reftable-backend.c · matheusbsbs/matheus-bagliano

jch

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1	#include "../git-compat-util.h"
2	#include "../abspath.h"
3	#include "../chdir-notify.h"
4	#include "../config.h"
5	#include "../dir.h"
6	#include "../environment.h"
7	#include "../fsck.h"
8	#include "../gettext.h"
9	#include "../hash.h"
10	#include "../hex.h"
11	#include "../ident.h"
12	#include "../iterator.h"
13	#include "../parse.h"
14	#include "../path.h"
15	#include "../refs.h"
16	#include "../reftable/reftable-basics.h"
17	#include "../reftable/reftable-error.h"
18	#include "../reftable/reftable-fsck.h"
19	#include "../reftable/reftable-iterator.h"
20	#include "../reftable/reftable-record.h"
21	#include "../reftable/reftable-stack.h"
22	#include "../repo-settings.h"
23	#include "../setup.h"
24	#include "../strmap.h"
25	#include "../trace2.h"
26	#include "../worktree.h"
27	#include "../write-or-die.h"
28	#include "refs-internal.h"
29
30	/*
31	* Used as a flag in ref_update::flags when the ref_update was via an
32	* update to HEAD.
33	*/
34	#define REF_UPDATE_VIA_HEAD (1 << 8)
35
36	struct reftable_backend {
37	struct reftable_stack *stack;
38	struct reftable_iterator it;
39	};
40
41	static void reftable_backend_on_reload(void *payload)
42	{
43	struct reftable_backend *be = payload;
44	reftable_iterator_destroy(&be->it);
45	}
46
47	static int reftable_backend_init(struct reftable_backend *be,
48	const char *path,
49	const struct reftable_stack_options *_opts)
50	{
51	struct reftable_stack_options opts = *_opts;
52	opts.on_reload = reftable_backend_on_reload;
53	opts.on_reload_payload = be;
54	return reftable_new_stack(&be->stack, path, &opts);
55	}
56
57	static void reftable_backend_release(struct reftable_backend *be)
58	{
59	reftable_stack_destroy(be->stack);
60	be->stack = NULL;
61	reftable_iterator_destroy(&be->it);
62	}
63
64	static int reftable_backend_read_ref(struct reftable_backend *be,
65	const char *refname,
66	struct object_id *oid,
67	struct strbuf *referent,
68	unsigned int *type)
69	{
70	struct reftable_ref_record ref = {0};
71	int ret;
72
73	if (!be->it.ops) {
74	ret = reftable_stack_init_ref_iterator(be->stack, &be->it);
75	if (ret)
76	goto done;
77	}
78
79	ret = reftable_iterator_seek_ref(&be->it, refname);
80	if (ret)
81	goto done;
82
83	ret = reftable_iterator_next_ref(&be->it, &ref);
84	if (ret)
85	goto done;
86
87	if (strcmp(ref.refname, refname) \|\|
88	reftable_ref_record_is_deletion(&ref)) {
89	ret = 1;
90	goto done;
91	}
92
93	if (ref.value_type == REFTABLE_REF_SYMREF) {
94	strbuf_reset(referent);
95	strbuf_addstr(referent, ref.value.symref);
96	*type \|= REF_ISSYMREF;
97	} else if (reftable_ref_record_val1(&ref)) {
98	unsigned int hash_id;
99
100	switch (reftable_stack_hash_id(be->stack)) {
101	case REFTABLE_HASH_SHA1:
102	hash_id = GIT_HASH_SHA1;
103	break;
104	case REFTABLE_HASH_SHA256:
105	hash_id = GIT_HASH_SHA256;
106	break;
107	default:
108	BUG("unhandled hash ID %d", reftable_stack_hash_id(be->stack));
109	}
110
111	oidread(oid, reftable_ref_record_val1(&ref),
112	&hash_algos[hash_id]);
113	} else {
114	BUG("unhandled reference value type %d", ref.value_type);
115	}
116
117	done:
118	assert(ret != REFTABLE_API_ERROR);
119	reftable_ref_record_release(&ref);
120	return ret;
121	}
122
123	struct reftable_ref_store {
124	struct ref_store base;
125
126	/*
127	* The main backend refers to the common dir and thus contains common
128	* refs as well as refs of the main repository.
129	*/
130	struct reftable_backend main_backend;
131	/*
132	* The worktree backend refers to the gitdir in case the refdb is opened
133	* via a worktree. It thus contains the per-worktree refs.
134	*/
135	struct reftable_backend worktree_backend;
136	/*
137	* Map of worktree backends by their respective worktree names. The map
138	* is populated lazily when we try to resolve `worktrees/$worktree` refs.
139	*/
140	struct strmap worktree_backends;
141	struct reftable_stack_options stack_options;
142
143	/*
144	* Options used when writing to or compacting the reftable stacks.
145	* These are parsed from the configuration lazily on first use via
146	* `reftable_be_write_options()` so that we don't have to access the
147	* configuration when initializing the ref store. Do not access these
148	* fields directly, but use the accessor instead.
149	*/
150	struct reftable_be_write_options {
151	struct reftable_write_options opts;
152	enum log_refs_config log_all_ref_updates;
153	bool initialized;
154	} write_opts_lazy_loaded;
155
156	unsigned int store_flags;
157	int err;
158	};
159
160	/*
161	* Downcast ref_store to reftable_ref_store. Die if ref_store is not a
162	* reftable_ref_store. required_flags is compared with ref_store's store_flags
163	* to ensure the ref_store has all required capabilities. "caller" is used in
164	* any necessary error messages.
