archive_entry.h revision 228759
1/*- 2 * Copyright (c) 2003-2008 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 * $FreeBSD: head/lib/libarchive/archive_entry.h 201096 2009-12-28 02:41:27Z kientzle $ 26 */ 27 28#ifndef ARCHIVE_ENTRY_H_INCLUDED 29#define ARCHIVE_ENTRY_H_INCLUDED 30 31/* 32 * Note: archive_entry.h is for use outside of libarchive; the 33 * configuration headers (config.h, archive_platform.h, etc.) are 34 * purely internal. Do NOT use HAVE_XXX configuration macros to 35 * control the behavior of this header! If you must conditionalize, 36 * use predefined compiler and/or platform macros. 37 */ 38 39#include <sys/types.h> 40#include <stddef.h> /* for wchar_t */ 41#include <time.h> 42 43#if defined(_WIN32) && !defined(__CYGWIN__) 44#include <windows.h> 45#endif 46 47/* Get appropriate definitions of standard POSIX-style types. */ 48/* These should match the types used in 'struct stat' */ 49#if defined(_WIN32) && !defined(__CYGWIN__) 50#define __LA_INT64_T __int64 51# if defined(__BORLANDC__) 52# define __LA_UID_T uid_t 53# define __LA_GID_T gid_t 54# define __LA_DEV_T dev_t 55# define __LA_MODE_T mode_t 56# else 57# define __LA_UID_T short 58# define __LA_GID_T short 59# define __LA_DEV_T unsigned int 60# define __LA_MODE_T unsigned short 61# endif 62#else 63#include <unistd.h> 64#define __LA_INT64_T int64_t 65#define __LA_UID_T uid_t 66#define __LA_GID_T gid_t 67#define __LA_DEV_T dev_t 68#define __LA_MODE_T mode_t 69#endif 70 71/* 72 * XXX Is this defined for all Windows compilers? If so, in what 73 * header? It would be nice to remove the __LA_INO_T indirection and 74 * just use plain ino_t everywhere. Likewise for the other types just 75 * above. 76 */ 77#define __LA_INO_T ino_t 78 79 80/* 81 * On Windows, define LIBARCHIVE_STATIC if you're building or using a 82 * .lib. The default here assumes you're building a DLL. Only 83 * libarchive source should ever define __LIBARCHIVE_BUILD. 84 */ 85#if ((defined __WIN32__) || (defined _WIN32) || defined(__CYGWIN__)) && (!defined LIBARCHIVE_STATIC) 86# ifdef __LIBARCHIVE_BUILD 87# ifdef __GNUC__ 88# define __LA_DECL __attribute__((dllexport)) extern 89# else 90# define __LA_DECL __declspec(dllexport) 91# endif 92# else 93# ifdef __GNUC__ 94# define __LA_DECL __attribute__((dllimport)) extern 95# else 96# define __LA_DECL __declspec(dllimport) 97# endif 98# endif 99#else 100/* Static libraries on all platforms and shared libraries on non-Windows. */ 101# define __LA_DECL 102#endif 103 104#ifdef __cplusplus 105extern "C" { 106#endif 107 108/* 109 * Description of an archive entry. 110 * 111 * You can think of this as "struct stat" with some text fields added in. 112 * 113 * TODO: Add "comment", "charset", and possibly other entries that are 114 * supported by "pax interchange" format. However, GNU, ustar, cpio, 115 * and other variants don't support these features, so they're not an 116 * excruciatingly high priority right now. 117 * 118 * TODO: "pax interchange" format allows essentially arbitrary 119 * key/value attributes to be attached to any entry. Supporting 120 * such extensions may make this library useful for special 121 * applications (e.g., a package manager could attach special 122 * package-management attributes to each entry). 123 */ 124struct archive_entry; 125 126/* 127 * File-type constants. These are returned from archive_entry_filetype() 128 * and passed to archive_entry_set_filetype(). 129 * 130 * These values match S_XXX defines on every platform I've checked, 131 * including Windows, AIX, Linux, Solaris, and BSD. They're 132 * (re)defined here because platforms generally don't define the ones 133 * they don't support. For example, Windows doesn't define S_IFLNK or 134 * S_IFBLK. Instead of having a mass of conditional logic and system 135 * checks to define any S_XXX values that aren't supported locally, 136 * I've just defined a new set of such constants so that 137 * libarchive-based applications can manipulate and identify archive 138 * entries properly even if the hosting platform can't store them on 139 * disk. 