1dd35e52c047f14316ac223ee529ce39ba3def3c
[wimlib] / src / write.c
1 /*
2  * write.c
3  *
4  * Support for writing WIM files; write a WIM file, overwrite a WIM file, write
5  * compressed file resources, etc.
6  */
7
8 /*
9  * Copyright (C) 2012, 2013 Eric Biggers
10  *
11  * This file is part of wimlib, a library for working with WIM files.
12  *
13  * wimlib is free software; you can redistribute it and/or modify it under the
14  * terms of the GNU General Public License as published by the Free
15  * Software Foundation; either version 3 of the License, or (at your option)
16  * any later version.
17  *
18  * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
19  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
20  * A PARTICULAR PURPOSE. See the GNU General Public License for more
21  * details.
22  *
23  * You should have received a copy of the GNU General Public License
24  * along with wimlib; if not, see http://www.gnu.org/licenses/.
25  */
26
27 #include "config.h"
28
29 #if defined(HAVE_SYS_FILE_H) && defined(HAVE_FLOCK)
30 /* On BSD, this should be included before "list.h" so that "list.h" can
31  * overwrite the LIST_HEAD macro. */
32 #  include <sys/file.h>
33 #endif
34
35 #ifdef __WIN32__
36 #  include "win32.h"
37 #endif
38
39 #include "list.h"
40 #include "wimlib_internal.h"
41 #include "buffer_io.h"
42 #include "dentry.h"
43 #include "lookup_table.h"
44 #include "xml.h"
45
46 #ifdef ENABLE_MULTITHREADED_COMPRESSION
47 #  include <pthread.h>
48 #endif
49
50 #include <unistd.h>
51 #include <fcntl.h>
52 #include <errno.h>
53
54 #ifdef WITH_NTFS_3G
55 #  include <time.h>
56 #  include <ntfs-3g/attrib.h>
57 #  include <ntfs-3g/inode.h>
58 #  include <ntfs-3g/dir.h>
59 #endif
60
61 #ifdef HAVE_ALLOCA_H
62 #  include <alloca.h>
63 #else
64 #  include <stdlib.h>
65 #endif
66
67 #include <limits.h>
68
69 #ifndef __WIN32__
70 #  include <sys/uio.h> /* for `struct iovec' */
71 #endif
72
73 /* Chunk table that's located at the beginning of each compressed resource in
74  * the WIM.  (This is not the on-disk format; the on-disk format just has an
75  * array of offsets.) */
76 struct chunk_table {
77         off_t file_offset;
78         u64 num_chunks;
79         u64 original_resource_size;
80         u64 bytes_per_chunk_entry;
81         u64 table_disk_size;
82         u64 cur_offset;
83         u64 *cur_offset_p;
84         u64 offsets[0];
85 };
86
87 /*
88  * Allocates and initializes a chunk table, and reserves space for it in the
89  * output file.
90  */
91 static int
92 begin_wim_resource_chunk_tab(const struct wim_lookup_table_entry *lte,
93                              int out_fd,
94                              off_t file_offset,
95                              struct chunk_table **chunk_tab_ret)
96 {
97         u64 size = wim_resource_size(lte);
98         u64 num_chunks = (size + WIM_CHUNK_SIZE - 1) / WIM_CHUNK_SIZE;
99         size_t alloc_size = sizeof(struct chunk_table) + num_chunks * sizeof(u64);
100         struct chunk_table *chunk_tab = CALLOC(1, alloc_size);
101
102         DEBUG("Begin chunk table for stream with size %"PRIu64, size);
103
104         if (!chunk_tab) {
105                 ERROR("Failed to allocate chunk table for %"PRIu64" byte "
106                       "resource", size);
107                 return WIMLIB_ERR_NOMEM;
108         }
109         chunk_tab->file_offset = file_offset;
110         chunk_tab->num_chunks = num_chunks;
111         chunk_tab->original_resource_size = size;
112         chunk_tab->bytes_per_chunk_entry = (size >= (1ULL << 32)) ? 8 : 4;
113         chunk_tab->table_disk_size = chunk_tab->bytes_per_chunk_entry *
114                                      (num_chunks - 1);
115         chunk_tab->cur_offset = 0;
116         chunk_tab->cur_offset_p = chunk_tab->offsets;
117
118         if (full_write(out_fd, chunk_tab,
119                        chunk_tab->table_disk_size) != chunk_tab->table_disk_size)
120         {
121                 ERROR_WITH_ERRNO("Failed to write chunk table in compressed "
122                                  "file resource");
123                 FREE(chunk_tab);
124                 return WIMLIB_ERR_WRITE;
125         }
126         *chunk_tab_ret = chunk_tab;
127         return 0;
128 }
129
130 /*
131  * compress_func_t- Pointer to a function to compresses a chunk
132  *                  of a WIM resource.  This may be either
133  *                  wimlib_xpress_compress() (xpress-compress.c) or
134  *                  wimlib_lzx_compress() (lzx-compress.c).
135  *
136  * @chunk:        Uncompressed data of the chunk.
137  * @chunk_size:   Size of the uncompressed chunk, in bytes.
138  * @out:          Pointer to output buffer of size at least (@chunk_size - 1) bytes.
139  *
140  * Returns the size of the compressed data written to @out in bytes, or 0 if the
141  * data could not be compressed to (@chunk_size - 1) bytes or fewer.
142  *
143  * As a special requirement, the compression code is optimized for the WIM
144  * format and therefore requires (@chunk_size <= 32768).
145  *
146  * As another special requirement, the compression code will read up to 8 bytes
147  * off the end of the @chunk array for performance reasons.  The values of these
148  * bytes will not affect the output of the compression, but the calling code
149  * must make sure that the buffer holding the uncompressed chunk is actually at
150  * least (@chunk_size + 8) bytes, or at least that these extra bytes are in
151  * mapped memory that will not cause a memory access violation if accessed.
152  */
153 typedef unsigned (*compress_func_t)(const void *chunk, unsigned chunk_size,
154                                     void *out);
155
156 static compress_func_t
157 get_compress_func(int out_ctype)
158 {
159         if (out_ctype == WIMLIB_COMPRESSION_TYPE_LZX)
160                 return wimlib_lzx_compress;
161         else
162                 return wimlib_xpress_compress;
163 }
164
165 /*
166  * Writes a chunk of a WIM resource to an output file.
167  *
168  * @chunk:        Uncompressed data of the chunk.
169  * @chunk_size:   Size of the chunk (<= WIM_CHUNK_SIZE)
170  * @out_fd:       File descriptor to write the chunk to.
171  * @compress:     Compression function to use (NULL if writing uncompressed
172  *                      data).
173  * @chunk_tab:    Pointer to chunk table being created.  It is updated with the
174  *                      offset of the chunk we write.
175  *
176  * Returns 0 on success; nonzero on failure.
177  */
178 static int
179 write_wim_resource_chunk(const void * restrict chunk,
180                          unsigned chunk_size,
181                          filedes_t out_fd,
182                          compress_func_t compress,
183                          struct chunk_table * restrict chunk_tab)
184 {
185         const void *out_chunk;
186         unsigned out_chunk_size;
187         if (compress) {
188                 void *compressed_chunk = alloca(chunk_size);
189
190                 out_chunk_size = (*compress)(chunk, chunk_size, compressed_chunk);
191                 if (out_chunk_size) {
192                         /* Write compressed */
193                         out_chunk = compressed_chunk;
194                 } else {
195                         /* Write uncompressed */
196                         out_chunk = chunk;
197                         out_chunk_size = chunk_size;
198                 }
199                 *chunk_tab->cur_offset_p++ = chunk_tab->cur_offset;
200                 chunk_tab->cur_offset += out_chunk_size;
201         } else {
202                 /* Write uncompressed */
203                 out_chunk = chunk;
204                 out_chunk_size = chunk_size;
205         }
206         if (full_write(out_fd, out_chunk, out_chunk_size) != out_chunk_size) {
207                 ERROR_WITH_ERRNO("Failed to write WIM resource chunk");
208                 return WIMLIB_ERR_WRITE;
209         }
210         return 0;
211 }
212
213 /*
214  * Finishes a WIM chunk table and writes it to the output file at the correct
215  * offset.
216  *
217  * The final size of the full compressed resource is returned in the
218  * @compressed_size_p.
219  */
220 static int
221 finish_wim_resource_chunk_tab(struct chunk_table *chunk_tab,
222                               filedes_t out_fd, u64 *compressed_size_p)
223 {
224         size_t bytes_written;
225
226         if (chunk_tab->bytes_per_chunk_entry == 8) {
227                 array_cpu_to_le64(chunk_tab->offsets, chunk_tab->num_chunks);
228         } else {
229                 for (u64 i = 0; i < chunk_tab->num_chunks; i++)
230                         ((u32*)chunk_tab->offsets)[i] =
231                                 cpu_to_le32(chunk_tab->offsets[i]);
232         }
233         bytes_written = full_pwrite(out_fd,
234                                     (u8*)chunk_tab->offsets + chunk_tab->bytes_per_chunk_entry,
235                                     chunk_tab->table_disk_size,
236                                     chunk_tab->file_offset);
237         if (bytes_written != chunk_tab->table_disk_size) {
238                 ERROR_WITH_ERRNO("Failed to write chunk table in compressed "
239                                  "file resource");
240                 return WIMLIB_ERR_WRITE;
241         }
242         *compressed_size_p = chunk_tab->cur_offset + chunk_tab->table_disk_size;
243         return 0;
244 }
245
246 static int
247 seek_and_truncate(filedes_t out_fd, off_t offset)
248 {
249         if (lseek(out_fd, offset, SEEK_SET) == -1 ||
250             ftruncate(out_fd, offset))
251         {
252                 ERROR_WITH_ERRNO("Failed to truncate output WIM file");
253                 return WIMLIB_ERR_WRITE;
254         } else {
255                 return 0;
256         }
257 }
258
259 static int
260 finalize_and_check_sha1(SHA_CTX * restrict sha_ctx,
261                         struct wim_lookup_table_entry * restrict lte)
262 {
263         u8 md[SHA1_HASH_SIZE];
264         sha1_final(md, sha_ctx);
265         if (lte->unhashed) {
266                 copy_hash(lte->hash, md);
267         } else if (!hashes_equal(md, lte->hash)) {
268                 ERROR("WIM resource has incorrect hash!");
269                 if (lte_filename_valid(lte)) {
270                         ERROR("We were reading it from \"%"TS"\"; maybe "
271                               "it changed while we were reading it.",
272                               lte->file_on_disk);
273                 }
274                 return WIMLIB_ERR_INVALID_RESOURCE_HASH;
275         }
276         return 0;
277 }
278
279
280 struct write_resource_ctx {
281         compress_func_t compress;
282         struct chunk_table *chunk_tab;
283         filedes_t out_fd;
284         SHA_CTX sha_ctx;
285         bool doing_sha;
286 };
287
288 static int
289 write_resource_cb(const void *restrict chunk, size_t chunk_size,
290                   void *restrict _ctx)
291 {
292         struct write_resource_ctx *ctx = _ctx;
293
294         if (ctx->doing_sha)
295                 sha1_update(&ctx->sha_ctx, chunk, chunk_size);
296         return write_wim_resource_chunk(chunk, chunk_size,
297                                         ctx->out_fd, ctx->compress,
298                                         ctx->chunk_tab);
299 }
300
301 /*
302  * Write a resource to an output WIM.
