6f6822ed03a4e748185e8e816560ed9ea7a254ab
[wimlib] / src / dentry.c
1 /*
2  * dentry.c
3  *
4  * A dentry (directory entry) contains the metadata for a file.  In the WIM file
5  * format, the dentries are stored in the "metadata resource" section right
6  * after the security data.  Each image in the WIM file has its own metadata
7  * resource with its own security data and dentry tree.  Dentries in different
8  * images may share file resources by referring to the same lookup table
9  * entries.
10  *
11  * Copyright (C) 2010 Carl Thijssen
12  * Copyright (C) 2012 Eric Biggers
13  *
14  * wimlib - Library for working with WIM files 
15  *
16  * This library is free software; you can redistribute it and/or modify it under
17  * the terms of the GNU Lesser General Public License as published by the Free
18  * Software Foundation; either version 2.1 of the License, or (at your option) any
19  * later version.
20  *
21  * This library is distributed in the hope that it will be useful, but WITHOUT ANY
22  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
23  * PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
24  *
25  * You should have received a copy of the GNU Lesser General Public License along
26  * with this library; if not, write to the Free Software Foundation, Inc., 59
27  * Temple Place, Suite 330, Boston, MA 02111-1307 USA 
28  */
29
30 #include "wimlib_internal.h"
31 #include "dentry.h"
32 #include "io.h"
33 #include "timestamp.h"
34 #include "lookup_table.h"
35 #include <unistd.h>
36 #include <sys/stat.h>
37
38
39 /* Transfers file attributes from a `stat' buffer to a struct dentry. */
40 void stbuf_to_dentry(const struct stat *stbuf, struct dentry *dentry)
41 {
42         if (S_ISDIR(stbuf->st_mode))
43                 dentry->attributes = WIM_FILE_ATTRIBUTE_DIRECTORY;
44         else
45                 dentry->attributes = WIM_FILE_ATTRIBUTE_NORMAL;
46 }
47
48 /* Transfers file attributes from a struct dentry to a `stat' buffer. */
49 void dentry_to_stbuf(const struct dentry *dentry, struct stat *stbuf, 
50                      const struct lookup_table *table)
51 {
52         struct lookup_table_entry *lte;
53
54         if (dentry_is_directory(dentry))
55                 stbuf->st_mode = S_IFDIR | 0755;
56         else
57                 stbuf->st_mode = S_IFREG | 0644;
58
59         if (table)
60                 lte = lookup_resource(table, dentry->hash);
61         else
62                 lte = NULL;
63
64         if (lte) {
65                 stbuf->st_nlink = lte->refcnt;
66                 stbuf->st_size = lte->resource_entry.original_size;
67         } else {
68                 stbuf->st_nlink = 1;
69                 stbuf->st_size = 0;
70         }
71         stbuf->st_uid     = getuid();
72         stbuf->st_gid     = getgid();
73         stbuf->st_atime   = ms_timestamp_to_unix(dentry->last_access_time);
74         stbuf->st_mtime   = ms_timestamp_to_unix(dentry->last_write_time);
75         stbuf->st_ctime   = ms_timestamp_to_unix(dentry->creation_time);
76         stbuf->st_blocks  = (stbuf->st_size + 511) / 512;
77 }
78
79 /* Makes all timestamp fields for the dentry be the current time. */
80 void dentry_update_all_timestamps(struct dentry *dentry)
81 {
82         u64 now = get_timestamp();
83         dentry->creation_time       = now;
84         dentry->last_access_time    = now;
85         dentry->last_write_time     = now;
86 }
87
88 /* 
89  * Calls a function on all directory entries in a directory tree.  It is called
90  * on a parent before its children.
91  */
92 int for_dentry_in_tree(struct dentry *root, 
93                        int (*visitor)(struct dentry*, void*), void *arg)
94 {
95         int ret;
96         struct dentry *child;
97
98         ret = visitor(root, arg);
99
100         if (ret != 0)
101                 return ret;
102
103         child = root->children;
104
105         if (!child)
106                 return 0;
107
108         do {
109                 ret = for_dentry_in_tree(child, visitor, arg);
110                 if (ret != 0)
111                         return ret;
112                 child = child->next;
113         } while (child != root->children);
114         return 0;
115 }
116
117 /* 
118  * Like for_dentry_in_tree(), but the visitor function is always called on a
119  * dentry's children before on itself.