165	*/
166	static struct reftable_ref_store reftable_be_downcast(struct ref_store ref_store,
167	unsigned int required_flags,
168	const char *caller)
169	{
170	struct reftable_ref_store *refs;
171
172	if (ref_store->be != &refs_be_reftable)
173	BUG("ref_store is type \"%s\" not \"reftables\" in %s",
174	ref_store->be->name, caller);
175
176	refs = (struct reftable_ref_store *)ref_store;
177
178	if ((refs->store_flags & required_flags) != required_flags)
179	BUG("operation %s requires abilities 0x%x, but only have 0x%x",
180	caller, required_flags, refs->store_flags);
181
182	return refs;
183	}
184
185	static int backend_for_worktree(struct reftable_backend **out,
186	struct reftable_ref_store *store,
187	const char *worktree_name)
188	{
189	struct strbuf worktree_dir = STRBUF_INIT;
190	int ret;
191
192	*out = strmap_get(&store->worktree_backends, worktree_name);
193	if (*out) {
194	ret = 0;
195	goto out;
196	}
197
198	strbuf_addf(&worktree_dir, "%s/worktrees/%s/reftable",
199	store->base.repo->commondir, worktree_name);
200
201	CALLOC_ARRAY(*out, 1);
202	store->err = ret = reftable_backend_init(*out, worktree_dir.buf,
203	&store->stack_options);
204	if (ret < 0) {
205	free(*out);
206	goto out;
207	}
208
209	strmap_put(&store->worktree_backends, worktree_name, *out);
210
211	out:
212	strbuf_release(&worktree_dir);
213	return ret;
214	}
215
216	/*
217	* Some refs are global to the repository (refs/heads/{*}), while others are
218	* local to the worktree (eg. HEAD, refs/bisect/{*}). We solve this by having
219	* multiple separate databases (ie. multiple reftable/ directories), one for
220	* the shared refs, one for the current worktree refs, and one for each
221	* additional worktree. For reading, we merge the view of both the shared and
222	* the current worktree's refs, when necessary.
223	*
224	* This function also optionally assigns the rewritten reference name that is
225	* local to the stack. This translation is required when using worktree refs
226	* like `worktrees/$worktree/refs/heads/foo` as worktree stacks will store
227	* those references in their normalized form.
228	*/
229	static int backend_for(struct reftable_backend **out,
230	struct reftable_ref_store *store,
231	const char *refname,
232	const char **rewritten_ref,
233	int reload)
234	{
235	const char *wtname;
236	int wtname_len;
237	int ret;
238
239	if (!refname) {
240	*out = &store->main_backend;
241	ret = 0;
242	goto out;
243	}
244
245	switch (parse_worktree_ref(refname, &wtname, &wtname_len, rewritten_ref)) {
246	case REF_WORKTREE_OTHER: {
247	static struct strbuf wtname_buf = STRBUF_INIT;
248
249	/*
250	* We're using a static buffer here so that we don't need to
251	* allocate the worktree name whenever we look up a reference.
252	* This could be avoided if the strmap interface knew how to
253	* handle keys with a length.
254	*/
255	strbuf_reset(&wtname_buf);
256	strbuf_add(&wtname_buf, wtname, wtname_len);
257
258	/*
259	* There is an edge case here: when the worktree references the
260	* current worktree, then we set up the stack once via
261	* `worktree_backends` and once via `worktree_backend`. This is
262	* wasteful, but in the reading case it shouldn't matter. And
263	* in the writing case we would notice that the stack is locked
264	* already and error out when trying to write a reference via
265	* both stacks.
266	*/
267	ret = backend_for_worktree(out, store, wtname_buf.buf);
268
269	goto out;
270	}
271	case REF_WORKTREE_CURRENT:
272	/*
273	* If there is no worktree stack then we're currently in the
274	* main worktree. We thus return the main stack in that case.
275	*/
276	if (!store->worktree_backend.stack)
277	*out = &store->main_backend;
278	else
279	*out = &store->worktree_backend;
280	ret = 0;
281	goto out;
282	case REF_WORKTREE_MAIN:
283	case REF_WORKTREE_SHARED:
284	*out = &store->main_backend;
285	ret = 0;
286	goto out;
287	default:
288	BUG("unhandled worktree reference type");
289	}
290
291	out:
292	if (reload && !ret)
293	ret = reftable_stack_reload((*out)->stack);
294	return ret;
295	}
296
297	static void fill_reftable_log_record(struct reftable_log_record log, const struct ident_split split)
298	{
299	const char *tz_begin;
300	int sign = 1;
301
302	reftable_log_record_release(log);
303	log->value_type = REFTABLE_LOG_UPDATE;
304	log->value.update.name =
305	xstrndup(split->name_begin, split->name_end - split->name_begin);
306	log->value.update.email =
307	xstrndup(split->mail_begin, split->mail_end - split->mail_begin);
308	log->value.update.time = atol(split->date_begin);
309
310	tz_begin = split->tz_begin;
311	if (*tz_begin == '-') {
312	sign = -1;
313	tz_begin++;
314	}
315	if (*tz_begin == '+') {
316	sign = 1;
317	tz_begin++;
318	}
319
320	log->value.update.tz_offset = sign * atoi(tz_begin);
321	}
322
323	static int reftable_be_config(const char var, const char value,
324	const struct config_context *ctx,
325	void *payload)
326	{
327	struct reftable_ref_store *refs = payload;
328	struct reftable_be_write_options *opts = &refs->write_opts_lazy_loaded;
329
330	if (!strcmp(var, "reftable.blocksize")) {
331	unsigned long block_size = git_config_ulong(var, value, ctx->kvi);
332	if (block_size > 16777215)
333	die("reftable block size cannot exceed 16MB");
334	opts->opts.block_size = block_size;
335	} else if (!strcmp(var, "reftable.restartinterval")) {
336	unsigned long restart_interval = git_config_ulong(var, value, ctx->kvi);
337	if (restart_interval > UINT16_MAX)
338	die("reftable block size cannot exceed %u", (unsigned)UINT16_MAX);
339	opts->opts.restart_interval = restart_interval;
340	} else if (!strcmp(var, "reftable.indexobjects")) {
341	opts->opts.skip_index_objects = !git_config_bool(var, value);
342	} else if (!strcmp(var, "reftable.geometricfactor")) {
343	unsigned long factor = git_config_ulong(var, value, ctx->kvi);
344	if (factor > UINT8_MAX)
345	die("reftable geometric factor cannot exceed %u", (unsigned)UINT8_MAX);
