1 /*
2 * crit-bit tree implementation, does no allocations internally
3 * For more information on crit-bit trees: https://cr.yp.to/critbit.html
4 * Based on Adam Langley's adaptation of Dan Bernstein's public domain code
5 * git clone https://github.com/agl/critbit.git
6 *
7 * This is adapted to store arbitrary data (not just NUL-terminated C strings
8 * and allocates no memory internally. The user needs to allocate
9 * "struct cb_node" and fill cb_node.k[] with arbitrary match data
10 * for memcmp.
11 * If "klen" is variable, then it should be embedded into "c_node.k[]"
12 * Recursion is bound by the maximum value of "klen" used.
13 */
14 #ifndef CBTREE_H
15 #define CBTREE_H
16
17 #include "git-compat-util.h"
18
19 struct cb_node;
20 struct cb_node {
21 struct cb_node *child[2];
22 /*
23 * n.b. uint32_t for `byte' is excessive for OIDs,
24 * we may consider shorter variants if nothing else gets stored.
25 */
26 uint32_t byte;
27 uint8_t otherbits;
28 uint8_t k[FLEX_ARRAY]; /* arbitrary data, unaligned */
29 };
30
31 struct cb_tree {
32 struct cb_node *root;
33 };
34
35 enum cb_next {
36 CB_CONTINUE = 0,
37 CB_BREAK = 1
38 };
39
40 #define CBTREE_INIT { 0 }
41
cb_init(struct cb_tree * t)42 static inline void cb_init(struct cb_tree *t)
43 {
44 struct cb_tree blank = CBTREE_INIT;
45 memcpy(t, &blank, sizeof(*t));
46 }
47
48 struct cb_node *cb_lookup(struct cb_tree *, const uint8_t *k, size_t klen);
49 struct cb_node *cb_insert(struct cb_tree *, struct cb_node *, size_t klen);
50 struct cb_node *cb_unlink(struct cb_tree *t, const uint8_t *k, size_t klen);
51
52 typedef enum cb_next (*cb_iter)(struct cb_node *, void *arg);
53
54 void cb_each(struct cb_tree *, const uint8_t *kpfx, size_t klen,
55 cb_iter, void *arg);
56
57 #endif /* CBTREE_H */
58