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36 * @(#)bt_search.c 8.8 (Berkeley) 7/31/94
37 * $DragonFly: src/lib/libcr/db/btree/Attic/bt_search.c,v 1.3 2003/11/12 18:07:01 eirikn Exp $
40 #include <sys/types.h>
47 static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *));
48 static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *));
52 * Search a btree for a key.
57 * exactp: pointer to exact match flag
60 * The EPG for matching record, if any, or the EPG for the location
61 * of the key, if it were inserted into the tree, is entered into
62 * the bt_cur field of the tree. A pointer to the field is returned.
65 __bt_search(t, key, exactp)
71 indx_t base, index, lim;
77 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
80 /* Do a binary search on the current page. */
82 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
83 t->bt_cur.index = index = base + (lim >> 1);
84 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
85 if (h->flags & P_BLEAF) {
98 * If it's a leaf page, we're almost done. If no duplicates
99 * are allowed, or we have an exact match, we're done. Else,
100 * it's possible that there were matching keys on this page,
101 * which later deleted, and we're on a page with no matches
102 * while there are matches on other pages. If at the start or
103 * end of a page, check the adjacent page.
105 if (h->flags & P_BLEAF) {
106 if (!F_ISSET(t, B_NODUPS)) {
108 h->prevpg != P_INVALID &&
109 __bt_sprev(t, h, key, exactp))
111 if (base == NEXTINDEX(h) &&
112 h->nextpg != P_INVALID &&
113 __bt_snext(t, h, key, exactp))
117 t->bt_cur.index = base;
122 * No match found. Base is the smallest index greater than
123 * key and may be zero or a last + 1 index. If it's non-zero,
124 * decrement by one, and record the internal page which should
125 * be a parent page for the key. If a split later occurs, the
126 * inserted page will be to the right of the saved page.
128 index = base ? base - 1 : base;
130 next: BT_PUSH(t, h->pgno, index);
131 pg = GETBINTERNAL(h, index)->pgno;
132 mpool_put(t->bt_mp, h, 0);
138 * Check for an exact match after the key.
144 * exactp: pointer to exact match flag
147 * If an exact match found.
150 __bt_snext(t, h, key, exactp)
159 * Get the next page. The key is either an exact
160 * match, or not as good as the one we already have.
162 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
165 if (__bt_cmp(t, key, &e) == 0) {
166 mpool_put(t->bt_mp, h, 0);
171 mpool_put(t->bt_mp, e.page, 0);
177 * Check for an exact match before the key.
183 * exactp: pointer to exact match flag
186 * If an exact match found.
189 __bt_sprev(t, h, key, exactp)
198 * Get the previous page. The key is either an exact
199 * match, or not as good as the one we already have.
201 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
203 e.index = NEXTINDEX(e.page) - 1;
204 if (__bt_cmp(t, key, &e) == 0) {
205 mpool_put(t->bt_mp, h, 0);
210 mpool_put(t->bt_mp, e.page, 0);