303  *
304  * @lte:  Lookup table entry for the resource, which could be in another WIM,
305  *        in an external file, or in another location.
306  *
307  * @out_fd:  File descriptor opened to the output WIM.
308  *
309  * @out_ctype:  One of the WIMLIB_COMPRESSION_TYPE_* constants to indicate
310  *              which compression algorithm to use.
311  *
312  * @out_res_entry:  On success, this is filled in with the offset, flags,
313  *                  compressed size, and uncompressed size of the resource
314  *                  in the output WIM.
315  *
316  * @flags:  WIMLIB_RESOURCE_FLAG_RECOMPRESS to force data to be recompressed
317  *          even if it could otherwise be copied directly from the input.
318  *
319  * Additional notes:  The SHA1 message digest of the uncompressed data is
320  * calculated (except when doing a raw copy --- see below).  If the @unhashed
321  * flag is set on the lookup table entry, this message digest is simply copied
322  * to it; otherwise, the message digest is compared with the existing one, and
323  * the function will fail if they do not match.
324  */
325 int
326 write_wim_resource(struct wim_lookup_table_entry *lte,
327                    filedes_t out_fd, int out_ctype,
328                    struct resource_entry *out_res_entry,
329                    int flags)
330 {
331         struct write_resource_ctx write_ctx;
332         u64 read_size;
333         u64 new_size;
334         off_t offset;
335         int ret;
336
337         flags &= ~WIMLIB_RESOURCE_FLAG_RECOMPRESS;
338
339         /* Get current position in output WIM */
340         offset = filedes_offset(out_fd);
341         if (offset == -1) {
342                 ERROR_WITH_ERRNO("Can't get position in output WIM");
343                 return WIMLIB_ERR_WRITE;
344         }
345
346         /* If we are not forcing the data to be recompressed, and the input
347          * resource is located in a WIM with the same compression type as that
348          * desired other than no compression, we can simply copy the compressed
349          * data without recompressing it.  This also means we must skip
350          * calculating the SHA1, as we never will see the uncompressed data. */
351         if (!(flags & WIMLIB_RESOURCE_FLAG_RECOMPRESS) &&
352             lte->resource_location == RESOURCE_IN_WIM &&
353             out_ctype != WIMLIB_COMPRESSION_TYPE_NONE &&
354             wimlib_get_compression_type(lte->wim) == out_ctype)
355         {
356                 flags |= WIMLIB_RESOURCE_FLAG_RAW;
357                 write_ctx.doing_sha = false;
358                 read_size = lte->resource_entry.size;
359         } else {
360                 write_ctx.doing_sha = true;
361                 sha1_init(&write_ctx.sha_ctx);
362                 read_size = lte->resource_entry.original_size;
363         }
364
365         /* Initialize the chunk table and set the compression function if
366          * compressing the resource. */
367         if (out_ctype == WIMLIB_COMPRESSION_TYPE_NONE ||
368             (flags & WIMLIB_RESOURCE_FLAG_RAW)) {
369                 write_ctx.compress = NULL;
370                 write_ctx.chunk_tab = NULL;
371         } else {
372                 write_ctx.compress = get_compress_func(out_ctype);
373                 ret = begin_wim_resource_chunk_tab(lte, out_fd,
374                                                    offset,
375                                                    &write_ctx.chunk_tab);
376                 if (ret)
377                         return ret;
378         }
379
380         /* Write the entire resource by reading the entire resource and feeding
381          * the data through the write_resource_cb function. */
382         write_ctx.out_fd = out_fd;
383 try_write_again:
384         ret = read_resource_prefix(lte, read_size,
385                                    write_resource_cb, &write_ctx, flags);
386         if (ret)
387                 goto out_free_chunk_tab;
388
389         /* Verify SHA1 message digest of the resource, or set the hash for the
390          * first time. */
391         if (write_ctx.doing_sha) {
392                 ret = finalize_and_check_sha1(&write_ctx.sha_ctx, lte);
393                 if (ret)
394                         goto out_free_chunk_tab;
395         }
396
397         out_res_entry->flags = lte->resource_entry.flags;
398         out_res_entry->original_size = wim_resource_size(lte);
399         out_res_entry->offset = offset;
400         if (flags & WIMLIB_RESOURCE_FLAG_RAW) {
401                 /* Doing a raw write:  The new compressed size is the same as
402                  * the compressed size in the other WIM. */
403                 new_size = lte->resource_entry.size;
404         } else if (out_ctype == WIMLIB_COMPRESSION_TYPE_NONE) {
405                 /* Using WIMLIB_COMPRESSION_TYPE_NONE:  The new compressed size
406                  * is the original size. */
407                 new_size = lte->resource_entry.original_size;
408                 out_res_entry->flags &= ~WIM_RESHDR_FLAG_COMPRESSED;
409         } else {
410                 /* Using a different compression type:  Call
411                  * finish_wim_resource_chunk_tab() and it will provide the new
412                  * compressed size. */
413                 ret = finish_wim_resource_chunk_tab(write_ctx.chunk_tab, out_fd,
414                                                     &new_size);
415                 if (ret)
416                         goto out_free_chunk_tab;
417                 if (new_size >= wim_resource_size(lte)) {
418                         /* Oops!  We compressed the resource to larger than the original
419                          * size.  Write the resource uncompressed instead. */
420                         DEBUG("Compressed %"PRIu64" => %"PRIu64" bytes; "
421                               "writing uncompressed instead",
422                               wim_resource_size(lte), new_size);
423                         ret = seek_and_truncate(out_fd, offset);
424                         if (ret)
425                                 goto out_free_chunk_tab;
426                         write_ctx.compress = NULL;
427                         write_ctx.doing_sha = false;
428                         out_ctype = WIMLIB_COMPRESSION_TYPE_NONE;
429                         goto try_write_again;
430                 }
431                 out_res_entry->flags |= WIM_RESHDR_FLAG_COMPRESSED;
432         }
433         out_res_entry->size = new_size;
434         ret = 0;
435 out_free_chunk_tab:
436         FREE(write_ctx.chunk_tab);
437         return ret;
438 }
439
440 #ifdef ENABLE_MULTITHREADED_COMPRESSION
441
442 /* Blocking shared queue (solves the producer-consumer problem) */
443 struct shared_queue {
444         unsigned size;
445         unsigned front;
446         unsigned back;
447         unsigned filled_slots;
448         void **array;
449         pthread_mutex_t lock;
450         pthread_cond_t msg_avail_cond;
451         pthread_cond_t space_avail_cond;
452 };
453
454 static int
455 shared_queue_init(struct shared_queue *q, unsigned size)
456 {
457         wimlib_assert(size != 0);
458         q->array = CALLOC(sizeof(q->array[0]), size);
459         if (!q->array)
460                 goto err;
461         q->filled_slots = 0;
462         q->front = 0;
463         q->back = size - 1;
464         q->size = size;
465         if (pthread_mutex_init(&q->lock, NULL)) {
466                 ERROR_WITH_ERRNO("Failed to initialize mutex");
467                 goto err;
468         }
469         if (pthread_cond_init(&q->msg_avail_cond, NULL)) {
470                 ERROR_WITH_ERRNO("Failed to initialize condition variable");
471                 goto err_destroy_lock;
472         }
473         if (pthread_cond_init(&q->space_avail_cond, NULL)) {
474                 ERROR_WITH_ERRNO("Failed to initialize condition variable");
475                 goto err_destroy_msg_avail_cond;
476         }
477         return 0;
478 err_destroy_msg_avail_cond:
479         pthread_cond_destroy(&q->msg_avail_cond);
480 err_destroy_lock:
481         pthread_mutex_destroy(&q->lock);
482 err:
483         return WIMLIB_ERR_NOMEM;
484 }
485
486 static void
487 shared_queue_destroy(struct shared_queue *q)
488 {
489         FREE(q->array);
490         pthread_mutex_destroy(&q->lock);
491         pthread_cond_destroy(&q->msg_avail_cond);
492         pthread_cond_destroy(&q->space_avail_cond);
493 }
494
495 static void
496 shared_queue_put(struct shared_queue *q, void *obj)
497 {
498         pthread_mutex_lock(&q->lock);
499         while (q->filled_slots == q->size)
500                 pthread_cond_wait(&q->space_avail_cond, &q->lock);
501
502         q->back = (q->back + 1) % q->size;
503         q->array[q->back] = obj;
504         q->filled_slots++;
505
506         pthread_cond_broadcast(&q->msg_avail_cond);
507         pthread_mutex_unlock(&q->lock);
508 }
509
510 static void *
511 shared_queue_get(struct shared_queue *q)
512 {
513         void *obj;
514
515         pthread_mutex_lock(&q->lock);
516         while (q->filled_slots == 0)
517                 pthread_cond_wait(&q->msg_avail_cond, &q->lock);
518
519         obj = q->array[q->front];
520         q->array[q->front] = NULL;
521         q->front = (q->front + 1) % q->size;
522         q->filled_slots--;
523
524         pthread_cond_broadcast(&q->space_avail_cond);
525         pthread_mutex_unlock(&q->lock);
526         return obj;
527 }
528
529 struct compressor_thread_params {
530         struct shared_queue *res_to_compress_queue;
531         struct shared_queue *compressed_res_queue;
532         compress_func_t compress;
533 };
534
535 #define MAX_CHUNKS_PER_MSG 2
536
537 struct message {
538         struct wim_lookup_table_entry *lte;
539         u8 *uncompressed_chunks[MAX_CHUNKS_PER_MSG];
540         u8 *compressed_chunks[MAX_CHUNKS_PER_MSG];
541         unsigned uncompressed_chunk_sizes[MAX_CHUNKS_PER_MSG];
542         struct iovec out_chunks[MAX_CHUNKS_PER_MSG];
543         size_t total_out_bytes;
544         unsigned num_chunks;
545         struct list_head list;
546         bool complete;
547         u64 begin_chunk;
548 };
549
550 static void
551 compress_chunks(struct message *msg, compress_func_t compress)
552 {
553         msg->total_out_bytes = 0;
554         for (unsigned i = 0; i < msg->num_chunks; i++) {
555                 unsigned len = compress(msg->uncompressed_chunks[i],
556                                         msg->uncompressed_chunk_sizes[i],
557                                         msg->compressed_chunks[i]);
558                 void *out_chunk;
559                 unsigned out_len;
560                 if (len) {
561                         /* To be written compressed */
562                         out_chunk = msg->compressed_chunks[i];
563                         out_len = len;
564                 } else {
565                         /* To be written uncompressed */
566                         out_chunk = msg->uncompressed_chunks[i];
567                         out_len = msg->uncompressed_chunk_sizes[i];
568                 }
569                 msg->out_chunks[i].iov_base = out_chunk;
570                 msg->out_chunks[i].iov_len = out_len;
571                 msg->total_out_bytes += out_len;
572         }
573 }
574
575 /* Compressor thread routine.  This is a lot simpler than the main thread
576  * routine: just repeatedly get a group of chunks from the
577  * res_to_compress_queue, compress them, and put them in the
578  * compressed_res_queue.  A NULL pointer indicates that the thread should stop.
