-
Notifications
You must be signed in to change notification settings - Fork 256
/
text-io.c
548 lines (499 loc) · 14 KB
/
text-io.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <libgen.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <limits.h>
#include <sys/mman.h>
#if CONFIG_ACL
#include <sys/acl.h>
#endif
#if CONFIG_SELINUX
#include <selinux/selinux.h>
#endif
#include "text.h"
#include "text-internal.h"
#include "text-util.h"
#include "util.h"
struct TextSave { /* used to hold context between text_save_{begin,commit} calls */
Text *txt; /* text to operate on */
char *filename; /* filename to save to as given to text_save_begin */
char *tmpname; /* temporary name used for atomic rename(2) */
int fd; /* file descriptor to write data to using text_save_write */
int dirfd; /* directory file descriptor, relative to which we save */
enum TextSaveMethod type; /* method used to save file */
};
/* Allocate blocks holding the actual file content in chunks of size: */
#ifndef BLOCK_SIZE
#define BLOCK_SIZE (1 << 20)
#endif
/* Files smaller than this value are copied on load, larger ones are mmap(2)-ed
* directly. Hence the former can be truncated, while doing so on the latter
* results in havoc. */
#define BLOCK_MMAP_SIZE (1 << 26)
/* allocate a new block of MAX(size, BLOCK_SIZE) bytes */
Block *block_alloc(size_t size) {
Block *blk = calloc(1, sizeof *blk);
if (!blk)
return NULL;
if (BLOCK_SIZE > size)
size = BLOCK_SIZE;
if (!(blk->data = malloc(size))) {
free(blk);
return NULL;
}
blk->type = BLOCK_TYPE_MALLOC;
blk->size = size;
return blk;
}
Block *block_read(size_t size, int fd) {
Block *blk = block_alloc(size);
if (!blk)
return NULL;
char *data = blk->data;
size_t rem = size;
while (rem > 0) {
ssize_t len = read(fd, data, rem);
if (len == -1) {
block_free(blk);
return NULL;
} else if (len == 0) {
break;
} else {
data += len;
rem -= len;
}
}
blk->len = size - rem;
return blk;
}
Block *block_mmap(size_t size, int fd, off_t offset) {
Block *blk = calloc(1, sizeof *blk);
if (!blk)
return NULL;
if (size) {
blk->data = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, offset);
if (blk->data == MAP_FAILED) {
free(blk);
return NULL;
}
}
blk->type = BLOCK_TYPE_MMAP_ORIG;
blk->size = size;
blk->len = size;
return blk;
}
Block *block_load(int dirfd, const char *filename, enum TextLoadMethod method, struct stat *info) {
Block *block = NULL;
int fd = openat(dirfd, filename, O_RDONLY);
if (fd == -1)
goto out;
if (fstat(fd, info) == -1)
goto out;
if (!S_ISREG(info->st_mode)) {
errno = S_ISDIR(info->st_mode) ? EISDIR : ENOTSUP;
goto out;
}
// XXX: use lseek(fd, 0, SEEK_END); instead?
