db2/btree/bt_compare.c

   1 /*-
   2  * See the file LICENSE for redistribution information.
   3  *
   4  * Copyright (c) 1996, 1997, 1998
   5  *      Sleepycat Software.  All rights reserved.
   6  */
   7 /*
   8  * Copyright (c) 1990, 1993, 1994, 1995, 1996
   9  *      Keith Bostic.  All rights reserved.
  10  */
  11 /*
  12  * Copyright (c) 1990, 1993, 1994, 1995
  13  *      The Regents of the University of California.  All rights reserved.
  14  *
  15  * This code is derived from software contributed to Berkeley by
  16  * Mike Olson.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  * 3. All advertising materials mentioning features or use of this software
  27  *    must display the following acknowledgement:
  28  *      This product includes software developed by the University of
  29  *      California, Berkeley and its contributors.
  30  * 4. Neither the name of the University nor the names of its contributors
  31  *    may be used to endorse or promote products derived from this software
  32  *    without specific prior written permission.
  33  *
  34  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  35  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  36  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  37  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  38  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  39  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  40  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  41  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  42  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  43  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  44  * SUCH DAMAGE.
  45  */
  46
  47 #include "config.h"
  48
  49 #ifndef lint
  50 static const char sccsid[] = "@(#)bt_compare.c  10.14 (Sleepycat) 10/9/98";
  51 #endif /* not lint */
  52
  53 #ifndef NO_SYSTEM_INCLUDES
  54 #include <sys/types.h>
  55
  56 #include <string.h>
  57 #endif
  58
  59 #include "db_int.h"
  60 #include "db_page.h"
  61 #include "btree.h"
  62
  63 /*
  64  * __bam_cmp --
  65  *      Compare a key to a given record.
  66  *
  67  * PUBLIC: int __bam_cmp __P((DB *, const DBT *,
  68  * PUBLIC:    PAGE *, u_int32_t, int (*)(const DBT *, const DBT *)));
  69  */
  70 int
  71 __bam_cmp(dbp, dbt, h, indx, func)
  72         DB *dbp;
  73         const DBT *dbt;
  74         PAGE *h;
  75         u_int32_t indx;
  76         int (*func)__P((const DBT *, const DBT *));
  77 {
  78         BINTERNAL *bi;
  79         BKEYDATA *bk;
  80         BOVERFLOW *bo;
  81         DBT pg_dbt;
  82         int ret;
  83
  84         /*
  85          * Returns:
  86          *      < 0 if dbt is < page record
  87          *      = 0 if dbt is = page record
  88          *      > 0 if dbt is > page record
  89          *
  90          * !!!
  91          * We do not clear the pg_dbt DBT even though it's likely to contain
  92          * random bits.  That should be okay, because the app's comparison
  93          * routine had better not be looking at fields other than data/size.
  94          * We don't clear it because we go through this path a lot and it's
  95          * expensive.
  96          */
  97         if (TYPE(h) == P_LBTREE || TYPE(h) == P_DUPLICATE) {
  98                 bk = GET_BKEYDATA(h, indx);
  99                 if (B_TYPE(bk->type) == B_OVERFLOW)
 100                         bo = (BOVERFLOW *)bk;
 101                 else {
 102                         pg_dbt.data = bk->data;
 103                         pg_dbt.size = bk->len;
 104                         return (func(dbt, &pg_dbt));
 105                 }
 106         } else {
 107                 /*
 108                  * The following code guarantees that the left-most key on an
 109                  * internal page at any level of the btree is less than any
 110                  * user specified key.  This saves us from having to update the
 111                  * leftmost key on an internal page when the user inserts a new
 112                  * key in the tree smaller than anything we've seen before.
 113                  */
 114                 if (indx == 0 && h->prev_pgno == PGNO_INVALID)
 115                         return (1);
 116
 117                 bi = GET_BINTERNAL(h, indx);
 118                 if (B_TYPE(bi->type) == B_OVERFLOW)
 119                         bo = (BOVERFLOW *)(bi->data);
 120                 else {
 121                         pg_dbt.data = bi->data;
 122                         pg_dbt.size = bi->len;
 123                         return (func(dbt, &pg_dbt));
 124                 }
 125         }
 126
 127         /*
 128          * Overflow.
 129          *
 130          * XXX
 131          * We ignore __db_moff() errors, because we have no way of returning
 132          * them.
 133          */
 134         (void) __db_moff(dbp,
 135             dbt, bo->pgno, bo->tlen, func == __bam_defcmp ? NULL : func, &ret);
 136         return (ret);
 137 }
 138
 139 /*
 140  * __bam_defcmp --
 141  *      Default comparison routine.
 142  *
 143  * PUBLIC: int __bam_defcmp __P((const DBT *, const DBT *));
 144  */
 145 int
 146 __bam_defcmp(a, b)
 147         const DBT *a, *b;
 148 {
 149         size_t len;
 150         u_int8_t *p1, *p2;
 151
 152         /*
 153          * Returns:
 154          *      < 0 if a is < b
 155          *      = 0 if a is = b
 156          *      > 0 if a is > b
 157          *
 158          * XXX
 159          * If a size_t doesn't fit into a long, or if the difference between
 160          * any two characters doesn't fit into an int, this routine can lose.
 161          * What we need is a signed integral type that's guaranteed to be at
 162          * least as large as a size_t, and there is no such thing.
 163          */
 164         len = a->size > b->size ? b->size : a->size;
 165         for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2)
 166                 if (*p1 != *p2)
 167                         return ((long)*p1 - (long)*p2);
 168         return ((long)a->size - (long)b->size);
 169 }
 170
 171 /*
 172  * __bam_defpfx --
 173  *      Default prefix routine.
 174  *
 175  * PUBLIC: size_t __bam_defpfx __P((const DBT *, const DBT *));
 176  */
 177 size_t
 178 __bam_defpfx(a, b)
 179         const DBT *a, *b;
 180 {
 181         size_t cnt, len;
 182         u_int8_t *p1, *p2;
 183
 184         cnt = 1;
 185         len = a->size > b->size ? b->size : a->size;
 186         for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2, ++cnt)
 187                 if (*p1 != *p2)
 188                         return (cnt);
 189
 190         /*
 191          * We know that a->size must be <= b->size, or they wouldn't be
 192          * in this order.
 193          */
 194         return (a->size < b->size ? a->size + 1 : a->size);
 195 }