579  * */
580 static void *
581 compressor_thread_proc(void *arg)
582 {
583         struct compressor_thread_params *params = arg;
584         struct shared_queue *res_to_compress_queue = params->res_to_compress_queue;
585         struct shared_queue *compressed_res_queue = params->compressed_res_queue;
586         compress_func_t compress = params->compress;
587         struct message *msg;
588
589         DEBUG("Compressor thread ready");
590         while ((msg = shared_queue_get(res_to_compress_queue)) != NULL) {
591                 compress_chunks(msg, compress);
592                 shared_queue_put(compressed_res_queue, msg);
593         }
594         DEBUG("Compressor thread terminating");
595         return NULL;
596 }
597 #endif /* ENABLE_MULTITHREADED_COMPRESSION */
598
599 static void
600 do_write_streams_progress(union wimlib_progress_info *progress,
601                           wimlib_progress_func_t progress_func,
602                           uint64_t size_added)
603 {
604         progress->write_streams.completed_bytes += size_added;
605         progress->write_streams.completed_streams++;
606         if (progress_func &&
607             progress->write_streams.completed_bytes >= progress->write_streams._private)
608         {
609                 progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
610                               progress);
611                 if (progress->write_streams._private == progress->write_streams.total_bytes) {
612                         progress->write_streams._private = ~0;
613                 } else {
614                         progress->write_streams._private =
615                                 min(progress->write_streams.total_bytes,
616                                     progress->write_streams.completed_bytes +
617                                         progress->write_streams.total_bytes / 100);
618                 }
619         }
620 }
621
622 struct serial_write_stream_ctx {
623         filedes_t out_fd;
624         int out_ctype;
625         int write_resource_flags;
626 };
627
628 static int
629 serial_write_stream(struct wim_lookup_table_entry *lte, void *_ctx)
630 {
631         struct serial_write_stream_ctx *ctx = _ctx;
632         return write_wim_resource(lte, ctx->out_fd,
633                                   ctx->out_ctype, &lte->output_resource_entry,
634                                   ctx->write_resource_flags);
635 }
636
637 /* Write a list of streams, taking into account that some streams may be
638  * duplicates that are checksummed and discarded on the fly, and also delegating
639  * the actual writing of a stream to a function @write_stream_cb, which is
640  * passed the context @write_stream_ctx. */
641 static int
642 do_write_stream_list(struct list_head *stream_list,
643                      struct wim_lookup_table *lookup_table,
644                      int (*write_stream_cb)(struct wim_lookup_table_entry *, void *),
645                      void *write_stream_ctx,
646                      wimlib_progress_func_t progress_func,
647                      union wimlib_progress_info *progress)
648 {
649         int ret = 0;
650         struct wim_lookup_table_entry *lte;
651
652         /* For each stream in @stream_list ... */
653         while (!list_empty(stream_list)) {
654                 lte = container_of(stream_list->next,
655                                    struct wim_lookup_table_entry,
656                                    write_streams_list);
657                 list_del(&lte->write_streams_list);
658                 if (lte->unhashed && !lte->unique_size) {
659                         /* Unhashed stream that shares a size with some other
660                          * stream in the WIM we are writing.  The stream must be
661                          * checksummed to know if we need to write it or not. */
662                         struct wim_lookup_table_entry *tmp;
663                         u32 orig_refcnt = lte->out_refcnt;
664
665                         ret = hash_unhashed_stream(lte, lookup_table, &tmp);
666                         if (ret)
667                                 break;
668                         if (tmp != lte) {
669                                 lte = tmp;
670                                 /* We found a duplicate stream. */
671                                 if (orig_refcnt != tmp->out_refcnt) {
672                                         /* We have already written, or are going
673                                          * to write, the duplicate stream.  So
674                                          * just skip to the next stream. */
675                                         DEBUG("Discarding duplicate stream of length %"PRIu64,
676                                               wim_resource_size(lte));
677                                         lte->no_progress = 0;
678                                         goto skip_to_progress;
679                                 }
680                         }
681                 }
682
683                 /* Here, @lte is either a hashed stream or an unhashed stream
684                  * with a unique size.  In either case we know that the stream
685                  * has to be written.  In either case the SHA1 message digest
686                  * will be calculated over the stream while writing it; however,
687                  * in the former case this is done merely to check the data,
688                  * while in the latter case this is done because we do not have
689                  * the SHA1 message digest yet.  */
690                 wimlib_assert(lte->out_refcnt != 0);
691                 lte->deferred = 0;
692                 lte->no_progress = 0;
693                 ret = (*write_stream_cb)(lte, write_stream_ctx);
694                 if (ret)
695                         break;
696                 /* In parallel mode, some streams are deferred for later,
697                  * serialized processing; ignore them here. */
698                 if (lte->deferred)
699                         continue;
700                 if (lte->unhashed) {
701                         list_del(&lte->unhashed_list);
702                         lookup_table_insert(lookup_table, lte);
703                         lte->unhashed = 0;
704                 }
705         skip_to_progress:
706                 if (!lte->no_progress) {
707                         do_write_streams_progress(progress,
708                                                   progress_func,
709                                                   wim_resource_size(lte));
710                 }
711         }
712         return ret;
713 }
714
715 static int
716 do_write_stream_list_serial(struct list_head *stream_list,
717                             struct wim_lookup_table *lookup_table,
718                             filedes_t out_fd,
719                             int out_ctype,
720                             int write_resource_flags,
721                             wimlib_progress_func_t progress_func,
722                             union wimlib_progress_info *progress)
723 {
724         struct serial_write_stream_ctx ctx = {
725                 .out_fd = out_fd,
726                 .out_ctype = out_ctype,
727                 .write_resource_flags = write_resource_flags,
728         };
729         return do_write_stream_list(stream_list,
730                                     lookup_table,
731                                     serial_write_stream,
732                                     &ctx,
733                                     progress_func,
734                                     progress);
735 }
736
737 static inline int
738 write_flags_to_resource_flags(int write_flags)
739 {
740         int resource_flags = 0;
741
742         if (write_flags & WIMLIB_WRITE_FLAG_RECOMPRESS)
743                 resource_flags |= WIMLIB_RESOURCE_FLAG_RECOMPRESS;
744         return resource_flags;
745 }
746
747 static int
748 write_stream_list_serial(struct list_head *stream_list,
749                          struct wim_lookup_table *lookup_table,
750                          filedes_t out_fd,
751                          int out_ctype,
752                          int write_resource_flags,
753                          wimlib_progress_func_t progress_func,
754                          union wimlib_progress_info *progress)
755 {
756         DEBUG("Writing stream list (serial version)");
757         progress->write_streams.num_threads = 1;
758         if (progress_func)
759                 progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS, progress);
760         return do_write_stream_list_serial(stream_list,
761                                            lookup_table,
762                                            out_fd,
763                                            out_ctype,
764                                            write_resource_flags,
765                                            progress_func,
766                                            progress);
767 }
768
769 #ifdef ENABLE_MULTITHREADED_COMPRESSION
770 static int
771 write_wim_chunks(struct message *msg, filedes_t out_fd,
772                  struct chunk_table *chunk_tab)
773 {
774         for (unsigned i = 0; i < msg->num_chunks; i++) {
775                 *chunk_tab->cur_offset_p++ = chunk_tab->cur_offset;
776                 chunk_tab->cur_offset += msg->out_chunks[i].iov_len;
777         }
778         if (full_writev(out_fd, msg->out_chunks,
779                         msg->num_chunks) != msg->total_out_bytes)
780         {
781                 ERROR_WITH_ERRNO("Failed to write WIM chunks");
782                 return WIMLIB_ERR_WRITE;
783         }
784         return 0;
785 }
786
787 struct main_writer_thread_ctx {
788         struct list_head *stream_list;
789         struct wim_lookup_table *lookup_table;
790         filedes_t out_fd;
791         int out_ctype;
792         int write_resource_flags;
793         struct shared_queue *res_to_compress_queue;
794         struct shared_queue *compressed_res_queue;
795         size_t num_messages;
796         wimlib_progress_func_t progress_func;
797         union wimlib_progress_info *progress;
798
799         struct list_head available_msgs;
800         struct list_head outstanding_streams;
801         struct list_head serial_streams;
802         size_t num_outstanding_messages;
803
804         SHA_CTX next_sha_ctx;
805         u64 next_chunk;
806         u64 next_num_chunks;
807         struct wim_lookup_table_entry *next_lte;
808
809         struct message *msgs;
810         struct message *next_msg;
811         struct chunk_table *cur_chunk_tab;
812 };
813
814 static int
815 init_message(struct message *msg)
816 {
817         for (size_t i = 0; i < MAX_CHUNKS_PER_MSG; i++) {
818                 msg->compressed_chunks[i] = MALLOC(WIM_CHUNK_SIZE);
819                 msg->uncompressed_chunks[i] = MALLOC(WIM_CHUNK_SIZE);
820                 if (msg->compressed_chunks[i] == NULL ||
821                     msg->uncompressed_chunks[i] == NULL)
822                         return WIMLIB_ERR_NOMEM;
823         }
824         return 0;
825 }
826
827 static void
828 destroy_message(struct message *msg)
829 {
830         for (size_t i = 0; i < MAX_CHUNKS_PER_MSG; i++) {
831                 FREE(msg->compressed_chunks[i]);
832                 FREE(msg->uncompressed_chunks[i]);
833         }
834 }
835
836 static void
837 free_messages(struct message *msgs, size_t num_messages)
838 {
839         if (msgs) {
840                 for (size_t i = 0; i < num_messages; i++)
841                         destroy_message(&msgs[i]);
842                 FREE(msgs);
843         }
844 }
845
846 static struct message *
847 allocate_messages(size_t num_messages)
848 {
849         struct message *msgs;
850
851         msgs = CALLOC(num_messages, sizeof(struct message));
852         if (!msgs)
853                 return NULL;
854         for (size_t i = 0; i < num_messages; i++) {
855                 if (init_message(&msgs[i])) {
856                         free_messages(msgs, num_messages);
857                         return NULL;
858                 }
859         }
860         return msgs;
861 }
862
863 static void
864 main_writer_thread_destroy_ctx(struct main_writer_thread_ctx *ctx)
865 {
866         while (ctx->num_outstanding_messages--)
867                 shared_queue_get(ctx->compressed_res_queue);
868         free_messages(ctx->msgs, ctx->num_messages);
869         FREE(ctx->cur_chunk_tab);
870 }
871
872 static int
873 main_writer_thread_init_ctx(struct main_writer_thread_ctx *ctx)
874 {
875         /* Pre-allocate all the buffers that will be needed to do the chunk
876          * compression. */
877         ctx->msgs = allocate_messages(ctx->num_messages);
878         if (!ctx->msgs)
879                 return WIMLIB_ERR_NOMEM;
880
881         /* Initially, all the messages are available to use. */
882         INIT_LIST_HEAD(&ctx->available_msgs);
883         for (size_t i = 0; i < ctx->num_messages; i++)
884                 list_add_tail(&ctx->msgs[i].list, &ctx->available_msgs);
885
886         /* outstanding_streams is the list of streams that currently have had
887          * chunks sent off for compression.