size_t size = info->st_size;
if (size == 0)
goto out;
if (method == TEXT_LOAD_READ || (method == TEXT_LOAD_AUTO && size < BLOCK_MMAP_SIZE))
block = block_read(size, fd);
else
block = block_mmap(size, fd, 0);
out:
if (fd != -1)
close(fd);
return block;
}
void block_free(Block *blk) {
if (!blk)
return;
if (blk->type == BLOCK_TYPE_MALLOC)
free(blk->data);
else if ((blk->type == BLOCK_TYPE_MMAP_ORIG || blk->type == BLOCK_TYPE_MMAP) && blk->data)
munmap(blk->data, blk->size);
free(blk);
}
/* check whether block has enough free space to store len bytes */
bool block_capacity(Block *blk, size_t len) {
return blk->size - blk->len >= len;
}
/* append data to block, assumes there is enough space available */
const char *block_append(Block *blk, const char *data, size_t len) {
char *dest = memcpy(blk->data + blk->len, data, len);
blk->len += len;
return dest;
}
/* insert data into block at an arbitrary position, this should only be used with
* data of the most recently created piece. */
bool block_insert(Block *blk, size_t pos, const char *data, size_t len) {
if (pos > blk->len || !block_capacity(blk, len))
return false;
if (blk->len == pos)
return block_append(blk, data, len);
char *insert = blk->data + pos;
memmove(insert + len, insert, blk->len - pos);
memcpy(insert, data, len);
blk->len += len;
return true;
}
/* delete data from a block at an arbitrary position, this should only be used with
* data of the most recently created piece. */
bool block_delete(Block *blk, size_t pos, size_t len) {
size_t end;
if (!addu(pos, len, &end) || end > blk->len)
return false;
if (blk->len == pos) {
blk->len -= len;
return true;
}
char *delete = blk->data + pos;
memmove(delete, delete + len, blk->len - pos - len);
blk->len -= len;
return true;
}
Text *text_load(const char *filename) {
return text_load_method(filename, TEXT_LOAD_AUTO);
}
Text *text_loadat(int dirfd, const char *filename) {
return text_loadat_method(dirfd, filename, TEXT_LOAD_AUTO);
}
Text *text_load_method(const char *filename, enum TextLoadMethod method) {
return text_loadat_method(AT_FDCWD, filename, method);
}
static ssize_t write_all(int fd, const char *buf, size_t count) {
size_t rem = count;
while (rem > 0) {
ssize_t written = write(fd, buf, rem > INT_MAX ? INT_MAX : rem);
if (written < 0) {
if (errno == EAGAIN || errno == EINTR)
continue;
return -1;
} else if (written == 0) {
break;
}
rem -= written;
buf += written;
}
return count - rem;
}
static bool preserve_acl(int src, int dest) {
#if CONFIG_ACL
acl_t acl = acl_get_fd(src);
if (!acl)
return errno == ENOTSUP ? true : false;
if (acl_set_fd(dest, acl) == -1) {
acl_free(acl);
return false;
}
acl_free(acl);
#endif /* CONFIG_ACL */
return true;
}
static bool preserve_selinux_context(int src, int dest) {
#if CONFIG_SELINUX
char *context = NULL;
if (!is_selinux_enabled())
return true;
if (fgetfilecon(src, &context) == -1)
return errno == ENOTSUP ? true : false;
if (fsetfilecon(dest, context) == -1) {
freecon(context);
return false;
}
freecon(context);
#endif /* CONFIG_SELINUX */
return true;
}
static int mkstempat(int dirfd, char *template) {
if (dirfd == AT_FDCWD)
return mkstemp(template);
// FIXME: not thread safe
int fd = -1;
int cwd = open(".", O_RDONLY|O_DIRECTORY);
if (cwd == -1)
goto err;
if (fchdir(dirfd) == -1)
goto err;
fd = mkstemp(template);
err:
if (cwd != -1) {
fchdir(cwd);
close(cwd);
}
return fd;
}
/* Create a new file named `.filename.vis.XXXXXX` (where `XXXXXX` is a
* randomly generated, unique suffix) and try to preserve all important
* meta data. After the file content has been written to this temporary
* file, text_save_commit_atomic will atomically move it to its final
* (possibly already existing) destination using rename(2).
