db/btree/bt_utils.c

   1 /*-
   2  * Copyright (c) 1990, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Mike Olson.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)bt_utils.c  8.8 (Berkeley) 7/20/94";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <sys/param.h>
  42
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46
  47 #include <db.h>
  48 #include "btree.h"
  49
  50 /*
  51  * __bt_ret --
  52  *      Build return key/data pair.
  53  *
  54  * Parameters:
  55  *      t:      tree
  56  *      e:      key/data pair to be returned
  57  *      key:    user's key structure (NULL if not to be filled in)
  58  *      rkey:   memory area to hold key
  59  *      data:   user's data structure (NULL if not to be filled in)
  60  *      rdata:  memory area to hold data
  61  *       copy:  always copy the key/data item
  62  *
  63  * Returns:
  64  *      RET_SUCCESS, RET_ERROR.
  65  */
  66 int
  67 __bt_ret(t, e, key, rkey, data, rdata, copy)
  68         BTREE *t;
  69         EPG *e;
  70         DBT *key, *rkey, *data, *rdata;
  71         int copy;
  72 {
  73         BLEAF *bl;
  74         void *p;
  75
  76         bl = GETBLEAF(e->page, e->index);
  77
  78         /*
  79          * We must copy big keys/data to make them contiguous.  Otherwise,
  80          * leave the page pinned and don't copy unless the user specified
  81          * concurrent access.
  82          */
  83         if (key == NULL)
  84                 goto dataonly;
  85
  86         if (bl->flags & P_BIGKEY) {
  87                 if (__ovfl_get(t, bl->bytes,
  88                     &key->size, &rkey->data, &rkey->size))
  89                         return (RET_ERROR);
  90                 key->data = rkey->data;
  91         } else if (copy || F_ISSET(t, B_DB_LOCK)) {
  92                 if (bl->ksize > rkey->size) {
  93                         p = (void *)(rkey->data == NULL ?
  94                             malloc(bl->ksize) : realloc(rkey->data, bl->ksize));
  95                         if (p == NULL)
  96                                 return (RET_ERROR);
  97                         rkey->data = p;
  98                         rkey->size = bl->ksize;
  99                 }
 100                 memmove(rkey->data, bl->bytes, bl->ksize);
 101                 key->size = bl->ksize;
 102                 key->data = rkey->data;
 103         } else {
 104                 key->size = bl->ksize;
 105                 key->data = bl->bytes;
 106         }
 107
 108 dataonly:
 109         if (data == NULL)
 110                 return (RET_SUCCESS);
 111
 112         if (bl->flags & P_BIGDATA) {
 113                 if (__ovfl_get(t, bl->bytes + bl->ksize,
 114                     &data->size, &rdata->data, &rdata->size))
 115                         return (RET_ERROR);
 116                 data->data = rdata->data;
 117         } else if (copy || F_ISSET(t, B_DB_LOCK)) {
 118                 /* Use +1 in case the first record retrieved is 0 length. */
 119                 if (bl->dsize + 1 > rdata->size) {
 120                         p = (void *)(rdata->data == NULL ?
 121                             malloc(bl->dsize + 1) :
 122                             realloc(rdata->data, bl->dsize + 1));
 123                         if (p == NULL)
 124                                 return (RET_ERROR);
 125                         rdata->data = p;
 126                         rdata->size = bl->dsize + 1;
 127                 }
 128                 memmove(rdata->data, bl->bytes + bl->ksize, bl->dsize);
 129                 data->size = bl->dsize;
 130                 data->data = rdata->data;
 131         } else {
 132                 data->size = bl->dsize;
 133                 data->data = bl->bytes + bl->ksize;
 134         }
 135
 136         return (RET_SUCCESS);
 137 }
 138
 139 /*
 140  * __BT_CMP -- Compare a key to a given record.
