packfile: express constants in terms of the_hash_algo
[git/git.git] / refs / packed-backend.c
CommitLineData
67be7c5a 1#include "../cache.h"
44c2339e 2#include "../config.h"
67be7c5a
MH
3#include "../refs.h"
4#include "refs-internal.h"
67be7c5a
MH
5#include "packed-backend.h"
6#include "../iterator.h"
7#include "../lockfile.h"
fb9c2d27 8#include "../chdir-notify.h"
67be7c5a 9
5b633610
MH
10enum mmap_strategy {
11 /*
12 * Don't use mmap() at all for reading `packed-refs`.
13 */
14 MMAP_NONE,
67be7c5a
MH
15
16 /*
5b633610
MH
17 * Can use mmap() for reading `packed-refs`, but the file must
18 * not remain mmapped. This is the usual option on Windows,
19 * where you cannot rename a new version of a file onto a file
20 * that is currently mmapped.
67be7c5a 21 */
5b633610 22 MMAP_TEMPORARY,
67be7c5a 23
5b633610
MH
24 /*
25 * It is OK to leave the `packed-refs` file mmapped while
26 * arbitrary other code is running.
27 */
28 MMAP_OK
67be7c5a
MH
29};
30
5b633610
MH
31#if defined(NO_MMAP)
32static enum mmap_strategy mmap_strategy = MMAP_NONE;
33#elif defined(MMAP_PREVENTS_DELETE)
34static enum mmap_strategy mmap_strategy = MMAP_TEMPORARY;
35#else
36static enum mmap_strategy mmap_strategy = MMAP_OK;
37#endif
38
f0a7dc86 39struct packed_ref_store;
67be7c5a
MH
40
41/*
cff28ca9
MH
42 * A `snapshot` represents one snapshot of a `packed-refs` file.
43 *
44 * Normally, this will be a mmapped view of the contents of the
45 * `packed-refs` file at the time the snapshot was created. However,
46 * if the `packed-refs` file was not sorted, this might point at heap
47 * memory holding the contents of the `packed-refs` file with its
48 * records sorted by refname.
49 *
50 * `snapshot` instances are reference counted (via
51 * `acquire_snapshot()` and `release_snapshot()`). This is to prevent
52 * an instance from disappearing while an iterator is still iterating
53 * over it. Instances are garbage collected when their `referrers`
54 * count goes to zero.
55 *
56 * The most recent `snapshot`, if available, is referenced by the
57 * `packed_ref_store`. Its freshness is checked whenever
58 * `get_snapshot()` is called; if the existing snapshot is obsolete, a
59 * new snapshot is taken.
67be7c5a 60 */
cff28ca9 61struct snapshot {
f0a7dc86
MH
62 /*
63 * A back-pointer to the packed_ref_store with which this
cff28ca9 64 * snapshot is associated:
f0a7dc86
MH
65 */
66 struct packed_ref_store *refs;
67
5b633610
MH
68 /* Is the `packed-refs` file currently mmapped? */
69 int mmapped;
70
71 /*
4a2854f7
MH
72 * The contents of the `packed-refs` file:
73 *
74 * - buf -- a pointer to the start of the memory
75 * - start -- a pointer to the first byte of actual references
76 * (i.e., after the header line, if one is present)
77 * - eof -- a pointer just past the end of the reference
78 * contents
79 *
80 * If the `packed-refs` file was already sorted, `buf` points
81 * at the mmapped contents of the file. If not, it points at
82 * heap-allocated memory containing the contents, sorted. If
83 * there were no contents (e.g., because the file didn't
84 * exist), `buf`, `start`, and `eof` are all NULL.
5b633610 85 */
4a2854f7 86 char *buf, *start, *eof;
5b633610 87
daa45408 88 /*
cff28ca9
MH
89 * What is the peeled state of the `packed-refs` file that
90 * this snapshot represents? (This is usually determined from
91 * the file's header.)
daa45408
MH
92 */
93 enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled;
94
67be7c5a 95 /*
cff28ca9
MH
96 * Count of references to this instance, including the pointer
97 * from `packed_ref_store::snapshot`, if any. The instance
98 * will not be freed as long as the reference count is
99 * nonzero.
67be7c5a
MH
100 */
101 unsigned int referrers;
102
cff28ca9
MH
103 /*
104 * The metadata of the `packed-refs` file from which this
105 * snapshot was created, used to tell if the file has been
106 * replaced since we read it.
107 */
67be7c5a
MH
108 struct stat_validity validity;
109};
67be7c5a
MH
110
111/*
cff28ca9
MH
112 * A `ref_store` representing references stored in a `packed-refs`
113 * file. It implements the `ref_store` interface, though it has some
114 * limitations:
115 *
116 * - It cannot store symbolic references.
117 *
118 * - It cannot store reflogs.
119 *
120 * - It does not support reference renaming (though it could).
121 *
122 * On the other hand, it can be locked outside of a reference
123 * transaction. In that case, it remains locked even after the
124 * transaction is done and the new `packed-refs` file is activated.
67be7c5a
MH
125 */
126struct packed_ref_store {
e0cc8ac8
MH
127 struct ref_store base;
128
67be7c5a
MH
129 unsigned int store_flags;
130
131 /* The path of the "packed-refs" file: */
132 char *path;
133
134 /*
cff28ca9
MH
135 * A snapshot of the values read from the `packed-refs` file,
136 * if it might still be current; otherwise, NULL.
67be7c5a 137 */
cff28ca9 138 struct snapshot *snapshot;
67be7c5a
MH
139
140 /*
141 * Lock used for the "packed-refs" file. Note that this (and
142 * thus the enclosing `packed_ref_store`) must not be freed.
143 */
144 struct lock_file lock;
42dfa7ec
MH
145
146 /*
147 * Temporary file used when rewriting new contents to the
148 * "packed-refs" file. Note that this (and thus the enclosing
149 * `packed_ref_store`) must not be freed.
150 */
076aa2cb 151 struct tempfile *tempfile;
67be7c5a
MH
152};
153
14b3c344 154/*
cff28ca9 155 * Increment the reference count of `*snapshot`.
14b3c344 156 */
cff28ca9 157static void acquire_snapshot(struct snapshot *snapshot)
14b3c344 158{
cff28ca9 159 snapshot->referrers++;
14b3c344
MH
160}
161
5b633610 162/*
cff28ca9 163 * If the buffer in `snapshot` is active, then either munmap the
5b633610
MH
164 * memory and close the file, or free the memory. Then set the buffer
165 * pointers to NULL.
166 */
cff28ca9 167static void clear_snapshot_buffer(struct snapshot *snapshot)
5b633610 168{
cff28ca9
MH
169 if (snapshot->mmapped) {
170 if (munmap(snapshot->buf, snapshot->eof - snapshot->buf))
5b633610 171 die_errno("error ummapping packed-refs file %s",
cff28ca9
MH
172 snapshot->refs->path);
173 snapshot->mmapped = 0;
5b633610 174 } else {
cff28ca9 175 free(snapshot->buf);
5b633610 176 }
4a2854f7 177 snapshot->buf = snapshot->start = snapshot->eof = NULL;
5b633610
MH
178}
179
14b3c344 180/*
cff28ca9
MH
181 * Decrease the reference count of `*snapshot`. If it goes to zero,
182 * free `*snapshot` and return true; otherwise return false.
14b3c344 183 */
cff28ca9 184static int release_snapshot(struct snapshot *snapshot)
14b3c344 185{
cff28ca9
MH
186 if (!--snapshot->referrers) {
187 stat_validity_clear(&snapshot->validity);
188 clear_snapshot_buffer(snapshot);
189 free(snapshot);
14b3c344
MH
190 return 1;
191 } else {
192 return 0;
193 }
194}
195
e0cc8ac8
MH
196struct ref_store *packed_ref_store_create(const char *path,
197 unsigned int store_flags)
67be7c5a
MH
198{
199 struct packed_ref_store *refs = xcalloc(1, sizeof(*refs));
e0cc8ac8 200 struct ref_store *ref_store = (struct ref_store *)refs;
67be7c5a 201
e0cc8ac8 202 base_ref_store_init(ref_store, &refs_be_packed);
67be7c5a 203 refs->store_flags = store_flags;
e0cc8ac8 204
67be7c5a 205 refs->path = xstrdup(path);
fb9c2d27
JK
206 chdir_notify_reparent("packed-refs", &refs->path);
207
e0cc8ac8 208 return ref_store;
67be7c5a
MH
209}
210
e0cc8ac8
MH
211/*
212 * Downcast `ref_store` to `packed_ref_store`. Die if `ref_store` is
213 * not a `packed_ref_store`. Also die if `packed_ref_store` doesn't
214 * support at least the flags specified in `required_flags`. `caller`
215 * is used in any necessary error messages.