*
* This approach does not work if:
*
* - the file is a symbolic link
* - the file is a hard link
* - file ownership can not be preserved
* - file group can not be preserved
* - directory permissions do not allow creation of a new file
* - POSIX ACL can not be preserved (if enabled)
* - SELinux security context can not be preserved (if enabled)
*/
static bool text_save_begin_atomic(TextSave *ctx) {
int oldfd, saved_errno;
if ((oldfd = openat(ctx->dirfd, ctx->filename, O_RDONLY)) == -1 && errno != ENOENT)
goto err;
struct stat oldmeta = { 0 };
if (oldfd != -1 && fstatat(ctx->dirfd, ctx->filename, &oldmeta, AT_SYMLINK_NOFOLLOW) == -1)
goto err;
if (oldfd != -1) {
if (S_ISLNK(oldmeta.st_mode)) /* symbolic link */
goto err;
if (oldmeta.st_nlink > 1) /* hard link */
goto err;
}
char suffix[] = ".vis.XXXXXX";
size_t len = strlen(ctx->filename) + sizeof("./.") + sizeof(suffix);
char *dir = strdup(ctx->filename);
char *base = strdup(ctx->filename);
if (!(ctx->tmpname = malloc(len)) || !dir || !base) {
free(dir);
free(base);
goto err;
}
snprintf(ctx->tmpname, len, "%s/.%s%s", dirname(dir), basename(base), suffix);
free(dir);
free(base);
if ((ctx->fd = mkstempat(ctx->dirfd, ctx->tmpname)) == -1)
goto err;
if (oldfd == -1) {
mode_t mask = umask(0);
umask(mask);
if (fchmod(ctx->fd, 0666 & ~mask) == -1)
goto err;
} else {
if (fchmod(ctx->fd, oldmeta.st_mode) == -1)
goto err;
if (!preserve_acl(oldfd, ctx->fd) || !preserve_selinux_context(oldfd, ctx->fd))
goto err;
/* change owner if necessary */
if (oldmeta.st_uid != getuid() && fchown(ctx->fd, oldmeta.st_uid, (uid_t)-1) == -1)
goto err;
/* change group if necessary, in case of failure some editors reset
* the group permissions to the same as for others */
if (oldmeta.st_gid != getgid() && fchown(ctx->fd, (uid_t)-1, oldmeta.st_gid) == -1)
goto err;
close(oldfd);
}
ctx->type = TEXT_SAVE_ATOMIC;
return true;
err:
saved_errno = errno;
if (oldfd != -1)
close(oldfd);
if (ctx->fd != -1)
close(ctx->fd);
ctx->fd = -1;
free(ctx->tmpname);
ctx->tmpname = NULL;
errno = saved_errno;
return false;
}
static bool text_save_commit_atomic(TextSave *ctx) {
if (fsync(ctx->fd) == -1)
return false;
struct stat meta = { 0 };
if (fstat(ctx->fd, &meta) == -1)
return false;
bool close_failed = (close(ctx->fd) == -1);
ctx->fd = -1;
if (close_failed)
return false;
if (renameat(ctx->dirfd, ctx->tmpname, ctx->dirfd, ctx->filename) == -1)
return false;
free(ctx->tmpname);
ctx->tmpname = NULL;
int dir = openat(ctx->dirfd, dirname(ctx->filename), O_DIRECTORY|O_RDONLY);
if (dir == -1)
return false;
if (fsync(dir) == -1 && errno != EINVAL) {
close(dir);
return false;
}
if (close(dir) == -1)
return false;
text_saved(ctx->txt, &meta);
return true;
}
static bool text_save_begin_inplace(TextSave *ctx) {
Text *txt = ctx->txt;
struct stat now = { 0 };
int newfd = -1, saved_errno;
if ((ctx->fd = openat(ctx->dirfd, ctx->filename, O_CREAT|O_WRONLY, 0666)) == -1)
goto err;
if (fstat(ctx->fd, &now) == -1)
goto err;
struct stat loaded = text_stat(txt);
Block *block = text_block_mmaped(txt);
if (block && now.st_dev == loaded.st_dev && now.st_ino == loaded.st_ino) {
/* The file we are going to overwrite is currently mmap-ed from
* text_load, therefore we copy the mmap-ed block to a temporary
* file and remap it at the same position such that all pointers
* from the various pieces are still valid.
