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 1.1 2007/12/30 04:58:21 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
 185         switch (res->strategy) {
 186         case ARCHIVE_ENTRY_LINKIFY_LIKE_TAR:
 187                 le = find_entry(res, *e);
 188                 if (le != NULL) {
 189                         archive_entry_set_size(*e, 0);
 190                         archive_entry_copy_hardlink(*e,
 191                             archive_entry_pathname(le->canonical));
 192                 } else
 193                         insert_entry(res, *e);
 194                 return;
 195         case ARCHIVE_ENTRY_LINKIFY_LIKE_MTREE:
 196                 le = find_entry(res, *e);
 197                 if (le != NULL) {
 198                         archive_entry_copy_hardlink(*e,
 199                             archive_entry_pathname(le->canonical));
 200                 } else
 201                         insert_entry(res, *e);
 202                 return;
 203         case ARCHIVE_ENTRY_LINKIFY_LIKE_OLD_CPIO:
 204                 /* This one is trivial. */
 205                 return;
 206         case ARCHIVE_ENTRY_LINKIFY_LIKE_NEW_CPIO:
 207                 le = find_entry(res, *e);
 208                 if (le != NULL) {
 209                         /*
 210                          * Put the new entry in le, return the
 211                          * old entry from le.
 212                          */
 213                         t = *e;
 214                         *e = le->entry;
 215                         le->entry = t;
 216                         /* Make the old entry into a hardlink. */
 217                         archive_entry_set_size(*e, 0);
 218                         archive_entry_copy_hardlink(*e,
 219                             archive_entry_pathname(le->canonical));
 220                         /* If we ran out of links, return the
 221                          * final entry as well. */
 222                         if (le->links == 0) {
 223                                 *f = le->entry;
 224                                 le->entry = NULL;
 225                         }
 226                 } else {
 227                         /*
 228                          * If we haven't seen it, tuck it away
 229                          * for future use.
 230                          */
 231                         le = insert_entry(res, *e);
 232                         le->entry = *e;
 233                         *e = NULL;
 234                 }
 235                 return;
 236         default:
 237                 break;
 238         }
 239         return;
 240 }
 241
 242 static struct links_entry *
 243 find_entry(struct archive_entry_linkresolver *res,
 244     struct archive_entry *entry)
 245 {
 246         struct links_entry      *le;
 247         int                      hash, bucket;
 248         dev_t                    dev;
 249         ino_t                    ino;
 250
 251         /* Free a held entry. */
 252         if (res->spare != NULL) {
 253                 archive_entry_free(res->spare->canonical);
 254                 archive_entry_free(res->spare->entry);
 255                 free(res->spare);
 256                 res->spare = NULL;
 257         }
 258
 259         /* If the links cache overflowed and got flushed, don't bother. */
 260         if (res->buckets == NULL)
 261                 return (NULL);
 262
 263         dev = archive_entry_dev(entry);
 264         ino = archive_entry_ino(entry);
 265         hash = dev ^ ino;
 266
 267         /* Try to locate this entry in the links cache. */
 268         bucket = hash % res->number_buckets;
 269         for (le = res->buckets[bucket]; le != NULL; le = le->next) {
 270                 if (le->hash == hash
 271                     && dev == archive_entry_dev(le->canonical)
 272                     && ino == archive_entry_ino(le->canonical)) {
 273                         /*
 274                          * Decrement link count each time and release
 275                          * the entry if it hits zero.  This saves
 276                          * memory and is necessary for detecting
 277                          * missed links.