216 */
217static struct packed_ref_store *packed_downcast(struct ref_store *ref_store,
218 unsigned int required_flags,
219 const char *caller)
220{
221 struct packed_ref_store *refs;
222
223 if (ref_store->be != &refs_be_packed)
033abf97 224 BUG("ref_store is type \"%s\" not \"packed\" in %s",
e0cc8ac8
MH
225 ref_store->be->name, caller);
226
227 refs = (struct packed_ref_store *)ref_store;
228
229 if ((refs->store_flags & required_flags) != required_flags)
033abf97 230 BUG("unallowed operation (%s), requires %x, has %x\n",
e0cc8ac8
MH
231 caller, required_flags, refs->store_flags);
232
233 return refs;
234}
235
cff28ca9 236static void clear_snapshot(struct packed_ref_store *refs)
67be7c5a 237{
cff28ca9
MH
238 if (refs->snapshot) {
239 struct snapshot *snapshot = refs->snapshot;
67be7c5a 240
cff28ca9
MH
241 refs->snapshot = NULL;
242 release_snapshot(snapshot);
67be7c5a
MH
243 }
244}
245
735267aa
MH
246static NORETURN void die_unterminated_line(const char *path,
247 const char *p, size_t len)
67be7c5a 248{
735267aa
MH
249 if (len < 80)
250 die("unterminated line in %s: %.*s", path, (int)len, p);
251 else
252 die("unterminated line in %s: %.75s...", path, p);
253}
67be7c5a 254
735267aa
MH
255static NORETURN void die_invalid_line(const char *path,
256 const char *p, size_t len)
257{
258 const char *eol = memchr(p, '\n', len);
259
260 if (!eol)
261 die_unterminated_line(path, p, len);
262 else if (eol - p < 80)
263 die("unexpected line in %s: %.*s", path, (int)(eol - p), p);
264 else
265 die("unexpected line in %s: %.75s...", path, p);
266
267}
268
cff28ca9 269struct snapshot_record {
02b920f3
MH
270 const char *start;
271 size_t len;
272};
273
cff28ca9 274static int cmp_packed_ref_records(const void *v1, const void *v2)
02b920f3 275{
cff28ca9 276 const struct snapshot_record *e1 = v1, *e2 = v2;
02b920f3
MH
277 const char *r1 = e1->start + GIT_SHA1_HEXSZ + 1;
278 const char *r2 = e2->start + GIT_SHA1_HEXSZ + 1;
279
280 while (1) {
281 if (*r1 == '\n')
282 return *r2 == '\n' ? 0 : -1;
283 if (*r1 != *r2) {
284 if (*r2 == '\n')
285 return 1;
286 else
287 return (unsigned char)*r1 < (unsigned char)*r2 ? -1 : +1;
288 }
289 r1++;
290 r2++;
67be7c5a
MH
291 }
292}
293
d1cf1551 294/*
cff28ca9
MH
295 * Compare a snapshot record at `rec` to the specified NUL-terminated
296 * refname.
d1cf1551 297 */
cff28ca9 298static int cmp_record_to_refname(const char *rec, const char *refname)
d1cf1551
MH
299{
300 const char *r1 = rec + GIT_SHA1_HEXSZ + 1;
301 const char *r2 = refname;
302
303 while (1) {
304 if (*r1 == '\n')
305 return *r2 ? -1 : 0;
306 if (!*r2)
307 return 1;
308 if (*r1 != *r2)
309 return (unsigned char)*r1 < (unsigned char)*r2 ? -1 : +1;
310 r1++;
311 r2++;
312 }
313}
67be7c5a
MH
314
315/*
cff28ca9
MH
316 * `snapshot->buf` is not known to be sorted. Check whether it is, and
317 * if not, sort it into new memory and munmap/free the old storage.
67be7c5a 318 */
cff28ca9 319static void sort_snapshot(struct snapshot *snapshot)
67be7c5a 320{
cff28ca9 321 struct snapshot_record *records = NULL;
02b920f3
MH
322 size_t alloc = 0, nr = 0;
323 int sorted = 1;
324 const char *pos, *eof, *eol;
325 size_t len, i;
326 char *new_buffer, *dst;
67be7c5a 327
4a2854f7 328 pos = snapshot->start;
cff28ca9 329 eof = snapshot->eof;
67be7c5a 330
4a2854f7 331 if (pos == eof)
02b920f3 332 return;
67be7c5a 333
4a2854f7
MH
334 len = eof - pos;
335
02b920f3 336 /*
cff28ca9 337 * Initialize records based on a crude estimate of the number
02b920f3
MH
338 * of references in the file (we'll grow it below if needed):
339 */
cff28ca9 340 ALLOC_GROW(records, len / 80 + 20, alloc);
02b920f3
MH
341
342 while (pos < eof) {
343 eol = memchr(pos, '\n', eof - pos);
344 if (!eol)
345 /* The safety check should prevent this. */
346 BUG("unterminated line found in packed-refs");
347 if (eol - pos < GIT_SHA1_HEXSZ + 2)
cff28ca9 348 die_invalid_line(snapshot->refs->path,
02b920f3
MH
349 pos, eof - pos);
350 eol++;
351 if (eol < eof && *eol == '^') {
352 /*
353 * Keep any peeled line together with its
354 * reference:
355 */
356 const char *peeled_start = eol;
357
358 eol = memchr(peeled_start, '\n', eof - peeled_start);
359 if (!eol)
360 /* The safety check should prevent this. */
361 BUG("unterminated peeled line found in packed-refs");
362 eol++;
363 }
364
cff28ca9
MH
365 ALLOC_GROW(records, nr + 1, alloc);
366 records[nr].start = pos;
367 records[nr].len = eol - pos;
02b920f3
MH
368 nr++;
369
370 if (sorted &&
371 nr > 1 &&
cff28ca9
MH
372 cmp_packed_ref_records(&records[nr - 2],
373 &records[nr - 1]) >= 0)
02b920f3 374 sorted = 0;
67be7c5a 375
02b920f3
MH
376 pos = eol;
377 }
378
379 if (sorted)
380 goto cleanup;
381
cff28ca9
MH
382 /* We need to sort the memory. First we sort the records array: */
383 QSORT(records, nr, cmp_packed_ref_records);
02b920f3
MH
384
385 /*
386 * Allocate a new chunk of memory, and copy the old memory to
cff28ca9 387 * the new in the order indicated by `records` (not bothering
02b920f3
MH
388 * with the header line):
389 */
390 new_buffer = xmalloc(len);
391 for (dst = new_buffer, i = 0; i < nr; i++) {
cff28ca9
MH
392 memcpy(dst, records[i].start, records[i].len);
393 dst += records[i].len;
02b920f3
MH
394 }
395
396 /*
397 * Now munmap the old buffer and use the sorted buffer in its
398 * place:
399 */
cff28ca9 400 clear_snapshot_buffer(snapshot);
4a2854f7 401 snapshot->buf = snapshot->start = new_buffer;
cff28ca9 402 snapshot->eof = new_buffer + len;
02b920f3
MH
403
404cleanup:
cff28ca9 405 free(records);
67be7c5a
MH
406}
407
408/*
02b920f3
MH
409 * Return a pointer to the start of the record that contains the
410 * character `*p` (which must be within the buffer). If no other
411 * record start is found, return `buf`.
412 */
413static const char *find_start_of_record(const char *buf, const char *p)
414{
415 while (p > buf && (p[-1] != '\n' || p[0] == '^'))
416 p--;
417 return p;
418}
419
d1cf1551
MH
420/*
421 * Return a pointer to the start of the record following the record
422 * that contains `*p`. If none is found before `end`, return `end`.