120  */
121 int for_dentry_in_tree_depth(struct dentry *root, 
122                              int (*visitor)(struct dentry*, void*), void *arg)
123 {
124         int ret;
125         struct dentry *child;
126         struct dentry *next;
127
128         child = root->children;
129         if (child) {
130                 do {
131                         next = child->next;
132                         ret = for_dentry_in_tree_depth(child, visitor, arg);
133                         if (ret != 0)
134                                 return ret;
135                         child = next;
136                 } while (child != root->children);
137         }
138         return visitor(root, arg);
139 }
140
141 /* 
142  * Calculate the full path of @dentry, based on its parent's full path and on
143  * its UTF-8 file name. 
144  */
145 int calculate_dentry_full_path(struct dentry *dentry, void *ignore)
146 {
147         int parent_len;
148         int len;
149         char *parent_full_path;
150         char *full_path;
151
152         FREE(dentry->full_path_utf8);
153
154         if (dentry_is_root(dentry)) {
155                 dentry->full_path_utf8 = MALLOC(2);
156                 if (!dentry->full_path_utf8) {
157                         ERROR("Out of memory!\n");
158                         return WIMLIB_ERR_NOMEM;
159                 }
160
161                 dentry->full_path_utf8[0] = '/';
162                 dentry->full_path_utf8[1] = '\0';
163                 dentry->full_path_utf8_len = 1;
164                 return 0;
165         }
166
167         if (dentry_is_root(dentry->parent)) {
168                 parent_len = 0;
169                 parent_full_path = "";
170         } else {
171                 parent_len = dentry->parent->full_path_utf8_len;
172                 parent_full_path = dentry->parent->full_path_utf8;
173         }
174
175         len = parent_len + 1 + dentry->file_name_utf8_len;
176         full_path = MALLOC(len + 1);
177         if (!full_path) {
178                 ERROR("Out of memory!\n");
179                 return WIMLIB_ERR_NOMEM;
180         }
181
182         memcpy(full_path, parent_full_path, parent_len);
183         full_path[parent_len] = '/';
184         memcpy(full_path + parent_len + 1, dentry->file_name_utf8, 
185                                 dentry->file_name_utf8_len);
186         full_path[len] = '\0';
187         dentry->full_path_utf8 = full_path;
188         dentry->full_path_utf8_len = len;
189         return 0;
190 }
191
192 /* 
193  * Recursively calculates the subdir offsets for a directory tree. 
194  *
195  * @dentry:  The root of the directory tree.
196  * @subdir_offset_p:  The current subdirectory offset; i.e., the subdirectory
197  *      offset for @dentry. 
198  */
199 void calculate_subdir_offsets(struct dentry *dentry, u64 *subdir_offset_p)
200 {
201         struct dentry *child;
202
203         child = dentry->children;
204         dentry->subdir_offset = *subdir_offset_p;
205         if (child) {
206
207                 /* Advance the subdir offset by the amount of space the children
208                  * of this dentry take up. */
209                 do {
210                         *subdir_offset_p += child->length;
211                         child = child->next;
212                 } while (child != dentry->children);
213
214                 /* End-of-directory dentry on disk. */
215                 *subdir_offset_p += 8;
216
217                 /* Recursively call calculate_subdir_offsets() on all the
218                  * children. */
219                 do {
220                         calculate_subdir_offsets(child, subdir_offset_p);
221                         child = child->next;
222                 } while (child != dentry->children);
223         } else {
224                 /* On disk, childless directories have a valid subdir_offset
225                  * that points to an 8-byte end-of-directory dentry.  Regular
226                  * files have a subdir_offset of 0. */
227                 if (dentry_is_directory(dentry))
228                         *subdir_offset_p += 8;
229                 else
230                         dentry->subdir_offset = 0;
231         }
232 }
233
234
235 /* Returns the child of @dentry that has the file name @name.  
