NetBSD/lib/libc/DB/btree/bt_search.c

120 lines
3.7 KiB
C

/*-
* Copyright (c) 1990 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 5.9 (Berkeley) 2/14/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <stdio.h>
#include <db.h>
#include "btree.h"
/*
* __BT_SEARCH -- Search a btree for a key.
*
* Parameters:
* t: tree to search
* key: key to find
* exactp: pointer to exact match flag
*
* Returns:
* EPG for matching record, if any, or the EPG for the location of the
* key, if it were inserted into the tree.
*
* Warnings:
* The EPG returned is in static memory, and will be overwritten by the
* next search of any kind in any tree.
*/
EPG *
__bt_search(t, key, exactp)
BTREE *t;
const DBT *key;
int *exactp;
{
register indx_t index;
register int base, cmp, lim;
register PAGE *h;
pgno_t pg;
static EPG e;
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. */
e.page = h;
for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
e.index = index = base + (lim >> 1);
if ((cmp = __bt_cmp(t, key, &e)) == 0) {
if (h->flags & P_BLEAF) {
*exactp = 1;
return (&e);
}
goto next;
}
if (cmp > 0) {
base = index + 1;
--lim;
}
}
/* If it's a leaf page, we're done. */
if (h->flags & P_BLEAF) {
e.index = base;
*exactp = 0;
return (&e);
}
/*
* 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);
}
}