319 lines
8.1 KiB
C
319 lines
8.1 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Mike Olson.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)seq.c 5.4 (Berkeley) 3/3/91";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/types.h>
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#include <errno.h>
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#include <db.h>
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#include <stdlib.h>
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#include "btree.h"
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/*
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* _BT_SEQINIT -- Initialize a sequential scan on the btree.
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*
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* Sets the tree's notion of the current scan location correctly
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* given a key and a direction.
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*
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* Parameters:
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* t -- tree in which to initialize scan
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* key -- key for initial scan position
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* flags -- R_NEXT, R_PREV
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*
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* Returns:
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* RET_SUCCESS, RET_ERROR, or RET_SPECIAL if there's no data
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* in the tree to scan.
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*
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* Side Effects:
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* Changes current scan position for the tree. Almost certainly
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* changes current page, as well. Sets BTF_SEQINIT bit in tree
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* flags, so that we know we've initialized a scan.
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*/
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int
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_bt_seqinit(t, key, flags)
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BTREE_P t;
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DBT *key;
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int flags;
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{
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BTITEM *item;
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BTHEADER *h;
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CURSOR *c;
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IDATUM *id;
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index_t last;
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/*
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* Figure out if we really have to search for the key that the
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* user supplied. If key is null, then this is an unkeyed scan
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* and we can just start from an endpoint.
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*/
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c = &(t->bt_cursor);
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if (flags == R_CURSOR) {
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if (key->data != (u_char *) NULL) {
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/* key supplied, find first instance of it */
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item = _bt_first(t, key);
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c->c_index = item->bti_index;
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c->c_pgno = t->bt_curpage->h_pgno;
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} else {
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errno = EINVAL;
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return (RET_ERROR);
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}
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} else {
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/*
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* Unkeyed scan. For backward scans, find the last item
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* in the tree; for forward scans, find the first item.
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*/
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if (_bt_getpage(t, (pgno_t) P_ROOT) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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if (flags == R_LAST || flags == R_PREV) {
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/* backward scan */
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while (!(h->h_flags & F_LEAF)) {
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last = NEXTINDEX(h) - 1;
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id = (IDATUM *) GETDATUM(h,last);
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if (_bt_getpage(t, id->i_pgno) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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}
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/* skip empty pages */
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while (NEXTINDEX(h) == 0 && h->h_prevpg != P_NONE) {
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if (_bt_getpage(t, h->h_prevpg) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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}
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c->c_pgno = h->h_pgno;
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if (NEXTINDEX(h) > 0)
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c->c_index = NEXTINDEX(h) - 1;
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else
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c->c_index = 0;
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} else if (flags == R_FIRST || flags == R_NEXT) {
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/* forward scan */
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while (!(h->h_flags & F_LEAF)) {
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id = (IDATUM *) GETDATUM(h,0);
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if (_bt_getpage(t, id->i_pgno) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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}
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/* skip empty pages */
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while (NEXTINDEX(h) == 0 && h->h_nextpg != P_NONE) {
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if (_bt_getpage(t, h->h_nextpg) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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}
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c->c_pgno = h->h_pgno;
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c->c_index = 0;
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} else {
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/* no flags passed in */
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errno = EINVAL;
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return (RET_ERROR);
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}
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}
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/* okay, scan is initialized */
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t->bt_flags |= BTF_SEQINIT;
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/* don't need the descent stack anymore */
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while (_bt_pop(t) != P_NONE)
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continue;
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if (c->c_index == NEXTINDEX(t->bt_curpage))
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return (RET_SPECIAL);
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return (RET_SUCCESS);
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}
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/*
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* _BT_SEQADVANCE -- Advance the sequential scan on this tree.
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*
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* Moves the current location pointer for the scan on this tree one
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* spot in the requested direction.
