lib/libc/DB/btree/bt_overflow.c

   1 /*-
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * 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_overflow.c       5.8 (Berkeley) 2/16/93";
  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  * Big key/data code.
  52  *
  53  * Big key and data entries are stored on linked lists of pages.  The initial
  54  * reference is byte string stored with the key or data and is the page number
  55  * and size.  The actual record is stored in a chain of pages linked by the
  56  * nextpg field of the PAGE header.
  57  *
  58  * The first page of the chain has a special property.  If the record is used
  59  * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
  60  * in the header.
  61  *
  62  * XXX
  63  * A single DBT is written to each chain, so a lot of space on the last page
  64  * is wasted.  This is a fairly major bug for some data sets.
  65  */
  66
  67 /*
  68  * __OVFL_GET -- Get an overflow key/data item.
  69  *
  70  * Parameters:
  71  *      t:      tree
  72  *      p:      pointer to { pgno_t, size_t }
  73  *      buf:    storage address
  74  *      bufsz:  storage size
  75  *
  76  * Returns:
  77  *      RET_ERROR, RET_SUCCESS
  78  */
  79 int
  80 __ovfl_get(t, p, ssz, buf, bufsz)
  81         BTREE *t;
  82         void *p;
  83         size_t *ssz;
  84         char **buf;
  85         size_t *bufsz;
  86 {
  87         PAGE *h;
  88         pgno_t pg;
  89         size_t nb, plen, sz;
  90
  91         memmove(&pg, p, sizeof(pgno_t));
  92         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(size_t));
  93         *ssz = sz;
  94
  95 #ifdef DEBUG
  96         if (pg == P_INVALID || sz == 0)
  97                 abort();
  98 #endif
  99         /* Make the buffer bigger as necessary. */
 100         if (*bufsz < sz) {
 101                 if ((*buf = realloc(*buf, sz)) == NULL)
 102                         return (RET_ERROR);
 103                 *bufsz = sz;
 104         }
 105
 106         /*
 107          * Step through the linked list of pages, copying the data on each one
 108          * into the buffer.  Never copy more than the data's length.
 109          */
 110         plen = t->bt_psize - BTDATAOFF;
 111         for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
 112                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 113                         return (RET_ERROR);
 114
 115                 nb = MIN(sz, plen);
 116                 memmove(p, (char *)h + BTDATAOFF, nb);
 117                 mpool_put(t->bt_mp, h, 0);
 118
 119                 if ((sz -= nb) == 0)
 120                         break;
 121         }
 122         return (RET_SUCCESS);
 123 }
 124
 125 /*
 126  * __OVFL_PUT -- Store an overflow key/data item.
 127  *
 128  * Parameters:
 129  *      t:      tree
 130  *      data:   DBT to store
 131  *      pgno:   storage page number
 132  *
 133  * Returns:
 134  *      RET_ERROR, RET_SUCCESS
 135  */
 136 int
 137 __ovfl_put(t, dbt, pg)
 138         BTREE *t;
 139         const DBT *dbt;
 140         pgno_t *pg;
 141 {
 142         PAGE *h, *last;
 143         void *p;
 144         pgno_t npg;
 145         size_t nb, plen, sz;
 146
 147         /*
 148          * Allocate pages and copy the key/data record into them.  Store the
 149          * number of the first page in the chain.
 150          */
 151         plen = t->bt_psize - BTDATAOFF;
 152         for (last = NULL, p = dbt->data, sz = dbt->size;;
 153             p = (char *)p + plen, last = h) {
 154                 if ((h = __bt_new(t, &npg)) == NULL)
 155                         return (RET_ERROR);
 156
 157                 h->pgno = npg;
 158                 h->nextpg = h->prevpg = P_INVALID;
 159                 h->flags = P_OVERFLOW;
 160                 h->lower = h->upper = 0;
 161
 162                 nb = MIN(sz, plen);
 163                 memmove((char *)h + BTDATAOFF, p, nb);
 164
 165                 if (last) {
 166                         last->nextpg = h->pgno;
 167                         mpool_put(t->bt_mp, last, MPOOL_DIRTY);
 168                 } else
 169                         *pg = h->pgno;
 170
 171                 if ((sz -= nb) == 0) {
 172                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 173                         break;
 174                 }
 175         }
 176         return (RET_SUCCESS);
 177 }
 178
 179 /*
 180  * __OVFL_DELETE -- Delete an overflow chain.
 181  *
 182  * Parameters:
 183  *      t:      tree
 184  *      p:      pointer to { pgno_t, size_t }
 185  *
 186  * Returns:
 187  *      RET_ERROR, RET_SUCCESS
 188  */
 189 int
 190 __ovfl_delete(t, p)
 191         BTREE *t;
 192         void *p;
 193 {
 194         PAGE *h;
 195         pgno_t pg;
 196         size_t plen, sz;
 197
 198         memmove(&pg, p, sizeof(pgno_t));
 199         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(size_t));
 200
 201 #ifdef DEBUG
 202         if (pg == P_INVALID || sz == 0)
 203                 abort();
 204 #endif
 205         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 206                 return (RET_ERROR);
 207
 208         /* Don't delete chains used by internal pages. */
 209         if (h->flags & P_PRESERVE) {
 210                 mpool_put(t->bt_mp, h, 0);
 211                 return (RET_SUCCESS);
 212         }
 213
 214         /* Step through the chain, calling the free routine for each page. */
 215         for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
 216                 pg = h->nextpg;
 217                 __bt_free(t, h);
 218                 if (sz <= plen)
 219                         break;
 220                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 221                         return (RET_ERROR);
 222         }
 223         return (RET_SUCCESS);
 224 }