db/btree/bt_overflow-fbsd.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  * 4. 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
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)bt_overflow.c       8.5 (Berkeley) 7/16/94";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/db/btree/bt_overflow.c,v 1.6 2009/03/05 00:57:01 delphij Exp $");
  38
  39 #include <sys/param.h>
  40
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44
  45 #include <db.h>
  46 #include "btree.h"
  47
  48 /*
  49  * Big key/data code.
  50  *
  51  * Big key and data entries are stored on linked lists of pages.  The initial
  52  * reference is byte string stored with the key or data and is the page number
  53  * and size.  The actual record is stored in a chain of pages linked by the
  54  * nextpg field of the PAGE header.
  55  *
  56  * The first page of the chain has a special property.  If the record is used
  57  * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
  58  * in the header.
  59  *
  60  * XXX
  61  * A single DBT is written to each chain, so a lot of space on the last page
  62  * is wasted.  This is a fairly major bug for some data sets.
  63  */
  64
  65 /*
  66  * __OVFL_GET -- Get an overflow key/data item.
  67  *
  68  * Parameters:
  69  *      t:      tree
  70  *      p:      pointer to { pgno_t, u_int32_t }
  71  *      buf:    storage address
  72  *      bufsz:  storage size
  73  *
  74  * Returns:
  75  *      RET_ERROR, RET_SUCCESS
  76  */
  77 int
  78 __ovfl_get(BTREE *t, void *p, size_t *ssz, void **buf, size_t *bufsz)
  79 {
  80         PAGE *h;
  81         pgno_t pg;
  82         size_t nb, plen;
  83         u_int32_t sz;
  84
  85         memmove(&pg, p, sizeof(pgno_t));
  86         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
  87         *ssz = sz;
  88
  89 #ifdef DEBUG
  90         if (pg == P_INVALID || sz == 0)
  91                 LIBC_ABORT("%s", pg == P_INVALID ? "pg == P_INVALID" : "sz == 0");
  92 #endif
  93         /* Make the buffer bigger as necessary. */
  94         if (*bufsz < sz) {
  95                 *buf = reallocf(*buf, sz);
  96                 if (*buf == NULL)
  97                         return (RET_ERROR);
  98                 *bufsz = sz;
  99         }
 100
 101         /*
 102          * Step through the linked list of pages, copying the data on each one
 103          * into the buffer.  Never copy more than the data's length.
 104          */
 105         plen = t->bt_psize - BTDATAOFF;
 106         for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
 107                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 108                         return (RET_ERROR);
 109
 110                 nb = MIN(sz, plen);
 111                 memmove(p, (char *)h + BTDATAOFF, nb);
 112                 mpool_put(t->bt_mp, h, 0);
 113
 114                 if ((sz -= nb) == 0)
 115                         break;
 116         }
 117         return (RET_SUCCESS);
 118 }
 119
 120 /*
 121  * __OVFL_PUT -- Store an overflow key/data item.
 122  *
 123  * Parameters:
 124  *      t:      tree
 125  *      data:   DBT to store
 126  *      pgno:   storage page number
 127  *
 128  * Returns:
 129  *      RET_ERROR, RET_SUCCESS
 130  */
 131 int
 132 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg)
 133 {
 134         PAGE *h, *last;
 135         void *p;
 136         pgno_t npg;
 137         size_t nb, plen;
 138         u_int32_t sz;
 139
 140         /*
 141          * Allocate pages and copy the key/data record into them.  Store the
 142          * number of the first page in the chain.
 143          */
 144         plen = t->bt_psize - BTDATAOFF;
 145         for (last = NULL, p = dbt->data, sz = dbt->size;;
 146             p = (char *)p + plen, last = h) {
 147                 if ((h = __bt_new(t, &npg)) == NULL)
 148                         return (RET_ERROR);
 149
 150                 h->pgno = npg;
 151                 h->nextpg = h->prevpg = P_INVALID;
 152                 h->flags = P_OVERFLOW;
 153                 h->lower = h->upper = 0;
 154
 155                 nb = MIN(sz, plen);
 156                 memmove((char *)h + BTDATAOFF, p, nb);
 157
 158                 if (last) {
 159                         last->nextpg = h->pgno;
 160                         mpool_put(t->bt_mp, last, MPOOL_DIRTY);
 161                 } else
 162                         *pg = h->pgno;
 163
 164                 if ((sz -= nb) == 0) {
 165                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 166                         break;
 167                 }
 168         }
 169         return (RET_SUCCESS);
 170 }
 171
 172 /*
 173  * __OVFL_DELETE -- Delete an overflow chain.
 174  *
 175  * Parameters:
 176  *      t:      tree
 177  *      p:      pointer to { pgno_t, u_int32_t }
 178  *
 179  * Returns:
 180  *      RET_ERROR, RET_SUCCESS
 181  */
 182 int
 183 __ovfl_delete(BTREE *t, void *p)
 184 {
 185         PAGE *h;
 186         pgno_t pg;
 187         size_t plen;
 188         u_int32_t sz;
 189
 190         memmove(&pg, p, sizeof(pgno_t));
 191         memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
 192
 193 #ifdef DEBUG
 194         if (pg == P_INVALID || sz == 0)
 195                 LIBC_ABORT("%s", pg == P_INVALID ? "pg == P_INVALID" : "sz == 0");
 196 #endif
 197         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 198                 return (RET_ERROR);
 199
 200         /* Don't delete chains used by internal pages. */
 201         if (h->flags & P_PRESERVE) {
 202                 mpool_put(t->bt_mp, h, 0);
 203                 return (RET_SUCCESS);
 204         }
 205
 206         /* Step through the chain, calling the free routine for each page. */
 207         for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
 208                 pg = h->nextpg;
 209                 __bt_free(t, h);
 210                 if (sz <= plen)
 211                         break;
 212                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 213                         return (RET_ERROR);
 214         }
 215         return (RET_SUCCESS);
 216 }