423 */
424static const char *find_end_of_record(const char *p, const char *end)
425{
426 while (++p < end && (p[-1] != '\n' || p[0] == '^'))
427 ;
428 return p;
429}
430
02b920f3
MH
431/*
432 * We want to be able to compare mmapped reference records quickly,
433 * without totally parsing them. We can do so because the records are
434 * LF-terminated, and the refname should start exactly (GIT_SHA1_HEXSZ
435 * + 1) bytes past the beginning of the record.
436 *
437 * But what if the `packed-refs` file contains garbage? We're willing
438 * to tolerate not detecting the problem, as long as we don't produce
439 * totally garbled output (we can't afford to check the integrity of
440 * the whole file during every Git invocation). But we do want to be
441 * sure that we never read past the end of the buffer in memory and
442 * perform an illegal memory access.
443 *
444 * Guarantee that minimum level of safety by verifying that the last
445 * record in the file is LF-terminated, and that it has at least
446 * (GIT_SHA1_HEXSZ + 1) characters before the LF. Die if either of
447 * these checks fails.
448 */
cff28ca9 449static void verify_buffer_safe(struct snapshot *snapshot)
02b920f3 450{
4a2854f7 451 const char *start = snapshot->start;
cff28ca9 452 const char *eof = snapshot->eof;
02b920f3
MH
453 const char *last_line;
454
4a2854f7 455 if (start == eof)
02b920f3
MH
456 return;
457
4a2854f7 458 last_line = find_start_of_record(start, eof - 1);
02b920f3 459 if (*(eof - 1) != '\n' || eof - last_line < GIT_SHA1_HEXSZ + 2)
cff28ca9 460 die_invalid_line(snapshot->refs->path,
02b920f3
MH
461 last_line, eof - last_line);
462}
463
ba41a8b6
KG
464#define SMALL_FILE_SIZE (32*1024)
465
5b633610
MH
466/*
467 * Depending on `mmap_strategy`, either mmap or read the contents of
cff28ca9 468 * the `packed-refs` file into the snapshot. Return 1 if the file
01caf20d
MH
469 * existed and was read, or 0 if the file was absent or empty. Die on
470 * errors.
5b633610 471 */
cff28ca9 472static int load_contents(struct snapshot *snapshot)
5b633610
MH
473{
474 int fd;
475 struct stat st;
476 size_t size;
477 ssize_t bytes_read;
478
cff28ca9 479 fd = open(snapshot->refs->path, O_RDONLY);
5b633610
MH
480 if (fd < 0) {
481 if (errno == ENOENT) {
482 /*
483 * This is OK; it just means that no
484 * "packed-refs" file has been written yet,
485 * which is equivalent to it being empty,
486 * which is its state when initialized with
487 * zeros.
488 */
489 return 0;
490 } else {
cff28ca9 491 die_errno("couldn't read %s", snapshot->refs->path);
5b633610
MH
492 }
493 }
494
cff28ca9 495 stat_validity_update(&snapshot->validity, fd);
5b633610
MH
496
497 if (fstat(fd, &st) < 0)
cff28ca9 498 die_errno("couldn't stat %s", snapshot->refs->path);
5b633610
MH
499 size = xsize_t(st.st_size);
500
01caf20d 501 if (!size) {
09427e83 502 close(fd);
01caf20d 503 return 0;
ba41a8b6 504 } else if (mmap_strategy == MMAP_NONE || size <= SMALL_FILE_SIZE) {
cff28ca9
MH
505 snapshot->buf = xmalloc(size);
506 bytes_read = read_in_full(fd, snapshot->buf, size);
5b633610 507 if (bytes_read < 0 || bytes_read != size)
cff28ca9 508 die_errno("couldn't read %s", snapshot->refs->path);
cff28ca9 509 snapshot->mmapped = 0;
01caf20d 510 } else {
cff28ca9 511 snapshot->buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
cff28ca9 512 snapshot->mmapped = 1;
5b633610
MH
513 }
514 close(fd);
515
4a2854f7
MH
516 snapshot->start = snapshot->buf;
517 snapshot->eof = snapshot->buf + size;
518
5b633610
MH
519 return 1;
520}
521
d1cf1551 522/*
cff28ca9 523 * Find the place in `snapshot->buf` where the start of the record for
d1cf1551
MH
524 * `refname` starts. If `mustexist` is true and the reference doesn't
525 * exist, then return NULL. If `mustexist` is false and the reference
526 * doesn't exist, then return the point where that reference would be
4a14f8d0
MH
527 * inserted, or `snapshot->eof` (which might be NULL) if it would be
528 * inserted at the end of the file. In the latter mode, `refname`
529 * doesn't have to be a proper reference name; for example, one could
530 * search for "refs/replace/" to find the start of any replace
531 * references.
d1cf1551 532 *
cff28ca9
MH
533 * The record is sought using a binary search, so `snapshot->buf` must
534 * be sorted.
d1cf1551 535 */
cff28ca9 536static const char *find_reference_location(struct snapshot *snapshot,
d1cf1551
MH
537 const char *refname, int mustexist)
538{
539 /*
540 * This is not *quite* a garden-variety binary search, because
541 * the data we're searching is made up of records, and we
542 * always need to find the beginning of a record to do a
543 * comparison. A "record" here is one line for the reference
544 * itself and zero or one peel lines that start with '^'. Our
545 * loop invariant is described in the next two comments.
546 */
547
548 /*
549 * A pointer to the character at the start of a record whose
550 * preceding records all have reference names that come
551 * *before* `refname`.
552 */
4a2854f7 553 const char *lo = snapshot->start;
d1cf1551
MH
554
555 /*
556 * A pointer to a the first character of a record whose
557 * reference name comes *after* `refname`.
558 */
cff28ca9 559 const char *hi = snapshot->eof;
d1cf1551 560
4a14f8d0 561 while (lo != hi) {
d1cf1551
MH
562 const char *mid, *rec;
563 int cmp;
564
565 mid = lo + (hi - lo) / 2;
566 rec = find_start_of_record(lo, mid);
cff28ca9 567 cmp = cmp_record_to_refname(rec, refname);
d1cf1551
MH
568 if (cmp < 0) {
569 lo = find_end_of_record(mid, hi);
570 } else if (cmp > 0) {
571 hi = rec;
572 } else {
573 return rec;
574 }
575 }
576
577 if (mustexist)
578 return NULL;
579 else
580 return lo;
581}
582
67be7c5a 583/*
cff28ca9
MH
584 * Create a newly-allocated `snapshot` of the `packed-refs` file in
585 * its current state and return it. The return value will already have
586 * its reference count incremented.
67be7c5a
MH
587 *
588 * A comment line of the form "# pack-refs with: " may contain zero or
589 * more traits. We interpret the traits as follows:
590 *
02b920f3 591 * Neither `peeled` nor `fully-peeled`:
67be7c5a
MH
592 *
593 * Probably no references are peeled. But if the file contains a
594 * peeled value for a reference, we will use it.
595 *
02b920f3 596 * `peeled`:
67be7c5a
MH
597 *
598 * References under "refs/tags/", if they *can* be peeled, *are*
599 * peeled in this file. References outside of "refs/tags/" are
600 * probably not peeled even if they could have been, but if we find
601 * a peeled value for such a reference we will use it.
602 *
02b920f3 603 * `fully-peeled`:
67be7c5a
MH
604 *
605 * All references in the file that can be peeled are peeled.
606 * Inversely (and this is more important), any references in the
607 * file for which no peeled value is recorded is not peelable. This
608 * trait should typically be written alongside "peeled" for
609 * compatibility with older clients, but we do not require it
610 * (i.e., "peeled" is a no-op if "fully-peeled" is set).
02b920f3
MH
611 *
612 * `sorted`:
613 *
614 * The references in this file are known to be sorted by refname.
