NetBSD/lib/libc/db/btree/updutils.c

175 lines
5.1 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[] = "@(#)updutils.c 5.2 (Berkeley) 2/22/91";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <db.h>
#include <stdlib.h>
#include <string.h>
#include "btree.h"
/*
* _BT_FIXSCAN -- Adjust a scan to cope with a change in tree structure.
*
* If the user has an active scan on the database, and we delete an
* item from the page the cursor is pointing at, we need to figure
* out what to do about it. Basically, the solution is to point
* "between" keys in the tree, using the CRSR_BEFORE flag. The
* requirement is that the user should not miss any data in the
* tree during a scan, just because he happened to do some deletions
* or insertions while it was active.
*
* In order to guarantee that the scan progresses properly, we need
* to save the key of any deleted item we were pointing at, so that
* we can check later insertions against it.
*
* Parameters:
* t -- tree to adjust
* index -- index of item at which change was made
* newd -- new datum (for insertions only)
* op -- operation (DELETE or INSERT) causing change
*
* Returns:
* RET_SUCCESS, RET_ERROR (errno is set).
*
* Side Effects:
* None.
*/
int
_bt_fixscan(t, index, newd, op)
BTREE_P t;
index_t index;
DATUM *newd;
int op;
{
CURSOR *c;
DATUM *d;
c = &(t->bt_cursor);
if (op == DELETE) {
if (index < c->c_index)
c->c_index--;
else if (index == c->c_index) {
if (!(c->c_flags & CRSR_BEFORE)) {
if (_bt_crsrkey(t) == RET_ERROR)
return (RET_ERROR);
c->c_flags |= CRSR_BEFORE;
}
}
} else {
/*
* If we previously deleted the object at this location,
* and now we're inserting a new one, we need to do the
* right thing -- the cursor should come either before
* or after the new item, depending on the key that was
* here, and the new one.
*/
if (c->c_flags & CRSR_BEFORE) {
if (index <= c->c_index) {
char *tmp;
int itmp;
pgno_t chain;
int r;
d = (DATUM *) GETDATUM(t->bt_curpage, index);
if (d->d_flags & D_BIGKEY) {
bcopy(&(newd->d_bytes[0]),
(char *) &chain,
sizeof(chain));
if (_bt_getbig(t, chain, &tmp, &itmp)
== RET_ERROR)
return (RET_ERROR);
} else
tmp = &(newd->d_bytes[0]);
r = (*(t->bt_compare))(tmp, c->c_key);
if (r < 0)
c->c_index++;
if (d->d_flags & D_BIGKEY)
(void) free (tmp);
}
} else if (index <= c->c_index)
c->c_index++;
}
return (RET_SUCCESS);
}
/*
* _BT_CRSRKEY -- Save a copy of the key of the record that the cursor
* is pointing to. The record is about to be deleted.
*
* Parameters:
* t -- btree
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*
* Side Effects:
* Allocates memory for the copy which should be released when
* it is no longer needed.
*/
int
_bt_crsrkey(t)
BTREE_P t;
{
CURSOR *c;
DATUM *d;
pgno_t pgno;
int ignore;
c = &(t->bt_cursor);
d = (DATUM *) GETDATUM(t->bt_curpage, c->c_index);
if (d->d_flags & D_BIGKEY) {
bcopy(&(d->d_bytes[0]), (char *) &pgno, sizeof(pgno));
return (_bt_getbig(t, pgno, &(c->c_key), &ignore));
} else {
if ((c->c_key = (char *) malloc(d->d_ksize)) == (char *) NULL)
return (RET_ERROR);
bcopy(&(d->d_bytes[0]), c->c_key, (size_t) (d->d_ksize));
}
return (RET_SUCCESS);
}