146132Smao /*- 246132Smao * Copyright (c) 1990 The Regents of the University of California. 346132Smao * All rights reserved. 446132Smao * 546132Smao * This code is derived from software contributed to Berkeley by 646132Smao * Mike Olson. 746132Smao * 846132Smao * %sccs.include.redist.c% 946132Smao */ 1046132Smao 1146132Smao #if defined(LIBC_SCCS) && !defined(lint) 12*51105Sbostic static char sccsid[] = "@(#)bt_search.c 5.4 (Berkeley) 09/12/91"; 1346132Smao #endif /* LIBC_SCCS and not lint */ 1446132Smao 1546132Smao #include <sys/types.h> 1646132Smao #include <db.h> 1750989Sbostic #include <stdio.h> 1846132Smao #include "btree.h" 1946132Smao 2046132Smao /* 2150989Sbostic * __BT_SEARCH -- Search a btree for a key. 2246132Smao * 2350989Sbostic * Parameters: 2450989Sbostic * t: tree to search 2550989Sbostic * key: key to find 2650989Sbostic * exactp: pointer to exact match flag 2746132Smao * 2850989Sbostic * Returns: 2950989Sbostic * EPG for matching record, if any, or the EPG for the location of the 3050989Sbostic * key, if it were inserted into the tree. 3146132Smao * 3250989Sbostic * Warnings: 3350989Sbostic * The EPG returned is in static memory, and will be overwritten by the 3450989Sbostic * next search of any kind in any tree. 3546132Smao */ 3650989Sbostic EPG * 3750989Sbostic __bt_search(t, key, exactp) 3850989Sbostic BTREE *t; 3950989Sbostic const DBT *key; 4050989Sbostic int *exactp; 4146132Smao { 4250989Sbostic register index_t index; 4350989Sbostic register int base, cmp, lim; 4450989Sbostic register PAGE *h; 4550989Sbostic pgno_t pg; 4650989Sbostic static EPG e; 4746132Smao 4850989Sbostic for (pg = P_ROOT;;) { 4950989Sbostic if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 5050989Sbostic return (NULL); 5146132Smao 5250989Sbostic /* Do a binary search on the current page. */ 5350989Sbostic e.page = h; 5450989Sbostic for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 5550989Sbostic e.index = index = base + (lim >> 1); 5650989Sbostic if ((cmp = __bt_cmp(t, key, &e)) == 0) { 5750989Sbostic if (h->flags & P_BLEAF) { 5850989Sbostic *exactp = 1; 5950989Sbostic return (&e); 6050989Sbostic } 6150989Sbostic goto next; 6246132Smao } 6350989Sbostic if (cmp > 0) { 6450989Sbostic base = index + 1; 6550989Sbostic --lim; 6646132Smao } 6746132Smao } 6846132Smao 6950989Sbostic /* 7050989Sbostic * No match found. Base is the smallest index greater than 7150989Sbostic * key but may be an illegal index. Use base if it's a leaf 7250989Sbostic * page, decrement it by one if it's an internal page. This 7350989Sbostic * is safe because internal pages can't be empty. 7450989Sbostic */ 7550989Sbostic index = h->flags & P_BLEAF ? base : base - 1; 7650989Sbostic 7750989Sbostic /* If it's a leaf page, we're done. */ 7850989Sbostic if (h->flags & P_BLEAF) { 7950989Sbostic e.index = index; 8050989Sbostic *exactp = 0; 8150989Sbostic return (&e); 8246132Smao } 8346132Smao 84*51105Sbostic next: if (__bt_push(t, h->pgno, index) == RET_ERROR) 8550989Sbostic return (NULL); 8650989Sbostic pg = GETBINTERNAL(h, index)->pgno; 8750989Sbostic mpool_put(t->bt_mp, h, 0); 8846132Smao } 8946132Smao } 90