67be7c5a 615 */
cff28ca9 616static struct snapshot *create_snapshot(struct packed_ref_store *refs)
67be7c5a 617{
cff28ca9 618 struct snapshot *snapshot = xcalloc(1, sizeof(*snapshot));
02b920f3 619 int sorted = 0;
67be7c5a 620
cff28ca9
MH
621 snapshot->refs = refs;
622 acquire_snapshot(snapshot);
623 snapshot->peeled = PEELED_NONE;
67be7c5a 624
cff28ca9
MH
625 if (!load_contents(snapshot))
626 return snapshot;
67be7c5a 627
36f23534 628 /* If the file has a header line, process it: */
cff28ca9 629 if (snapshot->buf < snapshot->eof && *snapshot->buf == '#') {
27a41841 630 char *tmp, *p, *eol;
a8811695 631 struct string_list traits = STRING_LIST_INIT_NODUP;
9308b7f3 632
cff28ca9
MH
633 eol = memchr(snapshot->buf, '\n',
634 snapshot->eof - snapshot->buf);
36f23534 635 if (!eol)
5b633610 636 die_unterminated_line(refs->path,
cff28ca9
MH
637 snapshot->buf,
638 snapshot->eof - snapshot->buf);
67be7c5a 639
27a41841 640 tmp = xmemdupz(snapshot->buf, eol - snapshot->buf);
67be7c5a 641
27a41841 642 if (!skip_prefix(tmp, "# pack-refs with:", (const char **)&p))
5b633610 643 die_invalid_line(refs->path,
cff28ca9
MH
644 snapshot->buf,
645 snapshot->eof - snapshot->buf);
36f23534 646
a8811695
MH
647 string_list_split_in_place(&traits, p, ' ', -1);
648
649 if (unsorted_string_list_has_string(&traits, "fully-peeled"))
cff28ca9 650 snapshot->peeled = PEELED_FULLY;
a8811695 651 else if (unsorted_string_list_has_string(&traits, "peeled"))
cff28ca9 652 snapshot->peeled = PEELED_TAGS;
02b920f3
MH
653
654 sorted = unsorted_string_list_has_string(&traits, "sorted");
655
36f23534
MH
656 /* perhaps other traits later as well */
657
658 /* The "+ 1" is for the LF character. */
4a2854f7 659 snapshot->start = eol + 1;
a8811695
MH
660
661 string_list_clear(&traits, 0);
27a41841 662 free(tmp);
67be7c5a
MH
663 }
664
cff28ca9 665 verify_buffer_safe(snapshot);
67be7c5a 666
02b920f3 667 if (!sorted) {
cff28ca9 668 sort_snapshot(snapshot);
02b920f3
MH
669
670 /*
671 * Reordering the records might have moved a short one
672 * to the end of the buffer, so verify the buffer's
673 * safety again:
674 */
cff28ca9 675 verify_buffer_safe(snapshot);
02b920f3
MH
676 }
677
cff28ca9 678 if (mmap_strategy != MMAP_OK && snapshot->mmapped) {
02b920f3
MH
679 /*
680 * We don't want to leave the file mmapped, so we are
681 * forced to make a copy now:
682 */
4a2854f7 683 size_t size = snapshot->eof - snapshot->start;
02b920f3
MH
684 char *buf_copy = xmalloc(size);
685
4a2854f7 686 memcpy(buf_copy, snapshot->start, size);
cff28ca9 687 clear_snapshot_buffer(snapshot);
4a2854f7 688 snapshot->buf = snapshot->start = buf_copy;
cff28ca9 689 snapshot->eof = buf_copy + size;
02b920f3
MH
690 }
691
cff28ca9 692 return snapshot;
67be7c5a
MH
693}
694
695/*
cff28ca9
MH
696 * Check that `refs->snapshot` (if present) still reflects the
697 * contents of the `packed-refs` file. If not, clear the snapshot.
67be7c5a 698 */
cff28ca9 699static void validate_snapshot(struct packed_ref_store *refs)
67be7c5a 700{
cff28ca9
MH
701 if (refs->snapshot &&
702 !stat_validity_check(&refs->snapshot->validity, refs->path))
703 clear_snapshot(refs);
67be7c5a
MH
704}
705
706/*
cff28ca9
MH
707 * Get the `snapshot` for the specified packed_ref_store, creating and
708 * populating it if it hasn't been read before or if the file has been
709 * changed (according to its `validity` field) since it was last read.
710 * On the other hand, if we hold the lock, then assume that the file
711 * hasn't been changed out from under us, so skip the extra `stat()`
712 * call in `stat_validity_check()`. This function does *not* increase
713 * the snapshot's reference count on behalf of the caller.
67be7c5a 714 */
cff28ca9 715static struct snapshot *get_snapshot(struct packed_ref_store *refs)
67be7c5a
MH
716{
717 if (!is_lock_file_locked(&refs->lock))
cff28ca9 718 validate_snapshot(refs);
67be7c5a 719
cff28ca9
MH
720 if (!refs->snapshot)
721 refs->snapshot = create_snapshot(refs);
67be7c5a 722
cff28ca9 723 return refs->snapshot;
67be7c5a
MH
724}
725
e0cc8ac8 726static int packed_read_raw_ref(struct ref_store *ref_store,
99afe91a 727 const char *refname, struct object_id *oid,
e0cc8ac8 728 struct strbuf *referent, unsigned int *type)
67be7c5a 729{
e0cc8ac8
MH
730 struct packed_ref_store *refs =
731 packed_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
cff28ca9 732 struct snapshot *snapshot = get_snapshot(refs);
f3987ab3 733 const char *rec;
67be7c5a
MH
734
735 *type = 0;
736
cff28ca9 737 rec = find_reference_location(snapshot, refname, 1);
f3987ab3
MH
738
739 if (!rec) {
740 /* refname is not a packed reference. */
67be7c5a
MH
741 errno = ENOENT;
742 return -1;
743 }
744
99afe91a 745 if (get_oid_hex(rec, oid))
cff28ca9 746 die_invalid_line(refs->path, rec, snapshot->eof - rec);
f3987ab3 747
67be7c5a
MH
748 *type = REF_ISPACKED;
749 return 0;
750}
751
523ee2d7
MH
752/*
753 * This value is set in `base.flags` if the peeled value of the
754 * current reference is known. In that case, `peeled` contains the
78fb4579 755 * correct peeled value for the reference, which might be `null_oid`
523ee2d7
MH
756 * if the reference is not a tag or if it is broken.
757 */
758#define REF_KNOWS_PEELED 0x40
67be7c5a 759
523ee2d7 760/*
cff28ca9 761 * An iterator over a snapshot of a `packed-refs` file.
523ee2d7 762 */
67be7c5a
MH
763struct packed_ref_iterator {
764 struct ref_iterator base;
765
cff28ca9 766 struct snapshot *snapshot;
523ee2d7 767
cff28ca9 768 /* The current position in the snapshot's buffer: */
523ee2d7
MH
769 const char *pos;
770
cff28ca9 771 /* The end of the part of the buffer that will be iterated over: */
523ee2d7
MH
772 const char *eof;
773
cff28ca9 774 /* Scratch space for current values: */
523ee2d7 775 struct object_id oid, peeled;
523ee2d7
MH
776 struct strbuf refname_buf;
777
67be7c5a
MH
778 unsigned int flags;
779};
780
cff28ca9
MH
781/*
782 * Move the iterator to the next record in the snapshot, without
783 * respect for whether the record is actually required by the current
784 * iteration. Adjust the fields in `iter` and return `ITER_OK` or
785 * `ITER_DONE`. This function does not free the iterator in the case
786 * of `ITER_DONE`.
