237 lines
6.3 KiB
C
237 lines
6.3 KiB
C
/*-
|
|
* Copyright (c) 1990, 1993
|
|
* 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)
|
|
/* from: static char sccsid[] = "@(#)bt_search.c 8.4 (Berkeley) 12/10/93"; */
|
|
static char *rcsid = "$Id: bt_search.c,v 1.5 1994/01/24 03:59:45 cgd Exp $";
|
|
#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, *n;
|
|
indx_t index;
|
|
pgno_t pg;
|
|
int base, cmp, lim;
|
|
|
|
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, and duplicates aren't allowed, we're
|
|
* done. If duplicates are allowed, it's possible that there
|
|
* were duplicate keys on duplicate pages, and they were later
|
|
* deleted, so we could be on a page with no matches while
|
|
* there are matches on other pages. If we're at the start or
|
|
* end of a page, check on both sides.
|
|
*/
|
|
if (h->flags & P_BLEAF) {
|
|
t->bt_cur.index = base;
|
|
*exactp = 0;
|
|
if (!ISSET(t, B_NODUPS)) {
|
|
if (base == 0 &&
|
|
bt_sprev(t, h, key, exactp))
|
|
return (&t->bt_cur);
|
|
if (base == NEXTINDEX(h) &&
|
|
bt_snext(t, h, key, exactp))
|
|
return (&t->bt_cur);
|
|
}
|
|
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: if (__bt_push(t, h->pgno, index) == RET_ERROR)
|
|
return (NULL);
|
|
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 to search
|
|
* h: current page.
|
|
* key: key to find
|
|
* 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;
|
|
PAGE *tp;
|
|
pgno_t pg;
|
|
|
|
/* Skip until reach the end of the tree or a key. */
|
|
for (pg = h->nextpg; pg != P_INVALID;) {
|
|
if ((tp = mpool_get(t->bt_mp, pg, 0)) == NULL) {
|
|
mpool_put(t->bt_mp, h, 0);
|
|
return (NULL);
|
|
}
|
|
if (NEXTINDEX(tp) != 0)
|
|
break;
|
|
pg = tp->prevpg;
|
|
mpool_put(t->bt_mp, tp, 0);
|
|
}
|
|
/*
|
|
* The key is either an exact match, or not as good as
|
|
* the one we already have.
|
|
*/
|
|
if (pg != P_INVALID) {
|
|
e.page = tp;
|
|
e.index = NEXTINDEX(tp) - 1;
|
|
if (__bt_cmp(t, key, &e) == 0) {
|
|
mpool_put(t->bt_mp, h, 0);
|
|
t->bt_cur = e;
|
|
*exactp = 1;
|
|
return (1);
|
|
}
|
|
}
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* BT_SPREV -- Check for an exact match before the key.
|
|
*
|
|
* Parameters:
|
|
* t: tree to search
|
|
* h: current page.
|
|
* key: key to find
|
|
* 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;
|
|
PAGE *tp;
|
|
pgno_t pg;
|
|
|
|
/* Skip until reach the beginning of the tree or a key. */
|
|
for (pg = h->prevpg; pg != P_INVALID;) {
|
|
if ((tp = mpool_get(t->bt_mp, pg, 0)) == NULL) {
|
|
mpool_put(t->bt_mp, h, 0);
|
|
return (NULL);
|
|
}
|
|
if (NEXTINDEX(tp) != 0)
|
|
break;
|
|
pg = tp->prevpg;
|
|
mpool_put(t->bt_mp, tp, 0);
|
|
}
|
|
/*
|
|
* The key is either an exact match, or not as good as
|
|
* the one we already have.
|
|
*/
|
|
if (pg != P_INVALID) {
|
|
e.page = tp;
|
|
e.index = NEXTINDEX(tp) - 1;
|
|
if (__bt_cmp(t, key, &e) == 0) {
|
|
mpool_put(t->bt_mp, h, 0);
|
|
t->bt_cur = e;
|
|
*exactp = 1;
|
|
return (1);
|
|
}
|
|
}
|
|
return (0);
|
|
}
|