346	opts->opts.auto_compaction_factor = factor;
347	} else if (!strcmp(var, "reftable.locktimeout")) {
348	int64_t lock_timeout = git_config_int64(var, value, ctx->kvi);
349	if (lock_timeout > LONG_MAX)
350	die("reftable lock timeout cannot exceed %"PRIdMAX, (intmax_t)LONG_MAX);
351	if (lock_timeout < 0 && lock_timeout != -1)
352	die("reftable lock timeout does not support negative values other than -1");
353	opts->opts.lock_timeout_ms = lock_timeout;
354	} else if (!strcmp(var, "core.logallrefupdates")) {
355	opts->log_all_ref_updates = refs_parse_log_all_ref_updates_config(value);
356	}
357
358	return 0;
359	}
360
361	static const struct reftable_be_write_options reftable_be_write_options(struct reftable_ref_store refs)
362	{
363	struct reftable_be_write_options *opts = &refs->write_opts_lazy_loaded;
364	mode_t mask;
365
366	if (opts->initialized)
367	return opts;
368
369	mask = umask(0);
370	umask(mask);
371
372	opts->opts.default_permissions = calc_shared_perm(refs->base.repo, 0666 & ~mask);
373	opts->opts.disable_auto_compact =
374	!git_env_bool("GIT_TEST_REFTABLE_AUTOCOMPACTION", 1);
375	opts->opts.lock_timeout_ms = 100;
376	opts->log_all_ref_updates = LOG_REFS_UNSET;
377
378	repo_config(refs->base.repo, reftable_be_config, refs);
379
380	/*
381	* It is somewhat unfortunate that we have to mirror the default block
382	* size of the reftable library here. But given that the write options
383	* wouldn't be updated by the library here, and given that we require
384	* the proper block size to trim reflog message so that they fit, we
385	* must set up a proper value here.
386	*/
387	if (!opts->opts.block_size)
388	opts->opts.block_size = 4096;
389
390	opts->initialized = true;
391	return opts;
392	}
393
394	static void reftable_be_reparent(const char *name UNUSED,
395	const char *old_cwd,
396	const char *new_cwd,
397	void *payload)
398	{
399	struct reftable_ref_store *refs = payload;
400	char *tmp;
401
402	tmp = reparent_relative_path(old_cwd, new_cwd, refs->base.gitdir);
403	free(refs->base.gitdir);
404	refs->base.gitdir = tmp;
405	}
406
407	static struct ref_store reftable_be_init(struct repository repo,
408	const char *payload,
409	const char *gitdir,
410	const struct ref_store_init_options *opts)
411	{
412	struct reftable_ref_store refs = xcalloc(1, sizeof(refs));
413	struct strbuf ref_common_dir = STRBUF_INIT;
414	struct strbuf refdir = STRBUF_INIT;
415	struct strbuf path = STRBUF_INIT;
416	bool is_worktree;
417
418	refs_compute_filesystem_location(gitdir, payload, &is_worktree, &refdir,
419	&ref_common_dir);
420
421	base_ref_store_init(&refs->base, repo, refdir.buf, &refs_be_reftable);
422	strmap_init(&refs->worktree_backends);
423	refs->store_flags = opts->access_flags;
424
425	switch (repo->hash_algo->format_id) {
426	case GIT_SHA1_FORMAT_ID:
427	refs->stack_options.hash_id = REFTABLE_HASH_SHA1;
428	break;
429	case GIT_SHA256_FORMAT_ID:
430	refs->stack_options.hash_id = REFTABLE_HASH_SHA256;
431	break;
432	default:
433	BUG("unknown hash algorithm %d", repo->hash_algo->format_id);
434	}
435
436	/*
437	* Set up the main reftable stack that is hosted in GIT_COMMON_DIR.
438	* This stack contains both the shared and the main worktree refs.
439	*/
440	strbuf_addbuf(&path, &ref_common_dir);
441	if (!is_worktree) {
442	strbuf_reset(&path);
443	strbuf_realpath(&path, ref_common_dir.buf, 0);
444	}
445	strbuf_addstr(&path, "/reftable");
446	refs->err = reftable_backend_init(&refs->main_backend, path.buf,
447	&refs->stack_options);
448	if (refs->err)
449	goto done;
450
451	/*
452	* If we're in a worktree we also need to set up the worktree reftable
453	* stack that is contained in the per-worktree GIT_DIR.
454	*
455	* Ideally, we would also add the stack to our worktree stack map. But
456	* we have no way to figure out the worktree name here and thus can't
457	* do it efficiently.
458	*/
459	if (is_worktree) {
460	strbuf_addstr(&refdir, "/reftable");
461
462	refs->err = reftable_backend_init(&refs->worktree_backend, refdir.buf,
463	&refs->stack_options);
464	if (refs->err)
465	goto done;
466	}
467
468	chdir_notify_register(NULL, reftable_be_reparent, refs);
469
470	done:
471	assert(refs->err != REFTABLE_API_ERROR);
472	strbuf_release(&ref_common_dir);
473	strbuf_release(&refdir);
474	strbuf_release(&path);
475	return &refs->base;
476	}
477
478	static void reftable_be_release(struct ref_store *ref_store)
479	{
480	struct reftable_ref_store *refs = reftable_be_downcast(ref_store, 0, "release");
481	struct strmap_entry *entry;
482	struct hashmap_iter iter;
483
484	if (refs->main_backend.stack)
485	reftable_backend_release(&refs->main_backend);
486	if (refs->worktree_backend.stack)
487	reftable_backend_release(&refs->worktree_backend);
488
489	strmap_for_each_entry(&refs->worktree_backends, &iter, entry) {
490	struct reftable_backend *be = entry->value;
491	reftable_backend_release(be);
492	free(be);
493	}
494	strmap_clear(&refs->worktree_backends, 0);
495	chdir_notify_unregister(NULL, reftable_be_reparent, refs);
496	}
497
498	static int reftable_be_create_on_disk(struct ref_store *ref_store,
499	int flags UNUSED,
500	struct strbuf *err UNUSED)
501	{
502	struct reftable_ref_store *refs =
503	reftable_be_downcast(ref_store, REF_STORE_WRITE, "create");
504	struct strbuf sb = STRBUF_INIT;
505
506	strbuf_addf(&sb, "%s/reftable", refs->base.gitdir);
507	safe_create_dir(ref_store->repo, sb.buf, 1);
508	strbuf_reset(&sb);
509
510	strbuf_release(&sb);
511	return 0;
512	}
513
514	static int reftable_be_remove_on_disk(struct ref_store *ref_store,
515	struct strbuf *err)
516	{
517	struct reftable_ref_store *refs =
518	reftable_be_downcast(ref_store, REF_STORE_WRITE, "remove");
519	struct strbuf sb = STRBUF_INIT;
520	int ret = 0;
521
522	/*
523	* Release the ref store such that all stacks are closed. This is
524	* required so that the "tables.list" file is not open anymore, which
525	* would otherwise make it impossible to remove the file on Windows.