*/
size_t size = block->size;
char tmpname[32] = "/tmp/vis-XXXXXX";
newfd = mkstemp(tmpname);
if (newfd == -1)
goto err;
if (unlink(tmpname) == -1)
goto err;
ssize_t written = write_all(newfd, block->data, size);
if (written == -1 || (size_t)written != size)
goto err;
void *data = mmap(block->data, size, PROT_READ, MAP_SHARED|MAP_FIXED, newfd, 0);
if (data == MAP_FAILED)
goto err;
bool close_failed = (close(newfd) == -1);
newfd = -1;
if (close_failed)
goto err;
block->type = BLOCK_TYPE_MMAP;
}
/* overwrite the existing file content, if something goes wrong
* here we are screwed, TODO: make a backup before? */
if (ftruncate(ctx->fd, 0) == -1)
goto err;
ctx->type = TEXT_SAVE_INPLACE;
return true;
err:
saved_errno = errno;
if (newfd != -1)
close(newfd);
if (ctx->fd != -1)
close(ctx->fd);
ctx->fd = -1;
errno = saved_errno;
return false;
}
static bool text_save_commit_inplace(TextSave *ctx) {
if (fsync(ctx->fd) == -1)
return false;
struct stat meta = { 0 };
if (fstat(ctx->fd, &meta) == -1)
return false;
if (close(ctx->fd) == -1)
return false;
text_saved(ctx->txt, &meta);
return true;
}
TextSave *text_save_begin(Text *txt, int dirfd, const char *filename, enum TextSaveMethod type) {
if (!filename)
return NULL;
TextSave *ctx = calloc(1, sizeof *ctx);
if (!ctx)
return NULL;
ctx->txt = txt;
ctx->fd = -1;
ctx->dirfd = dirfd;
if (!(ctx->filename = strdup(filename)))
goto err;
errno = 0;
if ((type == TEXT_SAVE_AUTO || type == TEXT_SAVE_ATOMIC) && text_save_begin_atomic(ctx))
return ctx;
if (errno == ENOSPC)
goto err;
if ((type == TEXT_SAVE_AUTO || type == TEXT_SAVE_INPLACE) && text_save_begin_inplace(ctx))
return ctx;
err:
text_save_cancel(ctx);
return NULL;
}
bool text_save_commit(TextSave *ctx) {
if (!ctx)
return true;
bool ret;
switch (ctx->type) {
case TEXT_SAVE_ATOMIC:
ret = text_save_commit_atomic(ctx);
break;
case TEXT_SAVE_INPLACE:
ret = text_save_commit_inplace(ctx);
break;
default:
ret = false;
break;
}
text_save_cancel(ctx);
return ret;
}
void text_save_cancel(TextSave *ctx) {
if (!ctx)
return;
int saved_errno = errno;
if (ctx->fd != -1)
close(ctx->fd);
if (ctx->tmpname && ctx->tmpname[0])
unlinkat(ctx->dirfd, ctx->tmpname, 0);
free(ctx->tmpname);
free(ctx->filename);
free(ctx);
errno = saved_errno;
}
/* First try to save the file atomically using rename(2) if this does not
* work overwrite the file in place. However if something goes wrong during
* this overwrite the original file is permanently damaged.
*/
bool text_save(Text *txt, const char *filename) {
return text_saveat(txt, AT_FDCWD, filename);
}
bool text_saveat(Text *txt, int dirfd, const char *filename) {
return text_saveat_method(txt, dirfd, filename, TEXT_SAVE_AUTO);
}
bool text_save_method(Text *txt, const char *filename, enum TextSaveMethod method) {
return text_saveat_method(txt, AT_FDCWD, filename, method);
}
bool text_saveat_method(Text *txt, int dirfd, const char *filename, enum TextSaveMethod method) {
if (!filename) {
text_saved(txt, NULL);
return true;
}
TextSave *ctx = text_save_begin(txt, dirfd, filename, method);
if (!ctx)
return false;
Filerange range = (Filerange){ .start = 0, .end = text_size(txt) };
ssize_t written = text_save_write_range(ctx, &range);
if (written == -1 || (size_t)written != text_range_size(&range)) {
text_save_cancel(ctx);
return false;
}
return text_save_commit(ctx);
}
ssize_t text_save_write_range(TextSave *ctx, const Filerange *range) {
return text_write_range(ctx->txt, range, ctx->fd);
}
ssize_t text_write(const Text *txt, int fd) {
Filerange r = (Filerange){ .start = 0, .end = text_size(txt) };
return text_write_range(txt, &r, fd);
}
ssize_t text_write_range(const Text *txt, const Filerange *range, int fd) {
size_t size = text_range_size(range), rem = size;
for (Iterator it = text_iterator_get(txt, range->start);
rem > 0 && text_iterator_valid(&it);
text_iterator_next(&it)) {
size_t prem = it.end - it.text;
if (prem > rem)
prem = rem;
ssize_t written = write_all(fd, it.text, prem);
if (written == -1)
return -1;
rem -= written;
if ((size_t)written != prem)
break;
}
return size - rem;
}