787 */
523ee2d7
MH
788static int next_record(struct packed_ref_iterator *iter)
789{
790 const char *p = iter->pos, *eol;
791
792 strbuf_reset(&iter->refname_buf);
793
794 if (iter->pos == iter->eof)
795 return ITER_DONE;
796
797 iter->base.flags = REF_ISPACKED;
798
799 if (iter->eof - p < GIT_SHA1_HEXSZ + 2 ||
800 parse_oid_hex(p, &iter->oid, &p) ||
801 !isspace(*p++))
cff28ca9 802 die_invalid_line(iter->snapshot->refs->path,
523ee2d7
MH
803 iter->pos, iter->eof - iter->pos);
804
805 eol = memchr(p, '\n', iter->eof - p);
806 if (!eol)
cff28ca9 807 die_unterminated_line(iter->snapshot->refs->path,
523ee2d7
MH
808 iter->pos, iter->eof - iter->pos);
809
810 strbuf_add(&iter->refname_buf, p, eol - p);
811 iter->base.refname = iter->refname_buf.buf;
812
813 if (check_refname_format(iter->base.refname, REFNAME_ALLOW_ONELEVEL)) {
814 if (!refname_is_safe(iter->base.refname))
815 die("packed refname is dangerous: %s",
816 iter->base.refname);
817 oidclr(&iter->oid);
818 iter->base.flags |= REF_BAD_NAME | REF_ISBROKEN;
819 }
cff28ca9
MH
820 if (iter->snapshot->peeled == PEELED_FULLY ||
821 (iter->snapshot->peeled == PEELED_TAGS &&
523ee2d7
MH
822 starts_with(iter->base.refname, "refs/tags/")))
823 iter->base.flags |= REF_KNOWS_PEELED;
824
825 iter->pos = eol + 1;
826
827 if (iter->pos < iter->eof && *iter->pos == '^') {
828 p = iter->pos + 1;
829 if (iter->eof - p < GIT_SHA1_HEXSZ + 1 ||
830 parse_oid_hex(p, &iter->peeled, &p) ||
831 *p++ != '\n')
cff28ca9 832 die_invalid_line(iter->snapshot->refs->path,
523ee2d7
MH
833 iter->pos, iter->eof - iter->pos);
834 iter->pos = p;
835
836 /*
837 * Regardless of what the file header said, we
838 * definitely know the value of *this* reference. But
839 * we suppress it if the reference is broken:
840 */
841 if ((iter->base.flags & REF_ISBROKEN)) {
842 oidclr(&iter->peeled);
843 iter->base.flags &= ~REF_KNOWS_PEELED;
844 } else {
845 iter->base.flags |= REF_KNOWS_PEELED;
846 }
847 } else {
848 oidclr(&iter->peeled);
849 }
850
851 return ITER_OK;
852}
853
67be7c5a
MH
854static int packed_ref_iterator_advance(struct ref_iterator *ref_iterator)
855{
856 struct packed_ref_iterator *iter =
857 (struct packed_ref_iterator *)ref_iterator;
858 int ok;
859
523ee2d7 860 while ((ok = next_record(iter)) == ITER_OK) {
67be7c5a 861 if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
523ee2d7 862 ref_type(iter->base.refname) != REF_TYPE_PER_WORKTREE)
67be7c5a
MH
863 continue;
864
865 if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
523ee2d7
MH
866 !ref_resolves_to_object(iter->base.refname, &iter->oid,
867 iter->flags))
67be7c5a
MH
868 continue;
869
67be7c5a
MH
870 return ITER_OK;
871 }
872
67be7c5a
MH
873 if (ref_iterator_abort(ref_iterator) != ITER_DONE)
874 ok = ITER_ERROR;
875
876 return ok;
877}
878
879static int packed_ref_iterator_peel(struct ref_iterator *ref_iterator,
880 struct object_id *peeled)
881{
882 struct packed_ref_iterator *iter =
883 (struct packed_ref_iterator *)ref_iterator;
884
523ee2d7
MH
885 if ((iter->base.flags & REF_KNOWS_PEELED)) {
886 oidcpy(peeled, &iter->peeled);
887 return is_null_oid(&iter->peeled) ? -1 : 0;
888 } else if ((iter->base.flags & (REF_ISBROKEN | REF_ISSYMREF))) {
889 return -1;
890 } else {
ac2ed0d7 891 return !!peel_object(&iter->oid, peeled);
523ee2d7 892 }
67be7c5a
MH
893}
894
895static int packed_ref_iterator_abort(struct ref_iterator *ref_iterator)
896{
897 struct packed_ref_iterator *iter =
898 (struct packed_ref_iterator *)ref_iterator;
899 int ok = ITER_DONE;
900
523ee2d7 901 strbuf_release(&iter->refname_buf);
cff28ca9 902 release_snapshot(iter->snapshot);
67be7c5a
MH
903 base_ref_iterator_free(ref_iterator);
904 return ok;
905}
906
907static struct ref_iterator_vtable packed_ref_iterator_vtable = {
908 packed_ref_iterator_advance,
909 packed_ref_iterator_peel,
910 packed_ref_iterator_abort
911};
912
e0cc8ac8
MH
913static struct ref_iterator *packed_ref_iterator_begin(
914 struct ref_store *ref_store,
67be7c5a
MH
915 const char *prefix, unsigned int flags)
916{
e0cc8ac8 917 struct packed_ref_store *refs;
cff28ca9 918 struct snapshot *snapshot;
d1cf1551 919 const char *start;
67be7c5a
MH
920 struct packed_ref_iterator *iter;
921 struct ref_iterator *ref_iterator;
e0cc8ac8
MH
922 unsigned int required_flags = REF_STORE_READ;
923
924 if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN))
925 required_flags |= REF_STORE_ODB;
926 refs = packed_downcast(ref_store, required_flags, "ref_iterator_begin");
67be7c5a 927
cff28ca9
MH
928 /*
929 * Note that `get_snapshot()` internally checks whether the
930 * snapshot is up to date with what is on disk, and re-reads
931 * it if not.
932 */
933 snapshot = get_snapshot(refs);
523ee2d7 934
f3424297
MH
935 if (prefix && *prefix)
936 start = find_reference_location(snapshot, prefix, 0);
937 else
938 start = snapshot->start;
939
940 if (start == snapshot->eof)
523ee2d7
MH
941 return empty_ref_iterator_begin();
942
67be7c5a
MH
943 iter = xcalloc(1, sizeof(*iter));
944 ref_iterator = &iter->base;
8738a8a4 945 base_ref_iterator_init(ref_iterator, &packed_ref_iterator_vtable, 1);
67be7c5a 946
cff28ca9
MH
947 iter->snapshot = snapshot;
948 acquire_snapshot(snapshot);
67be7c5a 949
523ee2d7 950 iter->pos = start;
cff28ca9 951 iter->eof = snapshot->eof;
523ee2d7
MH
952 strbuf_init(&iter->refname_buf, 0);
953
954 iter->base.oid = &iter->oid;
67be7c5a
MH
955
956 iter->flags = flags;
957
d1cf1551
MH
958 if (prefix && *prefix)
959 /* Stop iteration after we've gone *past* prefix: */
960 ref_iterator = prefix_ref_iterator_begin(ref_iterator, prefix, 0);
961
67be7c5a
MH
962 return ref_iterator;
963}
964
965/*
966 * Write an entry to the packed-refs file for the specified refname.
3478983b
MH
967 * If peeled is non-NULL, write it as the entry's peeled value. On
968 * error, return a nonzero value and leave errno set at the value left
969 * by the failing call to `fprintf()`.
67be7c5a 970 */
3478983b 971static int write_packed_entry(FILE *fh, const char *refname,
41701882
MH
972 const struct object_id *oid,
973 const struct object_id *peeled)
67be7c5a 974{
41701882
MH
975 if (fprintf(fh, "%s %s\n", oid_to_hex(oid), refname) < 0 ||
976 (peeled && fprintf(fh, "^%s\n", oid_to_hex(peeled)) < 0))
3478983b
MH
977 return -1;
978
979 return 0;
67be7c5a
MH
980}
981
c8bed835 982int packed_refs_lock(struct ref_store *ref_store, int flags, struct strbuf *err)
67be7c5a 983{
e0cc8ac8
MH
984 struct packed_ref_store *refs =
985 packed_downcast(ref_store, REF_STORE_WRITE | REF_STORE_MAIN,
b7de57d8 986 "packed_refs_lock");
67be7c5a
MH
987 static int timeout_configured = 0;
988 static int timeout_value = 1000;
67be7c5a 989
67be7c5a
MH
990 if (!timeout_configured) {
991 git_config_get_int("core.packedrefstimeout", &timeout_value);
992 timeout_configured = 1;
993 }
994
42dfa7ec
MH
995 /*
996 * Note that we close the lockfile immediately because we
997 * don't write new content to it, but rather to a separate
998 * tempfile.
