decorate: allow const objects to be decorated
[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(const 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, const 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 if (++j >= size)
28 j = 0;
29 }
30 hash[j].base = base;
31 hash[j].decoration = decoration;
32 n->nr++;
33 return NULL;
34 }
35
36 static void grow_decoration(struct decoration *n)
37 {
38 int i;
39 int old_size = n->size;
40 struct object_decoration *old_hash = n->hash;
41
42 n->size = (old_size + 1000) * 3 / 2;
43 n->hash = xcalloc(n->size, sizeof(struct object_decoration));
44 n->nr = 0;
45
46 for (i = 0; i < old_size; i++) {
47 const struct object *base = old_hash[i].base;
48 void *decoration = old_hash[i].decoration;
49
50 if (!base)
51 continue;
52 insert_decoration(n, base, decoration);
53 }
54 free(old_hash);
55 }
56
57 /* Add a decoration pointer, return any old one */
58 void *add_decoration(struct decoration *n, const struct object *obj,
59 void *decoration)
60 {
61 int nr = n->nr + 1;
62
63 if (nr > n->size * 2 / 3)
64 grow_decoration(n);
65 return insert_decoration(n, obj, decoration);
66 }
67
68 /* Lookup a decoration pointer */
69 void *lookup_decoration(struct decoration *n, const struct object *obj)
70 {
71 int j;
72
73 /* nothing to lookup */
74 if (!n->size)
75 return NULL;
76 j = hash_obj(obj, n->size);
77 for (;;) {
78 struct object_decoration *ref = n->hash + j;
79 if (ref->base == obj)
80 return ref->decoration;
81 if (!ref->base)
82 return NULL;
83 if (++j == n->size)
84 j = 0;
85 }
86 }