120 lines
3.7 KiB
C
120 lines
3.7 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Mike Olson.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)bt_search.c 5.9 (Berkeley) 2/14/93";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/types.h>
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#include <stdio.h>
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#include <db.h>
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#include "btree.h"
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/*
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* __BT_SEARCH -- Search a btree for a key.
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*
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* Parameters:
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* t: tree to search
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* key: key to find
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* exactp: pointer to exact match flag
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*
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* Returns:
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* EPG for matching record, if any, or the EPG for the location of the
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* key, if it were inserted into the tree.
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*
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* Warnings:
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* The EPG returned is in static memory, and will be overwritten by the
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* next search of any kind in any tree.
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*/
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EPG *
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__bt_search(t, key, exactp)
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BTREE *t;
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const DBT *key;
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int *exactp;
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{
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register indx_t index;
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register int base, cmp, lim;
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register PAGE *h;
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pgno_t pg;
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static EPG e;
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BT_CLR(t);
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for (pg = P_ROOT;;) {
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (NULL);
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/* Do a binary search on the current page. */
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e.page = h;
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for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
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e.index = index = base + (lim >> 1);
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if ((cmp = __bt_cmp(t, key, &e)) == 0) {
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if (h->flags & P_BLEAF) {
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*exactp = 1;
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return (&e);
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}
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goto next;
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}
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if (cmp > 0) {
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base = index + 1;
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--lim;
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}
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}
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/* If it's a leaf page, we're done. */
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if (h->flags & P_BLEAF) {
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e.index = base;
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*exactp = 0;
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return (&e);
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}
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/*
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* No match found. Base is the smallest index greater than
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* key and may be zero or a last + 1 index. If it's non-zero,
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* decrement by one, and record the internal page which should
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* be a parent page for the key. If a split later occurs, the
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* inserted page will be to the right of the saved page.
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*/
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index = base ? base - 1 : base;
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next: if (__bt_push(t, h->pgno, index) == RET_ERROR)
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return (NULL);
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pg = GETBINTERNAL(h, index)->pgno;
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mpool_put(t->bt_mp, h, 0);
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}
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}
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