diff options
Diffstat (limited to 'lib/libc/db/btree/bt_get.c')
| -rw-r--r-- | lib/libc/db/btree/bt_get.c | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/lib/libc/db/btree/bt_get.c b/lib/libc/db/btree/bt_get.c new file mode 100644 index 0000000..28b2d60 --- /dev/null +++ b/lib/libc/db/btree/bt_get.c @@ -0,0 +1,238 @@ +/*- + * 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_get.c 8.2 (Berkeley) 9/7/93"; +#endif /* LIBC_SCCS and not lint */ + +#include <sys/types.h> + +#include <errno.h> +#include <stddef.h> +#include <stdio.h> + +#include <db.h> +#include "btree.h" + +/* + * __BT_GET -- Get a record from the btree. + * + * Parameters: + * dbp: pointer to access method + * key: key to find + * data: data to return + * flag: currently unused + * + * Returns: + * RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found. + */ +int +__bt_get(dbp, key, data, flags) + const DB *dbp; + const DBT *key; + DBT *data; + u_int flags; +{ + BTREE *t; + EPG *e; + int exact, status; + + t = dbp->internal; + + /* Toss any page pinned across calls. */ + if (t->bt_pinned != NULL) { + mpool_put(t->bt_mp, t->bt_pinned, 0); + t->bt_pinned = NULL; + } + + /* Get currently doesn't take any flags. */ + if (flags) { + errno = EINVAL; + return (RET_ERROR); + } + + if ((e = __bt_search(t, key, &exact)) == NULL) + return (RET_ERROR); + if (!exact) { + mpool_put(t->bt_mp, e->page, 0); + return (RET_SPECIAL); + } + + /* + * A special case is if we found the record but it's flagged for + * deletion. In this case, we want to find another record with the + * same key, if it exists. Rather than look around the tree we call + * __bt_first and have it redo the search, as __bt_first will not + * return keys marked for deletion. Slow, but should never happen. + */ + if (ISSET(t, B_DELCRSR) && e->page->pgno == t->bt_bcursor.pgno && + e->index == t->bt_bcursor.index) { + mpool_put(t->bt_mp, e->page, 0); + if ((e = __bt_first(t, key, &exact)) == NULL) + return (RET_ERROR); + if (!exact) + return (RET_SPECIAL); + } + + status = __bt_ret(t, e, NULL, data); + /* + * If the user is doing concurrent access, we copied the + * key/data, toss the page. + */ + if (ISSET(t, B_DB_LOCK)) + mpool_put(t->bt_mp, e->page, 0); + else + t->bt_pinned = e->page; + return (status); +} + +/* + * __BT_FIRST -- Find the first entry. + * + * Parameters: + * t: the tree + * key: the key + * + * Returns: + * The first entry in the tree greater than or equal to key. + */ +EPG * +__bt_first(t, key, exactp) + BTREE *t; + const DBT *key; + int *exactp; +{ + register PAGE *h; + register EPG *e; + EPG save; + pgno_t cpgno, pg; + indx_t cindex; + int found; + + /* + * Find any matching record; __bt_search pins the page. Only exact + * matches are tricky, otherwise just return the location of the key + * if it were to be inserted into the tree. + */ + if ((e = __bt_search(t, key, exactp)) == NULL) + return (NULL); + if (!*exactp) + return (e); + + if (ISSET(t, B_DELCRSR)) { + cpgno = t->bt_bcursor.pgno; + cindex = t->bt_bcursor.index; + } else { + cpgno = P_INVALID; + cindex = 0; /* GCC thinks it's uninitialized. */ + } + + /* + * Walk backwards, skipping empty pages, as long as the entry matches + * and there are keys left in the tree. Save a copy of each match in + * case we go too far. A special case is that we don't return a match + * on records that the cursor references that have already been flagged + * for deletion. + */ + save = *e; + h = e->page; + found = 0; + do { + if (cpgno != h->pgno || cindex != e->index) { + if (save.page->pgno != e->page->pgno) { + mpool_put(t->bt_mp, save.page, 0); + save = *e; + } else + save.index = e->index; + found = 1; + } + /* + * Make a special effort not to unpin the page the last (or + * original) match was on, but also make sure it's unpinned + * if an error occurs. + */ + while (e->index == 0) { + if (h->prevpg == P_INVALID) + goto done1; + if (h->pgno != save.page->pgno) + mpool_put(t->bt_mp, h, 0); + if ((h = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) { + if (h->pgno == save.page->pgno) + mpool_put(t->bt_mp, save.page, 0); + return (NULL); + } + e->page = h; + e->index = NEXTINDEX(h); + } + --e->index; + } while (__bt_cmp(t, key, e) == 0); + + /* + * Reach here with the last page that was looked at pinned, which may + * or may not be the same as the last (or original) match page. If + * it's not useful, release it. + */ +done1: if (h->pgno != save.page->pgno) + mpool_put(t->bt_mp, h, 0); + + /* + * If still haven't found a record, the only possibility left is the + * next one. Move forward one slot, skipping empty pages and check. + */ + if (!found) { + h = save.page; + if (++save.index == NEXTINDEX(h)) { + do { + pg = h->nextpg; + mpool_put(t->bt_mp, h, 0); + if (pg == P_INVALID) { + *exactp = 0; + return (e); + } + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (NULL); + } while ((save.index = NEXTINDEX(h)) == 0); + save.page = h; + } + if (__bt_cmp(t, key, &save) != 0) { + *exactp = 0; + return (e); + } + } + *e = save; + *exactp = 1; + return (e); +} |
