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/* $NetBSD: bt_search.c,v 1.8 1996/05/03 21:50:52 cgd Exp $ */
/*-
* 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)
#if 0
static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94";
#else
static char rcsid[] = "$NetBSD: bt_search.c,v 1.8 1996/05/03 21:50:52 cgd Exp $";
#endif
#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);
}
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