526	*/
527	reftable_be_release(ref_store);
528
529	strbuf_addf(&sb, "%s/reftable", refs->base.gitdir);
530	if (remove_dir_recursively(&sb, 0) < 0) {
531	strbuf_addf(err, "could not delete reftables: %s",
532	strerror(errno));
533	ret = -1;
534	}
535
536	strbuf_release(&sb);
537	return ret;
538	}
539
540	struct reftable_ref_iterator {
541	struct ref_iterator base;
542	struct reftable_ref_store *refs;
543	struct reftable_iterator iter;
544	struct reftable_ref_record ref;
545	struct object_id oid;
546	struct object_id peeled_oid;
547
548	char *prefix;
549	size_t prefix_len;
550	char **exclude_patterns;
551	size_t exclude_patterns_index;
552	size_t exclude_patterns_strlen;
553	unsigned int flags;
554	int err;
555	};
556
557	/*
558	* Handle exclude patterns. Returns either `1`, which tells the caller that the
559	* current reference shall not be shown. Or `0`, which indicates that it should
560	* be shown.
561	*/
562	static int should_exclude_current_ref(struct reftable_ref_iterator *iter)
563	{
564	while (iter->exclude_patterns[iter->exclude_patterns_index]) {
565	const char *pattern = iter->exclude_patterns[iter->exclude_patterns_index];
566	char *ref_after_pattern;
567	int cmp;
568
569	/*
570	* Lazily cache the pattern length so that we don't have to
571	* recompute it every time this function is called.
572	*/
573	if (!iter->exclude_patterns_strlen)
574	iter->exclude_patterns_strlen = strlen(pattern);
575
576	/*
577	* When the reference name is lexicographically bigger than the
578	* current exclude pattern we know that it won't ever match any
579	* of the following references, either. We thus advance to the
580	* next pattern and re-check whether it matches.
581	*
582	* Otherwise, if it's smaller, then we do not have a match and
583	* thus want to show the current reference.
584	*/
585	cmp = strncmp(iter->ref.refname, pattern,
586	iter->exclude_patterns_strlen);
587	if (cmp > 0) {
588	iter->exclude_patterns_index++;
589	iter->exclude_patterns_strlen = 0;
590	continue;
591	}
592	if (cmp < 0)
593	return 0;
594
595	/*
596	* The reference shares a prefix with the exclude pattern and
597	* shall thus be omitted. We skip all references that match the
598	* pattern by seeking to the first reference after the block of
599	* matches.
600	*
601	* This is done by appending the highest possible character to
602	* the pattern. Consequently, all references that have the
603	* pattern as prefix and whose suffix starts with anything in
604	* the range [0x00, 0xfe] are skipped. And given that 0xff is a
605	* non-printable character that shouldn't ever be in a ref name,
606	* we'd not yield any such record, either.
607	*
608	* Note that the seeked-to reference may also be excluded. This
609	* is not handled here though, but the caller is expected to
610	* loop and re-verify the next reference for us.
611	*/
612	ref_after_pattern = xstrfmt("%s%c", pattern, 0xff);
613	iter->err = reftable_iterator_seek_ref(&iter->iter, ref_after_pattern);
614	iter->exclude_patterns_index++;
615	iter->exclude_patterns_strlen = 0;
616	trace2_counter_add(TRACE2_COUNTER_ID_REFTABLE_RESEEKS, 1);
617
618	free(ref_after_pattern);
619	return 1;
620	}
621
622	return 0;
623	}
624
625	static int reftable_ref_iterator_advance(struct ref_iterator *ref_iterator)
626	{
627	struct reftable_ref_iterator *iter =
628	(struct reftable_ref_iterator *)ref_iterator;
629	struct reftable_ref_store *refs = iter->refs;
630	const char *referent = NULL;
631
632	while (!iter->err) {
633	int flags = 0;
634
635	iter->err = reftable_iterator_next_ref(&iter->iter, &iter->ref);
636	if (iter->err)
637	break;
638
639	/*
640	* The files backend only lists references contained in "refs/" unless
641	* the root refs are to be included. We emulate the same behaviour here.
