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

cde/programs/dtinfo/DtMmdb/btree_berkeley/bt_search.c

@@ -0,0 +1,120 @@
+/* $XConsortium: bt_search.c /main/3 1996/06/11 17:13:01 cde-hal $ */
+/*-
+ * Copyright (c) 1990, 1993
+ *	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[] = "@(#)bt_search.c	8.1 (Berkeley) 6/4/93";
+#endif /* LIBC_SCCS and not lint */
+
+#include <sys/types.h>
+
+#include <stdio.h>
+
+#include <db.h>
+#include "btree.h"
+
+/*
+ * __BT_SEARCH -- Search a btree for a key.
+ *
+ * Parameters:
+ *	t:	tree to search
+ *	key:	key to find
+ *	exactp:	pointer to exact match flag
+ *
+ * Returns:
+ *	EPG for matching record, if any, or the EPG for the location of the
+ *	key, if it were inserted into the tree.
+ *
+ * Warnings:
+ *	The EPG returned is in static memory, and will be overwritten by the
+ *	next search of any kind in any tree.
+ */
+EPG *
+__bt_search(t, key, exactp)
+	BTREE *t;
+	const DBT *key;
+	int *exactp;
+{
+	register indx_t index;
+	register int base, cmp, lim;
+	register PAGE *h;
+	pgno_t pg;
+	static EPG e;
+
+	BT_CLR(t);
+	for (pg = P_ROOT;;) {
+		if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
+			return (NULL);
+
+		/* Do a binary search on the current page. */
+		e.page = h;
+		for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
+			e.index = index = base + (lim >> 1);
+			if ((cmp = __bt_cmp(t, key, &e)) == 0) {
+				if (h->flags & P_BLEAF) {
+					*exactp = 1;
+					return (&e);
+				}
+				goto next;
+			}
+			if (cmp > 0) {
+				base = index + 1;
+				--lim;
+			}
+		}
+
+		/* If it's a leaf page, we're done. */
+		if (h->flags & P_BLEAF) {
+			e.index = base;
+			*exactp = 0;
+			return (&e);
+		}
+
+		/*
+		 * No match found.  Base is the smallest index greater than
+		 * key and may be zero or a last + 1 index.  If it's non-zero,
+		 * decrement by one, and record the internal page which should
+		 * be a parent page for the key.  If a split later occurs, the
+		 * inserted page will be to the right of the saved page.
+		 */
+		index = base ? base - 1 : base;
+
+next:		if (__bt_push(t, h->pgno, index) == RET_ERROR)
+			return (NULL);
+		pg = GETBINTERNAL(h, index)->pgno;
+		mpool_put(t->bt_mp, h, 0);
+	}
+}