bt_utils.c

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/*-
 * 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_utils.c 8.8 (Berkeley) 7/20/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "../include/db.h"
#include "btree.h"

/*
 * __bt_ret --
 * Build return key/data pair.
 *
 * Parameters:
 * t: tree
 * e: key/data pair to be returned
 * key: user's key structure (NULL if not to be filled in)
 * rkey: memory area to hold key
 * data: user's data structure (NULL if not to be filled in)
 * rdata: memory area to hold data
 * copy: always copy the key/data item
 *
 * Returns:
 * RET_SUCCESS, RET_ERROR.
 */
int
__bt_ret(t, e, key, rkey, data, rdata, copy)
 BTREE *t;
 EPG *e;
 DBT *key, *rkey, *data, *rdata;
 int copy;
{
 BLEAF *bl;
 void *p;

 bl = GETBLEAF(e->page, e->index);

 /*
 * We must copy big keys/data to make them contiguous. Otherwise,
 * leave the page pinned and don't copy unless the user specified
 * concurrent access.
 */
 if (key == NULL)
 goto dataonly;

 if (bl->flags & P_BIGKEY) {
 if (__ovfl_get(t, bl->bytes,
 &key->size, &rkey->data, &rkey->size))
 return (RET_ERROR);
 key->data = rkey->data;
 } else if (copy || F_ISSET(t, B_DB_LOCK)) {
 if (bl->ksize > rkey->size) {
 p = (void *)(rkey->data == NULL ?
 malloc(bl->ksize) : realloc(rkey->data, bl->ksize));
 if (p == NULL)
 return (RET_ERROR);
 rkey->data = p;
 rkey->size = bl->ksize;
 }
 memmove(rkey->data, bl->bytes, bl->ksize);
 key->size = bl->ksize;
 key->data = rkey->data;
 } else {
 key->size = bl->ksize;
 key->data = bl->bytes;
 }

dataonly:
 if (data == NULL)
 return (RET_SUCCESS);

 if (bl->flags & P_BIGDATA) {
 if (__ovfl_get(t, bl->bytes + bl->ksize,
 &data->size, &rdata->data, &rdata->size))
 return (RET_ERROR);
 data->data = rdata->data;
 } else if (copy || F_ISSET(t, B_DB_LOCK)) {
 /* Use +1 in case the first record retrieved is 0 length. */
 if (bl->dsize + 1 > rdata->size) {
 p = (void *)(rdata->data == NULL ?
 malloc(bl->dsize + 1) :
 realloc(rdata->data, bl->dsize + 1));
 if (p == NULL)
 return (RET_ERROR);
 rdata->data = p;
 rdata->size = bl->dsize + 1;
 }
 memmove(rdata->data, bl->bytes + bl->ksize, bl->dsize);
 data->size = bl->dsize;
 data->data = rdata->data;
 } else {
 data->size = bl->dsize;
 data->data = bl->bytes + bl->ksize;
 }

 return (RET_SUCCESS);
}

/*
 * __BT_CMP -- Compare a key to a given record.
 *
 * Parameters:
 * t: tree
 * k1: DBT pointer of first arg to comparison
 * e: pointer to EPG for comparison
 *
 * Returns:
 * < 0 if k1 is < record
 * = 0 if k1 is = record
 * > 0 if k1 is > record
 */
int
__bt_cmp(t, k1, e)
 BTREE *t;
 const DBT *k1;
 EPG *e;
{
 BINTERNAL *bi;
 BLEAF *bl;
 DBT k2;
 PAGE *h;
 void *bigkey;

 /*
 * The left-most key on internal pages, at any level of the tree, is
 * guaranteed by the following code to be less than any user key.
 * This saves us from having to update the leftmost key on an internal
 * page when the user inserts a new key in the tree smaller than
 * anything we've yet seen.
 */
 h = e->page;
 if (e->index == 0 && h->prevpg == P_INVALID && !(h->flags & P_BLEAF))
 return (1);

 bigkey = NULL;
 if (h->flags & P_BLEAF) {
 bl = GETBLEAF(h, e->index);
 if (bl->flags & P_BIGKEY)
 bigkey = bl->bytes;
 else {
 k2.data = bl->bytes;
 k2.size = bl->ksize;
 }
 } else {
 bi = GETBINTERNAL(h, e->index);
 if (bi->flags & P_BIGKEY)
 bigkey = bi->bytes;
 else {
 k2.data = bi->bytes;
 k2.size = bi->ksize;
 }
 }

 if (bigkey) {
 if (__ovfl_get(t, bigkey,
 &k2.size, &t->bt_rdata.data, &t->bt_rdata.size))
 return (RET_ERROR);
 k2.data = t->bt_rdata.data;
 }
 return ((*t->bt_cmp)(k1, &k2));
}

/*
 * __BT_DEFCMP -- Default comparison routine.
 *
 * Parameters:
 * a: DBT #1
 * b: DBT #2
 *
 * Returns:
 * < 0 if a is < b
 * = 0 if a is = b
 * > 0 if a is > b
 */
int
__bt_defcmp(a, b)
 const DBT *a, *b;
{
 register size_t len;
 register u_char *p1, *p2;

 /*
 * XXX
 * If a size_t doesn't fit in an int, this routine can lose.
 * What we need is a integral type which is guaranteed to be
 * larger than a size_t, and there is no such thing.
 */
 len = MIN(a->size, b->size);
 for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2)
 if (*p1 != *p2)
 return ((int)*p1 - (int)*p2);
 return ((int)a->size - (int)b->size);
}

/*
 * __BT_DEFPFX -- Default prefix routine.
 *
 * Parameters:
 * a: DBT #1
 * b: DBT #2
 *
 * Returns:
 * Number of bytes needed to distinguish b from a.
 */
size_t
__bt_defpfx(a, b)
 const DBT *a, *b;
{
 register u_char *p1, *p2;
 register size_t cnt, len;

 cnt = 1;
 len = MIN(a->size, b->size);
 for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2, ++cnt)
 if (*p1 != *p2)
 return (cnt);

 /* a->size must be <= b->size, or they wouldn't be in this order. */
 return (a->size < b->size ? a->size + 1 : a->size);
}