236  * Returns NULL if no child has the name. */
237 struct dentry *get_dentry_child_with_name(const struct dentry *dentry, 
238                                                         const char *name)
239 {
240         struct dentry *child;
241         size_t name_len;
242         
243         child = dentry->children;
244         if (child) {
245                 name_len = strlen(name);
246                 do {
247                         if (dentry_has_name(child, name, name_len))
248                                 return child;
249                         child = child->next;
250                 } while (child != dentry->children);
251         }
252         return NULL;
253 }
254
255 /* Retrieves the dentry that has the UTF-8 @path relative to the dentry
256  * @cur_dir.  Returns NULL if no dentry having the path is found. */
257 static struct dentry *get_dentry_relative_path(struct dentry *cur_dir, const char *path)
258 {
259         struct dentry *child;
260         size_t base_len;
261         const char *new_path;
262
263         if (*path == '\0')
264                 return cur_dir;
265
266         child = cur_dir->children;
267         if (child) {
268                 new_path = path_next_part(path, &base_len);
269                 do {
270                         if (dentry_has_name(child, path, base_len))
271                                 return get_dentry_relative_path(child, new_path);
272                         child = child->next;
273                 } while (child != cur_dir->children);
274         }
275         return NULL;
276 }
277
278 /* Returns the dentry corresponding to the UTF-8 @path, or NULL if there is no
279  * such dentry. */
280 struct dentry *get_dentry(WIMStruct *w, const char *path)
281 {
282         struct dentry *root = wim_root_dentry(w);
283         while (*path == '/')
284                 path++;
285         return get_dentry_relative_path(root, path);
286 }
287
288 /* Returns the parent directory for the @path. */
289 struct dentry *get_parent_dentry(WIMStruct *w, const char *path)
290 {
291         size_t path_len = strlen(path);
292         char buf[path_len + 1];
293
294         memcpy(buf, path, path_len + 1);
295
296         to_parent_name(buf, path_len);
297
298         return get_dentry(w, buf);
299 }
300
301 /* Prints the full path of a dentry. */
302 int print_dentry_full_path(struct dentry *dentry, void *ignore)
303 {
304         if (dentry->full_path_utf8)
305                 puts(dentry->full_path_utf8);
306         return 0;
307 }
308
309 /* Prints a directory entry.  @lookup_table is a pointer to the lookup table, or
310  * NULL if the resource entry for the dentry is not to be printed. */
311 int print_dentry(struct dentry *dentry, void *lookup_table)
312 {
313         struct lookup_table_entry *lte;
314         printf("[DENTRY]\n");
315         printf("Length            = %"PRIu64"\n", dentry->length);
316         printf("Attributes        = 0x%x\n", dentry->attributes);
317 #ifdef ENABLE_SECURITY_DATA
318         printf("Security ID       = %d\n", dentry->security_id);
319 #endif
320         printf("Subdir offset     = %"PRIu64"\n", dentry->subdir_offset);
321         /*printf("Unused1           = %"PRIu64"\n", dentry->unused1);*/
322         /*printf("Unused2           = %"PRIu64"\n", dentry->unused2);*/
323         printf("Creation Time     = %"PRIu64"\n", dentry->creation_time);
324         printf("Last Access Time  = %"PRIu64"\n", dentry->last_access_time);
325         printf("Last Write Time   = %"PRIu64"\n", dentry->last_write_time);
326         printf("Creation Time     = 0x%"PRIx64"\n", dentry->creation_time);
327         printf("Hash              = "); 
328         print_hash(dentry->hash); 
329         putchar('\n');
330         /*printf("Reparse Tag       = %u\n", dentry->reparse_tag);*/
331         printf("Hard Link Group   = %"PRIu64"\n", dentry->hard_link);
332         /*printf("Number of Streams = %hu\n", dentry->streams);*/
333         printf("Filename          = \"");
334         print_string(dentry->file_name, dentry->file_name_len);