642	*/
643	if (!starts_with(iter->ref.refname, "refs/") &&
644	!(iter->flags & REFS_FOR_EACH_INCLUDE_ROOT_REFS &&
645	is_root_ref(iter->ref.refname))) {
646	continue;
647	}
648
649	if (iter->prefix_len &&
650	strncmp(iter->prefix, iter->ref.refname, iter->prefix_len)) {
651	iter->err = 1;
652	break;
653	}
654
655	if (iter->ref.value_type == REFTABLE_REF_DELETION)
656	continue;
657
658	if (iter->exclude_patterns && should_exclude_current_ref(iter))
659	continue;
660
661	if (iter->flags & REFS_FOR_EACH_PER_WORKTREE_ONLY &&
662	parse_worktree_ref(iter->ref.refname, NULL, NULL, NULL) !=
663	REF_WORKTREE_CURRENT)
664	continue;
665
666	switch (iter->ref.value_type) {
667	case REFTABLE_REF_VAL1:
668	oidread(&iter->oid, iter->ref.value.val1,
669	refs->base.repo->hash_algo);
670	break;
671	case REFTABLE_REF_VAL2:
672	oidread(&iter->oid, iter->ref.value.val2.value,
673	refs->base.repo->hash_algo);
674	oidread(&iter->peeled_oid, iter->ref.value.val2.target_value,
675	refs->base.repo->hash_algo);
676	break;
677	case REFTABLE_REF_SYMREF:
678	referent = refs_resolve_ref_unsafe(&iter->refs->base,
679	iter->ref.refname,
680	RESOLVE_REF_READING,
681	&iter->oid, &flags);
682	if (!referent)
683	oidclr(&iter->oid, refs->base.repo->hash_algo);
684	break;
685	default:
686	BUG("unhandled reference value type %d", iter->ref.value_type);
687	}
688
689	if (is_null_oid(&iter->oid))
690	flags \|= REF_ISBROKEN;
691
692	if (check_refname_format(iter->ref.refname, REFNAME_ALLOW_ONELEVEL)) {
693	if (!refname_is_safe(iter->ref.refname))
694	die(_("refname is dangerous: %s"), iter->ref.refname);
695	oidclr(&iter->oid, refs->base.repo->hash_algo);
696	flags \|= REF_BAD_NAME \| REF_ISBROKEN;
697	}
698
699	if (iter->flags & REFS_FOR_EACH_OMIT_DANGLING_SYMREFS &&
700	flags & REF_ISSYMREF &&
701	flags & REF_ISBROKEN)
702	continue;
703
704	if (!(iter->flags & REFS_FOR_EACH_INCLUDE_BROKEN) &&
705	!ref_resolves_to_object(iter->ref.refname, refs->base.repo,
706	&iter->oid, flags))
707	continue;
708
709	memset(&iter->base.ref, 0, sizeof(iter->base.ref));
710	iter->base.ref.name = iter->ref.refname;
711	iter->base.ref.target = referent;
712	iter->base.ref.oid = &iter->oid;
713	if (iter->ref.value_type == REFTABLE_REF_VAL2)
714	iter->base.ref.peeled_oid = &iter->peeled_oid;
715	iter->base.ref.flags = flags;
716
717	break;
718	}
719
720	if (iter->err > 0)
721	return ITER_DONE;
722	if (iter->err < 0)
723	return ITER_ERROR;
724	return ITER_OK;
725	}
726
727	static int reftable_ref_iterator_seek(struct ref_iterator *ref_iterator,
728	const char *refname, unsigned int flags)
729	{
730	struct reftable_ref_iterator *iter =
731	(struct reftable_ref_iterator *)ref_iterator;
732
733	/* Unset any previously set prefix */
734	FREE_AND_NULL(iter->prefix);
735	iter->prefix_len = 0;
736
737	if (flags & REF_ITERATOR_SEEK_SET_PREFIX) {
738	iter->prefix = xstrdup_or_null(refname);
739	iter->prefix_len = refname ? strlen(refname) : 0;
740	}
741	iter->err = reftable_iterator_seek_ref(&iter->iter, refname);
742
743	return iter->err;
744	}
745
746	static void reftable_ref_iterator_release(struct ref_iterator *ref_iterator)
747	{
748	struct reftable_ref_iterator *iter =
749	(struct reftable_ref_iterator *)ref_iterator;
750	reftable_ref_record_release(&iter->ref);
751	reftable_iterator_destroy(&iter->iter);
752	if (iter->exclude_patterns) {
753	for (size_t i = 0; iter->exclude_patterns[i]; i++)
754	free(iter->exclude_patterns[i]);
755	free(iter->exclude_patterns);
756	}
757	free(iter->prefix);
758	}
759
760	static struct ref_iterator_vtable reftable_ref_iterator_vtable = {
761	.advance = reftable_ref_iterator_advance,
762	.seek = reftable_ref_iterator_seek,
763	.release = reftable_ref_iterator_release,
764	};
765
766	static int qsort_strcmp(const void va, const void vb)
767	{
768	const char a = (const char **)va;
769	const char b = (const char **)vb;
770	return strcmp(a, b);
771	}
772
773	static char filter_exclude_patterns(const char exclude_patterns)
774	{
775	size_t filtered_size = 0, filtered_alloc = 0;
776	char **filtered = NULL;
777
778	if (!exclude_patterns)
779	return NULL;
780
781	for (size_t i = 0; ; i++) {
782	const char *exclude_pattern = exclude_patterns[i];
783	int has_glob = 0;
784
785	if (!exclude_pattern)
786	break;
787
788	for (const char p = exclude_pattern; p; p++) {
789	has_glob = is_glob_special(*p);
790	if (has_glob)
791	break;
792	}
793	if (has_glob)
794	continue;
795
796	ALLOC_GROW(filtered, filtered_size + 1, filtered_alloc);
797	filtered[filtered_size++] = xstrdup(exclude_pattern);
798	}
799
800	if (filtered_size) {
801	QSORT(filtered, filtered_size, qsort_strcmp);
802	ALLOC_GROW(filtered, filtered_size + 1, filtered_alloc);
803	filtered[filtered_size++] = NULL;
804	}
805
806	return filtered;
807	}
808
809	static struct reftable_ref_iterator ref_iterator_for_stack(struct reftable_ref_store refs,
810	struct reftable_stack *stack,
811	const char *prefix,
812	const char **exclude_patterns,
813	int flags)
814	{
815	struct reftable_ref_iterator *iter;
816	int ret;
817
818	iter = xcalloc(1, sizeof(*iter));
819	base_ref_iterator_init(&iter->base, &reftable_ref_iterator_vtable);
820	iter->base.ref.oid = &iter->oid;
821	iter->flags = flags;
822	iter->refs = refs;
823	iter->exclude_patterns = filter_exclude_patterns(exclude_patterns);
824
825	ret = refs->err;
826	if (ret)
827	goto done;
828
829	ret = reftable_stack_reload(stack);
830	if (ret)
831	goto done;
832
833	ret = reftable_stack_init_ref_iterator(stack, &iter->iter);
834	if (ret)
835	goto done;
836
837	ret = reftable_ref_iterator_seek(&iter->base, prefix,
838	REF_ITERATOR_SEEK_SET_PREFIX);
839	if (ret)
840	goto done;
841
842	done:
843	iter->err = ret;
844	return iter;
845	}
846
847	static struct ref_iterator reftable_be_iterator_begin(struct ref_store ref_store,
848	const char *prefix,
849	const char **exclude_patterns,
850	unsigned int flags)
851	{
852	struct reftable_ref_iterator main_iter, worktree_iter;
853	struct reftable_ref_store *refs;
854	unsigned int required_flags = REF_STORE_READ;
855
856	if (!(flags & REFS_FOR_EACH_INCLUDE_BROKEN))
857	required_flags \|= REF_STORE_ODB;
858	refs = reftable_be_downcast(ref_store, required_flags, "ref_iterator_begin");
859
860	main_iter = ref_iterator_for_stack(refs, refs->main_backend.stack, prefix,
861	exclude_patterns, flags);
862
863	/*
864	* The worktree stack is only set when we're in an actual worktree
865	* right now. If we aren't, then we return the common reftable
866	* iterator, only.