 141  *
 142  * Parameters:
 143  *      t:      tree
 144  *      k1:     DBT pointer of first arg to comparison
 145  *      e:      pointer to EPG for comparison
 146  *
 147  * Returns:
 148  *      < 0 if k1 is < record
 149  *      = 0 if k1 is = record
 150  *      > 0 if k1 is > record
 151  */
 152 int
 153 __bt_cmp(t, k1, e)
 154         BTREE *t;
 155         const DBT *k1;
 156         EPG *e;
 157 {
 158         BINTERNAL *bi;
 159         BLEAF *bl;
 160         DBT k2;
 161         PAGE *h;
 162         void *bigkey;
 163
 164         /*
 165          * The left-most key on internal pages, at any level of the tree, is
 166          * guaranteed by the following code to be less than any user key.
 167          * This saves us from having to update the leftmost key on an internal
 168          * page when the user inserts a new key in the tree smaller than
 169          * anything we've yet seen.
 170          */
 171         h = e->page;
 172         if (e->index == 0 && h->prevpg == P_INVALID && !(h->flags & P_BLEAF))
 173                 return (1);
 174
 175         bigkey = NULL;
 176         if (h->flags & P_BLEAF) {
 177                 bl = GETBLEAF(h, e->index);
 178                 if (bl->flags & P_BIGKEY)
 179                         bigkey = bl->bytes;
 180                 else {
 181                         k2.data = bl->bytes;
 182                         k2.size = bl->ksize;
 183                 }
 184         } else {
 185                 bi = GETBINTERNAL(h, e->index);
 186                 if (bi->flags & P_BIGKEY)
 187                         bigkey = bi->bytes;
 188                 else {
 189                         k2.data = bi->bytes;
 190                         k2.size = bi->ksize;
 191                 }
 192         }
 193
 194         if (bigkey) {
 195                 if (__ovfl_get(t, bigkey,
 196                     &k2.size, &t->bt_rdata.data, &t->bt_rdata.size))
 197                         return (RET_ERROR);
 198                 k2.data = t->bt_rdata.data;
 199         }
 200         return ((*t->bt_cmp)(k1, &k2));
 201 }
 202
 203 /*
 204  * __BT_DEFCMP -- Default comparison routine.
 205  *
 206  * Parameters:
 207  *      a:      DBT #1
 208  *      b:      DBT #2
 209  *
 210  * Returns:
 211  *      < 0 if a is < b
 212  *      = 0 if a is = b
 213  *      > 0 if a is > b
 214  */
 215 int
 216 __bt_defcmp(a, b)
 217         const DBT *a, *b;
 218 {
 219         register size_t len;
 220         register u_char *p1, *p2;
 221
 222         /*
 223          * XXX
 224          * If a size_t doesn't fit in an int, this routine can lose.
 225          * What we need is a integral type which is guaranteed to be
 226          * larger than a size_t, and there is no such thing.
 227          */
 228         len = MIN(a->size, b->size);
 229         for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2)
 230                 if (*p1 != *p2)
 231                         return ((int)*p1 - (int)*p2);
 232         return ((int)a->size - (int)b->size);
 233 }
 234
 235 /*
 236  * __BT_DEFPFX -- Default prefix routine.
 237  *
 238  * Parameters:
 239  *      a:      DBT #1
 240  *      b:      DBT #2
 241  *
 242  * Returns:
 243  *      Number of bytes needed to distinguish b from a.
 244  */
 245 size_t
 246 __bt_defpfx(a, b)
 247         const DBT *a, *b;
 248 {
 249         register u_char *p1, *p2;
 250         register size_t cnt, len;
 251
 252         cnt = 1;
 253         len = MIN(a->size, b->size);
 254         for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2, ++cnt)
 255                 if (*p1 != *p2)
 256                         return (cnt);
 257
 258         /* a->size must be <= b->size, or they wouldn't be in this order. */
 259         return (a->size < b->size ? a->size + 1 : a->size);
 260 }