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35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
41 #include <sys/types.h>
48 static int __bt_snext(BTREE *, PAGE *, const DBT *, int *);
49 static int __bt_sprev(BTREE *, PAGE *, const DBT *, int *);
53 * Search a btree for a key.
58 * exactp: pointer to exact match flag
61 * The EPG for matching record, if any, or the EPG for the location
62 * of the key, if it were inserted into the tree, is entered into
63 * the bt_cur field of the tree. A pointer to the field is returned.
66 __bt_search(BTREE *t, const DBT *key, int *exactp)
69 indx_t base, idx, lim;
75 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
78 /* Do a binary search on the current page. */
80 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
81 t->bt_cur.index = idx = base + (lim >> 1);
82 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
83 if (h->flags & P_BLEAF) {
96 * If it's a leaf page, we're almost done. If no duplicates
97 * are allowed, or we have an exact match, we're done. Else,
98 * it's possible that there were matching keys on this page,
99 * which later deleted, and we're on a page with no matches
100 * while there are matches on other pages. If at the start or
101 * end of a page, check the adjacent page.
103 if (h->flags & P_BLEAF) {
104 if (!F_ISSET(t, B_NODUPS)) {
106 h->prevpg != P_INVALID &&
107 __bt_sprev(t, h, key, exactp))
109 if (base == NEXTINDEX(h) &&
110 h->nextpg != P_INVALID &&
111 __bt_snext(t, h, key, exactp))
115 t->bt_cur.index = base;
120 * No match found. Base is the smallest index greater than
121 * key and may be zero or a last + 1 index. If it's non-zero,
122 * decrement by one, and record the internal page which should
123 * be a parent page for the key. If a split later occurs, the
124 * inserted page will be to the right of the saved page.
126 idx = base ? base - 1 : base;
128 next: BT_PUSH(t, h->pgno, idx);
129 pg = GETBINTERNAL(h, idx)->pgno;
130 mpool_put(t->bt_mp, h, 0);
136 * Check for an exact match after the key.
142 * exactp: pointer to exact match flag
145 * If an exact match found.
148 __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp)
153 * Get the next page. The key is either an exact
154 * match, or not as good as the one we already have.
156 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
159 if (__bt_cmp(t, key, &e) == 0) {
160 mpool_put(t->bt_mp, h, 0);
165 mpool_put(t->bt_mp, e.page, 0);
171 * Check for an exact match before the key.
177 * exactp: pointer to exact match flag
180 * If an exact match found.
183 __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp)
188 * Get the previous page. The key is either an exact
189 * match, or not as good as the one we already have.
191 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
193 e.index = NEXTINDEX(e.page) - 1;
194 if (__bt_cmp(t, key, &e) == 0) {
195 mpool_put(t->bt_mp, h, 0);
200 mpool_put(t->bt_mp, e.page, 0);