867	*/
868	if (!refs->worktree_backend.stack)
869	return &main_iter->base;
870
871	/*
872	* Otherwise we merge both the common and the per-worktree refs into a
873	* single iterator.
874	*/
875	worktree_iter = ref_iterator_for_stack(refs, refs->worktree_backend.stack, prefix,
876	exclude_patterns, flags);
877	return merge_ref_iterator_begin(&worktree_iter->base, &main_iter->base,
878	ref_iterator_select, NULL);
879	}
880
881	static int reftable_be_read_raw_ref(struct ref_store *ref_store,
882	const char *refname,
883	struct object_id *oid,
884	struct strbuf *referent,
885	unsigned int *type,
886	int *failure_errno)
887	{
888	struct reftable_ref_store *refs =
889	reftable_be_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
890	struct reftable_backend *be;
891	int ret;
892
893	if (refs->err < 0)
894	return refs->err;
895
896	ret = backend_for(&be, refs, refname, &refname, 1);
897	if (ret)
898	return ret;
899
900	ret = reftable_backend_read_ref(be, refname, oid, referent, type);
901	if (ret < 0)
902	return ret;
903	if (ret > 0) {
904	*failure_errno = ENOENT;
905	return -1;
906	}
907
908	return 0;
909	}
910
911	static int reftable_be_read_symbolic_ref(struct ref_store *ref_store,
912	const char *refname,
913	struct strbuf *referent)
914	{
915	struct reftable_ref_store *refs =
916	reftable_be_downcast(ref_store, REF_STORE_READ, "read_symbolic_ref");
917	struct reftable_backend *be;
918	struct object_id oid;
919	unsigned int type = 0;
920	int ret;
921
922	ret = backend_for(&be, refs, refname, &refname, 1);
923	if (ret)
924	return ret;
925
926	ret = reftable_backend_read_ref(be, refname, &oid, referent, &type);
927	if (ret)
928	ret = -1;
929	else if (type == REF_ISSYMREF)
930	; /* happy */
931	else
932	ret = NOT_A_SYMREF;
933	return ret;
934	}
935
936	struct reftable_transaction_update {
937	struct ref_update *update;
938	struct object_id current_oid;
939	};
940
941	struct write_transaction_table_arg {
942	struct reftable_ref_store *refs;
943	struct reftable_backend *be;
944	struct reftable_addition *addition;
945	struct reftable_transaction_update *updates;
946	size_t updates_nr;
947	size_t updates_alloc;
948	size_t updates_expected;
949	uint64_t max_index;
950	};
951
952	struct reftable_transaction_data {
953	struct write_transaction_table_arg *args;
954	size_t args_nr, args_alloc;
955	};
956
957	static void free_transaction_data(struct reftable_transaction_data *tx_data)
958	{
959	if (!tx_data)
960	return;
961	for (size_t i = 0; i < tx_data->args_nr; i++) {
962	reftable_addition_destroy(tx_data->args[i].addition);
963	free(tx_data->args[i].updates);
964	}
965	free(tx_data->args);
966	free(tx_data);
967	}
968
969	/*
970	* Prepare transaction update for the given reference update. This will cause
971	* us to lock the corresponding reftable stack for concurrent modification.
972	*/
973	static int prepare_transaction_update(struct write_transaction_table_arg **out,
974	struct reftable_ref_store *refs,
975	struct reftable_transaction_data *tx_data,
976	struct ref_update *update,
977	struct strbuf *err)
978	{
979	struct write_transaction_table_arg *arg = NULL;
980	struct reftable_backend *be;
981	size_t i;
982	int ret;
983
984	/*
985	* This function gets called in a loop, and we don't want to repeatedly
986	* reload the stack for every single ref update. Instead, we manually
987	* reload further down in the case where we haven't yet prepared the
988	* specific `reftable_backend`.
989	*/
990	ret = backend_for(&be, refs, update->refname, NULL, 0);
991	if (ret)
992	return ret;
993
994	/*
995	* Search for a preexisting stack update. If there is one then we add
996	* the update to it, otherwise we set up a new stack update.
