Initial import of the CDE 2.1.30 sources from the Open Group.

cde/lib/tt/mini_isam/isbtree.c

@@ -0,0 +1,194 @@
+/*%%  (c) Copyright 1993, 1994 Hewlett-Packard Company			 */
+/*%%  (c) Copyright 1993, 1994 International Business Machines Corp.	 */
+/*%%  (c) Copyright 1993, 1994 Sun Microsystems, Inc.			 */
+/*%%  (c) Copyright 1993, 1994 Novell, Inc. 				 */
+/*%%  $XConsortium: isbtree.c /main/3 1995/10/23 11:35:52 rswiston $ 			 				 */
+#ifndef lint
+    static char sccsid[] = "@(#)isbtree.c 1.4 89/07/17 Copyr 1988 Sun Micro";
+#endif
+
+/*
+ * Copyright (c) 1988 by Sun Microsystems, Inc.
+ */
+
+/*
+ * isbtree.c
+ *
+ * Description:
+ *	B-tree operations: SEARCH
+ *	
+ */
+
+#include "isam_impl.h"
+
+extern int _iskeycmp();
+
+/* 
+ * _isbtree_create() 
+ *
+ * Create a B-tree path object that will used in subsequent operations.
+ */
+
+Btree *
+    _isbtree_create(fcb, pkeydesc2)
+Fcb			*fcb;
+Keydesc2		*pkeydesc2;
+{
+    register Btree	*p;
+    
+    p = (Btree *) _ismalloc(sizeof(*p));
+    memset((char *)p, 0, sizeof(*p));
+    
+    p->fcb = fcb;
+    p->keydesc2 = pkeydesc2;	
+    
+    return (p);
+}
+
+
+/* 
+ * _isbtr_destroy() 
+ *
+ * Destroy B-tree path object 
+ */
+
+void
+_isbtree_destroy(btree)
+    register Btree *btree;
+{
+    register int	i;
+    
+    for (i = 0; i < btree->depth;i++) {
+	_isdisk_unfix(btree->bufhdr[i]);
+    }
+    free((char *)btree);
+}
+
+
+/* 
+ * _isbtree_search() 
+ *
+ * Descend the B-tree, position pointer on or before the matched key.
+ */
+
+void
+_isbtree_search(btree, key)
+    register Btree  	*btree;
+char		*key;		     /* Search for this key */
+{
+    Keydesc2		*pkeydesc2 = btree->keydesc2;
+    Blkno		rootblkno = pkeydesc2->k2_rootnode;
+    int			keylength = pkeydesc2->k2_len;
+    int			index;		     /* Index to tables in btree */
+    /* Has value of 1, next 2, etc. */
+    int			elevation;	     /* Level - leaves have value 0 */
+    register char	*p;		     /* Pointer to key page */
+    int			nkeys;		     /* Number of keys in the page */
+    char		*key2;		     /* Equal or next lower key */
+    int			curpos;		     /* index of key2 in key page */
+    Blkno		blkno;
+    
+    /* Set comparison function. */
+    _iskeycmp_set(pkeydesc2, pkeydesc2->k2_nparts + 1);	/* +1 for recno field */
+    
+    index = 0;
+    blkno = rootblkno;
+    do {
+	btree->bufhdr[index] = 
+	    _isdisk_fix(btree->fcb,  btree->fcb->indfd, blkno, ISFIXREAD);
+	p = btree->bufhdr[index]->isb_buffer; /* pointer to buffer */
+	
+	/* Load some fields from the key page. */
+	nkeys = ldshort(p+BT_NKEYS_OFF);     /* Number of keys in the page */
+	elevation = ldshort(p+BT_LEVEL_OFF); /* Level of the page */
+	
+	/* Binary search in the key page to find equal or next lowere key. */
+	key2 = _isbsearch(key, p+BT_KEYS_OFF, nkeys, keylength, _iskeycmp);
+	
+	curpos = (key2) ? ((key2 - p - BT_NKEYS_OFF) / keylength) : 0;
+	
+	btree->curpos[index] = 
+	    (key2 == (char *)0 && elevation==0)? -1 : curpos;
+	
+	if (elevation > 0) 
+	    blkno = ldblkno(p + ISPAGESIZE - (curpos + 1) * BLKNOSIZE);
+	
+	index++;
+    } while (elevation > 0);
+    
+    btree->depth = index;
+}
+
+/* 
+ * _isbtree_current() 
+ *
+ * Get pointer to the current key 
+ */
+
+char *
+_isbtree_current(btree)
+    register Btree	*btree;
+{
+    int			curpos;
+    
+    assert(btree->depth > 0);
+    if ((curpos = btree->curpos[btree->depth - 1]) == -1)
+	return (NULL);
+    else
+	return (btree->bufhdr[btree->depth - 1]->isb_buffer 
+		+ BT_KEYS_OFF + curpos * btree->keydesc2->k2_len);
+}
+
+/* 
+ * _isbtree_next()
+ *
+ * Get pointer to the next key 
+ */
+
+char *
+_isbtree_next(btree)
+    register Btree	*btree;
+{
+    int			curpos;
+    int			depth = btree->depth;
+    register char	*p;
+    register int	level;
+    Blkno		blkno;
+    
+    assert(depth > 0);
+    
+    /* 
+     * Move up along the path, find first block where we can move to the right.
+     */
+    for (level = depth - 1; level >= 0; level--) {
+	p = btree->bufhdr[level]->isb_buffer;
+	
+	if (btree->curpos[level] < ldshort(p + BT_NKEYS_OFF) - 1)
+	    break;
+    }
+    
+    if (level < 0) {
+	/* Logical end of the index file. No next record. */
+	return (NULL);
+    }
+    
+    curpos = ++(btree->curpos[level]);
+    
+    while (++level < depth) {
+	
+	/* Get block number to block in next lower level. */
+	if (level > 0)
+	    blkno = ldblkno(p + ISPAGESIZE - (curpos + 1) * BLKNOSIZE);
+	
+	/* Unfix page in this level, fetch its right brother. */
+	_isdisk_unfix(btree->bufhdr[level]);
+	btree->bufhdr[level] = 
+	    _isdisk_fix(btree->fcb, btree->fcb->indfd, blkno, ISFIXREAD);
+	p = btree->bufhdr[level]->isb_buffer;
+	
+	curpos = btree->curpos[level] = 0;
+    }
+    
+    return (p + BT_KEYS_OFF + curpos * btree->keydesc2->k2_len);
+}
+