contrib/libarchive-2/libarchive/archive_entry_link_resolver.c

   1 /*-
   2  * Copyright (c) 2003-2007 Tim Kientzle
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "archive_platform.h"
  27 __FBSDID("$FreeBSD: src/lib/libarchive/archive_entry_link_resolver.c,v 1.3 2008/06/15 04:31:43 kientzle Exp $");
  28
  29 #ifdef HAVE_SYS_STAT_H
  30 #include <sys/stat.h>
  31 #endif
  32 #ifdef HAVE_ERRNO_H
  33 #include <errno.h>
  34 #endif
  35 #include <stdio.h>
  36 #ifdef HAVE_STDLIB_H
  37 #include <stdlib.h>
  38 #endif
  39 #ifdef HAVE_STRING_H
  40 #include <string.h>
  41 #endif
  42
  43 #include "archive.h"
  44 #include "archive_entry.h"
  45
  46 /*
  47  * This is mostly a pretty straightforward hash table implementation.
  48  * The only interesting bit is the different strategies used to
  49  * match up links.  These strategies match those used by various
  50  * archiving formats:
  51  *   tar - content stored with first link, remainder refer back to it.
  52  *       This requires us to match each subsequent link up with the
  53  *       first appearance.
  54  *   cpio - Old cpio just stored body with each link, match-ups were
  55  *       implicit.  This is trivial.
  56  *   new cpio - New cpio only stores body with last link, match-ups
  57  *       are implicit.  This is actually quite tricky; see the notes
  58  *       below.
  59  */
  60
  61 /* Users pass us a format code, we translate that into a strategy here. */
  62 #define ARCHIVE_ENTRY_LINKIFY_LIKE_TAR  0
  63 #define ARCHIVE_ENTRY_LINKIFY_LIKE_MTREE 1
  64 #define ARCHIVE_ENTRY_LINKIFY_LIKE_OLD_CPIO 2
  65 #define ARCHIVE_ENTRY_LINKIFY_LIKE_NEW_CPIO 3
  66
  67 /* Initial size of link cache. */
  68 #define links_cache_initial_size 1024
  69
  70 struct links_entry {
  71         struct links_entry      *next;
  72         struct links_entry      *previous;
  73         int                      links; /* # links not yet seen */
  74         int                      hash;
  75         struct archive_entry    *canonical;
  76         struct archive_entry    *entry;
  77 };
  78
  79 struct archive_entry_linkresolver {
  80         struct links_entry      **buckets;
  81         struct links_entry       *spare;
  82         unsigned long             number_entries;
  83         size_t                    number_buckets;
  84         int                       strategy;
  85 };
  86
  87 static struct links_entry *find_entry(struct archive_entry_linkresolver *,
  88                     struct archive_entry *);
  89 static void grow_hash(struct archive_entry_linkresolver *);
  90 static struct links_entry *insert_entry(struct archive_entry_linkresolver *,
  91                     struct archive_entry *);
  92 static struct links_entry *next_entry(struct archive_entry_linkresolver *);
  93
  94 struct archive_entry_linkresolver *
  95 archive_entry_linkresolver_new(void)
  96 {
  97         struct archive_entry_linkresolver *res;
  98         size_t i;
  99
 100         res = malloc(sizeof(struct archive_entry_linkresolver));
 101         if (res == NULL)
 102                 return (NULL);
 103         memset(res, 0, sizeof(struct archive_entry_linkresolver));
 104         res->number_buckets = links_cache_initial_size;
 105         res->buckets = malloc(res->number_buckets *
 106             sizeof(res->buckets[0]));
 107         if (res->buckets == NULL) {
 108                 free(res);
 109                 return (NULL);
 110         }
 111         for (i = 0; i < res->number_buckets; i++)
 112                 res->buckets[i] = NULL;
 113         return (res);
 114 }
 115
 116 void
 117 archive_entry_linkresolver_set_strategy(struct archive_entry_linkresolver *res,
 118     int fmt)
 119 {
 120         int fmtbase = fmt & ARCHIVE_FORMAT_BASE_MASK;
 121
 122         switch (fmtbase) {
 123         case ARCHIVE_FORMAT_CPIO:
 124                 switch (fmt) {
 125                 case ARCHIVE_FORMAT_CPIO_SVR4_NOCRC:
 126                 case ARCHIVE_FORMAT_CPIO_SVR4_CRC:
 127                         res->strategy = ARCHIVE_ENTRY_LINKIFY_LIKE_NEW_CPIO;
 128                         break;
 129                 default:
 130                         res->strategy = ARCHIVE_ENTRY_LINKIFY_LIKE_OLD_CPIO;
 131                         break;
 132                 }
 133                 break;
 134         case ARCHIVE_FORMAT_MTREE:
 135                 res->strategy = ARCHIVE_ENTRY_LINKIFY_LIKE_MTREE;
 136                 break;
 137         case ARCHIVE_FORMAT_TAR:
 138                 res->strategy = ARCHIVE_ENTRY_LINKIFY_LIKE_TAR;
 139                 break;
 140         default:
 141                 res->strategy = ARCHIVE_ENTRY_LINKIFY_LIKE_TAR;
 142                 break;
 143         }
 144 }
 145
 146 void
 147 archive_entry_linkresolver_free(struct archive_entry_linkresolver *res)
 148 {
 149         struct links_entry *le;
 150
 151         if (res == NULL)
 152                 return;
 153
 154         if (res->buckets != NULL) {
 155                 while ((le = next_entry(res)) != NULL)
 156                         archive_entry_free(le->entry);