888          *
889          * The first stream in outstanding_streams is the stream that is
890          * currently being written.
891          *
892          * The last stream in outstanding_streams is the stream that is
893          * currently being read and having chunks fed to the compressor threads.
894          * */
895         INIT_LIST_HEAD(&ctx->outstanding_streams);
896         ctx->num_outstanding_messages = 0;
897
898         ctx->next_msg = NULL;
899
900         /* Resources that don't need any chunks compressed are added to this
901          * list and written directly by the main thread. */
902         INIT_LIST_HEAD(&ctx->serial_streams);
903
904         ctx->cur_chunk_tab = NULL;
905
906         return 0;
907 }
908
909 static int
910 receive_compressed_chunks(struct main_writer_thread_ctx *ctx)
911 {
912         struct message *msg;
913         struct wim_lookup_table_entry *cur_lte;
914         int ret;
915
916         wimlib_assert(!list_empty(&ctx->outstanding_streams));
917         wimlib_assert(ctx->num_outstanding_messages != 0);
918
919         cur_lte = container_of(ctx->outstanding_streams.next,
920                                struct wim_lookup_table_entry,
921                                being_compressed_list);
922
923         /* Get the next message from the queue and process it.
924          * The message will contain 1 or more data chunks that have been
925          * compressed. */
926         msg = shared_queue_get(ctx->compressed_res_queue);
927         msg->complete = true;
928         --ctx->num_outstanding_messages;
929
930         /* Is this the next chunk in the current resource?  If it's not
931          * (i.e., an earlier chunk in a same or different resource
932          * hasn't been compressed yet), do nothing, and keep this
933          * message around until all earlier chunks are received.
934          *
935          * Otherwise, write all the chunks we can. */
936         while (cur_lte != NULL &&
937                !list_empty(&cur_lte->msg_list)
938                && (msg = container_of(cur_lte->msg_list.next,
939                                       struct message,
940                                       list))->complete)
941         {
942                 list_move(&msg->list, &ctx->available_msgs);
943                 if (msg->begin_chunk == 0) {
944                         /* This is the first set of chunks.  Leave space
945                          * for the chunk table in the output file. */
946                         off_t cur_offset = filedes_offset(ctx->out_fd);
947                         if (cur_offset == -1)
948                                 return WIMLIB_ERR_WRITE;
949                         ret = begin_wim_resource_chunk_tab(cur_lte,
950                                                            ctx->out_fd,
951                                                            cur_offset,
952                                                            &ctx->cur_chunk_tab);
953                         if (ret)
954                                 return ret;
955                 }
956
957                 /* Write the compressed chunks from the message. */
958                 ret = write_wim_chunks(msg, ctx->out_fd, ctx->cur_chunk_tab);
959                 if (ret)
960                         return ret;
961
962                 /* Was this the last chunk of the stream?  If so, finish
963                  * it. */
964                 if (list_empty(&cur_lte->msg_list) &&
965                     msg->begin_chunk + msg->num_chunks == ctx->cur_chunk_tab->num_chunks)
966                 {
967                         u64 res_csize;
968                         off_t offset;
969
970                         ret = finish_wim_resource_chunk_tab(ctx->cur_chunk_tab,
971                                                             ctx->out_fd,
972                                                             &res_csize);
973                         if (ret)
974                                 return ret;
975
976                         list_del(&cur_lte->being_compressed_list);
977
978                         /* Grab the offset of this stream in the output file
979                          * from the chunk table before we free it. */
980                         offset = ctx->cur_chunk_tab->file_offset;
981
982                         FREE(ctx->cur_chunk_tab);
983                         ctx->cur_chunk_tab = NULL;
984
985                         if (res_csize >= wim_resource_size(cur_lte)) {
986                                 /* Oops!  We compressed the resource to
987                                  * larger than the original size.  Write
988                                  * the resource uncompressed instead. */
989                                 DEBUG("Compressed %"PRIu64" => %"PRIu64" bytes; "
990                                       "writing uncompressed instead",
991                                       wim_resource_size(cur_lte), res_csize);
992                                 ret = seek_and_truncate(ctx->out_fd, offset);
993                                 if (ret)
994                                         return ret;
995                                 ret = write_wim_resource(cur_lte,
996                                                          ctx->out_fd,
997                                                          WIMLIB_COMPRESSION_TYPE_NONE,
998                                                          &cur_lte->output_resource_entry,
999                                                          ctx->write_resource_flags);
1000                                 if (ret)
1001                                         return ret;
1002                         } else {
1003                                 cur_lte->output_resource_entry.size =
1004                                         res_csize;
1005
1006                                 cur_lte->output_resource_entry.original_size =
1007                                         cur_lte->resource_entry.original_size;
1008
1009                                 cur_lte->output_resource_entry.offset =
1010                                         offset;
1011
1012                                 cur_lte->output_resource_entry.flags =
1013                                         cur_lte->resource_entry.flags |
1014                                                 WIM_RESHDR_FLAG_COMPRESSED;
1015                         }
1016
1017                         do_write_streams_progress(ctx->progress,
1018                                                   ctx->progress_func,
1019                                                   wim_resource_size(cur_lte));
1020
1021                         /* Since we just finished writing a stream, write any
1022                          * streams that have been added to the serial_streams
1023                          * list for direct writing by the main thread (e.g.
1024                          * resources that don't need to be compressed because
1025                          * the desired compression type is the same as the
1026                          * previous compression type). */
1027                         if (!list_empty(&ctx->serial_streams)) {
1028                                 ret = do_write_stream_list_serial(&ctx->serial_streams,
1029                                                                   ctx->lookup_table,
1030                                                                   ctx->out_fd,
1031                                                                   ctx->out_ctype,
1032                                                                   ctx->write_resource_flags,
1033                                                                   ctx->progress_func,
1034                                                                   ctx->progress);
1035                                 if (ret)
1036                                         return ret;
1037                         }
1038
1039                         /* Advance to the next stream to write. */
1040                         if (list_empty(&ctx->outstanding_streams)) {
1041                                 cur_lte = NULL;
1042                         } else {
1043                                 cur_lte = container_of(ctx->outstanding_streams.next,
1044                                                        struct wim_lookup_table_entry,
1045                                                        being_compressed_list);
1046                         }
1047                 }
1048         }
1049         return 0;
1050 }
1051
1052 /* Called when the main thread has read a new chunk of data. */
1053 static int
1054 main_writer_thread_cb(const void *chunk, size_t chunk_size, void *_ctx)
1055 {
1056         struct main_writer_thread_ctx *ctx = _ctx;
1057         int ret;
1058         struct message *next_msg;
1059         u64 next_chunk_in_msg;
1060
1061         /* Update SHA1 message digest for the stream currently being read by the
1062          * main thread. */
1063         sha1_update(&ctx->next_sha_ctx, chunk, chunk_size);
1064
1065         /* We send chunks of data to the compressor chunks in batches which we
1066          * refer to as "messages".  @next_msg is the message that is currently
1067          * being prepared to send off.  If it is NULL, that indicates that we
1068          * need to start a new message. */
1069         next_msg = ctx->next_msg;
1070         if (!next_msg) {
1071                 /* We need to start a new message.  First check to see if there
1072                  * is a message available in the list of available messages.  If
1073                  * so, we can just take one.  If not, all the messages (there is
1074                  * a fixed number of them, proportional to the number of
1075                  * threads) have been sent off to the compressor threads, so we
1076                  * receive messages from the compressor threads containing
1077                  * compressed chunks of data.
1078                  *
1079                  * We may need to receive multiple messages before one is
1080                  * actually available to use because messages received that are
1081                  * *not* for the very next set of chunks to compress must be
1082                  * buffered until it's time to write those chunks. */
1083                 while (list_empty(&ctx->available_msgs)) {
1084                         ret = receive_compressed_chunks(ctx);
1085                         if (ret)
1086                                 return ret;
1087                 }
1088
1089                 next_msg = container_of(ctx->available_msgs.next,
1090                                         struct message, list);
1091                 list_del(&next_msg->list);
1092                 next_msg->complete = false;
1093                 next_msg->begin_chunk = ctx->next_chunk;
1094                 next_msg->num_chunks = min(MAX_CHUNKS_PER_MSG,
1095                                            ctx->next_num_chunks - ctx->next_chunk);
1096                 ctx->next_msg = next_msg;
1097         }
1098
1099         /* Fill in the next chunk to compress */
1100         next_chunk_in_msg = ctx->next_chunk - next_msg->begin_chunk;
1101
1102         next_msg->uncompressed_chunk_sizes[next_chunk_in_msg] = chunk_size;
1103         memcpy(next_msg->uncompressed_chunks[next_chunk_in_msg],
1104                chunk, chunk_size);
1105         ctx->next_chunk++;
1106         if (++next_chunk_in_msg == next_msg->num_chunks) {
1107                 /* Send off an array of chunks to compress */
1108                 list_add_tail(&next_msg->list, &ctx->next_lte->msg_list);
1109                 shared_queue_put(ctx->res_to_compress_queue, next_msg);
1110                 ++ctx->num_outstanding_messages;
1111                 ctx->next_msg = NULL;
1112         }
1113         return 0;
1114 }
1115
1116 static int
1117 main_writer_thread_finish(void *_ctx)
1118 {
1119         struct main_writer_thread_ctx *ctx = _ctx;
1120         int ret;
1121         while (ctx->num_outstanding_messages != 0) {
1122                 ret = receive_compressed_chunks(ctx);
1123                 if (ret)
1124                         return ret;
1125         }
1126         wimlib_assert(list_empty(&ctx->outstanding_streams));
1127         return do_write_stream_list_serial(&ctx->serial_streams,
1128                                            ctx->lookup_table,
1129                                            ctx->out_fd,
1130                                            ctx->out_ctype,
1131                                            ctx->write_resource_flags,
1132                                            ctx->progress_func,
1133                                            ctx->progress);
1134 }
1135
1136 static int
1137 submit_stream_for_compression(struct wim_lookup_table_entry *lte,
1138                               struct main_writer_thread_ctx *ctx)
1139 {
1140         int ret;
1141
1142         /* Read the entire stream @lte, feeding its data chunks to the
1143          * compressor threads.  Also SHA1-sum the stream; this is required in
1144          * the case that @lte is unhashed, and a nice additional verification
1145          * when @lte is already hashed. */
1146         sha1_init(&ctx->next_sha_ctx);
1147         ctx->next_chunk = 0;
1148         ctx->next_num_chunks = wim_resource_chunks(lte);
1149         ctx->next_lte = lte;
1150         INIT_LIST_HEAD(&lte->msg_list);
1151         list_add_tail(&lte->being_compressed_list, &ctx->outstanding_streams);
1152         ret = read_resource_prefix(lte, wim_resource_size(lte),
1153                                    main_writer_thread_cb, ctx, 0);
1154         if (ret == 0) {
1155                 wimlib_assert(ctx->next_chunk == ctx->next_num_chunks);
1156                 ret = finalize_and_check_sha1(&ctx->next_sha_ctx, lte);
1157         }
1158         return ret;
1159 }
1160
1161 static int
1162 main_thread_process_next_stream(struct wim_lookup_table_entry *lte, void *_ctx)
1163 {
1164         struct main_writer_thread_ctx *ctx = _ctx;
1165         int ret;
1166
1167         if (wim_resource_size(lte) < 1000 ||
1168             ctx->out_ctype == WIMLIB_COMPRESSION_TYPE_NONE ||
1169             (lte->resource_location == RESOURCE_IN_WIM &&
1170              !(ctx->write_resource_flags & WIMLIB_RESOURCE_FLAG_RECOMPRESS) &&
1171              wimlib_get_compression_type(lte->wim) == ctx->out_ctype))
1172         {
1173                 /* Stream is too small or isn't being compressed.  Process it by
1174                  * the main thread when we have a chance.  We can't necessarily
1175                  * process it right here, as the main thread could be in the
1176                  * middle of writing a different stream. */
1177                 list_add_tail(&lte->write_streams_list, &ctx->serial_streams);
1178                 lte->deferred = 1;
1179                 ret = 0;
1180         } else {
1181                 ret = submit_stream_for_compression(lte, ctx);
1182         }
1183         lte->no_progress = 1;
1184         return ret;
1185 }
1186
1187 static long
1188 get_default_num_threads()
1189 {
1190 #ifdef __WIN32__
1191         return win32_get_number_of_processors();
1192 #else
1193         return sysconf(_SC_NPROCESSORS_ONLN);
1194 #endif
1195 }
1196
1197 /* Equivalent to write_stream_list_serial(), except this takes a @num_threads
1198  * parameter and will perform compression using that many threads.  Falls
1199  * back to write_stream_list_serial() on certain errors, such as a failure to
1200  * create the number of threads requested.