140 * 141 * These values are also used directly within some portable formats, 142 * such as cpio. If you find a platform that varies from these, the 143 * correct solution is to leave these alone and translate from these 144 * portable values to platform-native values when entries are read from 145 * or written to disk. 146 */ 147#define AE_IFMT 0170000 148#define AE_IFREG 0100000 149#define AE_IFLNK 0120000 150#define AE_IFSOCK 0140000 151#define AE_IFCHR 0020000 152#define AE_IFBLK 0060000 153#define AE_IFDIR 0040000 154#define AE_IFIFO 0010000 155 156/* 157 * Basic object manipulation 158 */ 159 160__LA_DECL struct archive_entry *archive_entry_clear(struct archive_entry *); 161/* The 'clone' function does a deep copy; all of the strings are copied too. */ 162__LA_DECL struct archive_entry *archive_entry_clone(struct archive_entry *); 163__LA_DECL void archive_entry_free(struct archive_entry *); 164__LA_DECL struct archive_entry *archive_entry_new(void); 165 166/* 167 * Retrieve fields from an archive_entry. 168 * 169 * There are a number of implicit conversions among these fields. For 170 * example, if a regular string field is set and you read the _w wide 171 * character field, the entry will implicitly convert narrow-to-wide 172 * using the current locale. Similarly, dev values are automatically 173 * updated when you write devmajor or devminor and vice versa. 174 * 175 * In addition, fields can be "set" or "unset." Unset string fields 176 * return NULL, non-string fields have _is_set() functions to test 177 * whether they've been set. You can "unset" a string field by 178 * assigning NULL; non-string fields have _unset() functions to 179 * unset them. 180 * 181 * Note: There is one ambiguity in the above; string fields will 182 * also return NULL when implicit character set conversions fail. 183 * This is usually what you want. 184 */ 185__LA_DECL time_t archive_entry_atime(struct archive_entry *); 186__LA_DECL long archive_entry_atime_nsec(struct archive_entry *); 187__LA_DECL int archive_entry_atime_is_set(struct archive_entry *); 188__LA_DECL time_t archive_entry_birthtime(struct archive_entry *); 189__LA_DECL long archive_entry_birthtime_nsec(struct archive_entry *); 190__LA_DECL int archive_entry_birthtime_is_set(struct archive_entry *); 191__LA_DECL time_t archive_entry_ctime(struct archive_entry *); 192__LA_DECL long archive_entry_ctime_nsec(struct archive_entry *); 193__LA_DECL int archive_entry_ctime_is_set(struct archive_entry *); 194__LA_DECL dev_t archive_entry_dev(struct archive_entry *); 195__LA_DECL dev_t archive_entry_devmajor(struct archive_entry *); 196__LA_DECL dev_t archive_entry_devminor(struct archive_entry *); 197__LA_DECL __LA_MODE_T archive_entry_filetype(struct archive_entry *); 198__LA_DECL void archive_entry_fflags(struct archive_entry *, 199 unsigned long * /* set */, 200 unsigned long * /* clear */); 201__LA_DECL const char *archive_entry_fflags_text(struct archive_entry *); 202__LA_DECL __LA_GID_T archive_entry_gid(struct archive_entry *); 203__LA_DECL const char *archive_entry_gname(struct archive_entry *); 204__LA_DECL const wchar_t *archive_entry_gname_w(struct archive_entry *); 205__LA_DECL const char *archive_entry_hardlink(struct archive_entry *); 206__LA_DECL const wchar_t *archive_entry_hardlink_w(struct archive_entry *); 207__LA_DECL __LA_INO_T archive_entry_ino(struct archive_entry *); 208__LA_DECL __LA_INT64_T archive_entry_ino64(struct archive_entry *); 209__LA_DECL __LA_MODE_T archive_entry_mode(struct archive_entry *); 210__LA_DECL time_t archive_entry_mtime(struct archive_entry *); 211__LA_DECL long archive_entry_mtime_nsec(struct archive_entry *); 212__LA_DECL int archive_entry_mtime_is_set(struct archive_entry *); 213__LA_DECL unsigned int archive_entry_nlink(struct archive_entry *); 214__LA_DECL const char *archive_entry_pathname(struct archive_entry *); 215__LA_DECL const wchar_t *archive_entry_pathname_w(struct archive_entry *); 216__LA_DECL dev_t archive_entry_rdev(struct archive_entry *); 217__LA_DECL dev_t archive_entry_rdevmajor(struct