999 */
67be7c5a
MH
1000 if (hold_lock_file_for_update_timeout(
1001 &refs->lock,
1002 refs->path,
c8bed835
MH
1003 flags, timeout_value) < 0) {
1004 unable_to_lock_message(refs->path, errno, err);
1005 return -1;
1006 }
1007
83a3069a 1008 if (close_lock_file_gently(&refs->lock)) {
c8bed835 1009 strbuf_addf(err, "unable to close %s: %s", refs->path, strerror(errno));
83a3069a 1010 rollback_lock_file(&refs->lock);
67be7c5a 1011 return -1;
c8bed835 1012 }
67be7c5a
MH
1013
1014 /*
1015 * Now that we hold the `packed-refs` lock, make sure that our
cff28ca9
MH
1016 * snapshot matches the current version of the file. Normally
1017 * `get_snapshot()` does that for us, but that function
1018 * assumes that when the file is locked, any existing snapshot
1019 * is still valid. We've just locked the file, but it might
1020 * have changed the moment *before* we locked it.
67be7c5a 1021 */
cff28ca9 1022 validate_snapshot(refs);
67be7c5a 1023
39c8df0c
MH
1024 /*
1025 * Now make sure that the packed-refs file as it exists in the
cff28ca9 1026 * locked state is loaded into the snapshot:
39c8df0c 1027 */
cff28ca9 1028 get_snapshot(refs);
67be7c5a
MH
1029 return 0;
1030}
1031
49aebcf4
MH
1032void packed_refs_unlock(struct ref_store *ref_store)
1033{
1034 struct packed_ref_store *refs = packed_downcast(
1035 ref_store,
1036 REF_STORE_READ | REF_STORE_WRITE,
1037 "packed_refs_unlock");
1038
1039 if (!is_lock_file_locked(&refs->lock))
033abf97 1040 BUG("packed_refs_unlock() called when not locked");
49aebcf4 1041 rollback_lock_file(&refs->lock);
49aebcf4
MH
1042}
1043
1044int packed_refs_is_locked(struct ref_store *ref_store)
1045{
1046 struct packed_ref_store *refs = packed_downcast(
1047 ref_store,
1048 REF_STORE_READ | REF_STORE_WRITE,
1049 "packed_refs_is_locked");
1050
1051 return is_lock_file_locked(&refs->lock);
1052}
1053
67be7c5a 1054/*
cff28ca9
MH
1055 * The packed-refs header line that we write out. Perhaps other traits
1056 * will be added later.
a8811695
MH
1057 *
1058 * Note that earlier versions of Git used to parse these traits by
1059 * looking for " trait " in the line. For this reason, the space after
1060 * the colon and the trailing space are required.
67be7c5a
MH
1061 */
1062static const char PACKED_REFS_HEADER[] =
02b920f3 1063 "# pack-refs with: peeled fully-peeled sorted \n";
67be7c5a 1064
e0cc8ac8
MH
1065static int packed_init_db(struct ref_store *ref_store, struct strbuf *err)
1066{
1067 /* Nothing to do. */
1068 return 0;
1069}
1070
67be7c5a 1071/*
cff28ca9
MH
1072 * Write the packed refs from the current snapshot to the packed-refs
1073 * tempfile, incorporating any changes from `updates`. `updates` must
1074 * be a sorted string list whose keys are the refnames and whose util
2775d872
MH
1075 * values are `struct ref_update *`. On error, rollback the tempfile,
1076 * write an error message to `err`, and return a nonzero value.
1077 *
1078 * The packfile must be locked before calling this function and will
1079 * remain locked when it is done.
67be7c5a 1080 */
2775d872
MH
1081static int write_with_updates(struct packed_ref_store *refs,
1082 struct string_list *updates,
1083 struct strbuf *err)
67be7c5a 1084{
2775d872
MH
1085 struct ref_iterator *iter = NULL;
1086 size_t i;
3478983b 1087 int ok;
67be7c5a 1088 FILE *out;
2775d872 1089 struct strbuf sb = STRBUF_INIT;
198b808e 1090 char *packed_refs_path;
67be7c5a 1091
67be7c5a 1092 if (!is_lock_file_locked(&refs->lock))
033abf97 1093 BUG("write_with_updates() called while unlocked");
67be7c5a 1094
198b808e
MH
1095 /*
1096 * If packed-refs is a symlink, we want to overwrite the
1097 * symlinked-to file, not the symlink itself. Also, put the
1098 * staging file next to it:
1099 */
1100 packed_refs_path = get_locked_file_path(&refs->lock);
1101 strbuf_addf(&sb, "%s.new", packed_refs_path);
2775d872 1102 free(packed_refs_path);
076aa2cb
JK
1103 refs->tempfile = create_tempfile(sb.buf);
1104 if (!refs->tempfile) {
42dfa7ec
MH
1105 strbuf_addf(err, "unable to create file %s: %s",
1106 sb.buf, strerror(errno));
1107 strbuf_release(&sb);
2775d872 1108 return -1;
42dfa7ec
MH
1109 }
1110 strbuf_release(&sb);
1111
076aa2cb 1112 out = fdopen_tempfile(refs->tempfile, "w");
3478983b
MH
1113 if (!out) {
1114 strbuf_addf(err, "unable to fdopen packed-refs tempfile: %s",
1115 strerror(errno));
1116 goto error;
1117 }
67be7c5a 1118
2775d872
MH
1119 if (fprintf(out, "%s", PACKED_REFS_HEADER) < 0)
1120 goto write_error;
1121
1122 /*
1123 * We iterate in parallel through the current list of refs and
1124 * the list of updates, processing an entry from at least one
1125 * of the lists each time through the loop. When the current
1126 * list of refs is exhausted, set iter to NULL. When the list
1127 * of updates is exhausted, leave i set to updates->nr.
1128 */
1129 iter = packed_ref_iterator_begin(&refs->base, "",
1130 DO_FOR_EACH_INCLUDE_BROKEN);
1131 if ((ok = ref_iterator_advance(iter)) != ITER_OK)
1132 iter = NULL;
1133
1134 i = 0;
67be7c5a 1135
2775d872
MH
1136 while (iter || i < updates->nr) {
1137 struct ref_update *update = NULL;
1138 int cmp;
1139
1140 if (i >= updates->nr) {
1141 cmp = -1;
1142 } else {
1143 update = updates->items[i].util;
1144
1145 if (!iter)
1146 cmp = +1;
1147 else
1148 cmp = strcmp(iter->refname, update->refname);
1149 }
1150
1151 if (!cmp) {
1152 /*
1153 * There is both an old value and an update
1154 * for this reference. Check the old value if
1155 * necessary:
1156 */
1157 if ((update->flags & REF_HAVE_OLD)) {
1158 if (is_null_oid(&update->old_oid)) {
1159 strbuf_addf(err, "cannot update ref '%s': "
1160 "reference already exists",
1161 update->refname);
1162 goto error;
9001dc2a 1163 } else if (!oideq(&update->old_oid, iter->oid)) {
2775d872
MH
1164 strbuf_addf(err, "cannot update ref '%s': "
1165 "is at %s but expected %s",
1166 update->refname,
1167 oid_to_hex(iter->oid),
1168 oid_to_hex(&update->old_oid));
1169 goto error;
1170 }
1171 }
1172
1173 /* Now figure out what to use for the new value: */
1174 if ((update->flags & REF_HAVE_NEW)) {
1175 /*
1176 * The update takes precedence. Skip
1177 * the iterator over the unneeded
1178 * value.
1179 */
1180 if ((ok = ref_iterator_advance(iter)) != ITER_OK)
1181 iter = NULL;
1182 cmp = +1;
1183 } else {
1184 /*
1185 * The update doesn't actually want to
1186 * change anything. We're done with it.
