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*57932Sbostic static char sccsid[] = "@(#)bt_search.c 5.8 (Berkeley) 02/11/93"; 1346132Smao #endif /* LIBC_SCCS and not lint */ 1446132Smao 1546132Smao #include <sys/types.h> 1656739Sbostic 1750989Sbostic #include <stdio.h> 1856739Sbostic 19*57932Sbostic #include <db.h> 2046132Smao #include "btree.h" 2146132Smao 2246132Smao /* 2350989Sbostic * __BT_SEARCH -- Search a btree for a key. 2446132Smao * 2550989Sbostic * Parameters: 2650989Sbostic * t: tree to search 2750989Sbostic * key: key to find 2850989Sbostic * exactp: pointer to exact match flag 2946132Smao * 3050989Sbostic * Returns: 3150989Sbostic * EPG for matching record, if any, or the EPG for the location of the 3250989Sbostic * key, if it were inserted into the tree. 3346132Smao * 3450989Sbostic * Warnings: 3550989Sbostic * The EPG returned is in static memory, and will be overwritten by the 3650989Sbostic * next search of any kind in any tree. 3746132Smao */ 3850989Sbostic EPG * 3950989Sbostic __bt_search(t, key, exactp) 4050989Sbostic BTREE *t; 4150989Sbostic const DBT *key; 4250989Sbostic int *exactp; 4346132Smao { 4450989Sbostic register index_t index; 4550989Sbostic register int base, cmp, lim; 4650989Sbostic register PAGE *h; 4750989Sbostic pgno_t pg; 4850989Sbostic static EPG e; 4946132Smao 5057449Sbostic BT_CLR(t); 5150989Sbostic for (pg = P_ROOT;;) { 5250989Sbostic if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 5350989Sbostic return (NULL); 5446132Smao 5550989Sbostic /* Do a binary search on the current page. */ 5650989Sbostic e.page = h; 5750989Sbostic for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 5850989Sbostic e.index = index = base + (lim >> 1); 5950989Sbostic if ((cmp = __bt_cmp(t, key, &e)) == 0) { 6050989Sbostic if (h->flags & P_BLEAF) { 6150989Sbostic *exactp = 1; 6250989Sbostic return (&e); 6350989Sbostic } 6450989Sbostic goto next; 6546132Smao } 6650989Sbostic if (cmp > 0) { 6750989Sbostic base = index + 1; 6850989Sbostic --lim; 6946132Smao } 7046132Smao } 7146132Smao 7250989Sbostic /* If it's a leaf page, we're done. */ 7350989Sbostic if (h->flags & P_BLEAF) { 7457448Sbostic e.index = base; 7550989Sbostic *exactp = 0; 7650989Sbostic return (&e); 7746132Smao } 7846132Smao 7957448Sbostic /* 8057448Sbostic * No match found. Base is the smallest index greater than 8157448Sbostic * key and may be zero or a last + 1 index. If it's non-zero, 8257448Sbostic * decrement by one, and record the internal page which should 8357448Sbostic * be a parent page for the key. If a split later occurs, the 8457448Sbostic * inserted page will be to the right of the saved page. 8557448Sbostic */ 8657448Sbostic index = base ? base - 1 : base; 8757448Sbostic 8851105Sbostic next: if (__bt_push(t, h->pgno, index) == RET_ERROR) 8950989Sbostic return (NULL); 9050989Sbostic pg = GETBINTERNAL(h, index)->pgno; 9150989Sbostic mpool_put(t->bt_mp, h, 0); 9246132Smao } 9346132Smao } 94