diff options
Diffstat (limited to 'db/btree/bt_search.c')
| -rw-r--r-- | db/btree/bt_search.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/db/btree/bt_search.c b/db/btree/bt_search.c new file mode 100644 index 0000000000..485afcbbf0 --- /dev/null +++ b/db/btree/bt_search.c @@ -0,0 +1,213 @@ +/*- + * Copyright (c) 1990, 1993, 1994 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Mike Olson. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#if defined(LIBC_SCCS) && !defined(lint) +static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94"; +#endif /* LIBC_SCCS and not lint */ + +#include <sys/types.h> + +#include <stdio.h> + +#include <db.h> +#include "btree.h" + +static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *)); +static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *)); + +/* + * __bt_search -- + * Search a btree for a key. + * + * Parameters: + * t: tree to search + * key: key to find + * exactp: pointer to exact match flag + * + * Returns: + * The EPG for matching record, if any, or the EPG for the location + * of the key, if it were inserted into the tree, is entered into + * the bt_cur field of the tree. A pointer to the field is returned. + */ +EPG * +__bt_search(t, key, exactp) + BTREE *t; + const DBT *key; + int *exactp; +{ + PAGE *h; + indx_t base, index, lim; + pgno_t pg; + int cmp; + + BT_CLR(t); + for (pg = P_ROOT;;) { + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (NULL); + + /* Do a binary search on the current page. */ + t->bt_cur.page = h; + for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { + t->bt_cur.index = index = base + (lim >> 1); + if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { + if (h->flags & P_BLEAF) { + *exactp = 1; + return (&t->bt_cur); + } + goto next; + } + if (cmp > 0) { + base = index + 1; + --lim; + } + } + + /* + * If it's a leaf page, we're almost done. If no duplicates + * are allowed, or we have an exact match, we're done. Else, + * it's possible that there were matching keys on this page, + * which later deleted, and we're on a page with no matches + * while there are matches on other pages. If at the start or + * end of a page, check the adjacent page. + */ + if (h->flags & P_BLEAF) { + if (!F_ISSET(t, B_NODUPS)) { + if (base == 0 && + h->prevpg != P_INVALID && + __bt_sprev(t, h, key, exactp)) + return (&t->bt_cur); + if (base == NEXTINDEX(h) && + h->nextpg != P_INVALID && + __bt_snext(t, h, key, exactp)) + return (&t->bt_cur); + } + *exactp = 0; + t->bt_cur.index = base; + return (&t->bt_cur); + } + + /* + * No match found. Base is the smallest index greater than + * key and may be zero or a last + 1 index. If it's non-zero, + * decrement by one, and record the internal page which should + * be a parent page for the key. If a split later occurs, the + * inserted page will be to the right of the saved page. + */ + index = base ? base - 1 : base; + +next: BT_PUSH(t, h->pgno, index); + pg = GETBINTERNAL(h, index)->pgno; + mpool_put(t->bt_mp, h, 0); + } +} + +/* + * __bt_snext -- + * Check for an exact match after the key. + * + * Parameters: + * t: tree + * h: current page + * key: key + * exactp: pointer to exact match flag + * + * Returns: + * If an exact match found. + */ +static int +__bt_snext(t, h, key, exactp) + BTREE *t; + PAGE *h; + const DBT *key; + int *exactp; +{ + EPG e; + + /* + * Get the next page. The key is either an exact + * match, or not as good as the one we already have. + */ + if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) + return (0); + e.index = 0; + if (__bt_cmp(t, key, &e) == 0) { + mpool_put(t->bt_mp, h, 0); + t->bt_cur = e; + *exactp = 1; + return (1); + } + mpool_put(t->bt_mp, e.page, 0); + return (0); +} + +/* + * __bt_sprev -- + * Check for an exact match before the key. + * + * Parameters: + * t: tree + * h: current page + * key: key + * exactp: pointer to exact match flag + * + * Returns: + * If an exact match found. + */ +static int +__bt_sprev(t, h, key, exactp) + BTREE *t; + PAGE *h; + const DBT *key; + int *exactp; +{ + EPG e; + + /* + * Get the previous page. The key is either an exact + * match, or not as good as the one we already have. + */ + if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) + return (0); + e.index = NEXTINDEX(e.page) - 1; + if (__bt_cmp(t, key, &e) == 0) { + mpool_put(t->bt_mp, h, 0); + t->bt_cur = e; + *exactp = 1; + return (1); + } + mpool_put(t->bt_mp, e.page, 0); + return (0); +} |