1187 */
1188 i++;
1189 cmp = -1;
1190 }
1191 } else if (cmp > 0) {
1192 /*
1193 * There is no old value but there is an
1194 * update for this reference. Make sure that
1195 * the update didn't expect an existing value:
1196 */
1197 if ((update->flags & REF_HAVE_OLD) &&
1198 !is_null_oid(&update->old_oid)) {
1199 strbuf_addf(err, "cannot update ref '%s': "
1200 "reference is missing but expected %s",
1201 update->refname,
1202 oid_to_hex(&update->old_oid));
1203 goto error;
1204 }
1205 }
1206
1207 if (cmp < 0) {
1208 /* Pass the old reference through. */
1209
1210 struct object_id peeled;
1211 int peel_error = ref_iterator_peel(iter, &peeled);
1212
1213 if (write_packed_entry(out, iter->refname,
41701882
MH
1214 iter->oid,
1215 peel_error ? NULL : &peeled))
2775d872
MH
1216 goto write_error;
1217
1218 if ((ok = ref_iterator_advance(iter)) != ITER_OK)
1219 iter = NULL;
1220 } else if (is_null_oid(&update->new_oid)) {
1221 /*
1222 * The update wants to delete the reference,
1223 * and the reference either didn't exist or we
1224 * have already skipped it. So we're done with
1225 * the update (and don't have to write
1226 * anything).
1227 */
1228 i++;
1229 } else {
1230 struct object_id peeled;
ac2ed0d7 1231 int peel_error = peel_object(&update->new_oid,
1232 &peeled);
2775d872
MH
1233
1234 if (write_packed_entry(out, update->refname,
41701882
MH
1235 &update->new_oid,
1236 peel_error ? NULL : &peeled))
2775d872
MH
1237 goto write_error;
1238
1239 i++;
3478983b 1240 }
67be7c5a
MH
1241 }
1242
3478983b 1243 if (ok != ITER_DONE) {
72d4a9a7
RS
1244 strbuf_addstr(err, "unable to write packed-refs file: "
1245 "error iterating over old contents");
3478983b
MH
1246 goto error;
1247 }
67be7c5a 1248
07f0542d 1249 if (close_tempfile_gently(refs->tempfile)) {
2775d872 1250 strbuf_addf(err, "error closing file %s: %s",
07f0542d 1251 get_tempfile_path(refs->tempfile),
2775d872
MH
1252 strerror(errno));
1253 strbuf_release(&sb);
07f0542d 1254 delete_tempfile(&refs->tempfile);
2775d872 1255 return -1;
67be7c5a 1256 }
3478983b 1257
2775d872
MH
1258 return 0;
1259
1260write_error:
1261 strbuf_addf(err, "error writing to %s: %s",
07f0542d 1262 get_tempfile_path(refs->tempfile), strerror(errno));
3478983b
MH
1263
1264error:
2775d872
MH
1265 if (iter)
1266 ref_iterator_abort(iter);
198b808e 1267
2775d872
MH
1268 delete_tempfile(&refs->tempfile);
1269 return -1;
67be7c5a
MH
1270}
1271
7c6bd25c
MH
1272int is_packed_transaction_needed(struct ref_store *ref_store,
1273 struct ref_transaction *transaction)
1274{
1275 struct packed_ref_store *refs = packed_downcast(
1276 ref_store,
1277 REF_STORE_READ,
1278 "is_packed_transaction_needed");
1279 struct strbuf referent = STRBUF_INIT;
1280 size_t i;
1281 int ret;
1282
1283 if (!is_lock_file_locked(&refs->lock))
1284 BUG("is_packed_transaction_needed() called while unlocked");
1285
1286 /*
1287 * We're only going to bother returning false for the common,
1288 * trivial case that references are only being deleted, their
1289 * old values are not being checked, and the old `packed-refs`
1290 * file doesn't contain any of those reference(s). This gives
1291 * false positives for some other cases that could
1292 * theoretically be optimized away:
1293 *
1294 * 1. It could be that the old value is being verified without
1295 * setting a new value. In this case, we could verify the
1296 * old value here and skip the update if it agrees. If it
1297 * disagrees, we could either let the update go through
1298 * (the actual commit would re-detect and report the
1299 * problem), or come up with a way of reporting such an
1300 * error to *our* caller.
1301 *
1302 * 2. It could be that a new value is being set, but that it
1303 * is identical to the current packed value of the
1304 * reference.
1305 *
1306 * Neither of these cases will come up in the current code,
1307 * because the only caller of this function passes to it a
1308 * transaction that only includes `delete` updates with no
1309 * `old_id`. Even if that ever changes, false positives only
1310 * cause an optimization to be missed; they do not affect
1311 * correctness.
1312 */
1313
1314 /*
1315 * Start with the cheap checks that don't require old
1316 * reference values to be read:
1317 */
1318 for (i = 0; i < transaction->nr; i++) {
1319 struct ref_update *update = transaction->updates[i];
1320
1321 if (update->flags & REF_HAVE_OLD)
1322 /* Have to check the old value -> needed. */
1323 return 1;
1324
1325 if ((update->flags & REF_HAVE_NEW) && !is_null_oid(&update->new_oid))
1326 /* Have to set a new value -> needed. */
1327 return 1;
1328 }
1329
1330 /*
1331 * The transaction isn't checking any old values nor is it
1332 * setting any nonzero new values, so it still might be able
1333 * to be skipped. Now do the more expensive check: the update
1334 * is needed if any of the updates is a delete, and the old
1335 * `packed-refs` file contains a value for that reference.
1336 */
1337 ret = 0;
1338 for (i = 0; i < transaction->nr; i++) {
1339 struct ref_update *update = transaction->updates[i];
1340 unsigned int type;
1341 struct object_id oid;
1342
1343 if (!(update->flags & REF_HAVE_NEW))
1344 /*
1345 * This reference isn't being deleted -> not
1346 * needed.
1347 */
1348 continue;
1349
1350 if (!refs_read_raw_ref(ref_store, update->refname,
ffb0b576 1351 &oid, &referent, &type) ||
7c6bd25c
MH
1352 errno != ENOENT) {
1353 /*
1354 * We have to actually delete that reference
1355 * -> this transaction is needed.
1356 */
1357 ret = 1;
1358 break;
1359 }
1360 }
1361
1362 strbuf_release(&referent);
1363 return ret;
1364}
1365
2775d872
MH
1366struct packed_transaction_backend_data {
1367 /* True iff the transaction owns the packed-refs lock. */
1368 int own_lock;
1369
1370 struct string_list updates;
1371};
1372
1373static void packed_transaction_cleanup(struct packed_ref_store *refs,
1374 struct ref_transaction *transaction)
67be7c5a 1375{
2775d872 1376 struct packed_transaction_backend_data *data = transaction->backend_data;
67be7c5a 1377
2775d872
MH
1378 if (data) {
1379 string_list_clear(&data->updates, 0);
67be7c5a 1380
07f0542d 1381 if (is_tempfile_active(refs->tempfile))
2775d872 1382 delete_tempfile(&refs->tempfile);
e5cc7d7d 1383
2775d872
MH
1384 if (data->own_lock && is_lock_file_locked(&refs->lock)) {
1385 packed_refs_unlock(&refs->base);
1386 data->own_lock = 0;
67be7c5a 1387 }
67be7c5a 1388
2775d872
MH
1389 free(data);
1390 transaction->backend_data = NULL;
67be7c5a
MH
1391 }
1392
2775d872 1393 transaction->state = REF_TRANSACTION_CLOSED;
e0cc8ac8
MH
1394}
1395
1396static int packed_transaction_prepare(struct ref_store *ref_store,
1397 struct ref_transaction *transaction,
1398 struct strbuf *err)
1399{
2775d872
MH
1400 struct packed_ref_store *refs = packed_downcast(
1401 ref_store,
1402 REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
1403 "ref_transaction_prepare");
1404 struct packed_transaction_backend_data *data;
1405 size_t i;
1406 int ret = TRANSACTION_GENERIC_ERROR;
1407
1408 /*
1409 * Note that we *don't* skip transactions with zero updates,
1410 * because such a transaction might be executed for the side
cff28ca9
MH
1411 * effect of ensuring that all of the references are peeled or
1412 * ensuring that the `packed-refs` file is sorted. If the
1413 * caller wants to optimize away empty transactions, it should
1414 * do so itself.