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*
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* Parameters:
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* t -- btree being scanned
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* flags -- for R_NEXT, R_PREV
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*
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* Returns:
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* RET_SUCCESS, RET_ERROR, or RET_SPECIAL if there is no
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* more data in the specified direction.
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*
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* Side Effects:
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* May change current page.
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*/
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int
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_bt_seqadvance(t, flags)
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BTREE_P t;
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int flags;
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{
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BTHEADER *h;
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CURSOR *c;
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index_t index;
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c = &(t->bt_cursor);
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index = c->c_index;
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if (_bt_getpage(t, c->c_pgno) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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/* by the time we get here, don't need the cursor key anymore */
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if (c->c_key != (char *) NULL)
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(void) free(c->c_key);
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if (flags == R_NEXT) {
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/*
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* This is a forward scan. If the cursor is pointing
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* at a virtual record (that is, it was pointing at
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* a record that got deleted), then we should return
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* the record it's pointing at now. Otherwise, we
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* should advance the scan. In either case, we need
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* to be careful not to run off the end of the current
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* page.
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*/
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if (c->c_flags & CRSR_BEFORE) {
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if (index >= NEXTINDEX(h)) {
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/* out of items on this page, get next page */
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if (h->h_nextpg == P_NONE) {
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/* tell caller we're done... */
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c->c_index = NEXTINDEX(h);
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return (RET_SPECIAL);
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}
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/* skip empty pages */
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do {
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if (_bt_getpage(t, h->h_nextpg)
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== RET_ERROR) {
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c->c_index = NEXTINDEX(h);
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return (RET_ERROR);
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}
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h = t->bt_curpage;
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c->c_pgno = h->h_pgno;
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} while (NEXTINDEX(h) == 0
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&& h->h_nextpg != P_NONE);
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if (NEXTINDEX(h) == 0) {
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/* tell caller we're done */
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c->c_index = NEXTINDEX(h);
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return (RET_SPECIAL);
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}
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index = 0;
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}
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c->c_flags &= ~CRSR_BEFORE;
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} else if (++index >= NEXTINDEX(h)) {
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/* out of items on this page, get next page */
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if (h->h_nextpg == P_NONE) {
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/* tell caller we're done... */
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c->c_index = NEXTINDEX(h);
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return (RET_SPECIAL);
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}
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/* skip empty pages */
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do {
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if (_bt_getpage(t, h->h_nextpg) == RET_ERROR) {
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c->c_index = NEXTINDEX(h);
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return (RET_ERROR);
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}
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h = t->bt_curpage;
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c->c_pgno = h->h_pgno;
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} while (NEXTINDEX(h) == 0 && h->h_nextpg != P_NONE);
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if (NEXTINDEX(h) == 0) {
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/* tell caller we're done */
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c->c_index = NEXTINDEX(h);
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return (RET_SPECIAL);
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}
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index = 0;
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}
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} else if (flags == R_PREV) {
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/* for backward scans, life is substantially easier */
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c->c_flags &= ~CRSR_BEFORE;
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if (c->c_key != (char *) NULL) {
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(void) free(c->c_key);
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c->c_key = (char *) NULL;
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}
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if (index == 0) {
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/* we may be done */
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c->c_index = 0;
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/* out of items on this page, get next page */
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if (h->h_prevpg == P_NONE)
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return (RET_SPECIAL);
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/* skip empty pages */
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do {
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if (_bt_getpage(t, h->h_prevpg) == RET_ERROR)
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return (RET_ERROR);
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h = t->bt_curpage;
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c->c_pgno = h->h_pgno;
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} while (NEXTINDEX(h) == 0 && h->h_prevpg != P_NONE);
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if (NEXTINDEX(h) == 0)
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return (RET_SPECIAL);
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index = NEXTINDEX(h) - 1;
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} else
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--index;
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} else {
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/* must specify a direction */
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errno = EINVAL;
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return (RET_ERROR);
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}
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c->c_index = index;
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return (RET_SUCCESS);
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}
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