oidtree.c

   1 /*
   2  * A wrapper around cbtree which stores oids
   3  * May be used to replace oid-array for prefix (abbreviation) matches
   4  */
   5 #include "git-compat-util.h"
   6 #include "oidtree.h"
   7 #include "hash.h"
   8
   9 struct oidtree_iter_data {
  10         oidtree_iter fn;
  11         void *arg;
  12         size_t *last_nibble_at;
  13         int algo;
  14         uint8_t last_byte;
  15 };
  16
  17 void oidtree_init(struct oidtree *ot)
  18 {
  19         cb_init(&ot->tree);
  20         mem_pool_init(&ot->mem_pool, 0);
  21 }
  22
  23 void oidtree_clear(struct oidtree *ot)
  24 {
  25         if (ot) {
  26                 mem_pool_discard(&ot->mem_pool, 0);
  27                 oidtree_init(ot);
  28         }
  29 }
  30
  31 void oidtree_insert(struct oidtree *ot, const struct object_id *oid)
  32 {
  33         struct cb_node *on;
  34         struct object_id k;
  35
  36         if (!oid->algo)
  37                 BUG("oidtree_insert requires oid->algo");
  38
  39         on = mem_pool_alloc(&ot->mem_pool, sizeof(*on) + sizeof(*oid));
  40
  41         /*
  42          * Clear the padding and copy the result in separate steps to
  43          * respect the 4-byte alignment needed by struct object_id.
  44          */
  45         oidcpy(&k, oid);
  46         memcpy(on->k, &k, sizeof(k));
  47
  48         /*
  49          * n.b. Current callers won't get us duplicates, here.  If a
  50          * future caller causes duplicates, there'll be a small leak
  51          * that won't be freed until oidtree_clear.  Currently it's not
  52          * worth maintaining a free list
  53          */
  54         cb_insert(&ot->tree, on, sizeof(*oid));
  55 }
  56
  57
  58 int oidtree_contains(struct oidtree *ot, const struct object_id *oid)
  59 {
  60         struct object_id k;
  61         size_t klen = sizeof(k);
  62
  63         oidcpy(&k, oid);
  64
  65         if (oid->algo == GIT_HASH_UNKNOWN)
  66                 klen -= sizeof(oid->algo);
  67
  68         /* cb_lookup relies on memcmp on the struct, so order matters: */
  69         klen += BUILD_ASSERT_OR_ZERO(offsetof(struct object_id, hash) <
  70                                 offsetof(struct object_id, algo));
  71
  72         return cb_lookup(&ot->tree, (const uint8_t *)&k, klen) ? 1 : 0;
  73 }
  74
  75 static enum cb_next iter(struct cb_node *n, void *arg)
  76 {
  77         struct oidtree_iter_data *x = arg;
  78         struct object_id k;
  79
  80         /* Copy to provide 4-byte alignment needed by struct object_id. */
  81         memcpy(&k, n->k, sizeof(k));
  82
  83         if (x->algo != GIT_HASH_UNKNOWN && x->algo != k.algo)
  84                 return CB_CONTINUE;
  85
  86         if (x->last_nibble_at) {
  87                 if ((k.hash[*x->last_nibble_at] ^ x->last_byte) & 0xf0)
  88                         return CB_CONTINUE;
  89         }
  90
  91         return x->fn(&k, x->arg);
  92 }
  93
  94 void oidtree_each(struct oidtree *ot, const struct object_id *oid,
  95                         size_t oidhexsz, oidtree_iter fn, void *arg)
  96 {
  97         size_t klen = oidhexsz / 2;
  98         struct oidtree_iter_data x = { 0 };
  99         assert(oidhexsz <= GIT_MAX_HEXSZ);
 100
 101         x.fn = fn;
 102         x.arg = arg;
 103         x.algo = oid->algo;
 104         if (oidhexsz & 1) {
 105                 x.last_byte = oid->hash[klen];
 106                 x.last_nibble_at = &klen;
 107         }
 108         cb_each(&ot->tree, (const uint8_t *)oid, klen, iter, &x);
 109 }