1201  *
1202  * High level description of the algorithm for writing compressed streams in
1203  * parallel:  We perform compression on chunks of size WIM_CHUNK_SIZE bytes
1204  * rather than on full files.  The currently executing thread becomes the main
1205  * thread and is entirely in charge of reading the data to compress (which may
1206  * be in any location understood by the resource code--- such as in an external
1207  * file being captured, or in another WIM file from which an image is being
1208  * exported) and actually writing the compressed data to the output file.
1209  * Additional threads are "compressor threads" and all execute the
1210  * compressor_thread_proc, where they repeatedly retrieve buffers of data from
1211  * the main thread, compress them, and hand them back to the main thread.
1212  *
1213  * Certain streams, such as streams that do not need to be compressed (e.g.
1214  * input compression type same as output compression type) or streams of very
1215  * small size are placed in a list (main_writer_thread_ctx.serial_list) and
1216  * handled entirely by the main thread at an appropriate time.
1217  *
1218  * At any given point in time, multiple streams may be having chunks compressed
1219  * concurrently.  The stream that the main thread is currently *reading* may be
1220  * later in the list that the stream that the main thread is currently
1221  * *writing*.
1222  */
1223 static int
1224 write_stream_list_parallel(struct list_head *stream_list,
1225                            struct wim_lookup_table *lookup_table,
1226                            filedes_t out_fd,
1227                            int out_ctype,
1228                            int write_resource_flags,
1229                            wimlib_progress_func_t progress_func,
1230                            union wimlib_progress_info *progress,
1231                            unsigned num_threads)
1232 {
1233         int ret;
1234         struct shared_queue res_to_compress_queue;
1235         struct shared_queue compressed_res_queue;
1236         pthread_t *compressor_threads = NULL;
1237
1238         if (num_threads == 0) {
1239                 long nthreads = get_default_num_threads();
1240                 if (nthreads < 1 || nthreads > UINT_MAX) {
1241                         WARNING("Could not determine number of processors! Assuming 1");
1242                         goto out_serial;
1243                 } else if (nthreads == 1) {
1244                         goto out_serial_quiet;
1245                 } else {
1246                         num_threads = nthreads;
1247                 }
1248         }
1249
1250         DEBUG("Writing stream list (parallel version, num_threads=%u)",
1251               num_threads);
1252
1253         progress->write_streams.num_threads = num_threads;
1254
1255         static const size_t MESSAGES_PER_THREAD = 2;
1256         size_t queue_size = (size_t)(num_threads * MESSAGES_PER_THREAD);
1257
1258         DEBUG("Initializing shared queues (queue_size=%zu)", queue_size);
1259
1260         ret = shared_queue_init(&res_to_compress_queue, queue_size);
1261         if (ret)
1262                 goto out_serial;
1263
1264         ret = shared_queue_init(&compressed_res_queue, queue_size);
1265         if (ret)
1266                 goto out_destroy_res_to_compress_queue;
1267
1268         struct compressor_thread_params params;
1269         params.res_to_compress_queue = &res_to_compress_queue;
1270         params.compressed_res_queue = &compressed_res_queue;
1271         params.compress = get_compress_func(out_ctype);
1272
1273         compressor_threads = MALLOC(num_threads * sizeof(pthread_t));
1274         if (!compressor_threads) {
1275                 ret = WIMLIB_ERR_NOMEM;
1276                 goto out_destroy_compressed_res_queue;
1277         }
1278
1279         for (unsigned i = 0; i < num_threads; i++) {
1280                 DEBUG("pthread_create thread %u of %u", i + 1, num_threads);
1281                 ret = pthread_create(&compressor_threads[i], NULL,
1282                                      compressor_thread_proc, &params);
1283                 if (ret != 0) {
1284                         ret = -1;
1285                         ERROR_WITH_ERRNO("Failed to create compressor "
1286                                          "thread %u of %u",
1287                                          i + 1, num_threads);
1288                         num_threads = i;
1289                         goto out_join;
1290                 }
1291         }
1292
1293         if (progress_func)
1294                 progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS, progress);
1295
1296         struct main_writer_thread_ctx ctx;
1297         ctx.stream_list           = stream_list;
1298         ctx.lookup_table          = lookup_table;
1299         ctx.out_fd                = out_fd;
1300         ctx.out_ctype             = out_ctype;
1301         ctx.res_to_compress_queue = &res_to_compress_queue;
1302         ctx.compressed_res_queue  = &compressed_res_queue;
1303         ctx.num_messages          = queue_size;
1304         ctx.write_resource_flags  = write_resource_flags;
1305         ctx.progress_func         = progress_func;
1306         ctx.progress              = progress;
1307         ret = main_writer_thread_init_ctx(&ctx);
1308         if (ret)
1309                 goto out_join;
1310         ret = do_write_stream_list(stream_list, lookup_table,
1311                                    main_thread_process_next_stream,
1312                                    &ctx, progress_func, progress);
1313         if (ret)
1314                 goto out_destroy_ctx;
1315
1316         /* The main thread has finished reading all streams that are going to be
1317          * compressed in parallel, and it now needs to wait for all remaining
1318          * chunks to be compressed so that the remaining streams can actually be
1319          * written to the output file.  Furthermore, any remaining streams that
1320          * had processing deferred to the main thread need to be handled.  These
1321          * tasks are done by the main_writer_thread_finish() function. */
1322         ret = main_writer_thread_finish(&ctx);
1323 out_destroy_ctx:
1324         main_writer_thread_destroy_ctx(&ctx);
1325 out_join:
1326         for (unsigned i = 0; i < num_threads; i++)
1327                 shared_queue_put(&res_to_compress_queue, NULL);
1328
1329         for (unsigned i = 0; i < num_threads; i++) {
1330                 if (pthread_join(compressor_threads[i], NULL)) {
1331                         WARNING_WITH_ERRNO("Failed to join compressor "
1332                                            "thread %u of %u",
1333                                            i + 1, num_threads);
1334                 }
1335         }
1336         FREE(compressor_threads);
1337 out_destroy_compressed_res_queue:
1338         shared_queue_destroy(&compressed_res_queue);
1339 out_destroy_res_to_compress_queue:
1340         shared_queue_destroy(&res_to_compress_queue);
1341         if (ret >= 0 && ret != WIMLIB_ERR_NOMEM)
1342                 return ret;
1343 out_serial:
1344         WARNING("Falling back to single-threaded compression");
1345 out_serial_quiet:
1346         return write_stream_list_serial(stream_list,
1347                                         lookup_table,
1348                                         out_fd,
1349                                         out_ctype,
1350                                         write_resource_flags,
1351                                         progress_func,
1352                                         progress);
1353
1354 }
1355 #endif
1356
1357 /*
1358  * Write a list of streams to a WIM (@out_fd) using the compression type
1359  * @out_ctype and up to @num_threads compressor threads.
