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 $ */
30 * Copyright (c) 1988 by Sun Microsystems, Inc.
37 * B-tree operations: SEARCH
42 #include "isam_impl.h"
48 * Create a B-tree path object that will used in subsequent operations.
52 _isbtree_create(Fcb *fcb, Keydesc2 *pkeydesc2)
56 p = (Btree *) _ismalloc(sizeof(*p));
57 memset((char *)p, 0, sizeof(*p));
60 p->keydesc2 = pkeydesc2;
69 * Destroy B-tree path object
73 _isbtree_destroy(Btree *btree)
77 for (i = 0; i < btree->depth;i++) {
78 _isdisk_unfix(btree->bufhdr[i]);
87 * Descend the B-tree, position pointer on or before the matched key.
91 _isbtree_search( Btree *btree, char *key)
93 Keydesc2 *pkeydesc2 = btree->keydesc2;
94 Blkno rootblkno = pkeydesc2->k2_rootnode;
95 int keylength = pkeydesc2->k2_len;
96 int index; /* Index to tables in btree */
97 /* Has value of 1, next 2, etc. */
98 int elevation; /* Level - leaves have value 0 */
99 char *p; /* Pointer to key page */
100 int nkeys; /* Number of keys in the page */
101 char *key2; /* Equal or next lower key */
102 int curpos; /* index of key2 in key page */
105 /* Set comparison function. */
106 _iskeycmp_set(pkeydesc2, pkeydesc2->k2_nparts + 1); /* +1 for recno field */
111 btree->bufhdr[index] =
112 _isdisk_fix(btree->fcb, btree->fcb->indfd, blkno, ISFIXREAD);
113 p = btree->bufhdr[index]->isb_buffer; /* pointer to buffer */
115 /* Load some fields from the key page. */
116 nkeys = ldshort(p+BT_NKEYS_OFF); /* Number of keys in the page */
117 elevation = ldshort(p+BT_LEVEL_OFF); /* Level of the page */
119 /* Binary search in the key page to find equal or next lowere key. */
120 key2 = _isbsearch(key, p+BT_KEYS_OFF, nkeys, keylength, _iskeycmp);
122 curpos = (key2) ? ((key2 - p - BT_NKEYS_OFF) / keylength) : 0;
124 btree->curpos[index] =
125 (key2 == (char *)0 && elevation==0)? -1 : curpos;
128 blkno = ldblkno(p + ISPAGESIZE - (curpos + 1) * BLKNOSIZE);
131 } while (elevation > 0);
133 btree->depth = index;
139 * Get pointer to the current key
143 _isbtree_current(Btree *btree)
147 assert(btree->depth > 0);
148 if ((curpos = btree->curpos[btree->depth - 1]) == -1)
151 return (btree->bufhdr[btree->depth - 1]->isb_buffer
152 + BT_KEYS_OFF + curpos * btree->keydesc2->k2_len);
158 * Get pointer to the next key
162 _isbtree_next(Btree *btree)
165 int depth = btree->depth;
173 * Move up along the path, find first block where we can move to the right.
175 for (level = depth - 1; level >= 0; level--) {
176 p = btree->bufhdr[level]->isb_buffer;
178 if (btree->curpos[level] < ldshort(p + BT_NKEYS_OFF) - 1)
183 /* Logical end of the index file. No next record. */
187 curpos = ++(btree->curpos[level]);
189 while (++level < depth) {
191 /* Get block number to block in next lower level. */
193 blkno = ldblkno(p + ISPAGESIZE - (curpos + 1) * BLKNOSIZE);
195 /* Unfix page in this level, fetch its right brother. */
196 _isdisk_unfix(btree->bufhdr[level]);
197 btree->bufhdr[level] =
198 _isdisk_fix(btree->fcb, btree->fcb->indfd, blkno, ISFIXREAD);
199 p = btree->bufhdr[level]->isb_buffer;
201 curpos = btree->curpos[level] = 0;
204 return (p + BT_KEYS_OFF + curpos * btree->keydesc2->k2_len);