archive_entry *); 218__LA_DECL dev_t archive_entry_rdevminor(struct archive_entry *); 219__LA_DECL const char *archive_entry_sourcepath(struct archive_entry *); 220__LA_DECL __LA_INT64_T archive_entry_size(struct archive_entry *); 221__LA_DECL int archive_entry_size_is_set(struct archive_entry *); 222__LA_DECL const char *archive_entry_strmode(struct archive_entry *); 223__LA_DECL const char *archive_entry_symlink(struct archive_entry *); 224__LA_DECL const wchar_t *archive_entry_symlink_w(struct archive_entry *); 225__LA_DECL __LA_UID_T archive_entry_uid(struct archive_entry *); 226__LA_DECL const char *archive_entry_uname(struct archive_entry *); 227__LA_DECL const wchar_t *archive_entry_uname_w(struct archive_entry *); 228 229/* 230 * Set fields in an archive_entry. 231 * 232 * Note that string 'set' functions do not copy the string, only the pointer. 233 * In contrast, 'copy' functions do copy the object pointed to. 234 * 235 * Note: As of libarchive 2.4, 'set' functions do copy the string and 236 * are therefore exact synonyms for the 'copy' versions. The 'copy' 237 * names will be retired in libarchive 3.0. 238 */ 239 240__LA_DECL void archive_entry_set_atime(struct archive_entry *, time_t, long); 241__LA_DECL void archive_entry_unset_atime(struct archive_entry *); 242#if defined(_WIN32) && !defined(__CYGWIN__) 243__LA_DECL void archive_entry_copy_bhfi(struct archive_entry *, 244 BY_HANDLE_FILE_INFORMATION *); 245#endif 246__LA_DECL void archive_entry_set_birthtime(struct archive_entry *, time_t, long); 247__LA_DECL void archive_entry_unset_birthtime(struct archive_entry *); 248__LA_DECL void archive_entry_set_ctime(struct archive_entry *, time_t, long); 249__LA_DECL void archive_entry_unset_ctime(struct archive_entry *); 250__LA_DECL void archive_entry_set_dev(struct archive_entry *, dev_t); 251__LA_DECL void archive_entry_set_devmajor(struct archive_entry *, dev_t); 252__LA_DECL void archive_entry_set_devminor(struct archive_entry *, dev_t); 253__LA_DECL void archive_entry_set_filetype(struct archive_entry *, unsigned int); 254__LA_DECL void archive_entry_set_fflags(struct archive_entry *, 255 unsigned long /* set */, unsigned long /* clear */); 256/* Returns pointer to start of first invalid token, or NULL if none. */ 257/* Note that all recognized tokens are processed, regardless. */ 258__LA_DECL const char *archive_entry_copy_fflags_text(struct archive_entry *, 259 const char *); 260__LA_DECL const wchar_t *archive_entry_copy_fflags_text_w(struct archive_entry *, 261 const wchar_t *); 262__LA_DECL void archive_entry_set_gid(struct archive_entry *, __LA_GID_T); 263__LA_DECL void archive_entry_set_gname(struct archive_entry *, const char *); 264__LA_DECL void archive_entry_copy_gname(struct archive_entry *, const char *); 265__LA_DECL void archive_entry_copy_gname_w(struct archive_entry *, const wchar_t *); 266__LA_DECL int archive_entry_update_gname_utf8(struct archive_entry *, const char *); 267__LA_DECL void archive_entry_set_hardlink(struct archive_entry *, const char *); 268__LA_DECL void archive_entry_copy_hardlink(struct archive_entry *, const char *); 269__LA_DECL void archive_entry_copy_hardlink_w(struct archive_entry *, const wchar_t *); 270__LA_DECL int archive_entry_update_hardlink_utf8(struct archive_entry *, const char *); 271#if ARCHIVE_VERSION_NUMBER >= 3000000 272/* Starting with libarchive 3.0, this will be synonym for ino64. */ 273__LA_DECL void archive_entry_set_ino(struct archive_entry *, __LA_INT64_T); 274#else 275__LA_DECL void archive_entry_set_ino(struct archive_entry *, unsigned long); 276#endif 277__LA_DECL void archive_entry_set_ino64(struct archive_entry *, __LA_INT64_T); 278__LA_DECL void archive_entry_set_link(struct archive_entry *, const char *); 279__LA_DECL void archive_entry_copy_link(struct archive_entry *, const char *); 280__LA_DECL void archive_entry_copy_link_w(struct archive_entry *, const wchar_t *); 281__LA_DECL int archive_entry_update_link_utf8(struct archive_entry *, const char *); 282__LA_DECL void archive_entry_set_mode(struct archive_entry *, __LA_MODE_T); 283__LA_DECL void archive_entry_set_mtime(struct archive_entry *, time_t, long); 284__LA_DECL void archive_entry_unset_mtime(struct archive_entry *); 285__LA_DECL void archive_entry_set_nlink(struct archive_entry *, unsigned int); 286__LA_DECL void archive_entry_set_pathname(struct archive_entry *, const char *); 287__LA_DECL void archive_entry_copy_pathname(struct archive_entry *, const char *); 288__LA_DECL void archive_entry_copy_pathname_w(struct archive_entry *, const wchar_t *); 289__LA_DECL int archive_entry_update_pathname_utf8(struct archive_entry *, const char *); 290__LA_DECL void archive_entry_set_perm(struct archive_entry *, __LA_MODE_T); 291__LA_DECL void archive_entry_set_rdev(struct archive_entry *, dev_t); 292__LA_DECL void archive_entry_set_rdevmajor(struct archive_entry *, dev_t); 293__LA_DECL void archive_entry_set_rdevminor(struct archive_entry *, dev_t); 294__LA_DECL void archive_entry_set_size(struct archive_entry *, __LA_INT64_T); 295__LA_DECL void archive_entry_unset_size(struct archive_entry *); 296__LA_DECL void archive_entry_copy_sourcepath(struct archive_entry *, const char *); 297__LA_DECL void archive_entry_set_symlink(struct archive_entry *, const char *); 298__LA_DECL void archive_entry_copy_symlink(struct archive_entry *, const char *); 299__LA_DECL void archive_entry_copy_symlink_w(struct archive_entry *, const wchar_t *); 300__LA_DECL int archive_entry_update_symlink_utf8(struct archive_entry *, const char *); 301__LA_DECL void archive_entry_set_uid(struct archive_entry *, __LA_UID_T); 302__LA_DECL void archive_entry_set_uname(struct archive_entry *, const char *); 303__LA_DECL void archive_entry_copy_uname(struct archive_entry *, const char *); 304__LA_DECL void archive_entry_copy_uname_w(struct archive_entry *, const wchar_t *); 305__LA_DECL int archive_entry_update_uname_utf8(struct archive_entry *, const char *); 306/* 307 * Routines to bulk copy fields to/from a platform-native "struct 308 * stat." Libarchive used to just store a struct stat inside of each 309 * archive_entry object, but this created issues when trying to 310 * manipulate archives on systems different than the ones they were 311 * created on. 312 * 313 * TODO: On Linux, provide both stat32 and stat64 versions of these functions. 314 */ 315__LA_DECL const struct stat *archive_entry_stat(struct archive_entry *); 316__LA_DECL void archive_entry_copy_stat(struct archive_entry *, const struct stat *); 317 318 319/* 320 * ACL routines. This used to simply store and return text-format ACL 321 * strings, but that proved insufficient for a number of reasons: 322 * = clients need control over uname/uid and gname/gid mappings 323 * = there are many different ACL text formats 324 * = would like to be able to read/convert archives containing ACLs 325 * on platforms that lack ACL libraries 326 * 327 * This last point, in particular, forces me to implement a reasonably 328 * complete set of ACL support routines. 329 * 330 * TODO: Extend this to support NFSv4/NTFS permissions. That should 331 * allow full ACL support on Mac OS, in particular, which uses 332 * POSIX.1e-style interfaces to manipulate NFSv4/NTFS permissions. 333 */ 334 335/* 336 * Permission bits mimic POSIX.1e. Note that I've not followed POSIX.1e's 337 * "permset"/"perm" abstract type nonsense. A permset is just a simple 338 * bitmap, following long-standing Unix tradition. 339 */ 340#define ARCHIVE_ENTRY_ACL_EXECUTE 1 341#define ARCHIVE_ENTRY_ACL_WRITE 2 342#define ARCHIVE_ENTRY_ACL_READ 4 343 344/* We need to be able to specify either or both of these. */ 345#define ARCHIVE_ENTRY_ACL_TYPE_ACCESS 256 346#define ARCHIVE_ENTRY_ACL_TYPE_DEFAULT 512 347 348/* Tag values mimic POSIX.1e */ 349#define ARCHIVE_ENTRY_ACL_USER 10001 /* Specified user. */ 350#define ARCHIVE_ENTRY_ACL_USER_OBJ 10002 /* User who owns the file. */ 351#define ARCHIVE_ENTRY_ACL_GROUP 10003 /* Specified group. */ 352#define ARCHIVE_ENTRY_ACL_GROUP_OBJ 10004 /* Group who owns the file. */ 353#define ARCHIVE_ENTRY_ACL_MASK 10005 /* Modify group access. */ 