335         puts("\"");
336         printf("Filename Length   = %hu\n", dentry->file_name_len);
337         printf("Filename (UTF-8)  = \"%s\"\n", dentry->file_name_utf8);
338         printf("Filename (UTF-8) Length = %hu\n", dentry->file_name_utf8_len);
339         printf("Short Name        = \"");
340         print_string(dentry->short_name, dentry->short_name_len);
341         puts("\"");
342         printf("Short Name Length = %hu\n", dentry->short_name_len);
343         printf("Full Path (UTF-8) = \"%s\"\n", dentry->full_path_utf8);
344         if (lookup_table) {
345                 lte = lookup_resource(lookup_table, dentry->hash);
346                 if (lte)
347                         print_lookup_table_entry(lte, NULL);
348                 else
349                         putchar('\n');
350         } else {
351                 putchar('\n');
352         }
353         return 0;
354 }
355
356 static inline void dentry_common_init(struct dentry *dentry)
357 {
358         memset(dentry, 0, sizeof(struct dentry));
359         dentry->refcnt = 1;
360 #ifdef ENABLE_SECURITY_DATA
361         dentry->security_id = -1;
362 #endif
363 }
364
365 /* 
366  * Creates an unlinked directory entry.
367  *
368  * @name:    The base name of the new dentry.
369  * @return:  A pointer to the new dentry, or NULL if out of memory.
370  */
371 struct dentry *new_dentry(const char *name)
372 {
373         struct dentry *dentry;
374         
375         dentry = MALLOC(sizeof(struct dentry));
376         if (!dentry)
377                 return NULL;
378
379         dentry_common_init(dentry);
380         if (change_dentry_name(dentry, name) != 0) {
381                 FREE(dentry);
382                 return NULL;
383         }
384
385         dentry_update_all_timestamps(dentry);
386         dentry->next   = dentry;
387         dentry->prev   = dentry;
388         dentry->parent = dentry;
389         return dentry;
390 }
391
392
393 void free_dentry(struct dentry *dentry)
394 {
395         FREE(dentry->file_name);
396         FREE(dentry->file_name_utf8);
397         FREE(dentry->short_name);
398         FREE(dentry->full_path_utf8);
399         FREE(dentry);
400 }
401
402 /* Arguments for do_free_dentry(). */
403 struct free_dentry_args {
404         struct lookup_table *lookup_table;
405         bool decrement_refcnt;
406 };
407
408 /* 
409  * This function is passed as an argument to for_dentry_in_tree_depth() in order
410  * to free a directory tree.  __args is a pointer to a `struct free_dentry_args'.
411  */
412 static int do_free_dentry(struct dentry *dentry, void *__args)
413 {
414         struct free_dentry_args *args = (struct free_dentry_args*)__args;
415
416         if (args->decrement_refcnt && !dentry_is_directory(dentry)) {
417                 lookup_table_decrement_refcnt(args->lookup_table, 
418                                               dentry->hash);
419         }
420
421         wimlib_assert(dentry->refcnt >= 1);
422         if (--dentry->refcnt == 0)
423                 free_dentry(dentry);
424         return 0;
425 }
426
427 /* 
428  * Unlinks and frees a dentry tree.
429  *
430  * @root:               The root of the tree.
431  * @lookup_table:       The lookup table for dentries.
432  * @decrement_refcnt:   True if the dentries in the tree are to have their 
433  *                      reference counts in the lookup table decremented.
434  */
435 void free_dentry_tree(struct dentry *root, struct lookup_table *lookup_table, 
436                       bool decrement_refcnt)
437 {
438         if (!root || !root->parent)
439                 return;
440
441         struct free_dentry_args args;
442         args.lookup_table        = lookup_table;
443         args.decrement_refcnt    = decrement_refcnt;
444         for_dentry_in_tree_depth(root, do_free_dentry, &args);
445 }
446
447 int increment_dentry_refcnt(struct dentry *dentry, void *ignore)
448 {
449         dentry->refcnt++;
450         return 0;
451 }
452
453 /* 
454  * Links a dentry into the directory tree.
