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/* $NetBSD: bt_get.c,v 1.6 1995/02/27 13:20:22 cgd Exp $ */
/*-
* 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)
#if 0
static char sccsid[] = "@(#)bt_get.c 8.2 (Berkeley) 9/7/93";
#else
static char rcsid[] = "$NetBSD: bt_get.c,v 1.6 1995/02/27 13:20:22 cgd Exp $";
#endif
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <db.h>
#include "btree.h"
/*
* __BT_GET -- Get a record from the btree.
*
* Parameters:
* dbp: pointer to access method
* key: key to find
* data: data to return
* flag: currently unused
*
* Returns:
* RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
*/
int
__bt_get(dbp, key, data, flags)
const DB *dbp;
const DBT *key;
DBT *data;
u_int flags;
{
BTREE *t;
EPG *e;
int exact, status;
t = dbp->internal;
/* Toss any page pinned across calls. */
if (t->bt_pinned != NULL) {
mpool_put(t->bt_mp, t->bt_pinned, 0);
t->bt_pinned = NULL;
}
/* Get currently doesn't take any flags. */
if (flags) {
errno = EINVAL;
return (RET_ERROR);
}
if ((e = __bt_search(t, key, &exact)) == NULL)
return (RET_ERROR);
if (!exact) {
mpool_put(t->bt_mp, e->page, 0);
return (RET_SPECIAL);
}
/*
* A special case is if we found the record but it's flagged for
* deletion. In this case, we want to find another record with the
* same key, if it exists. Rather than look around the tree we call
* __bt_first and have it redo the search, as __bt_first will not
* return keys marked for deletion. Slow, but should never happen.
*/
if (ISSET(t, B_DELCRSR) && e->page->pgno == t->bt_bcursor.pgno &&
e->index == t->bt_bcursor.index) {
mpool_put(t->bt_mp, e->page, 0);
if ((e = __bt_first(t, key, &exact)) == NULL)
return (RET_ERROR);
if (!exact)
return (RET_SPECIAL);
}
status = __bt_ret(t, e, NULL, data);
/*
* If the user is doing concurrent access, we copied the
* key/data, toss the page.
*/
if (ISSET(t, B_DB_LOCK))
mpool_put(t->bt_mp, e->page, 0);
else
t->bt_pinned = e->page;
return (status);
}
/*
* __BT_FIRST -- Find the first entry.
*
* Parameters:
* t: the tree
* key: the key
*
* Returns:
* The first entry in the tree greater than or equal to key.
*/
EPG *
__bt_first(t, key, exactp)
BTREE *t;
const DBT *key;
int *exactp;
{
register PAGE *h;
register EPG *e;
EPG save;
pgno_t cpgno, pg;
indx_t cindex;
int found;
/*
* Find any matching record; __bt_search pins the page. Only exact
* matches are tricky, otherwise just return the location of the key
* if it were to be inserted into the tree.
*/
if ((e = __bt_search(t, key, exactp)) == NULL)
return (NULL);
if (!*exactp)
return (e);
if (ISSET(t, B_DELCRSR)) {
cpgno = t->bt_bcursor.pgno;
cindex = t->bt_bcursor.index;
} else {
cpgno = P_INVALID;
cindex = 0; /* GCC thinks it's uninitialized. */
}
/*
* Walk backwards, skipping empty pages, as long as the entry matches
* and there are keys left in the tree. Save a copy of each match in
* case we go too far. A special case is that we don't return a match
* on records that the cursor references that have already been flagged
* for deletion.
*/
save = *e;
h = e->page;
found = 0;
do {
if (cpgno != h->pgno || cindex != e->index) {
if (save.page->pgno != e->page->pgno) {
mpool_put(t->bt_mp, save.page, 0);
save = *e;
} else
save.index = e->index;
found = 1;
}
/*
* Make a special effort not to unpin the page the last (or
* original) match was on, but also make sure it's unpinned
* if an error occurs.
*/
while (e->index == 0) {
if (h->prevpg == P_INVALID)
goto done1;
if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, 0);
if ((h = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) {
if (h->pgno == save.page->pgno)
mpool_put(t->bt_mp, save.page, 0);
return (NULL);
}
e->page = h;
e->index = NEXTINDEX(h);
}
--e->index;
} while (__bt_cmp(t, key, e) == 0);
/*
* Reach here with the last page that was looked at pinned, which may
* or may not be the same as the last (or original) match page. If
* it's not useful, release it.
*/
done1: if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, 0);
/*
* If still haven't found a record, the only possibility left is the
* next one. Move forward one slot, skipping empty pages and check.
*/
if (!found) {
h = save.page;
if (++save.index == NEXTINDEX(h)) {
do {
pg = h->nextpg;
mpool_put(t->bt_mp, h, 0);
if (pg == P_INVALID) {
*exactp = 0;
return (e);
}
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (NULL);
} while ((save.index = NEXTINDEX(h)) == 0);
save.page = h;
}
if (__bt_cmp(t, key, &save) != 0) {
*exactp = 0;
return (e);
}
}
*e = save;
*exactp = 1;
return (e);
}
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