354#define ARCHIVE_ENTRY_ACL_OTHER 10006 /* Public. */ 355 356/* 357 * Set the ACL by clearing it and adding entries one at a time. 358 * Unlike the POSIX.1e ACL routines, you must specify the type 359 * (access/default) for each entry. Internally, the ACL data is just 360 * a soup of entries. API calls here allow you to retrieve just the 361 * entries of interest. This design (which goes against the spirit of 362 * POSIX.1e) is useful for handling archive formats that combine 363 * default and access information in a single ACL list. 364 */ 365__LA_DECL void archive_entry_acl_clear(struct archive_entry *); 366__LA_DECL void archive_entry_acl_add_entry(struct archive_entry *, 367 int /* type */, int /* permset */, int /* tag */, 368 int /* qual */, const char * /* name */); 369__LA_DECL void archive_entry_acl_add_entry_w(struct archive_entry *, 370 int /* type */, int /* permset */, int /* tag */, 371 int /* qual */, const wchar_t * /* name */); 372 373/* 374 * To retrieve the ACL, first "reset", then repeatedly ask for the 375 * "next" entry. The want_type parameter allows you to request only 376 * access entries or only default entries. 377 */ 378__LA_DECL int archive_entry_acl_reset(struct archive_entry *, int /* want_type */); 379__LA_DECL int archive_entry_acl_next(struct archive_entry *, int /* want_type */, 380 int * /* type */, int * /* permset */, int * /* tag */, 381 int * /* qual */, const char ** /* name */); 382__LA_DECL int archive_entry_acl_next_w(struct archive_entry *, int /* want_type */, 383 int * /* type */, int * /* permset */, int * /* tag */, 384 int * /* qual */, const wchar_t ** /* name */); 385 386/* 387 * Construct a text-format ACL. The flags argument is a bitmask that 388 * can include any of the following: 389 * 390 * ARCHIVE_ENTRY_ACL_TYPE_ACCESS - Include access entries. 391 * ARCHIVE_ENTRY_ACL_TYPE_DEFAULT - Include default entries. 392 * ARCHIVE_ENTRY_ACL_STYLE_EXTRA_ID - Include extra numeric ID field in 393 * each ACL entry. (As used by 'star'.) 394 * ARCHIVE_ENTRY_ACL_STYLE_MARK_DEFAULT - Include "default:" before each 395 * default ACL entry. 396 */ 397#define ARCHIVE_ENTRY_ACL_STYLE_EXTRA_ID 1024 398#define ARCHIVE_ENTRY_ACL_STYLE_MARK_DEFAULT 2048 399__LA_DECL const wchar_t *archive_entry_acl_text_w(struct archive_entry *, 400 int /* flags */); 401 402/* Return a count of entries matching 'want_type' */ 403__LA_DECL int archive_entry_acl_count(struct archive_entry *, int /* want_type */); 404 405/* 406 * Private ACL parser. This is private because it handles some 407 * very weird formats that clients should not be messing with. 408 * Clients should only deal with their platform-native formats. 409 * Because of the need to support many formats cleanly, new arguments 410 * are likely to get added on a regular basis. Clients who try to use 411 * this interface are likely to be surprised when it changes. 412 * 413 * You were warned! 414 * 415 * TODO: Move this declaration out of the public header and into 416 * a private header. Warnings above are silly. 417 */ 418__LA_DECL int __archive_entry_acl_parse_w(struct archive_entry *, 419 const wchar_t *, int /* type */); 420 421/* 422 * extended attributes 423 */ 424 425__LA_DECL void archive_entry_xattr_clear(struct archive_entry *); 426__LA_DECL void archive_entry_xattr_add_entry(struct archive_entry *, 427 const char * /* name */, const void * /* value */, 428 size_t /* size */); 429 430/* 431 * To retrieve the xattr list, first "reset", then repeatedly ask for the 432 * "next" entry. 433 */ 434 435__LA_DECL int archive_entry_xattr_count(struct archive_entry *); 436__LA_DECL int archive_entry_xattr_reset(struct archive_entry *); 437__LA_DECL int archive_entry_xattr_next(struct archive_entry *, 438 const char ** /* name */, const void ** /* value */, size_t *); 439 440/* 441 * Utility to match up hardlinks. 442 * 443 * The 'struct archive_entry_linkresolver' is a cache of archive entries 444 * for files with multiple links. Here's how to use it: 445 * 1. Create a lookup object with archive_entry_linkresolver_new() 446 * 2. Tell it the archive format you're using. 