 157                 free(res->buckets);
 158                 res->buckets = NULL;
 159         }
 160         free(res);
 161 }
 162
 163 void
 164 archive_entry_linkify(struct archive_entry_linkresolver *res,
 165     struct archive_entry **e, struct archive_entry **f)
 166 {
 167         struct links_entry *le;
 168         struct archive_entry *t;
 169
 170         *f = NULL; /* Default: Don't return a second entry. */
 171
 172         if (*e == NULL) {
 173                 le = next_entry(res);
 174                 if (le != NULL) {
 175                         *e = le->entry;
 176                         le->entry = NULL;
 177                 }
 178                 return;
 179         }
 180
 181         /* If it has only one link, then we're done. */
 182         if (archive_entry_nlink(*e) == 1)
 183                 return;
 184         /* Directories never have hardlinks. */
 185         if (archive_entry_filetype(*e) == AE_IFDIR)
 186                 return;
 187
 188         switch (res->strategy) {
 189         case ARCHIVE_ENTRY_LINKIFY_LIKE_TAR:
 190                 le = find_entry(res, *e);
 191                 if (le != NULL) {
 192                         archive_entry_set_size(*e, 0);
 193                         archive_entry_copy_hardlink(*e,
 194                             archive_entry_pathname(le->canonical));
 195                 } else
 196                         insert_entry(res, *e);
 197                 return;
 198         case ARCHIVE_ENTRY_LINKIFY_LIKE_MTREE:
 199                 le = find_entry(res, *e);
 200                 if (le != NULL) {
 201                         archive_entry_copy_hardlink(*e,
 202                             archive_entry_pathname(le->canonical));
 203                 } else
 204                         insert_entry(res, *e);
 205                 return;
 206         case ARCHIVE_ENTRY_LINKIFY_LIKE_OLD_CPIO:
 207                 /* This one is trivial. */
 208                 return;
 209         case ARCHIVE_ENTRY_LINKIFY_LIKE_NEW_CPIO:
 210                 le = find_entry(res, *e);
 211                 if (le != NULL) {
 212                         /*
 213                          * Put the new entry in le, return the
 214                          * old entry from le.
 215                          */
 216                         t = *e;
 217                         *e = le->entry;
 218                         le->entry = t;
 219                         /* Make the old entry into a hardlink. */
 220                         archive_entry_set_size(*e, 0);
 221                         archive_entry_copy_hardlink(*e,
 222                             archive_entry_pathname(le->canonical));
 223                         /* If we ran out of links, return the
 224                          * final entry as well. */
 225                         if (le->links == 0) {
 226                                 *f = le->entry;
 227                                 le->entry = NULL;
 228                         }
 229                 } else {
 230                         /*
 231                          * If we haven't seen it, tuck it away
 232                          * for future use.
 233                          */
 234                         le = insert_entry(res, *e);
 235                         le->entry = *e;
 236                         *e = NULL;
 237                 }
 238                 return;
 239         default:
 240                 break;
 241         }
 242         return;
 243 }
 244
 245 static struct links_entry *
 246 find_entry(struct archive_entry_linkresolver *res,
 247     struct archive_entry *entry)
 248 {
 249         struct links_entry      *le;
 250         int                      hash, bucket;
 251         dev_t                    dev;
 252         ino_t                    ino;
 253
 254         /* Free a held entry. */
 255         if (res->spare != NULL) {
 256                 archive_entry_free(res->spare->canonical);
 257                 archive_entry_free(res->spare->entry);
 258                 free(res->spare);
 259                 res->spare = NULL;
 260         }
 261
 262         /* If the links cache overflowed and got flushed, don't bother. */
 263         if (res->buckets == NULL)
 264                 return (NULL);
 265
 266         dev = archive_entry_dev(entry);
 267         ino = archive_entry_ino(entry);
 268         hash = dev ^ ino;
 269
 270         /* Try to locate this entry in the links cache. */
 271         bucket = hash % res->number_buckets;
 272         for (le = res->buckets[bucket]; le != NULL; le = le->next) {
 273                 if (le->hash == hash
 274                     && dev == archive_entry_dev(le->canonical)
 275                     && ino == archive_entry_ino(le->canonical)) {
 276                         /*
 277                          * Decrement link count each time and release
 278                          * the entry if it hits zero.  This saves
 279                          * memory and is necessary for detecting
 280                          * missed links.
