Add a generic "object decorator" interface, and make object refs use it
[git/git.git] / decorate.c
1 /*
2 * decorate.c - decorate a git object with some arbitrary
3 * data.
4 */
5 #include "cache.h"
6 #include "object.h"
7 #include "decorate.h"
8
9 static unsigned int hash_obj(struct object *obj, unsigned int n)
10 {
11 unsigned int hash = *(unsigned int *)obj->sha1;
12 return hash % n;
13 }
14
15 static void *insert_decoration(struct decoration *n, struct object *base, void *decoration)
16 {
17 int size = n->size;
18 struct object_decoration *hash = n->hash;
19 int j = hash_obj(base, size);
20
21 while (hash[j].base) {
22 if (hash[j].base == base) {
23 void *old = hash[j].decoration;
24 hash[j].decoration = decoration;
25 return old;
26 }
27 j++;
28 if (++j >= size)
29 j = 0;
30 }
31 hash[j].base = base;
32 hash[j].decoration = decoration;
33 n->nr++;
34 return NULL;
35 }
36
37 static void grow_decoration(struct decoration *n)
38 {
39 int i;
40 int old_size = n->size;
41 struct object_decoration *old_hash;
42
43 old_size = n->size;
44 old_hash = n->hash;
45
46 n->size = (old_size + 1000) * 3 / 2;
47 n->hash = xcalloc(n->size, sizeof(struct object_decoration));
48 n->nr = 0;
49
50 for (i = 0; i < old_size; i++) {
51 struct object *base = old_hash[i].base;
52 void *decoration = old_hash[i].decoration;
53
54 if (!base)
55 continue;
56 insert_decoration(n, base, decoration);
57 }
58 free(old_hash);
59 }
60
61 /* Add a decoration pointer, return any old one */
62 void *add_decoration(struct decoration *n, struct object *obj, void *decoration)
63 {
64 int nr = n->nr + 1;
65
66 if (nr > n->size * 2 / 3)
67 grow_decoration(n);
68 return insert_decoration(n, obj, decoration);
69 }
70
71 /* Lookup a decoration pointer */
72 void *lookup_decoration(struct decoration *n, struct object *obj)
73 {
74 int j;
75
76 /* nothing to lookup */
77 if (!n->size)
78 return NULL;
79 j = hash_obj(obj, n->size);
80 for (;;) {
81 struct object_decoration *ref = n->hash + j;
82 if (ref->base == obj)
83 return ref->decoration;
84 if (!ref->base)
85 return NULL;
86 if (++j == n->size)
87 j = 0;
88 }
89 }