1360  */
1361 static int
1362 write_stream_list(struct list_head *stream_list,
1363                   struct wim_lookup_table *lookup_table,
1364                   filedes_t out_fd, int out_ctype, int write_flags,
1365                   unsigned num_threads, wimlib_progress_func_t progress_func)
1366 {
1367         struct wim_lookup_table_entry *lte;
1368         size_t num_streams = 0;
1369         u64 total_bytes = 0;
1370         u64 total_compression_bytes = 0;
1371         union wimlib_progress_info progress;
1372         int ret;
1373         int write_resource_flags;
1374
1375         if (list_empty(stream_list))
1376                 return 0;
1377
1378         write_resource_flags = write_flags_to_resource_flags(write_flags);
1379
1380         /* Calculate the total size of the streams to be written.  Note: this
1381          * will be the uncompressed size, as we may not know the compressed size
1382          * yet, and also this will assume that every unhashed stream will be
1383          * written (which will not necessarily be the case). */
1384         list_for_each_entry(lte, stream_list, write_streams_list) {
1385                 num_streams++;
1386                 total_bytes += wim_resource_size(lte);
1387                 if (out_ctype != WIMLIB_COMPRESSION_TYPE_NONE
1388                        && (wim_resource_compression_type(lte) != out_ctype ||
1389                            (write_resource_flags & WIMLIB_RESOURCE_FLAG_RECOMPRESS)))
1390                 {
1391                         total_compression_bytes += wim_resource_size(lte);
1392                 }
1393         }
1394         progress.write_streams.total_bytes       = total_bytes;
1395         progress.write_streams.total_streams     = num_streams;
1396         progress.write_streams.completed_bytes   = 0;
1397         progress.write_streams.completed_streams = 0;
1398         progress.write_streams.num_threads       = num_threads;
1399         progress.write_streams.compression_type  = out_ctype;
1400         progress.write_streams._private          = 0;
1401
1402 #ifdef ENABLE_MULTITHREADED_COMPRESSION
1403         if (total_compression_bytes >= 1000000 && num_threads != 1)
1404                 ret = write_stream_list_parallel(stream_list,
1405                                                  lookup_table,
1406                                                  out_fd,
1407                                                  out_ctype,
1408                                                  write_resource_flags,
1409                                                  progress_func,
1410                                                  &progress,
1411                                                  num_threads);
1412         else
1413 #endif
1414                 ret = write_stream_list_serial(stream_list,
1415                                                lookup_table,
1416                                                out_fd,
1417                                                out_ctype,
1418                                                write_resource_flags,
1419                                                progress_func,
1420                                                &progress);
1421         return ret;
1422 }
1423
1424 struct stream_size_table {
1425         struct hlist_head *array;
1426         size_t num_entries;
1427         size_t capacity;
1428 };
1429
1430 static int
1431 init_stream_size_table(struct stream_size_table *tab, size_t capacity)
1432 {
1433         tab->array = CALLOC(capacity, sizeof(tab->array[0]));
1434         if (!tab->array)
1435                 return WIMLIB_ERR_NOMEM;
1436         tab->num_entries = 0;
1437         tab->capacity = capacity;
1438         return 0;
1439 }
1440
1441 static void
1442 destroy_stream_size_table(struct stream_size_table *tab)
1443 {
1444         FREE(tab->array);
1445 }
1446
1447 static int
1448 stream_size_table_insert(struct wim_lookup_table_entry *lte, void *_tab)
1449 {
1450         struct stream_size_table *tab = _tab;
1451         size_t pos;
1452         struct wim_lookup_table_entry *same_size_lte;
1453         struct hlist_node *tmp;
1454
1455         pos = hash_u64(wim_resource_size(lte)) % tab->capacity;
1456         lte->unique_size = 1;
1457         hlist_for_each_entry(same_size_lte, tmp, &tab->array[pos], hash_list_2) {
1458                 if (wim_resource_size(same_size_lte) == wim_resource_size(lte)) {
1459                         lte->unique_size = 0;
1460                         same_size_lte->unique_size = 0;
1461                         break;
1462                 }
1463         }
1464
1465         hlist_add_head(&lte->hash_list_2, &tab->array[pos]);
1466         tab->num_entries++;
1467         return 0;
1468 }
1469
1470
1471 struct lte_overwrite_prepare_args {
1472         WIMStruct *wim;
1473         off_t end_offset;
1474         struct list_head stream_list;
1475         struct stream_size_table stream_size_tab;
1476 };
1477
1478 /* First phase of preparing streams for an in-place overwrite.  This is called
1479  * on all streams, both hashed and unhashed, except the metadata resources. */
1480 static int
1481 lte_overwrite_prepare(struct wim_lookup_table_entry *lte, void *_args)
1482 {
1483         struct lte_overwrite_prepare_args *args = _args;
1484
1485         wimlib_assert(!(lte->resource_entry.flags & WIM_RESHDR_FLAG_METADATA));
1486         if (lte->resource_location != RESOURCE_IN_WIM || lte->wim != args->wim)
1487                 list_add_tail(&lte->write_streams_list, &args->stream_list);
1488         lte->out_refcnt = lte->refcnt;
1489         stream_size_table_insert(lte, &args->stream_size_tab);
1490         return 0;
1491 }
1492
1493 /* Second phase of preparing streams for an in-place overwrite.  This is called
1494  * on existing metadata resources and hashed streams, but not unhashed streams.
1495  *
1496  * NOTE: lte->output_resource_entry is in union with lte->hash_list_2, so
1497  * lte_overwrite_prepare_2() must be called after lte_overwrite_prepare(), as
1498  * the latter uses lte->hash_list_2, while the former expects to set
1499  * lte->output_resource_entry. */
1500 static int
1501 lte_overwrite_prepare_2(struct wim_lookup_table_entry *lte, void *_args)
1502 {
1503         struct lte_overwrite_prepare_args *args = _args;
1504
1505         if (lte->resource_location == RESOURCE_IN_WIM && lte->wim == args->wim) {
1506                 /* We can't do an in place overwrite on the WIM if there are
1507                  * streams after the XML data. */
1508                 if (lte->resource_entry.offset +
1509                     lte->resource_entry.size > args->end_offset)
1510                 {
1511                 #ifdef ENABLE_ERROR_MESSAGES
1512                         ERROR("The following resource is after the XML data:");
1513                         print_lookup_table_entry(lte, stderr);
1514                 #endif
1515                         return WIMLIB_ERR_RESOURCE_ORDER;
1516                 }
1517                 copy_resource_entry(&lte->output_resource_entry,
1518                                     &lte->resource_entry);
1519         }
1520         return 0;
1521 }
1522
1523 /* Given a WIM that we are going to overwrite in place with zero or more
1524  * additional streams added, construct a list the list of new unique streams
1525  * ('struct wim_lookup_table_entry's) that must be written, plus any unhashed
1526  * streams that need to be added but may be identical to other hashed or
1527  * unhashed streams.  These unhashed streams are checksummed while the streams
1528  * are being written.  To aid this process, the member @unique_size is set to 1
1529  * on streams that have a unique size and therefore must be written.
1530  *
1531  * The out_refcnt member of each 'struct wim_lookup_table_entry' is set to
1532  * indicate the number of times the stream is referenced in only the streams
1533  * that are being written; this may still be adjusted later when unhashed
1534  * streams are being resolved.
1535  */
1536 static int
1537 prepare_streams_for_overwrite(WIMStruct *wim, off_t end_offset,
1538                               struct list_head *stream_list)
1539 {
1540         int ret;
1541         struct lte_overwrite_prepare_args args;
1542         unsigned i;
1543
1544         args.wim = wim;
1545         args.end_offset = end_offset;
1546         ret = init_stream_size_table(&args.stream_size_tab,
1547                                      wim->lookup_table->capacity);
1548         if (ret)
1549                 return ret;
1550
1551         INIT_LIST_HEAD(&args.stream_list);
1552         for (i = 0; i < wim->hdr.image_count; i++) {
1553                 struct wim_image_metadata *imd;
1554                 struct wim_lookup_table_entry *lte;
1555
1556                 imd = wim->image_metadata[i];
1557                 image_for_each_unhashed_stream(lte, imd)
1558                         lte_overwrite_prepare(lte, &args);
1559         }
1560         for_lookup_table_entry(wim->lookup_table, lte_overwrite_prepare, &args);
1561         list_transfer(&args.stream_list, stream_list);
1562
1563         for (i = 0; i < wim->hdr.image_count; i++) {
1564                 ret = lte_overwrite_prepare_2(wim->image_metadata[i]->metadata_lte,
1565                                               &args);
1566                 if (ret)
1567                         goto out_destroy_stream_size_table;
1568         }
1569         ret = for_lookup_table_entry(wim->lookup_table,
1570                                      lte_overwrite_prepare_2, &args);
1571 out_destroy_stream_size_table:
1572         destroy_stream_size_table(&args.stream_size_tab);
1573         return ret;
1574 }
1575
1576
1577 struct find_streams_ctx {
1578         struct list_head stream_list;
1579         struct stream_size_table stream_size_tab;
1580 };
1581
1582 static void
1583 inode_find_streams_to_write(struct wim_inode *inode,
1584                             struct wim_lookup_table *table,
1585                             struct list_head *stream_list,
1586                             struct stream_size_table *tab)
1587 {
1588         struct wim_lookup_table_entry *lte;
1589         for (unsigned i = 0; i <= inode->i_num_ads; i++) {
1590                 lte = inode_stream_lte(inode, i, table);
1591                 if (lte) {
1592                         if (lte->out_refcnt == 0) {
1593                                 if (lte->unhashed)
1594                                         stream_size_table_insert(lte, tab);
1595                                 list_add_tail(&lte->write_streams_list, stream_list);
1596                         }
1597                         lte->out_refcnt += inode->i_nlink;
1598                 }
1599         }
1600 }
1601
1602 static int
1603 image_find_streams_to_write(WIMStruct *w)
1604 {
1605         struct find_streams_ctx *ctx;
1606         struct wim_image_metadata *imd;
1607         struct wim_inode *inode;
1608         struct wim_lookup_table_entry *lte;
1609
1610         ctx = w->private;
1611         imd = wim_get_current_image_metadata(w);
1612
1613         image_for_each_unhashed_stream(lte, imd)
1614                 lte->out_refcnt = 0;
1615
1616         /* Go through this image's inodes to find any streams that have not been
1617          * found yet. */
1618         image_for_each_inode(inode, imd) {
1619                 inode_find_streams_to_write(inode, w->lookup_table,
1620                                             &ctx->stream_list,
1621                                             &ctx->stream_size_tab);
1622         }
1623         return 0;
1624 }
1625
1626 /* Given a WIM that from which one or all of the images is being written, build
1627  * the list of unique streams ('struct wim_lookup_table_entry's) that must be
1628  * written, plus any unhashed streams that need to be written but may be
1629  * identical to other hashed or unhashed streams being written.  These unhashed
1630  * streams are checksummed while the streams are being written.  To aid this
1631  * process, the member @unique_size is set to 1 on streams that have a unique
1632  * size and therefore must be written.
1633  *
1634  * The out_refcnt member of each 'struct wim_lookup_table_entry' is set to
1635  * indicate the number of times the stream is referenced in only the streams
1636  * that are being written; this may still be adjusted later when unhashed
1637  * streams are being resolved.
1638  */
1639 static int
1640 prepare_stream_list(WIMStruct *wim, int image, struct list_head *stream_list)
1641 {
1642         int ret;
1643         struct find_streams_ctx ctx;
1644
1645         for_lookup_table_entry(wim->lookup_table, lte_zero_out_refcnt, NULL);
1646         ret = init_stream_size_table(&ctx.stream_size_tab,
1647                                      wim->lookup_table->capacity);
1648         if (ret)
1649                 return ret;
1650         for_lookup_table_entry(wim->lookup_table, stream_size_table_insert,
1651                                &ctx.stream_size_tab);
1652         INIT_LIST_HEAD(&ctx.stream_list);
1653         wim->private = &ctx;
1654         ret = for_image(wim, image, image_find_streams_to_write);
1655         destroy_stream_size_table(&ctx.stream_size_tab);
1656         if (ret == 0)
1657                 list_transfer(&ctx.stream_list, stream_list);
1658         return ret;
1659 }
1660
1661 /* Writes the streams for the specified @image in @wim to @wim->out_fd.
1662  */
1663 static int
1664 write_wim_streams(WIMStruct *wim, int image, int write_flags,
1665                   unsigned num_threads,
1666                   wimlib_progress_func_t progress_func)
1667 {
1668         int ret;
1669         struct list_head stream_list;
1670
1671         ret = prepare_stream_list(wim, image, &stream_list);
1672         if (ret)
1673                 return ret;
1674         return write_stream_list(&stream_list,
1675                                  wim->lookup_table,
1676                                  wim->out_fd,
1677                                  wimlib_get_compression_type(wim),
1678                                  write_flags,
1679                                  num_threads,
1680                                  progress_func);
1681 }
1682
1683 /*
1684  * Finish writing a WIM file: write the lookup table, xml data, and integrity
1685  * table (optional), then overwrite the WIM header.
1686  *
1687  * write_flags is a bitwise OR of the following:
1688  *
1689  *      (public)  WIMLIB_WRITE_FLAG_CHECK_INTEGRITY:
1690  *              Include an integrity table.