455  *
456  * @dentry: The dentry to link.
457  * @parent: The dentry that will be the parent of @dentry.
458  */
459 void link_dentry(struct dentry *dentry, struct dentry *parent)
460 {
461         dentry->parent = parent;
462         if (parent->children) {
463                 /* Not an only child; link to siblings. */
464                 dentry->next = parent->children;
465                 dentry->prev = parent->children->prev;
466                 dentry->next->prev = dentry;
467                 dentry->prev->next = dentry;
468         } else {
469                 /* Only child; link to parent. */
470                 parent->children = dentry;
471                 dentry->next = dentry;
472                 dentry->prev = dentry;
473         }
474 }
475
476 /* Unlink a dentry from the directory tree. */
477 void unlink_dentry(struct dentry *dentry)
478 {
479         if (dentry_is_root(dentry))
480                 return;
481         if (dentry_is_only_child(dentry)) {
482                 dentry->parent->children = NULL;
483         } else {
484                 if (dentry_is_first_sibling(dentry))
485                         dentry->parent->children = dentry->next;
486                 dentry->next->prev = dentry->prev;
487                 dentry->prev->next = dentry->next;
488         }
489 }
490
491
492 /* Recalculates the length of @dentry based on its file name length and short
493  * name length.  */
494 static inline void recalculate_dentry_size(struct dentry *dentry)
495 {
496         dentry->length = WIM_DENTRY_DISK_SIZE + dentry->file_name_len + 
497                          2 + dentry->short_name_len;
498         /* Must be multiple of 8. */
499         dentry->length += (8 - dentry->length % 8) % 8;
500 }
501
502 /* Changes the name of a dentry to @new_name.  Only changes the file_name and
503  * file_name_utf8 fields; does not change the short_name, short_name_utf8, or
504  * full_path_utf8 fields.  Also recalculates its length. */
505 int change_dentry_name(struct dentry *dentry, const char *new_name)
506 {
507         size_t utf8_len;
508         size_t utf16_len;
509
510         FREE(dentry->file_name);
511
512         utf8_len = strlen(new_name);
513
514         dentry->file_name = utf8_to_utf16(new_name, utf8_len, &utf16_len);
515
516         if (!dentry->file_name)
517                 return WIMLIB_ERR_NOMEM;
518
519         FREE(dentry->file_name_utf8);
520         dentry->file_name_utf8 = MALLOC(utf8_len + 1);
521         if (!dentry->file_name_utf8) {
522                 FREE(dentry->file_name);
523                 dentry->file_name = NULL;
524                 return WIMLIB_ERR_NOMEM;
525         }
526
527         dentry->file_name_len = utf16_len;
528         dentry->file_name_utf8_len = utf8_len;
529         memcpy(dentry->file_name_utf8, new_name, utf8_len + 1);
530         recalculate_dentry_size(dentry);
531         return 0;
532 }
533
534 /* Parameters for calculate_dentry_statistics(). */
535 struct image_statistics {
536         struct lookup_table *lookup_table;
537         u64 *dir_count;
538         u64 *file_count;
539         u64 *total_bytes;
540         u64 *hard_link_bytes;
541 };
542
543 static int calculate_dentry_statistics(struct dentry *dentry, void *arg)
544 {
545         struct image_statistics *stats;
546         struct lookup_table_entry *lte; 
547         
548         stats = arg;
549         lte = lookup_resource(stats->lookup_table, dentry->hash);
550
551         if (dentry_is_directory(dentry) && !dentry_is_root(dentry))
552                 ++*stats->dir_count;
553         else
554                 ++*stats->file_count;
555
556         if (lte) {
557                 u64 size = lte->resource_entry.original_size;
558                 *stats->total_bytes += size;
559                 if (++lte->out_refcnt == 1)
560                         *stats->hard_link_bytes += size;
561         }
562         return 0;
563 }
564
565 void calculate_dir_tree_statistics(struct dentry *root, struct lookup_table *table, 
566                                    u64 *dir_count_ret, u64 *file_count_ret, 
567                                    u64 *total_bytes_ret, 
568                                    u64 *hard_link_bytes_ret)
569 {
570         struct image_statistics stats;
571         *dir_count_ret         = 0;
572         *file_count_ret        = 0;
573         *total_bytes_ret       = 0;
574         *hard_link_bytes_ret   = 0;
575         stats.lookup_table     = table;
576         stats.dir_count       = dir_count_ret;
577         stats.file_count      = file_count_ret;
578         stats.total_bytes     = total_bytes_ret;
579         stats.hard_link_bytes = hard_link_bytes_ret;
580         for_lookup_table_entry(table, zero_out_refcnts, NULL);
581         for_dentry_in_tree(root, calculate_dentry_statistics, &stats);
582 }
583
584 /* 
585  * Reads a directory entry from the metadata resource.
