate.c: compact table when growing
When growing the table, take the opportunity to "compact" it by removing
entries with NULL decoration.

Users may have "removed" decorations by passing NULL to
insert_decoration. An object's table entry can't actually be removed
during normal operation, as it would break the linear hash collision
search. But we can remove NULL decoration entries when rebuilding the
table.

Signed-off-by: Kevin Bracey <kevin@bracey.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-05-16 11:51:08 -07:00

89 lines
1.8 KiB
C

/*
* decorate.c - decorate a git object with some arbitrary
* data.
*/
#include "cache.h"
#include "object.h"
#include "decorate.h"
static unsigned int hash_obj(const struct object *obj, unsigned int n)
{
unsigned int hash;
memcpy(&hash, obj->sha1, sizeof(unsigned int));
return hash % n;
}
static void *insert_decoration(struct decoration *n, const struct object *base, void *decoration)
{
int size = n->size;
struct object_decoration *hash = n->hash;
unsigned int j = hash_obj(base, size);
while (hash[j].base) {
if (hash[j].base == base) {
void *old = hash[j].decoration;
hash[j].decoration = decoration;
return old;
}
if (++j >= size)
j = 0;
}
hash[j].base = base;
hash[j].decoration = decoration;
n->nr++;
return NULL;
}
static void grow_decoration(struct decoration *n)
{
int i;
int old_size = n->size;
struct object_decoration *old_hash = n->hash;
n->size = (old_size + 1000) * 3 / 2;
n->hash = xcalloc(n->size, sizeof(struct object_decoration));
n->nr = 0;
for (i = 0; i < old_size; i++) {
const struct object *base = old_hash[i].base;
void *decoration = old_hash[i].decoration;
if (!decoration)
continue;
insert_decoration(n, base, decoration);
}
free(old_hash);
}
/* Add a decoration pointer, return any old one */
void *add_decoration(struct decoration *n, const struct object *obj,
void *decoration)
{
int nr = n->nr + 1;
if (nr > n->size * 2 / 3)
grow_decoration(n);
return insert_decoration(n, obj, decoration);
}
/* Lookup a decoration pointer */
void *lookup_decoration(struct decoration *n, const struct object *obj)
{
unsigned int j;
/* nothing to lookup */
if (!n->size)
return NULL;
j = hash_obj(obj, n->size);
for (;;) {
struct object_decoration *ref = n->hash + j;
if (ref->base == obj)
return ref->decoration;
if (!ref->base)
return NULL;
if (++j == n->size)
j = 0;
}
}