1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Mike Olson. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char sccsid[] = "@(#)bt_search.c 8.1 (Berkeley) 6/4/93"; 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include <sys/types.h> 42 43 #include <stdio.h> 44 45 #include <db.h> 46 #include "btree.h" 47 48 /* 49 * __BT_SEARCH -- Search a btree for a key. 50 * 51 * Parameters: 52 * t: tree to search 53 * key: key to find 54 * exactp: pointer to exact match flag 55 * 56 * Returns: 57 * EPG for matching record, if any, or the EPG for the location of the 58 * key, if it were inserted into the tree. 59 * 60 * Warnings: 61 * The EPG returned is in static memory, and will be overwritten by the 62 * next search of any kind in any tree. 63 */ 64 EPG * 65 __bt_search(t, key, exactp) 66 BTREE *t; 67 const DBT *key; 68 int *exactp; 69 { 70 register indx_t index; 71 register int base, cmp, lim; 72 register PAGE *h; 73 pgno_t pg; 74 static EPG e; 75 76 BT_CLR(t); 77 for (pg = P_ROOT;;) { 78 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 79 return (NULL); 80 81 /* Do a binary search on the current page. */ 82 e.page = h; 83 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 84 e.index = index = base + (lim >> 1); 85 if ((cmp = __bt_cmp(t, key, &e)) == 0) { 86 if (h->flags & P_BLEAF) { 87 *exactp = 1; 88 return (&e); 89 } 90 goto next; 91 } 92 if (cmp > 0) { 93 base = index + 1; 94 --lim; 95 } 96 } 97 98 /* If it's a leaf page, we're done. */ 99 if (h->flags & P_BLEAF) { 100 e.index = base; 101 *exactp = 0; 102 return (&e); 103 } 104 105 /* 106 * No match found. Base is the smallest index greater than 107 * key and may be zero or a last + 1 index. If it's non-zero, 108 * decrement by one, and record the internal page which should 109 * be a parent page for the key. If a split later occurs, the 110 * inserted page will be to the right of the saved page. 111 */ 112 index = base ? base - 1 : base; 113 114 next: if (__bt_push(t, h->pgno, index) == RET_ERROR) 115 return (NULL); 116 pg = GETBINTERNAL(h, index)->pgno; 117 mpool_put(t->bt_mp, h, 0); 118 } 119 } 120