586  */
587 int read_dentry(const u8 metadata_resource[], u64 metadata_resource_len, 
588                                         u64 offset, struct dentry *dentry)
589 {
590         const u8 *p;
591         u64 calculated_size;
592         char *file_name;
593         char *file_name_utf8;
594         char *short_name;
595         u16 short_name_len;
596         u16 file_name_len;
597         size_t file_name_utf8_len;
598
599         dentry_common_init(dentry);
600
601         /*Make sure the dentry really fits into the metadata resource.*/
602         if (offset + 8 > metadata_resource_len) {
603                 ERROR("Directory entry starting at %"PRIu64" ends past the "
604                         "end of the metadata resource (size %"PRIu64")!\n",
605                         offset, metadata_resource_len);
606                 return WIMLIB_ERR_INVALID_DENTRY;
607         }
608
609         /* Before reading the whole entry, we need to read just the length.
610          * This is because an entry of length 8 (that is, just the length field)
611          * terminates the list of sibling directory entries. */
612
613         p = get_u64(&metadata_resource[offset], &dentry->length);
614
615         /* A zero length field (really a length of 8, since that's how big the
616          * directory entry is...) indicates that this is the end of directory
617          * dentry.  We do not read it into memory as an actual dentry, so just
618          * return true in that case. */
619         if (dentry->length == 0)
620                 return 0;
621
622         if (offset + dentry->length >= metadata_resource_len) {
623                 ERROR("Directory entry at offset %"PRIu64" and with size "
624                                 "%"PRIu64" ends past the end of the metadata resource "
625                                 "(size %"PRIu64")!\n", offset, dentry->length,
626                                 metadata_resource_len);
627                 return WIMLIB_ERR_INVALID_DENTRY;
628         }
629
630         /* If it is a recognized length, read the rest of the directory entry.
631          * Note: The root directory entry has no name, and its length does not
632          * include the short name length field.  */
633         if (dentry->length < WIM_DENTRY_DISK_SIZE) {
634                 ERROR("Directory entry has invalid length of "
635                                 "%"PRIu64" bytes\n", dentry->length);
636                 return WIMLIB_ERR_INVALID_DENTRY;
637         }
638
639         p = get_u32(p, &dentry->attributes);
640 #ifdef ENABLE_SECURITY_DATA
641         p = get_u32(p, &dentry->security_id);
642 #else
643         p += sizeof(u32);
644 #endif
645         p = get_u64(p, &dentry->subdir_offset);
646
647         /* 2 unused fields */
648         p += 2 * sizeof(u64);
649
650         p = get_u64(p, &dentry->creation_time);
651         p = get_u64(p, &dentry->last_access_time);
652         p = get_u64(p, &dentry->last_write_time);
653
654         p = get_bytes(p, WIM_HASH_SIZE, dentry->hash);
655         
656         /* Currently ignoring reparse_tag. */
657         p += sizeof(u32);
658
659         /* The reparse_reserved field does not actually exist. */
660
661         p = get_u64(p, &dentry->hard_link);
662         
663         /* Currently ignoring streams. */
664         p += sizeof(u16);
665
666         p = get_u16(p, &short_name_len);
667         p = get_u16(p, &file_name_len);
668
669         calculated_size = WIM_DENTRY_DISK_SIZE + file_name_len + 2 +
670                           short_name_len;
671
672         if (dentry->length < calculated_size) {
673                 ERROR("Unexpected end of directory entry! (Expected "
674                                 "%"PRIu64" bytes, got %"PRIu64" bytes. "
675                                 "short_name_len = %hu, file_name_len = %hu)\n", 
676                                 calculated_size, dentry->length,
677                                 short_name_len, file_name_len);
678                 return WIMLIB_ERR_INVALID_DENTRY;
679         }
680
681         /* Read the filename. */
682         file_name = MALLOC(file_name_len);
683         if (!file_name) {
