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bt_utils.c

/*-
 * 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 <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 contigous.  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);
}

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