 281                          */
 282                         --le->links;
 283                         if (le->links > 0)
 284                                 return (le);
 285                         /* Remove it from this hash bucket. */
 286                         if (le->previous != NULL)
 287                                 le->previous->next = le->next;
 288                         if (le->next != NULL)
 289                                 le->next->previous = le->previous;
 290                         if (res->buckets[bucket] == le)
 291                                 res->buckets[bucket] = le->next;
 292                         res->number_entries--;
 293                         /* Defer freeing this entry. */
 294                         res->spare = le;
 295                         return (le);
 296                 }
 297         }
 298         return (NULL);
 299 }
 300
 301 static struct links_entry *
 302 next_entry(struct archive_entry_linkresolver *res)
 303 {
 304         struct links_entry      *le;
 305         size_t                   bucket;
 306
 307         /* Free a held entry. */
 308         if (res->spare != NULL) {
 309                 archive_entry_free(res->spare->canonical);
 310                 free(res->spare);
 311                 res->spare = NULL;
 312         }
 313
 314         /* If the links cache overflowed and got flushed, don't bother. */
 315         if (res->buckets == NULL)
 316                 return (NULL);
 317
 318         /* Look for next non-empty bucket in the links cache. */
 319         for (bucket = 0; bucket < res->number_buckets; bucket++) {
 320                 le = res->buckets[bucket];
 321                 if (le != NULL) {
 322                         /* Remove it from this hash bucket. */
 323                         if (le->next != NULL)
 324                                 le->next->previous = le->previous;
 325                         res->buckets[bucket] = le->next;
 326                         res->number_entries--;
 327                         /* Defer freeing this entry. */
 328                         res->spare = le;
 329                         return (le);
 330                 }
 331         }
 332         return (NULL);
 333 }
 334
 335 static struct links_entry *
 336 insert_entry(struct archive_entry_linkresolver *res,
 337     struct archive_entry *entry)
 338 {
 339         struct links_entry *le;
 340         int                      hash, bucket;
 341
 342         /* Add this entry to the links cache. */
 343         le = malloc(sizeof(struct links_entry));
 344         if (le == NULL)
 345                 return (NULL);
 346         memset(le, 0, sizeof(*le));
 347         le->canonical = archive_entry_clone(entry);
 348
 349         /* If the links cache is getting too full, enlarge the hash table. */
 350         if (res->number_entries > res->number_buckets * 2)
 351                 grow_hash(res);
 352
 353         hash = archive_entry_dev(entry) ^ archive_entry_ino(entry);
 354         bucket = hash % res->number_buckets;
 355
 356         /* If we could allocate the entry, record it. */
 357         if (res->buckets[bucket] != NULL)
 358                 res->buckets[bucket]->previous = le;
 359         res->number_entries++;
 360         le->next = res->buckets[bucket];
 361         le->previous = NULL;
 362         res->buckets[bucket] = le;
 363         le->hash = hash;
 364         le->links = archive_entry_nlink(entry) - 1;
 365         return (le);
 366 }
 367
 368 static void
 369 grow_hash(struct archive_entry_linkresolver *res)
 370 {
 371         struct links_entry *le, **new_buckets;
 372         size_t new_size;
 373         size_t i, bucket;
 374
 375         /* Try to enlarge the bucket list. */
 376         new_size = res->number_buckets * 2;
 377         new_buckets = malloc(new_size * sizeof(struct links_entry *));
 378
 379         if (new_buckets != NULL) {
 380                 memset(new_buckets, 0,
 381                     new_size * sizeof(struct links_entry *));
 382                 for (i = 0; i < res->number_buckets; i++) {
 383                         while (res->buckets[i] != NULL) {
 384                                 /* Remove entry from old bucket. */
 385                                 le = res->buckets[i];
 386                                 res->buckets[i] = le->next;
 387
 388                                 /* Add entry to new bucket. */
 389                                 bucket = le->hash % new_size;
 390
 391                                 if (new_buckets[bucket] != NULL)
 392                                         new_buckets[bucket]->previous =
 393                                             le;
 394                                 le->next = new_buckets[bucket];
 395                                 le->previous = NULL;
 396                                 new_buckets[bucket] = le;
 397                         }
 398                 }
 399                 free(res->buckets);
 400                 res->buckets = new_buckets;
 401                 res->number_buckets = new_size;
 402         }
 403 }