684                 ERROR("Failed to allocate %hu bytes for dentry file name!\n",
685                                 file_name_len);
686                 return WIMLIB_ERR_NOMEM;
687         }
688         p = get_bytes(p, file_name_len, file_name);
689
690         /* Convert filename to UTF-8. */
691         file_name_utf8 = utf16_to_utf8(file_name, file_name_len, 
692                                        &file_name_utf8_len);
693
694         if (!file_name_utf8) {
695                 ERROR("Failed to allocate memory to convert UTF16 "
696                                 "filename (%hu bytes) to UTF8\n",
697                                 file_name_len);
698                 goto err_nomem2;
699         }
700
701         /* Undocumented padding between file name and short name.  This probably
702          * is supposed to be a terminating NULL character. */
703         p += 2;
704
705         /* Read the short filename. */
706         short_name = MALLOC(short_name_len);
707         if (!short_name) {
708                 ERROR("Failed to allocate %hu bytes for short filename\n",
709                                 short_name_len);
710                 goto err_nomem1;
711         }
712
713         get_bytes(p, short_name_len, short_name);
714
715         dentry->file_name          = file_name;
716         dentry->file_name_utf8     = file_name_utf8;
717         dentry->short_name         = short_name;
718         dentry->file_name_len      = file_name_len;
719         dentry->file_name_utf8_len = file_name_utf8_len;
720         dentry->short_name_len     = short_name_len;
721         return 0;
722 err_nomem1:
723         FREE(dentry->file_name_utf8);
724 err_nomem2:
725         FREE(dentry->file_name);
726         return WIMLIB_ERR_NOMEM;
727 }
728
729 /* 
730  * Writes a dentry to an output buffer.
731  *
732  * @dentry:  The dentry structure.
733  * @p:       The memory location to write the data to.
734  * @return:  True on success, false on failure.
735  */
736 static u8 *write_dentry(const struct dentry *dentry, u8 *p)
737 {
738         u8 *orig_p = p;
739         memset(p, 0, dentry->length);
740         p = put_u64(p, dentry->length);
741         p = put_u32(p, dentry->attributes);
742 #ifdef ENABLE_SECURITY_DATA
743         p = put_u32(p, dentry->security_id);
744 #else
745         p = put_u32(p, (u32)(-1));
746 #endif
747         p = put_u64(p, dentry->subdir_offset);
748         p = put_u64(p, 0); /* unused1 */
749         p = put_u64(p, 0); /* unused2 */
750         p = put_u64(p, dentry->creation_time);
751         p = put_u64(p, dentry->last_access_time);
752         p = put_u64(p, dentry->last_write_time);
753         p = put_bytes(p, WIM_HASH_SIZE, dentry->hash);
754         p = put_u32(p, 0); /* reparse_tag */
755         p = put_u64(p, dentry->hard_link);
756         p = put_u16(p, 0); /*streams */
757         p = put_u16(p, dentry->short_name_len);
758         p = put_u16(p, dentry->file_name_len);
759         p = put_bytes(p, dentry->file_name_len, (u8*)dentry->file_name);
760         p = put_u16(p, 0); /* filename padding, 2 bytes. */
761         p = put_bytes(p, dentry->short_name_len, (u8*)dentry->short_name);
762         return orig_p + dentry->length;
763 }
764
765 /* Recursive function that writes a dentry tree rooted at @tree, not including
766  * @tree itself, which has already been written, except in the case of the root
767  * dentry, which is written right away, along with an end-of-directory entry. */
768 u8 *write_dentry_tree(const struct dentry *tree, u8 *p)
769 {
770         const struct dentry *child;
771
772         if (dentry_is_root(tree)) {
773                 p = write_dentry(tree, p);
774
775                 /* write end of directory entry */
776                 p = put_u64(p, 0);
777         } else {
778                 /* Nothing to do for a regular file. */
779                 if (dentry_is_regular_file(tree))
780                         return p;
781         }
782
783         /* Write child dentries and end-of-directory entry. */
784         child = tree->children;
785         if (child) {
786                 do {
787                         p = write_dentry(child, p);