997	*/
998	for (i = 0; !arg && i < tx_data->args_nr; i++)
999	if (tx_data->args[i].be == be)
1000	arg = &tx_data->args[i];
1001
1002	if (!arg) {
1003	struct reftable_addition *addition;
1004
1005	ret = reftable_stack_new_addition(&addition, be->stack,
1006	&reftable_be_write_options(refs)->opts,
1007	REFTABLE_STACK_NEW_ADDITION_RELOAD);
1008	if (ret) {
1009	if (ret == REFTABLE_LOCK_ERROR)
1010	strbuf_addstr(err, "cannot lock references");
1011	return ret;
1012	}
1013
1014	ALLOC_GROW(tx_data->args, tx_data->args_nr + 1,
1015	tx_data->args_alloc);
1016	arg = &tx_data->args[tx_data->args_nr++];
1017	arg->refs = refs;
1018	arg->be = be;
1019	arg->addition = addition;
1020	arg->updates = NULL;
1021	arg->updates_nr = 0;
1022	arg->updates_alloc = 0;
1023	arg->updates_expected = 0;
1024	arg->max_index = 0;
1025	}
1026
1027	arg->updates_expected++;
1028
1029	if (out)
1030	*out = arg;
1031
1032	return 0;
1033	}
1034
1035	/*
1036	* Queue a reference update for the correct stack. We potentially need to
1037	* handle multiple stack updates in a single transaction when it spans across
1038	* multiple worktrees.
1039	*/
1040	static int queue_transaction_update(struct reftable_ref_store *refs,
1041	struct reftable_transaction_data *tx_data,
1042	struct ref_update *update,
1043	struct object_id *current_oid,
1044	struct strbuf *err)
1045	{
1046	struct write_transaction_table_arg *arg = NULL;
1047	int ret;
1048
1049	if (update->backend_data)
1050	BUG("reference update queued more than once");
1051
1052	ret = prepare_transaction_update(&arg, refs, tx_data, update, err);
1053	if (ret < 0)
1054	return ret;
1055
1056	ALLOC_GROW(arg->updates, arg->updates_nr + 1,
1057	arg->updates_alloc);
1058	arg->updates[arg->updates_nr].update = update;
1059	oidcpy(&arg->updates[arg->updates_nr].current_oid, current_oid);
1060	update->backend_data = &arg->updates[arg->updates_nr++];
1061
1062	return 0;
1063	}
1064
1065	static enum ref_transaction_error prepare_single_update(struct reftable_ref_store *refs,
1066	struct reftable_transaction_data *tx_data,
1067	struct ref_transaction *transaction,
1068	struct reftable_backend *be,
1069	struct ref_update *u,
1070	size_t update_idx,
1071	struct string_list *refnames_to_check,
1072	unsigned int head_type,
1073	struct strbuf *head_referent,
1074	struct strbuf *referent,
1075	struct strbuf *err)
1076	{
1077	enum ref_transaction_error ret = 0;
1078	struct object_id current_oid = {0};
1079	const char *rewritten_ref;
1080
1081	/*
1082	* There is no need to reload the respective backends here as
1083	* we have already reloaded them when preparing the transaction
1084	* update. And given that the stacks have been locked there
1085	* shouldn't have been any concurrent modifications of the
1086	* stack.
1087	*/
1088	ret = backend_for(&be, refs, u->refname, &rewritten_ref, 0);
1089	if (ret)
1090	return REF_TRANSACTION_ERROR_GENERIC;
1091
1092	if (u->flags & REF_LOG_USE_PROVIDED_OIDS) {
1093	if (!(u->flags & REF_HAVE_OLD) \|\|
1094	!(u->flags & REF_HAVE_NEW) \|\|
1095	!(u->flags & REF_LOG_ONLY)) {
1096	strbuf_addf(err, _("trying to write reflog for '%s' "
1097	"with incomplete values"), u->refname);
1098	return REF_TRANSACTION_ERROR_GENERIC;
1099	}
1100
1101	if (queue_transaction_update(refs, tx_data, u, &u->old_oid, err))
1102	return REF_TRANSACTION_ERROR_GENERIC;
1103	return 0;
1104	}
1105
1106	/*
1107	* When we update the reference that HEAD points to we enqueue
1108	* a second log-only update for HEAD so that its reflog is
1109	* updated accordingly.
1110	*/
1111	if (head_type == REF_ISSYMREF &&
1112	!(u->flags & REF_LOG_ONLY) &&
1113	!(u->flags & REF_UPDATE_VIA_HEAD) &&
1114	!strcmp(rewritten_ref, head_referent->buf)) {
1115	/*
1116	* First make sure that HEAD is not already in the
1117	* transaction. This check is O(lg N) in the transaction
1118	* size, but it happens at most once per transaction.
1119	*/
1120	if (string_list_has_string(&transaction->refnames, "HEAD")) {
1121	/* An entry already existed */
1122	strbuf_addf(err,
1123	_("multiple updates for 'HEAD' (including one "
1124	"via its referent '%s') are not allowed"),
1125	u->refname);
1126	return REF_TRANSACTION_ERROR_NAME_CONFLICT;
1127	}
1128
1129	ref_transaction_add_update(
1130	transaction, "HEAD",
1131	u->flags \| REF_LOG_ONLY \| REF_NO_DEREF,
1132	&u->new_oid, &u->old_oid, &u->peeled, NULL, NULL,
1133	NULL, u->msg);
1134	}
1135
1136	ret = reftable_backend_read_ref(be, rewritten_ref,
1137	&current_oid, referent, &u->type);
1138	if (ret < 0)
1139	return REF_TRANSACTION_ERROR_GENERIC;
1140	if (ret > 0 && !ref_update_expects_existing_old_ref(u)) {
1141	struct string_list_item *item;
1142	/*
1143	* The reference does not exist, and we either have no
1144	* old object ID or expect the reference to not exist.
1145	* We can thus skip below safety checks as well as the
1146	* symref splitting. But we do want to verify that
1147	* there is no conflicting reference here so that we
1148	* can output a proper error message instead of failing
1149	* at a later point.
1150	*/
1151	item = string_list_append(refnames_to_check, u->refname);
1152	item->util = xmalloc(sizeof(update_idx));
1153	memcpy(item->util, &update_idx, sizeof(update_idx));
1154
1155	/*
1156	* There is no need to write the reference deletion
1157	* when the reference in question doesn't exist.