447 * 3. Hand each archive_entry to archive_entry_linkify(). 448 * That function will return 0, 1, or 2 entries that should 449 * be written. 450 * 4. Call archive_entry_linkify(resolver, NULL) until 451 * no more entries are returned. 452 * 5. Call archive_entry_link_resolver_free(resolver) to free resources. 453 * 454 * The entries returned have their hardlink and size fields updated 455 * appropriately. If an entry is passed in that does not refer to 456 * a file with multiple links, it is returned unchanged. The intention 457 * is that you should be able to simply filter all entries through 458 * this machine. 459 * 460 * To make things more efficient, be sure that each entry has a valid 461 * nlinks value. The hardlink cache uses this to track when all links 462 * have been found. If the nlinks value is zero, it will keep every 463 * name in the cache indefinitely, which can use a lot of memory. 464 * 465 * Note that archive_entry_size() is reset to zero if the file 466 * body should not be written to the archive. Pay attention! 467 */ 468struct archive_entry_linkresolver; 469 470/* 471 * There are three different strategies for marking hardlinks. 472 * The descriptions below name them after the best-known 473 * formats that rely on each strategy: 474 * 475 * "Old cpio" is the simplest, it always returns any entry unmodified. 476 * As far as I know, only cpio formats use this. Old cpio archives 477 * store every link with the full body; the onus is on the dearchiver 478 * to detect and properly link the files as they are restored. 479 * "tar" is also pretty simple; it caches a copy the first time it sees 480 * any link. Subsequent appearances are modified to be hardlink 481 * references to the first one without any body. Used by all tar 482 * formats, although the newest tar formats permit the "old cpio" strategy 483 * as well. This strategy is very simple for the dearchiver, 484 * and reasonably straightforward for the archiver. 485 * "new cpio" is trickier. It stores the body only with the last 486 * occurrence. The complication is that we might not 487 * see every link to a particular file in a single session, so 488 * there's no easy way to know when we've seen the last occurrence. 489 * The solution here is to queue one link until we see the next. 490 * At the end of the session, you can enumerate any remaining 491 * entries by calling archive_entry_linkify(NULL) and store those 492 * bodies. If you have a file with three links l1, l2, and l3, 493 * you'll get the following behavior if you see all three links: 494 * linkify(l1) => NULL (the resolver stores l1 internally) 495 * linkify(l2) => l1 (resolver stores l2, you write l1) 496 * linkify(l3) => l2, l3 (all links seen, you can write both). 497 * If you only see l1 and l2, you'll get this behavior: 498 * linkify(l1) => NULL 499 * linkify(l2) => l1 500 * linkify(NULL) => l2 (at end, you retrieve remaining links) 501 * As the name suggests, this strategy is used by newer cpio variants. 502 * It's noticably more complex for the archiver, slightly more complex 503 * for the dearchiver than the tar strategy, but makes it straightforward 504 * to restore a file using any link by simply continuing to scan until 505 * you see a link that is stored with a body. In contrast, the tar 506 * strategy requires you to rescan the archive from the beginning to 507 * correctly extract an arbitrary link. 508 */ 509 510__LA_DECL struct archive_entry_linkresolver *archive_entry_linkresolver_new(void); 511__LA_DECL void archive_entry_linkresolver_set_strategy( 512 struct archive_entry_linkresolver *, int /* format_code */); 513__LA_DECL void archive_entry_linkresolver_free(struct archive_entry_linkresolver *); 514__LA_DECL void archive_entry_linkify(struct archive_entry_linkresolver *, 515 struct archive_entry **, struct archive_entry **); 516 517#ifdef __cplusplus 518} 519#endif 520 521/* This is meaningless outside of this header. */ 522#undef __LA_DECL 523 524#endif /* !ARCHIVE_ENTRY_H_INCLUDED */ 525