lib/libc/db/btree/bt_overflow.c

   1 /*      $NetBSD: bt_overflow.c,v 1.16 2008/09/11 12:58:00 joerg Exp $   */
   2
   3 /*-
   4  * Copyright (c) 1990, 1993, 1994
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Mike Olson.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #if HAVE_NBTOOL_CONFIG_H
  36 #include "nbtool_config.h"
  37 #endif
  38
  39 #include <sys/cdefs.h>
  40 __RCSID("$NetBSD: bt_overflow.c,v 1.16 2008/09/11 12:58:00 joerg Exp $");
  41
  42 #include "namespace.h"
  43 #include <sys/param.h>
  44
  45 #include <assert.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <string.h>
  49
  50 #include <db.h>
  51 #include "btree.h"
  52
  53 /*
  54  * Big key/data code.
  55  *
  56  * Big key and data entries are stored on linked lists of pages.  The initial
  57  * reference is byte string stored with the key or data and is the page number
  58  * and size.  The actual record is stored in a chain of pages linked by the
  59  * nextpg field of the PAGE header.
  60  *
  61  * The first page of the chain has a special property.  If the record is used
  62  * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
  63  * in the header.
  64  *
  65  * XXX
  66  * A single DBT is written to each chain, so a lot of space on the last page
  67  * is wasted.  This is a fairly major bug for some data sets.
  68  */
  69
  70 /*
  71  * __OVFL_GET -- Get an overflow key/data item.
  72  *
  73  * Parameters:
  74  *      t:      tree
  75  *      p:      pointer to { pgno_t, uint32_t }
  76  *      buf:    storage address
  77  *      bufsz:  storage size
  78  *
  79  * Returns:
  80  *      RET_ERROR, RET_SUCCESS
  81  */
  82 int
  83 __ovfl_get(BTREE *t, void *p, size_t *ssz, void **buf, size_t *bufsz)
  84 {
  85         PAGE *h;
  86         pgno_t pg;
  87         uint32_t sz, nb, plen;
  88         size_t temp;
  89
  90         memmove(&pg, p, sizeof(pgno_t));
  91         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(uint32_t));
  92         *ssz = sz;
  93
  94 #ifdef DEBUG
  95         if (pg == P_INVALID || sz == 0)
  96                 abort();
  97 #endif
  98         /* Make the buffer bigger as necessary. */
  99         if (*bufsz < sz) {
 100                 *buf = (char *)(*buf == NULL ? malloc(sz) : realloc(*buf, sz));
 101                 if (*buf == 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         temp = t->bt_psize - BTDATAOFF;
 111         _DBFIT(temp, uint32_t);
 112         plen = (uint32_t)temp;
 113         for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
 114                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 115                         return (RET_ERROR);
 116
 117                 nb = MIN(sz, plen);
 118                 memmove(p, (char *)(void *)h + BTDATAOFF, nb);
 119                 mpool_put(t->bt_mp, h, 0);
 120
 121                 if ((sz -= nb) == 0)
 122                         break;
 123         }
 124         return (RET_SUCCESS);
 125 }
 126
 127 /*
 128  * __OVFL_PUT -- Store an overflow key/data item.
 129  *
 130  * Parameters:
 131  *      t:      tree
 132  *      data:   DBT to store
 133  *      pgno:   storage page number
 134  *
 135  * Returns:
 136  *      RET_ERROR, RET_SUCCESS
 137  */
 138 int
 139 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg)
 140 {
 141         PAGE *h, *last;
 142         void *p;
 143         pgno_t npg;
 144         uint32_t sz, nb, plen;
 145         size_t temp;
 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         temp = t->bt_psize - BTDATAOFF;
 152         _DBFIT(temp, uint32_t);
 153         plen = (uint32_t)temp;
 154         last = NULL;
 155         p = dbt->data;
 156         temp = dbt->size;
 157         _DBFIT(temp, uint32_t);
 158         sz = temp;
 159         for (;; p = (char *)p + plen, last = h) {
 160                 if ((h = __bt_new(t, &npg)) == NULL)
 161                         return (RET_ERROR);
 162
 163                 h->pgno = npg;
 164                 h->nextpg = h->prevpg = P_INVALID;
 165                 h->flags = P_OVERFLOW;
 166                 h->lower = h->upper = 0;
 167
 168                 nb = MIN(sz, plen);
 169                 (void)memmove((char *)(void *)h + BTDATAOFF, p, (size_t)nb);
 170
 171                 if (last) {
 172                         last->nextpg = h->pgno;
 173                         mpool_put(t->bt_mp, last, MPOOL_DIRTY);
 174                 } else
 175                         *pg = h->pgno;
 176
 177                 if ((sz -= nb) == 0) {
 178                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 179                         break;
 180                 }
 181         }
 182         return (RET_SUCCESS);
 183 }
 184
 185 /*
 186  * __OVFL_DELETE -- Delete an overflow chain.
 187  *
 188  * Parameters:
 189  *      t:      tree
 190  *      p:      pointer to { pgno_t, uint32_t }
 191  *
 192  * Returns:
 193  *      RET_ERROR, RET_SUCCESS
 194  */
 195 int
 196 __ovfl_delete(BTREE *t, void *p)
 197 {
 198         PAGE *h;
 199         pgno_t pg;
 200         uint32_t sz, plen;
 201         size_t temp;
 202
 203         (void)memmove(&pg, p, sizeof(pgno_t));
 204         (void)memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(uint32_t));
 205
 206 #ifdef DEBUG
 207         if (pg == P_INVALID || sz == 0)
 208                 abort();
 209 #endif
 210         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 211                 return (RET_ERROR);
 212
 213         /* Don't delete chains used by internal pages. */
 214         if (h->flags & P_PRESERVE) {
 215                 mpool_put(t->bt_mp, h, 0);
 216                 return (RET_SUCCESS);
 217         }
 218
 219         /* Step through the chain, calling the free routine for each page. */
 220         temp = t->bt_psize - BTDATAOFF;
 221         _DBFIT(temp, uint32_t);
 222         plen = (uint32_t)temp;
 223         for (;; sz -= plen) {
 224                 pg = h->nextpg;
 225                 __bt_free(t, h);
 226                 if (sz <= plen)
 227                         break;
 228                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 229                         return (RET_ERROR);
 230         }
 231         return (RET_SUCCESS);
 232 }