1691  *
1692  *      (public)  WIMLIB_WRITE_FLAG_SHOW_PROGRESS:
1693  *              Show progress information when (if) writing the integrity table.
1694  *
1695  *      (private) WIMLIB_WRITE_FLAG_NO_LOOKUP_TABLE:
1696  *              Don't write the lookup table.
1697  *
1698  *      (private) WIMLIB_WRITE_FLAG_REUSE_INTEGRITY_TABLE:
1699  *              When (if) writing the integrity table, re-use entries from the
1700  *              existing integrity table, if possible.
1701  *
1702  *      (private) WIMLIB_WRITE_FLAG_CHECKPOINT_AFTER_XML:
1703  *              After writing the XML data but before writing the integrity
1704  *              table, write a temporary WIM header and flush the stream so that
1705  *              the WIM is less likely to become corrupted upon abrupt program
1706  *              termination.
1707  *
1708  *      (private) WIMLIB_WRITE_FLAG_FSYNC:
1709  *              fsync() the output file before closing it.
1710  *
1711  */
1712 int
1713 finish_write(WIMStruct *w, int image, int write_flags,
1714              wimlib_progress_func_t progress_func)
1715 {
1716         int ret;
1717         struct wim_header hdr;
1718
1719         /* @hdr will be the header for the new WIM.  First copy all the data
1720          * from the header in the WIMStruct; then set all the fields that may
1721          * have changed, including the resource entries, boot index, and image
1722          * count.  */
1723         memcpy(&hdr, &w->hdr, sizeof(struct wim_header));
1724
1725         /* Set image count and boot index correctly for single image writes */
1726         if (image != WIMLIB_ALL_IMAGES) {
1727                 hdr.image_count = 1;
1728                 if (hdr.boot_idx == image)
1729                         hdr.boot_idx = 1;
1730                 else
1731                         hdr.boot_idx = 0;
1732         }
1733
1734         /* In the WIM header, there is room for the resource entry for a
1735          * metadata resource labeled as the "boot metadata".  This entry should
1736          * be zeroed out if there is no bootable image (boot_idx 0).  Otherwise,
1737          * it should be a copy of the resource entry for the image that is
1738          * marked as bootable.  This is not well documented...  */
1739         if (hdr.boot_idx == 0) {
1740                 zero_resource_entry(&hdr.boot_metadata_res_entry);
1741         } else {
1742                 copy_resource_entry(&hdr.boot_metadata_res_entry,
1743                             &w->image_metadata[ hdr.boot_idx- 1
1744                                         ]->metadata_lte->output_resource_entry);
1745         }
1746
1747         if (!(write_flags & WIMLIB_WRITE_FLAG_NO_LOOKUP_TABLE)) {
1748                 ret = write_lookup_table(w, image, &hdr.lookup_table_res_entry);
1749                 if (ret)
1750                         goto out_close_wim;
1751         }
1752
1753         ret = write_xml_data(w->wim_info, image, w->out_fd,
1754                              (write_flags & WIMLIB_WRITE_FLAG_NO_LOOKUP_TABLE) ?
1755                               wim_info_get_total_bytes(w->wim_info) : 0,
1756                              &hdr.xml_res_entry);
1757         if (ret)
1758                 goto out_close_wim;
1759
1760         if (write_flags & WIMLIB_WRITE_FLAG_CHECK_INTEGRITY) {
1761                 if (write_flags & WIMLIB_WRITE_FLAG_CHECKPOINT_AFTER_XML) {
1762                         struct wim_header checkpoint_hdr;
1763                         memcpy(&checkpoint_hdr, &hdr, sizeof(struct wim_header));
1764                         zero_resource_entry(&checkpoint_hdr.integrity);
1765                         ret = write_header(&checkpoint_hdr, w->out_fd);
1766                         if (ret)
1767                                 goto out_close_wim;
1768                 }
1769
1770                 off_t old_lookup_table_end;
1771                 off_t new_lookup_table_end;
1772                 if (write_flags & WIMLIB_WRITE_FLAG_REUSE_INTEGRITY_TABLE) {
1773                         old_lookup_table_end = w->hdr.lookup_table_res_entry.offset +
1774                                                w->hdr.lookup_table_res_entry.size;
1775                 } else {
1776                         old_lookup_table_end = 0;
1777                 }
1778                 new_lookup_table_end = hdr.lookup_table_res_entry.offset +
1779                                        hdr.lookup_table_res_entry.size;
1780
1781                 ret = write_integrity_table(w->out_fd,
1782                                             &hdr.integrity,
1783                                             new_lookup_table_end,
1784                                             old_lookup_table_end,
1785                                             progress_func);
1786                 if (ret)
1787                         goto out_close_wim;
1788         } else {
1789                 zero_resource_entry(&hdr.integrity);
1790         }
1791
1792         ret = write_header(&hdr, w->out_fd);
1793         if (ret)
1794                 goto out_close_wim;
1795
1796         if (write_flags & WIMLIB_WRITE_FLAG_FSYNC) {
1797                 if (fsync(w->out_fd)) {
1798                         ERROR_WITH_ERRNO("Error syncing data to WIM file");
1799                         ret = WIMLIB_ERR_WRITE;
1800                 }
1801         }
1802 out_close_wim:
1803         if (close(w->out_fd)) {
1804                 ERROR_WITH_ERRNO("Failed to close the output WIM file");
1805                 if (ret == 0)
1806                         ret = WIMLIB_ERR_WRITE;
1807         }
1808         w->out_fd = INVALID_FILEDES;
1809         return ret;
1810 }
1811
1812 #if defined(HAVE_SYS_FILE_H) && defined(HAVE_FLOCK)
1813 int
1814 lock_wim(WIMStruct *w, filedes_t fd)
1815 {
1816         int ret = 0;
1817         if (fd != INVALID_FILEDES && !w->wim_locked) {
1818                 ret = flock(fd, LOCK_EX | LOCK_NB);
1819                 if (ret != 0) {
1820                         if (errno == EWOULDBLOCK) {
1821                                 ERROR("`%"TS"' is already being modified or has been "
1822                                       "mounted read-write\n"
1823                                       "        by another process!", w->filename);
1824                                 ret = WIMLIB_ERR_ALREADY_LOCKED;
1825                         } else {
1826                                 WARNING_WITH_ERRNO("Failed to lock `%"TS"'",
1827                                                    w->filename);
1828                                 ret = 0;
1829                         }
1830                 } else {
1831                         w->wim_locked = 1;
1832                 }
1833         }
1834         return ret;
1835 }
1836 #endif
1837
1838 static int
1839 open_wim_writable(WIMStruct *w, const tchar *path, int open_flags)
1840 {
1841         w->out_fd = topen(path, open_flags, 0644);
1842         if (w->out_fd == INVALID_FILEDES) {
1843                 ERROR_WITH_ERRNO("Failed to open `%"TS"' for writing", path);
1844                 return WIMLIB_ERR_OPEN;
1845         }
1846         return 0;
1847 }
1848
1849
1850 void
1851 close_wim_writable(WIMStruct *w)
1852 {
1853         if (w->out_fd != INVALID_FILEDES) {
1854                 if (close(w->out_fd))
1855                         WARNING_WITH_ERRNO("Failed to close output WIM");
1856                 w->out_fd = INVALID_FILEDES;
1857         }
1858 }
1859
1860 /* Open file stream and write dummy header for WIM. */
1861 int
1862 begin_write(WIMStruct *w, const tchar *path, int write_flags)
1863 {
1864         int ret;
1865         int open_flags = O_TRUNC | O_CREAT;
1866         if (write_flags & WIMLIB_WRITE_FLAG_CHECK_INTEGRITY)
1867                 open_flags |= O_RDWR;
1868         else
1869                 open_flags |= O_WRONLY;
1870         ret = open_wim_writable(w, path, open_flags);
1871         if (ret)
1872                 return ret;
1873         /* Write dummy header. It will be overwritten later. */
1874         ret = write_header(&w->hdr, w->out_fd);
1875         if (ret)
1876                 return ret;
1877         if (lseek(w->out_fd, WIM_HEADER_DISK_SIZE, SEEK_SET) == -1) {
1878                 ERROR_WITH_ERRNO("Failed to seek to end of WIM header");
1879                 return WIMLIB_ERR_WRITE;
1880         }
1881         return 0;
1882 }
1883
1884 /* Writes a stand-alone WIM to a file.  */
1885 WIMLIBAPI int
1886 wimlib_write(WIMStruct *w, const tchar *path,
1887              int image, int write_flags, unsigned num_threads,
1888              wimlib_progress_func_t progress_func)
1889 {
1890         int ret;
1891
1892         if (!path)
1893                 return WIMLIB_ERR_INVALID_PARAM;
1894
1895         write_flags &= WIMLIB_WRITE_MASK_PUBLIC;
1896
1897         if (image != WIMLIB_ALL_IMAGES &&
1898              (image < 1 || image > w->hdr.image_count))
1899                 return WIMLIB_ERR_INVALID_IMAGE;
1900
1901         if (w->hdr.total_parts != 1) {
1902                 ERROR("Cannot call wimlib_write() on part of a split WIM");
1903                 return WIMLIB_ERR_SPLIT_UNSUPPORTED;
1904         }
1905
1906         ret = begin_write(w, path, write_flags);
1907         if (ret)
1908                 goto out_close_wim;
1909
1910         ret = write_wim_streams(w, image, write_flags, num_threads,
1911                                 progress_func);
1912         if (ret)
1913                 goto out_close_wim;
1914
1915         if (progress_func)
1916                 progress_func(WIMLIB_PROGRESS_MSG_WRITE_METADATA_BEGIN, NULL);
1917
1918         ret = for_image(w, image, write_metadata_resource);
1919         if (ret)
1920                 goto out_close_wim;
1921
1922         if (progress_func)
1923                 progress_func(WIMLIB_PROGRESS_MSG_WRITE_METADATA_END, NULL);
1924
1925         ret = finish_write(w, image, write_flags, progress_func);
1926         /* finish_write() closed the WIM for us */
1927         goto out;
1928 out_close_wim:
1929         close_wim_writable(w);
1930 out:
1931         DEBUG("wimlib_write(path=%"TS") = %d", path, ret);
1932         return ret;
1933 }
1934
1935 static bool
1936 any_images_modified(WIMStruct *w)
1937 {
1938         for (int i = 0; i < w->hdr.image_count; i++)
1939                 if (w->image_metadata[i]->modified)
1940                         return true;
1941         return false;
1942 }
1943
1944 /*
1945  * Overwrite a WIM, possibly appending streams to it.
1946  *
1947  * A WIM looks like (or is supposed to look like) the following:
1948  *
1949  *                   Header (212 bytes)
1950  *                   Streams and metadata resources (variable size)
1951  *                   Lookup table (variable size)
1952  *                   XML data (variable size)
1953  *                   Integrity table (optional) (variable size)
1954  *
1955  * If we are not adding any streams or metadata resources, the lookup table is
1956  * unchanged--- so we only need to overwrite the XML data, integrity table, and
1957  * header.  This operation is potentially unsafe if the program is abruptly
1958  * terminated while the XML data or integrity table are being overwritten, but
1959  * before the new header has been written.  To partially alleviate this problem,
1960  * a special flag (WIMLIB_WRITE_FLAG_CHECKPOINT_AFTER_XML) is passed to
1961  * finish_write() to cause a temporary WIM header to be written after the XML
1962  * data has been written.  This may prevent the WIM from becoming corrupted if
1963  * the program is terminated while the integrity table is being calculated (but
1964  * no guarantees, due to write re-ordering...).