788                         child = child->next;
789                 } while (child != tree->children);
790         }
791
792         /* write end of directory entry */
793         p = put_u64(p, 0);
794
795         /* Recurse on children. */
796         if (child) {
797                 do {
798                         p = write_dentry_tree(child, p);
799                         child = child->next;
800                 } while (child != tree->children);
801         }
802         return p;
803 }
804
805 /* Reads the children of a dentry, and all their children, ..., etc. from the
806  * metadata resource and into the dentry tree.
807  *
808  * @metadata_resource:  An array that contains the uncompressed metadata
809  *                              resource for the WIM file.
810  * @metadata_resource_len:      The length of @metadata_resource.
811  * @dentry:     A pointer to a struct dentry that is the root of the directory tree
812  *              and has already been read from the metadata resource.  It does not 
813  *              need to be the real root, because this procedure is called 
814  *              recursively.
815  * @return:     True on success, false on failure. 
816  */
817 int read_dentry_tree(const u8 metadata_resource[], u64 metadata_resource_len,
818                      struct dentry *dentry)
819 {
820         u64 cur_offset = dentry->subdir_offset;
821         struct dentry *prev_child = NULL;
822         struct dentry *first_child = NULL;
823         struct dentry *child;
824         struct dentry cur_child;
825         int ret;
826
827         /* If @dentry is a regular file, nothing more needs to be done for this
828          * branch. */
829         if (cur_offset == 0)
830                 return 0;
831
832         /* Find and read all the children of @dentry. */
833         while (1) {
834
835                 /* Read next child of @dentry into @cur_child. */
836                 ret = read_dentry(metadata_resource, metadata_resource_len, 
837                                   cur_offset, &cur_child);
838                 if (ret != 0)
839                         break;
840
841                 /* Check for end of directory. */
842                 if (cur_child.length == 0) {
843                         ret = 0;
844                         break;
845                 }
846
847                 /* Not end of directory.  Allocate this child permanently and
848                  * link it to the parent and previous child. */
849                 child = MALLOC(sizeof(struct dentry));
850                 if (!child) {
851                         ERROR("Failed to allocate %zu bytes for new dentry!\n",
852                                         sizeof(struct dentry));
853                         ret = WIMLIB_ERR_NOMEM;
854                         break;
855                 }
856                 memcpy(child, &cur_child, sizeof(struct dentry));
857
858                 if (prev_child) {
859                         prev_child->next = child;
860                         child->prev = prev_child;
861                 } else {
862                         first_child = child;
863                 }
864
865                 child->parent = dentry;
866                 prev_child = child;
867
868                 /* If there are children of this child, call this procedure
869                  * recursively. */
870                 if (child->subdir_offset != 0) {
871                         ret = read_dentry_tree(metadata_resource, 
872                                                metadata_resource_len, child);
873                         if (ret != 0)
874                                 break;
875                 }
876
877                 /* Advance to the offset of the next child. */
878                 cur_offset += child->length;
879         }
880
881         /* Link last child to first one, and set parent's
882          * children pointer to the first child.  */
883         if (prev_child) {
884                 prev_child->next = first_child;
885                 first_child->prev = prev_child;
886         }
887         dentry->children = first_child;
888         return ret;
889 }