1 /* $OpenBSD: bt_overflow.c,v 1.11 2015/01/16 16:48:51 deraadt 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 #include <stdio.h> 36 #include <stdlib.h> 37 #include <string.h> 38 39 #include <db.h> 40 #include "btree.h" 41 42 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b)) 43 44 /* 45 * Big key/data code. 46 * 47 * Big key and data entries are stored on linked lists of pages. The initial 48 * reference is byte string stored with the key or data and is the page number 49 * and size. The actual record is stored in a chain of pages linked by the 50 * nextpg field of the PAGE header. 51 * 52 * The first page of the chain has a special property. If the record is used 53 * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set 54 * in the header. 55 * 56 * XXX 57 * A single DBT is written to each chain, so a lot of space on the last page 58 * is wasted. This is a fairly major bug for some data sets. 59 */ 60 61 /* 62 * __OVFL_GET -- Get an overflow key/data item. 63 * 64 * Parameters: 65 * t: tree 66 * p: pointer to { pgno_t, u_int32_t } 67 * buf: storage address 68 * bufsz: storage size 69 * 70 * Returns: 71 * RET_ERROR, RET_SUCCESS 72 */ 73 int 74 __ovfl_get(BTREE *t, void *p, size_t *ssz, void **buf, size_t *bufsz) 75 { 76 PAGE *h; 77 pgno_t pg; 78 size_t nb, plen; 79 u_int32_t sz; 80 void *tp; 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 tp = realloc(*buf, sz); 93 if (tp == NULL) 94 return (RET_ERROR); 95 *buf = tp; 96 *bufsz = sz; 97 } 98 99 /* 100 * Step through the linked list of pages, copying the data on each one 101 * into the buffer. Never copy more than the data's length. 102 */ 103 plen = t->bt_psize - BTDATAOFF; 104 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) { 105 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 106 return (RET_ERROR); 107 108 nb = MINIMUM(sz, plen); 109 memmove(p, (char *)h + BTDATAOFF, nb); 110 mpool_put(t->bt_mp, h, 0); 111 112 if ((sz -= nb) == 0) 113 break; 114 } 115 return (RET_SUCCESS); 116 } 117 118 /* 119 * __OVFL_PUT -- Store an overflow key/data item. 120 * 121 * Parameters: 122 * t: tree 123 * data: DBT to store 124 * pgno: storage page number 125 * 126 * Returns: 127 * RET_ERROR, RET_SUCCESS 128 */ 129 int 130 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg) 131 { 132 PAGE *h, *last; 133 void *p; 134 pgno_t npg; 135 size_t nb, plen; 136 u_int32_t sz; 137 138 /* 139 * Allocate pages and copy the key/data record into them. Store the 140 * number of the first page in the chain. 141 */ 142 plen = t->bt_psize - BTDATAOFF; 143 for (last = NULL, p = dbt->data, sz = dbt->size;; 144 p = (char *)p + plen, last = h) { 145 if ((h = __bt_new(t, &npg)) == NULL) 146 return (RET_ERROR); 147 148 h->pgno = npg; 149 h->nextpg = h->prevpg = P_INVALID; 150 h->flags = P_OVERFLOW; 151 h->lower = h->upper = 0; 152 153 nb = MINIMUM(sz, plen); 154 memmove((char *)h + BTDATAOFF, p, nb); 155 156 if (last) { 157 last->nextpg = h->pgno; 158 mpool_put(t->bt_mp, last, MPOOL_DIRTY); 159 } else 160 *pg = h->pgno; 161 162 if ((sz -= nb) == 0) { 163 mpool_put(t->bt_mp, h, MPOOL_DIRTY); 164 break; 165 } 166 } 167 return (RET_SUCCESS); 168 } 169 170 /* 171 * __OVFL_DELETE -- Delete an overflow chain. 172 * 173 * Parameters: 174 * t: tree 175 * p: pointer to { pgno_t, u_int32_t } 176 * 177 * Returns: 178 * RET_ERROR, RET_SUCCESS 179 */ 180 int 181 __ovfl_delete(BTREE *t, void *p) 182 { 183 PAGE *h; 184 pgno_t pg; 185 size_t plen; 186 u_int32_t sz; 187 188 memmove(&pg, p, sizeof(pgno_t)); 189 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t)); 190 191 #ifdef DEBUG 192 if (pg == P_INVALID || sz == 0) 193 abort(); 194 #endif 195 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 196 return (RET_ERROR); 197 198 /* Don't delete chains used by internal pages. */ 199 if (h->flags & P_PRESERVE) { 200 mpool_put(t->bt_mp, h, 0); 201 return (RET_SUCCESS); 202 } 203 204 /* Step through the chain, calling the free routine for each page. */ 205 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) { 206 pg = h->nextpg; 207 __bt_free(t, h); 208 if (sz <= plen) 209 break; 210 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 211 return (RET_ERROR); 212 } 213 return (RET_SUCCESS); 214 } 215