2775d872
MH
1415 */
1416
1417 data = xcalloc(1, sizeof(*data));
1418 string_list_init(&data->updates, 0);
1419
1420 transaction->backend_data = data;
1421
1422 /*
1423 * Stick the updates in a string list by refname so that we
1424 * can sort them:
1425 */
1426 for (i = 0; i < transaction->nr; i++) {
1427 struct ref_update *update = transaction->updates[i];
1428 struct string_list_item *item =
1429 string_list_append(&data->updates, update->refname);
1430
1431 /* Store a pointer to update in item->util: */
1432 item->util = update;
1433 }
1434 string_list_sort(&data->updates);
1435
1436 if (ref_update_reject_duplicates(&data->updates, err))
1437 goto failure;
1438
1439 if (!is_lock_file_locked(&refs->lock)) {
1440 if (packed_refs_lock(ref_store, 0, err))
1441 goto failure;
1442 data->own_lock = 1;
1443 }
1444
1445 if (write_with_updates(refs, &data->updates, err))
1446 goto failure;
1447
1448 transaction->state = REF_TRANSACTION_PREPARED;
1449 return 0;
1450
1451failure:
1452 packed_transaction_cleanup(refs, transaction);
1453 return ret;
e0cc8ac8
MH
1454}
1455
1456static int packed_transaction_abort(struct ref_store *ref_store,
1457 struct ref_transaction *transaction,
1458 struct strbuf *err)
1459{
2775d872
MH
1460 struct packed_ref_store *refs = packed_downcast(
1461 ref_store,
1462 REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
1463 "ref_transaction_abort");
1464
1465 packed_transaction_cleanup(refs, transaction);
1466 return 0;
e0cc8ac8
MH
1467}
1468
1469static int packed_transaction_finish(struct ref_store *ref_store,
1470 struct ref_transaction *transaction,
1471 struct strbuf *err)
1472{
2775d872
MH
1473 struct packed_ref_store *refs = packed_downcast(
1474 ref_store,
1475 REF_STORE_READ | REF_STORE_WRITE | REF_STORE_ODB,
1476 "ref_transaction_finish");
1477 int ret = TRANSACTION_GENERIC_ERROR;
1478 char *packed_refs_path;
1479
cff28ca9 1480 clear_snapshot(refs);
5b633610 1481
2775d872
MH
1482 packed_refs_path = get_locked_file_path(&refs->lock);
1483 if (rename_tempfile(&refs->tempfile, packed_refs_path)) {
1484 strbuf_addf(err, "error replacing %s: %s",
1485 refs->path, strerror(errno));
1486 goto cleanup;
1487 }
1488
2775d872
MH
1489 ret = 0;
1490
1491cleanup:
1492 free(packed_refs_path);
1493 packed_transaction_cleanup(refs, transaction);
1494 return ret;
e0cc8ac8
MH
1495}
1496
1497static int packed_initial_transaction_commit(struct ref_store *ref_store,
1498 struct ref_transaction *transaction,
1499 struct strbuf *err)
1500{
1501 return ref_transaction_commit(transaction, err);
1502}
1503
1504static int packed_delete_refs(struct ref_store *ref_store, const char *msg,
1505 struct string_list *refnames, unsigned int flags)
1506{
2fb330ca
MH
1507 struct packed_ref_store *refs =
1508 packed_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
1509 struct strbuf err = STRBUF_INIT;
1510 struct ref_transaction *transaction;
1511 struct string_list_item *item;
1512 int ret;
1513
1514 (void)refs; /* We need the check above, but don't use the variable */
1515
1516 if (!refnames->nr)
1517 return 0;
1518
1519 /*
1520 * Since we don't check the references' old_oids, the
1521 * individual updates can't fail, so we can pack all of the
1522 * updates into a single transaction.
1523 */
1524
1525 transaction = ref_store_transaction_begin(ref_store, &err);
1526 if (!transaction)
1527 return -1;
1528
1529 for_each_string_list_item(item, refnames) {
1530 if (ref_transaction_delete(transaction, item->string, NULL,
1531 flags, msg, &err)) {
1532 warning(_("could not delete reference %s: %s"),
1533 item->string, err.buf);
1534 strbuf_reset(&err);
1535 }
1536 }
1537
1538 ret = ref_transaction_commit(transaction, &err);
1539
1540 if (ret) {
1541 if (refnames->nr == 1)
1542 error(_("could not delete reference %s: %s"),
1543 refnames->items[0].string, err.buf);
1544 else
1545 error(_("could not delete references: %s"), err.buf);
1546 }
1547
1548 ref_transaction_free(transaction);
1549 strbuf_release(&err);
1550 return ret;
e0cc8ac8
MH
1551}
1552
1553static int packed_pack_refs(struct ref_store *ref_store, unsigned int flags)
1554{
1555 /*
1556 * Packed refs are already packed. It might be that loose refs
1557 * are packed *into* a packed refs store, but that is done by
1558 * updating the packed references via a transaction.
1559 */
1560 return 0;
1561}
1562
1563static int packed_create_symref(struct ref_store *ref_store,
1564 const char *refname, const char *target,
1565 const char *logmsg)
1566{
033abf97 1567 BUG("packed reference store does not support symrefs");
e0cc8ac8
MH
1568}
1569
1570static int packed_rename_ref(struct ref_store *ref_store,
1571 const char *oldrefname, const char *newrefname,
1572 const char *logmsg)
1573{
033abf97 1574 BUG("packed reference store does not support renaming references");
e0cc8ac8
MH
1575}
1576
3b48045c
JH
1577static int packed_copy_ref(struct ref_store *ref_store,
1578 const char *oldrefname, const char *newrefname,
1579 const char *logmsg)
1580{
033abf97 1581 BUG("packed reference store does not support copying references");
3b48045c
JH
1582}
1583
e0cc8ac8
MH
1584static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_store)
1585{
1586 return empty_ref_iterator_begin();
1587}
1588
1589static int packed_for_each_reflog_ent(struct ref_store *ref_store,
1590 const char *refname,
1591 each_reflog_ent_fn fn, void *cb_data)
1592{
1593 return 0;
1594}
1595
1596static int packed_for_each_reflog_ent_reverse(struct ref_store *ref_store,
1597 const char *refname,
1598 each_reflog_ent_fn fn,
1599 void *cb_data)
1600{
1601 return 0;
1602}
1603
1604static int packed_reflog_exists(struct ref_store *ref_store,
1605 const char *refname)
1606{
1607 return 0;
1608}
1609
1610static int packed_create_reflog(struct ref_store *ref_store,
1611 const char *refname, int force_create,
1612 struct strbuf *err)
1613{
033abf97 1614 BUG("packed reference store does not support reflogs");
e0cc8ac8
MH
1615}
1616
1617static int packed_delete_reflog(struct ref_store *ref_store,
1618 const char *refname)
1619{
1620 return 0;
1621}
1622
1623static int packed_reflog_expire(struct ref_store *ref_store,
0155f710 1624 const char *refname, const struct object_id *oid,
e0cc8ac8
MH
1625 unsigned int flags,
1626 reflog_expiry_prepare_fn prepare_fn,
1627 reflog_expiry_should_prune_fn should_prune_fn,
1628 reflog_expiry_cleanup_fn cleanup_fn,
1629 void *policy_cb_data)
1630{
1631 return 0;
1632}
1633
1634struct ref_storage_be refs_be_packed = {
1635 NULL,
1636 "packed",
1637 packed_ref_store_create,
1638 packed_init_db,
1639 packed_transaction_prepare,
1640 packed_transaction_finish,
1641 packed_transaction_abort,
1642 packed_initial_transaction_commit,
1643
1644 packed_pack_refs,
e0cc8ac8
MH
1645 packed_create_symref,
1646 packed_delete_refs,
1647 packed_rename_ref,
3b48045c 1648 packed_copy_ref,
e0cc8ac8
MH
1649
1650 packed_ref_iterator_begin,
1651 packed_read_raw_ref,
1652
1653 packed_reflog_iterator_begin,
1654 packed_for_each_reflog_ent,
1655 packed_for_each_reflog_ent_reverse,
1656 packed_reflog_exists,
1657 packed_create_reflog,
1658 packed_delete_reflog,
1659 packed_reflog_expire
1660};