Net2/usr/src/lib/libc/db/btree/seq.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[] = "@(#)seq.c 5.4 (Berkeley) 3/3/91";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <errno.h>
#include <db.h>
#include <stdlib.h>
#include "btree.h"
/*
* _BT_SEQINIT -- Initialize a sequential scan on the btree.
*
* Sets the tree's notion of the current scan location correctly
* given a key and a direction.
*
* Parameters:
* t -- tree in which to initialize scan
* key -- key for initial scan position
* flags -- R_NEXT, R_PREV
*
* Returns:
* RET_SUCCESS, RET_ERROR, or RET_SPECIAL if there's no data
* in the tree to scan.
*
* Side Effects:
* Changes current scan position for the tree. Almost certainly
* changes current page, as well. Sets BTF_SEQINIT bit in tree
* flags, so that we know we've initialized a scan.
*/
int
_bt_seqinit(t, key, flags)
BTREE_P t;
DBT *key;
int flags;
{
BTITEM *item;
BTHEADER *h;
CURSOR *c;
IDATUM *id;
index_t last;
/*
* Figure out if we really have to search for the key that the
* user supplied. If key is null, then this is an unkeyed scan
* and we can just start from an endpoint.
*/
c = &(t->bt_cursor);
if (flags == R_CURSOR) {
if (key->data != (u_char *) NULL) {
/* key supplied, find first instance of it */
item = _bt_first(t, key);
c->c_index = item->bti_index;
c->c_pgno = t->bt_curpage->h_pgno;
} else {
errno = EINVAL;
return (RET_ERROR);
}
} else {
/*
* Unkeyed scan. For backward scans, find the last item
* in the tree; for forward scans, find the first item.
*/
if (_bt_getpage(t, (pgno_t) P_ROOT) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
if (flags == R_LAST || flags == R_PREV) {
/* backward scan */
while (!(h->h_flags & F_LEAF)) {
last = NEXTINDEX(h) - 1;
id = (IDATUM *) GETDATUM(h,last);
if (_bt_getpage(t, id->i_pgno) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
}
/* skip empty pages */
while (NEXTINDEX(h) == 0 && h->h_prevpg != P_NONE) {
if (_bt_getpage(t, h->h_prevpg) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
}
c->c_pgno = h->h_pgno;
if (NEXTINDEX(h) > 0)
c->c_index = NEXTINDEX(h) - 1;
else
c->c_index = 0;
} else if (flags == R_FIRST || flags == R_NEXT) {
/* forward scan */
while (!(h->h_flags & F_LEAF)) {
id = (IDATUM *) GETDATUM(h,0);
if (_bt_getpage(t, id->i_pgno) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
}
/* skip empty pages */
while (NEXTINDEX(h) == 0 && h->h_nextpg != P_NONE) {
if (_bt_getpage(t, h->h_nextpg) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
}
c->c_pgno = h->h_pgno;
c->c_index = 0;
} else {
/* no flags passed in */
errno = EINVAL;
return (RET_ERROR);
}
}
/* okay, scan is initialized */
t->bt_flags |= BTF_SEQINIT;
/* don't need the descent stack anymore */
while (_bt_pop(t) != P_NONE)
continue;
if (c->c_index == NEXTINDEX(t->bt_curpage))
return (RET_SPECIAL);
return (RET_SUCCESS);
}
/*
* _BT_SEQADVANCE -- Advance the sequential scan on this tree.
*
* Moves the current location pointer for the scan on this tree one
* spot in the requested direction.
*
* Parameters:
* t -- btree being scanned
* flags -- for R_NEXT, R_PREV
*
* Returns:
* RET_SUCCESS, RET_ERROR, or RET_SPECIAL if there is no
* more data in the specified direction.
*
* Side Effects:
* May change current page.
*/
int
_bt_seqadvance(t, flags)
BTREE_P t;
int flags;
{
BTHEADER *h;
CURSOR *c;
index_t index;
c = &(t->bt_cursor);
index = c->c_index;
if (_bt_getpage(t, c->c_pgno) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
/* by the time we get here, don't need the cursor key anymore */
if (c->c_key != (char *) NULL)
(void) free(c->c_key);
if (flags == R_NEXT) {
/*
* This is a forward scan. If the cursor is pointing
* at a virtual record (that is, it was pointing at
* a record that got deleted), then we should return
* the record it's pointing at now. Otherwise, we
* should advance the scan. In either case, we need
* to be careful not to run off the end of the current
* page.
*/
if (c->c_flags & CRSR_BEFORE) {
if (index >= NEXTINDEX(h)) {
/* out of items on this page, get next page */
if (h->h_nextpg == P_NONE) {
/* tell caller we're done... */
c->c_index = NEXTINDEX(h);
return (RET_SPECIAL);
}
/* skip empty pages */
do {
if (_bt_getpage(t, h->h_nextpg)
== RET_ERROR) {
c->c_index = NEXTINDEX(h);
return (RET_ERROR);
}
h = t->bt_curpage;
c->c_pgno = h->h_pgno;
} while (NEXTINDEX(h) == 0
&& h->h_nextpg != P_NONE);
if (NEXTINDEX(h) == 0) {
/* tell caller we're done */
c->c_index = NEXTINDEX(h);
return (RET_SPECIAL);
}
index = 0;
}
c->c_flags &= ~CRSR_BEFORE;
} else if (++index >= NEXTINDEX(h)) {
/* out of items on this page, get next page */
if (h->h_nextpg == P_NONE) {
/* tell caller we're done... */
c->c_index = NEXTINDEX(h);
return (RET_SPECIAL);
}
/* skip empty pages */
do {
if (_bt_getpage(t, h->h_nextpg) == RET_ERROR) {
c->c_index = NEXTINDEX(h);
return (RET_ERROR);
}
h = t->bt_curpage;
c->c_pgno = h->h_pgno;
} while (NEXTINDEX(h) == 0 && h->h_nextpg != P_NONE);
if (NEXTINDEX(h) == 0) {
/* tell caller we're done */
c->c_index = NEXTINDEX(h);
return (RET_SPECIAL);
}
index = 0;
}
} else if (flags == R_PREV) {
/* for backward scans, life is substantially easier */
c->c_flags &= ~CRSR_BEFORE;
if (c->c_key != (char *) NULL) {
(void) free(c->c_key);
c->c_key = (char *) NULL;
}
if (index == 0) {
/* we may be done */
c->c_index = 0;
/* out of items on this page, get next page */
if (h->h_prevpg == P_NONE)
return (RET_SPECIAL);
/* skip empty pages */
do {
if (_bt_getpage(t, h->h_prevpg) == RET_ERROR)
return (RET_ERROR);
h = t->bt_curpage;
c->c_pgno = h->h_pgno;
} while (NEXTINDEX(h) == 0 && h->h_prevpg != P_NONE);
if (NEXTINDEX(h) == 0)
return (RET_SPECIAL);
index = NEXTINDEX(h) - 1;
} else
--index;
} else {
/* must specify a direction */
errno = EINVAL;
return (RET_ERROR);
}
c->c_index = index;
return (RET_SUCCESS);
}