 278                          */
 279                         --le->links;
 280                         if (le->links > 0)
 281                                 return (le);
 282                         /* Remove it from this hash bucket. */
 283                         if (le->previous != NULL)
 284                                 le->previous->next = le->next;
 285                         if (le->next != NULL)
 286                                 le->next->previous = le->previous;
 287                         if (res->buckets[bucket] == le)
 288                                 res->buckets[bucket] = le->next;
 289                         res->number_entries--;
 290                         /* Defer freeing this entry. */
 291                         res->spare = le;
 292                         return (le);
 293                 }
 294         }
 295         return (NULL);
 296 }
 297
 298 static struct links_entry *
 299 next_entry(struct archive_entry_linkresolver *res)
 300 {
 301         struct links_entry      *le;
 302         size_t                   bucket;
 303
 304         /* Free a held entry. */
 305         if (res->spare != NULL) {
 306                 archive_entry_free(res->spare->canonical);
 307                 free(res->spare);
 308                 res->spare = NULL;
 309         }
 310
 311         /* If the links cache overflowed and got flushed, don't bother. */
 312         if (res->buckets == NULL)
 313                 return (NULL);
 314
 315         /* Look for next non-empty bucket in the links cache. */
 316         for (bucket = 0; bucket < res->number_buckets; bucket++) {
 317                 le = res->buckets[bucket];
 318                 if (le != NULL) {
 319                         /* Remove it from this hash bucket. */
 320                         if (le->next != NULL)
 321                                 le->next->previous = le->previous;
 322                         res->buckets[bucket] = le->next;
 323                         res->number_entries--;
 324                         /* Defer freeing this entry. */
 325                         res->spare = le;
 326                         return (le);
 327                 }
 328         }
 329         return (NULL);
 330 }
 331
 332 static struct links_entry *
 333 insert_entry(struct archive_entry_linkresolver *res,
 334     struct archive_entry *entry)
 335 {
 336         struct links_entry *le;
 337         int                      hash, bucket;
 338
 339         /* Add this entry to the links cache. */
 340         le = malloc(sizeof(struct links_entry));
 341         if (le == NULL)
 342                 return (NULL);
 343         memset(le, 0, sizeof(*le));
 344         le->canonical = archive_entry_clone(entry);
 345
 346         /* If the links cache is getting too full, enlarge the hash table. */
 347         if (res->number_entries > res->number_buckets * 2)
 348                 grow_hash(res);
 349
 350         hash = archive_entry_dev(entry) ^ archive_entry_ino(entry);
 351         bucket = hash % res->number_buckets;
 352
 353         /* If we could allocate the entry, record it. */
 354         if (res->buckets[bucket] != NULL)
 355                 res->buckets[bucket]->previous = le;
 356         res->number_entries++;
 357         le->next = res->buckets[bucket];
 358         le->previous = NULL;
 359         res->buckets[bucket] = le;
 360         le->hash = hash;
 361         le->links = archive_entry_nlink(entry) - 1;
 362         return (le);
 363 }
 364
 365 static void
 366 grow_hash(struct archive_entry_linkresolver *res)
 367 {
 368         struct links_entry *le, **new_buckets;
 369         size_t new_size;
 370         size_t i, bucket;
 371
 372         /* Try to enlarge the bucket list. */
 373         new_size = res->number_buckets * 2;
 374         new_buckets = malloc(new_size * sizeof(struct links_entry *));
 375
 376         if (new_buckets != NULL) {
 377                 memset(new_buckets, 0,
 378                     new_size * sizeof(struct links_entry *));
 379                 for (i = 0; i < res->number_buckets; i++) {
 380                         while (res->buckets[i] != NULL) {
 381                                 /* Remove entry from old bucket. */
 382                                 le = res->buckets[i];
 383                                 res->buckets[i] = le->next;
 384
 385                                 /* Add entry to new bucket. */
 386                                 bucket = le->hash % new_size;
 387
 388                                 if (new_buckets[bucket] != NULL)
 389                                         new_buckets[bucket]->previous =
 390                                             le;
 391                                 le->next = new_buckets[bucket];
 392                                 le->previous = NULL;
 393                                 new_buckets[bucket] = le;
 394                         }
 395                 }
 396                 free(res->buckets);
 397                 res->buckets = new_buckets;
 398                 res->number_buckets = new_size;
 399         }
 400 }