2 * CDE - Common Desktop Environment
4 * Copyright (c) 1993-2012, The Open Group. All rights reserved.
6 * These libraries and programs are free software; you can
7 * redistribute them and/or modify them under the terms of the GNU
8 * Lesser General Public License as published by the Free Software
9 * Foundation; either version 2 of the License, or (at your option)
12 * These libraries and programs are distributed in the hope that
13 * they will be useful, but WITHOUT ANY WARRANTY; without even the
14 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
15 * PURPOSE. See the GNU Lesser General Public License for more
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with these libraries and programs; if not, write
20 * to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
21 * Floor, Boston, MA 02110-1301 USA
23 /*%% (c) Copyright 1993, 1994 Hewlett-Packard Company */
24 /*%% (c) Copyright 1993, 1994 International Business Machines Corp. */
25 /*%% (c) Copyright 1993, 1994 Sun Microsystems, Inc. */
26 /*%% (c) Copyright 1993, 1994 Novell, Inc. */
27 /*%% $XConsortium: isbtree.c /main/3 1995/10/23 11:35:52 rswiston $ */
29 static char sccsid[] = "@(#)isbtree.c 1.4 89/07/17 Copyr 1988 Sun Micro";
33 * Copyright (c) 1988 by Sun Microsystems, Inc.
40 * B-tree operations: SEARCH
45 #include "isam_impl.h"
47 extern int _iskeycmp();
52 * Create a B-tree path object that will used in subsequent operations.
56 _isbtree_create(Fcb *fcb, Keydesc2 *pkeydesc2)
60 p = (Btree *) _ismalloc(sizeof(*p));
61 memset((char *)p, 0, sizeof(*p));
64 p->keydesc2 = pkeydesc2;
73 * Destroy B-tree path object
77 _isbtree_destroy(Btree *btree)
81 for (i = 0; i < btree->depth;i++) {
82 _isdisk_unfix(btree->bufhdr[i]);
91 * Descend the B-tree, position pointer on or before the matched key.
95 _isbtree_search( Btree *btree, char *key)
97 Keydesc2 *pkeydesc2 = btree->keydesc2;
98 Blkno rootblkno = pkeydesc2->k2_rootnode;
99 int keylength = pkeydesc2->k2_len;
100 int index; /* Index to tables in btree */
101 /* Has value of 1, next 2, etc. */
102 int elevation; /* Level - leaves have value 0 */
103 char *p; /* Pointer to key page */
104 int nkeys; /* Number of keys in the page */
105 char *key2; /* Equal or next lower key */
106 int curpos; /* index of key2 in key page */
109 /* Set comparison function. */
110 _iskeycmp_set(pkeydesc2, pkeydesc2->k2_nparts + 1); /* +1 for recno field */
115 btree->bufhdr[index] =
116 _isdisk_fix(btree->fcb, btree->fcb->indfd, blkno, ISFIXREAD);
117 p = btree->bufhdr[index]->isb_buffer; /* pointer to buffer */
119 /* Load some fields from the key page. */
120 nkeys = ldshort(p+BT_NKEYS_OFF); /* Number of keys in the page */
121 elevation = ldshort(p+BT_LEVEL_OFF); /* Level of the page */
123 /* Binary search in the key page to find equal or next lowere key. */
124 key2 = _isbsearch(key, p+BT_KEYS_OFF, nkeys, keylength, _iskeycmp);
126 curpos = (key2) ? ((key2 - p - BT_NKEYS_OFF) / keylength) : 0;
128 btree->curpos[index] =
129 (key2 == (char *)0 && elevation==0)? -1 : curpos;
132 blkno = ldblkno(p + ISPAGESIZE - (curpos + 1) * BLKNOSIZE);
135 } while (elevation > 0);
137 btree->depth = index;
143 * Get pointer to the current key
147 _isbtree_current(Btree *btree)
151 assert(btree->depth > 0);
152 if ((curpos = btree->curpos[btree->depth - 1]) == -1)
155 return (btree->bufhdr[btree->depth - 1]->isb_buffer
156 + BT_KEYS_OFF + curpos * btree->keydesc2->k2_len);
162 * Get pointer to the next key
166 _isbtree_next(Btree *btree)
169 int depth = btree->depth;
177 * Move up along the path, find first block where we can move to the right.
179 for (level = depth - 1; level >= 0; level--) {
180 p = btree->bufhdr[level]->isb_buffer;
182 if (btree->curpos[level] < ldshort(p + BT_NKEYS_OFF) - 1)
187 /* Logical end of the index file. No next record. */
191 curpos = ++(btree->curpos[level]);
193 while (++level < depth) {
195 /* Get block number to block in next lower level. */
197 blkno = ldblkno(p + ISPAGESIZE - (curpos + 1) * BLKNOSIZE);
199 /* Unfix page in this level, fetch its right brother. */
200 _isdisk_unfix(btree->bufhdr[level]);
201 btree->bufhdr[level] =
202 _isdisk_fix(btree->fcb, btree->fcb->indfd, blkno, ISFIXREAD);
203 p = btree->bufhdr[level]->isb_buffer;
205 curpos = btree->curpos[level] = 0;
208 return (p + BT_KEYS_OFF + curpos * btree->keydesc2->k2_len);