lib/libc/db/btree/bt_overflow.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. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)bt_overflow.c    8.5 (Berkeley) 7/16/94
  33  * $DragonFly: src/lib/libc/db/btree/bt_overflow.c,v 1.4 2005/11/12 23:01:54 swildner Exp $
  34  */
  35
  36 #include <sys/param.h>
  37
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41
  42 #include <db.h>
  43 #include "btree.h"
  44
  45 /*
  46  * Big key/data code.
  47  *
  48  * Big key and data entries are stored on linked lists of pages.  The initial
  49  * reference is byte string stored with the key or data and is the page number
  50  * and size.  The actual record is stored in a chain of pages linked by the
  51  * nextpg field of the PAGE header.
  52  *
  53  * The first page of the chain has a special property.  If the record is used
  54  * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
  55  * in the header.
  56  *
  57  * XXX
  58  * A single DBT is written to each chain, so a lot of space on the last page
  59  * is wasted.  This is a fairly major bug for some data sets.
  60  */
  61
  62 /*
  63  * __OVFL_GET -- Get an overflow key/data item.
  64  *
  65  * Parameters:
  66  *      t:      tree
  67  *      p:      pointer to { pgno_t, u_int32_t }
  68  *      buf:    storage address
  69  *      bufsz:  storage size
  70  *
  71  * Returns:
  72  *      RET_ERROR, RET_SUCCESS
  73  */
  74 int
  75 __ovfl_get(BTREE *t, void *p, size_t *ssz, void **buf, size_t *bufsz)
  76 {
  77         PAGE *h;
  78         pgno_t pg;
  79         size_t nb, plen;
  80         u_int32_t sz;
  81
  82         memmove(&pg, p, sizeof(pgno_t));
  83         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
  84         *ssz = sz;
  85
  86 #ifdef DEBUG
  87         if (pg == P_INVALID || sz == 0)
  88                 abort();
  89 #endif
  90         /* Make the buffer bigger as necessary. */
  91         if (*bufsz < sz) {
  92                 *buf = (char *)(*buf == NULL ? malloc(sz) : reallocf(*buf, sz));
  93                 if (*buf == NULL)
  94                         return (RET_ERROR);
  95                 *bufsz = sz;
  96         }
  97
  98         /*
  99          * Step through the linked list of pages, copying the data on each one
 100          * into the buffer.  Never copy more than the data's length.
 101          */
 102         plen = t->bt_psize - BTDATAOFF;
 103         for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
 104                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 105                         return (RET_ERROR);
 106
 107                 nb = MIN(sz, plen);
 108                 memmove(p, (char *)h + BTDATAOFF, nb);
 109                 mpool_put(t->bt_mp, h, 0);
 110
 111                 if ((sz -= nb) == 0)
 112                         break;
 113         }
 114         return (RET_SUCCESS);
 115 }
 116
 117 /*
 118  * __OVFL_PUT -- Store an overflow key/data item.
 119  *
 120  * Parameters:
 121  *      t:      tree
 122  *      data:   DBT to store
 123  *      pgno:   storage page number
 124  *
 125  * Returns:
 126  *      RET_ERROR, RET_SUCCESS
 127  */
 128 int
 129 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg)
 130 {
 131         PAGE *h, *last;
 132         void *p;
 133         pgno_t npg;
 134         size_t nb, plen;
 135         u_int32_t sz;
 136
 137         /*
 138          * Allocate pages and copy the key/data record into them.  Store the
 139          * number of the first page in the chain.
 140          */
 141         plen = t->bt_psize - BTDATAOFF;
 142         for (last = NULL, p = dbt->data, sz = dbt->size;;
 143             p = (char *)p + plen, last = h) {
 144                 if ((h = __bt_new(t, &npg)) == NULL)
 145                         return (RET_ERROR);
 146
 147                 h->pgno = npg;
 148                 h->nextpg = h->prevpg = P_INVALID;
 149                 h->flags = P_OVERFLOW;
 150                 h->lower = h->upper = 0;
 151
 152                 nb = MIN(sz, plen);
 153                 memmove((char *)h + BTDATAOFF, p, nb);
 154
 155                 if (last) {
 156                         last->nextpg = h->pgno;
 157                         mpool_put(t->bt_mp, last, MPOOL_DIRTY);
 158                 } else
 159                         *pg = h->pgno;
 160
 161                 if ((sz -= nb) == 0) {
 162                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 163                         break;
 164                 }
 165         }
 166         return (RET_SUCCESS);
 167 }
 168
 169 /*
 170  * __OVFL_DELETE -- Delete an overflow chain.
 171  *
 172  * Parameters:
 173  *      t:      tree
 174  *      p:      pointer to { pgno_t, u_int32_t }
 175  *
 176  * Returns:
 177  *      RET_ERROR, RET_SUCCESS
 178  */
 179 int
 180 __ovfl_delete(BTREE *t, void *p)
 181 {
 182         PAGE *h;
 183         pgno_t pg;
 184         size_t plen;
 185         u_int32_t sz;
 186
 187         memmove(&pg, p, sizeof(pgno_t));
 188         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
 189
 190 #ifdef DEBUG
 191         if (pg == P_INVALID || sz == 0)
 192                 abort();
 193 #endif
 194         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 195                 return (RET_ERROR);
 196
 197         /* Don't delete chains used by internal pages. */
 198         if (h->flags & P_PRESERVE) {
 199                 mpool_put(t->bt_mp, h, 0);
 200                 return (RET_SUCCESS);
 201         }
 202
 203         /* Step through the chain, calling the free routine for each page. */
 204         for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
 205                 pg = h->nextpg;
 206                 __bt_free(t, h);
 207                 if (sz <= plen)
 208                         break;
 209                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 210                         return (RET_ERROR);
 211         }
 212         return (RET_SUCCESS);
 213 }