/*- * Copyright (c) 1990, 1993, 1994 * 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 8.9 (Berkeley) 10/26/95"; #endif /* LIBC_SCCS and not lint */ #include <sys/types.h> #include <stdio.h> #include "db-int.h" #include "btree.h" static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *)); static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *)); /* * __bt_search -- * Search a btree for a key. * * Parameters: * t: tree to search * key: key to find * exactp: pointer to exact match flag * * Returns: * The EPG for matching record, if any, or the EPG for the location * of the key, if it were inserted into the tree, is entered into * the bt_cur field of the tree. A pointer to the field is returned. */ EPG * __bt_search(BTREE *t, const DBT *key, int *exactp) { PAGE *h; indx_t base, idx, lim; db_pgno_t pg; int cmp; 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. */ t->bt_cur.page = h; for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { t->bt_cur.index = idx = base + (lim >> 1); if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { if (h->flags & P_BLEAF) { *exactp = 1; return (&t->bt_cur); } goto next; } if (cmp > 0) { base = idx + 1; --lim; } } /* * If it's a leaf page, we're almost done. If no duplicates * are allowed, or we have an exact match, we're done. Else, * it's possible that there were matching keys on this page, * which later deleted, and we're on a page with no matches * while there are matches on other pages. If at the start or * end of a page, check the adjacent page. */ if (h->flags & P_BLEAF) { if (!F_ISSET(t, B_NODUPS)) { if (base == 0 && h->prevpg != P_INVALID && __bt_sprev(t, h, key, exactp)) return (&t->bt_cur); if (base == NEXTINDEX(h) && h->nextpg != P_INVALID && __bt_snext(t, h, key, exactp)) return (&t->bt_cur); } *exactp = 0; t->bt_cur.index = base; return (&t->bt_cur); } /* * 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. */ idx = base ? base - 1 : base; next: BT_PUSH(t, h->pgno, idx); pg = GETBINTERNAL(h, idx)->pgno; mpool_put(t->bt_mp, h, 0); } } /* * __bt_snext -- * Check for an exact match after the key. * * Parameters: * t: tree * h: current page * key: key * exactp: pointer to exact match flag * * Returns: * If an exact match found. */ static int __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp) { BINTERNAL *bi; EPG e; EPGNO *parent; indx_t idx = 0; db_pgno_t pgno; unsigned int level; /* * Get the next page. The key is either an exact * match, or not as good as the one we already have. */ if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) return (0); e.index = 0; if (__bt_cmp(t, key, &e) != 0) { mpool_put(t->bt_mp, e.page, 0); return (0); } mpool_put(t->bt_mp, h, 0); t->bt_cur = e; *exactp = 1; /* * Adjust the stack for the movement. * * Move up the stack. */ for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { /* Get the parent page. */ if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) return (0); /* Move to the next index. */ if (parent->index != NEXTINDEX(h) - 1) { idx = parent->index + 1; BT_PUSH(t, h->pgno, idx); break; } mpool_put(t->bt_mp, h, 0); } /* Restore the stack. */ while (level--) { /* Push the next level down onto the stack. */ bi = GETBINTERNAL(h, idx); pgno = bi->pgno; BT_PUSH(t, pgno, 0); /* Lose the currently pinned page. */ mpool_put(t->bt_mp, h, 0); /* Get the next level down. */ if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) return (0); idx = 0; } mpool_put(t->bt_mp, h, 0); return (1); } /* * __bt_sprev -- * Check for an exact match before the key. * * Parameters: * t: tree * h: current page * key: key * exactp: pointer to exact match flag * * Returns: * If an exact match found. */ static int __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp) { BINTERNAL *bi; EPG e; EPGNO *parent; indx_t idx = 0; db_pgno_t pgno; unsigned int level; /* * Get the previous page. The key is either an exact * match, or not as good as the one we already have. */ if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) return (0); e.index = NEXTINDEX(e.page) - 1; if (__bt_cmp(t, key, &e) != 0) { mpool_put(t->bt_mp, e.page, 0); return (0); } mpool_put(t->bt_mp, h, 0); t->bt_cur = e; *exactp = 1; /* * Adjust the stack for the movement. * * Move up the stack. */ for (level = 0; (parent = BT_POP(t)) != NULL; ++level) { /* Get the parent page. */ if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL) return (1); /* Move to the next index. */ if (parent->index != 0) { idx = parent->index - 1; BT_PUSH(t, h->pgno, idx); break; } mpool_put(t->bt_mp, h, 0); } /* Restore the stack. */ while (level--) { /* Push the next level down onto the stack. */ bi = GETBINTERNAL(h, idx); pgno = bi->pgno; /* Lose the currently pinned page. */ mpool_put(t->bt_mp, h, 0); /* Get the next level down. */ if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL) return (1); idx = NEXTINDEX(h) - 1; BT_PUSH(t, pgno, idx); } mpool_put(t->bt_mp, h, 0); return (1); }