1965  *
1966  * If we are adding new streams or images (metadata resources), the lookup table
1967  * needs to be changed, and those streams need to be written.  In this case, we
1968  * try to perform a safe update of the WIM file by writing the streams *after*
1969  * the end of the previous WIM, then writing the new lookup table, XML data, and
1970  * (optionally) integrity table following the new streams.  This will produce a
1971  * layout like the following:
1972  *
1973  *                   Header (212 bytes)
1974  *                   (OLD) Streams and metadata resources (variable size)
1975  *                   (OLD) Lookup table (variable size)
1976  *                   (OLD) XML data (variable size)
1977  *                   (OLD) Integrity table (optional) (variable size)
1978  *                   (NEW) Streams and metadata resources (variable size)
1979  *                   (NEW) Lookup table (variable size)
1980  *                   (NEW) XML data (variable size)
1981  *                   (NEW) Integrity table (optional) (variable size)
1982  *
1983  * At all points, the WIM is valid as nothing points to the new data yet.  Then,
1984  * the header is overwritten to point to the new lookup table, XML data, and
1985  * integrity table, to produce the following layout:
1986  *
1987  *                   Header (212 bytes)
1988  *                   Streams and metadata resources (variable size)
1989  *                   Nothing (variable size)
1990  *                   More Streams and metadata resources (variable size)
1991  *                   Lookup table (variable size)
1992  *                   XML data (variable size)
1993  *                   Integrity table (optional) (variable size)
1994  *
1995  * This method allows an image to be appended to a large WIM very quickly, and
1996  * is is crash-safe except in the case of write re-ordering, but the
1997  * disadvantage is that a small hole is left in the WIM where the old lookup
1998  * table, xml data, and integrity table were.  (These usually only take up a
1999  * small amount of space compared to the streams, however.)
2000  */
2001 static int
2002 overwrite_wim_inplace(WIMStruct *w, int write_flags,
2003                       unsigned num_threads,
2004                       wimlib_progress_func_t progress_func)
2005 {
2006         int ret;
2007         struct list_head stream_list;
2008         off_t old_wim_end;
2009         u64 old_lookup_table_end, old_xml_begin, old_xml_end;
2010         int open_flags;
2011
2012         DEBUG("Overwriting `%"TS"' in-place", w->filename);
2013
2014         /* Make sure that the integrity table (if present) is after the XML
2015          * data, and that there are no stream resources, metadata resources, or
2016          * lookup tables after the XML data.  Otherwise, these data would be
2017          * overwritten. */
2018         old_xml_begin = w->hdr.xml_res_entry.offset;
2019         old_xml_end = old_xml_begin + w->hdr.xml_res_entry.size;
2020         old_lookup_table_end = w->hdr.lookup_table_res_entry.offset +
2021                                w->hdr.lookup_table_res_entry.size;
2022         if (w->hdr.integrity.offset != 0 && w->hdr.integrity.offset < old_xml_end) {
2023                 ERROR("Didn't expect the integrity table to be before the XML data");
2024                 return WIMLIB_ERR_RESOURCE_ORDER;
2025         }
2026
2027         if (old_lookup_table_end > old_xml_begin) {
2028                 ERROR("Didn't expect the lookup table to be after the XML data");
2029                 return WIMLIB_ERR_RESOURCE_ORDER;
2030         }
2031
2032         /* Set @old_wim_end, which indicates the point beyond which we don't
2033          * allow any file and metadata resources to appear without returning
2034          * WIMLIB_ERR_RESOURCE_ORDER (due to the fact that we would otherwise
2035          * overwrite these resources). */
2036         if (!w->deletion_occurred && !any_images_modified(w)) {
2037                 /* If no images have been modified and no images have been
2038                  * deleted, a new lookup table does not need to be written.  We
2039                  * shall write the new XML data and optional integrity table
2040                  * immediately after the lookup table.  Note that this may
2041                  * overwrite an existing integrity table. */
2042                 DEBUG("Skipping writing lookup table "
2043                       "(no images modified or deleted)");
2044                 old_wim_end = old_lookup_table_end;
2045                 write_flags |= WIMLIB_WRITE_FLAG_NO_LOOKUP_TABLE |
2046                                WIMLIB_WRITE_FLAG_CHECKPOINT_AFTER_XML;
2047         } else if (w->hdr.integrity.offset) {
2048                 /* Old WIM has an integrity table; begin writing new streams
2049                  * after it. */
2050                 old_wim_end = w->hdr.integrity.offset + w->hdr.integrity.size;
2051         } else {
2052                 /* No existing integrity table; begin writing new streams after
2053                  * the old XML data. */
2054                 old_wim_end = old_xml_end;
2055         }
2056
2057         ret = prepare_streams_for_overwrite(w, old_wim_end, &stream_list);
2058         if (ret)
2059                 return ret;
2060
2061         open_flags = 0;
2062         if (write_flags & WIMLIB_WRITE_FLAG_CHECK_INTEGRITY)
2063                 open_flags |= O_RDWR;
2064         else
2065                 open_flags |= O_WRONLY;
2066         ret = open_wim_writable(w, w->filename, open_flags);
2067         if (ret)
2068                 return ret;
2069
2070         ret = lock_wim(w, w->out_fd);
2071         if (ret) {
2072                 close_wim_writable(w);
2073                 return ret;
2074         }
2075
2076         if (lseek(w->out_fd, old_wim_end, SEEK_SET) == -1) {
2077                 ERROR_WITH_ERRNO("Can't seek to end of WIM");
2078                 close_wim_writable(w);
2079                 w->wim_locked = 0;
2080                 return WIMLIB_ERR_WRITE;
2081         }
2082
2083         DEBUG("Writing newly added streams (offset = %"PRIu64")",
2084               old_wim_end);
2085         ret = write_stream_list(&stream_list,
2086                                 w->lookup_table,
2087                                 w->out_fd,
2088                                 wimlib_get_compression_type(w),
2089                                 write_flags,
2090                                 num_threads,
2091                                 progress_func);
2092         if (ret)
2093                 goto out_truncate;
2094
2095         for (int i = 0; i < w->hdr.image_count; i++) {
2096                 if (w->image_metadata[i]->modified) {
2097                         select_wim_image(w, i + 1);
2098                         ret = write_metadata_resource(w);
2099                         if (ret)
2100                                 goto out_truncate;
2101                 }
2102         }
2103         write_flags |= WIMLIB_WRITE_FLAG_REUSE_INTEGRITY_TABLE;
2104         ret = finish_write(w, WIMLIB_ALL_IMAGES, write_flags,
2105                            progress_func);
2106 out_truncate:
2107         close_wim_writable(w);
2108         if (ret != 0 && !(write_flags & WIMLIB_WRITE_FLAG_NO_LOOKUP_TABLE)) {
2109                 WARNING("Truncating `%"TS"' to its original size (%"PRIu64" bytes)",
2110                         w->filename, old_wim_end);
2111                 /* Return value of truncate() is ignored because this is already
2112                  * an error path. */
2113                 (void)ttruncate(w->filename, old_wim_end);
2114         }
2115         w->wim_locked = 0;
2116         return ret;
2117 }
2118
2119 static int
2120 overwrite_wim_via_tmpfile(WIMStruct *w, int write_flags,
2121                           unsigned num_threads,
2122                           wimlib_progress_func_t progress_func)
2123 {
2124         size_t wim_name_len;
2125         int ret;
2126
2127         DEBUG("Overwriting `%"TS"' via a temporary file", w->filename);
2128
2129         /* Write the WIM to a temporary file in the same directory as the
2130          * original WIM. */
2131         wim_name_len = tstrlen(w->filename);
2132         tchar tmpfile[wim_name_len + 10];
2133         tmemcpy(tmpfile, w->filename, wim_name_len);
2134         randomize_char_array_with_alnum(tmpfile + wim_name_len, 9);
2135         tmpfile[wim_name_len + 9] = T('\0');
2136
2137         ret = wimlib_write(w, tmpfile, WIMLIB_ALL_IMAGES,
2138                            write_flags | WIMLIB_WRITE_FLAG_FSYNC,
2139                            num_threads, progress_func);
2140         if (ret) {
2141                 ERROR("Failed to write the WIM file `%"TS"'", tmpfile);
2142                 goto out_unlink;
2143         }
2144
2145         close_wim(w);
2146
2147         DEBUG("Renaming `%"TS"' to `%"TS"'", tmpfile, w->filename);
2148         /* Rename the new file to the old file .*/
2149         if (trename(tmpfile, w->filename) != 0) {
2150                 ERROR_WITH_ERRNO("Failed to rename `%"TS"' to `%"TS"'",
2151                                  tmpfile, w->filename);
2152                 ret = WIMLIB_ERR_RENAME;
2153                 goto out_unlink;
2154         }
2155
2156         if (progress_func) {
2157                 union wimlib_progress_info progress;
2158                 progress.rename.from = tmpfile;
2159                 progress.rename.to = w->filename;
2160                 progress_func(WIMLIB_PROGRESS_MSG_RENAME, &progress);
2161         }
2162         goto out;
2163 out_unlink:
2164         /* Remove temporary file. */
2165         if (tunlink(tmpfile) != 0)
2166                 WARNING_WITH_ERRNO("Failed to remove `%"TS"'", tmpfile);
2167 out:
2168         return ret;
2169 }
2170
2171 /*
2172  * Writes a WIM file to the original file that it was read from, overwriting it.
2173  */
2174 WIMLIBAPI int
2175 wimlib_overwrite(WIMStruct *w, int write_flags,
2176                  unsigned num_threads,
2177                  wimlib_progress_func_t progress_func)
2178 {
2179         write_flags &= WIMLIB_WRITE_MASK_PUBLIC;
2180
2181         if (!w->filename)
2182                 return WIMLIB_ERR_NO_FILENAME;
2183
2184         if (w->hdr.total_parts != 1) {
2185                 ERROR("Cannot modify a split WIM");
2186                 return WIMLIB_ERR_SPLIT_UNSUPPORTED;
2187         }
2188
2189         if ((!w->deletion_occurred || (write_flags & WIMLIB_WRITE_FLAG_SOFT_DELETE))
2190             && !(write_flags & WIMLIB_WRITE_FLAG_REBUILD))
2191         {
2192                 int ret;
2193                 ret = overwrite_wim_inplace(w, write_flags, num_threads,
2194                                             progress_func);
2195                 if (ret == WIMLIB_ERR_RESOURCE_ORDER)
2196                         WARNING("Falling back to re-building entire WIM");
2197                 else
2198                         return ret;
2199         }
2200         return overwrite_wim_via_tmpfile(w, write_flags, num_threads,
2201                                          progress_func);
2202 }