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);
}