1158	*/
1159	if ((u->flags & REF_HAVE_NEW) && !ref_update_has_null_new_value(u)) {
1160	ret = queue_transaction_update(refs, tx_data, u,
1161	&current_oid, err);
1162	if (ret)
1163	return REF_TRANSACTION_ERROR_GENERIC;
1164	}
1165
1166	return 0;
1167	}
1168	if (ret > 0) {
1169	/* The reference does not exist, but we expected it to. */
1170	strbuf_addf(err, _("cannot lock ref '%s': "
1171	"unable to resolve reference '%s'"),
1172	ref_update_original_update_refname(u), u->refname);
1173	return REF_TRANSACTION_ERROR_NONEXISTENT_REF;
1174	}
1175
1176	if (u->type & REF_ISSYMREF) {
1177	/*
1178	* The reftable stack is locked at this point already,
1179	* so it is safe to call `refs_resolve_ref_unsafe()`
1180	* here without causing races.
1181	*/
1182	const char *resolved = refs_resolve_ref_unsafe(&refs->base, u->refname, 0,
1183	&current_oid, NULL);
1184
1185	if (u->flags & REF_NO_DEREF) {
1186	if (u->flags & REF_HAVE_OLD && !resolved) {
1187	strbuf_addf(err, _("cannot lock ref '%s': "
1188	"error reading reference"), u->refname);
1189	return REF_TRANSACTION_ERROR_GENERIC;
1190	}
1191	} else {
1192	struct ref_update *new_update;
1193	int new_flags;
1194
1195	new_flags = u->flags;
1196	if (!strcmp(rewritten_ref, "HEAD"))
1197	new_flags \|= REF_UPDATE_VIA_HEAD;
1198
1199	if (string_list_has_string(&transaction->refnames, referent->buf)) {
1200	strbuf_addf(err,
1201	_("multiple updates for '%s' (including one "
1202	"via symref '%s') are not allowed"),
1203	referent->buf, u->refname);
1204	return REF_TRANSACTION_ERROR_NAME_CONFLICT;
1205	}
1206
1207	/*
1208	* If we are updating a symref (eg. HEAD), we should also
1209	* update the branch that the symref points to.
1210	*
1211	* This is generic functionality, and would be better
1212	* done in refs.c, but the current implementation is
1213	* intertwined with the locking in files-backend.c.
1214	*/
1215	new_update = ref_transaction_add_update(
1216	transaction, referent->buf, new_flags,
1217	u->new_target ? NULL : &u->new_oid,
1218	u->old_target ? NULL : &u->old_oid,
1219	&u->peeled, u->new_target, u->old_target,
1220	u->committer_info, u->msg);
1221
1222	new_update->parent_update = u;
1223
1224	/* Change the symbolic ref update to log only. */
1225	u->flags \|= REF_LOG_ONLY \| REF_NO_DEREF;
1226	}
1227	}
1228
1229	/*
1230	* Verify that the old object matches our expectations. Note
1231	* that the error messages here do not make a lot of sense in
1232	* the context of the reftable backend as we never lock
1233	* individual refs. But the error messages match what the files
1234	* backend returns, which keeps our tests happy.
1235	*/
1236	if (u->old_target) {
1237	if (!(u->type & REF_ISSYMREF)) {
1238	strbuf_addf(err, _("cannot lock ref '%s': "
1239	"expected symref with target '%s': "
1240	"but is a regular ref"),
1241	ref_update_original_update_refname(u),
1242	u->old_target);
1243	return REF_TRANSACTION_ERROR_EXPECTED_SYMREF;
1244	}
1245
1246	ret = ref_update_check_old_target(referent->buf, u, err);
1247	if (ret)
1248	return ret;
1249	} else if ((u->flags & (REF_LOG_ONLY \| REF_HAVE_OLD)) == REF_HAVE_OLD) {
1250	if (oideq(&current_oid, &u->old_oid)) {
1251	/*
1252	* Normally matching the expected old oid is enough. Either we
1253	* found the ref at the expected state, or we are creating and
1254	* expect the null oid (and likewise found nothing).
1255	*
1256	* But there is one exception for the null oid: if we found a
1257	* symref pointing to nothing we'll also get the null oid. In
1258	* regular recursive mode, that's good (we'll write to what the
1259	* symref points to, which doesn't exist). But in no-deref
1260	* mode, it means we'll clobber the symref, even though the
1261	* caller asked for this to be a creation event. So flag
1262	* that case to preserve the dangling symref.
1263	*
1264	* Everything else is OK and we can fall through to the
1265	* end of the conditional chain.
1266	*/
1267	if ((u->flags & REF_NO_DEREF) &&
1268	referent->len &&
1269	is_null_oid(&u->old_oid)) {
1270	strbuf_addf(err, _("cannot lock ref '%s': "
1271	"dangling symref already exists"),
1272	ref_update_original_update_refname(u));
1273	return REF_TRANSACTION_ERROR_CREATE_EXISTS;
1274	}
1275	} else if (is_null_oid(&u->old_oid)) {
1276	strbuf_addf(err, _("cannot lock ref '%s': "
1277	"reference already exists"),
1278	ref_update_original_update_refname(u));
1279	return REF_TRANSACTION_ERROR_CREATE_EXISTS;
1280	} else if (is_null_oid(&current_oid)) {
1281	strbuf_addf(err, _("cannot lock ref '%s': "
1282	"reference is missing but expected %s"),
1283	ref_update_original_update_refname(u),
1284	oid_to_hex(&u->old_oid));
1285	return REF_TRANSACTION_ERROR_NONEXISTENT_REF;
1286	} else {
1287	strbuf_addf(err, _("cannot lock ref '%s': "
1288	"is at %s but expected %s"),
1289	ref_update_original_update_refname(u),
1290	oid_to_hex(&current_oid),
1291	oid_to_hex(&u->old_oid));
1292	return REF_TRANSACTION_ERROR_INCORRECT_OLD_VALUE;
1293	}
1294	}
1295
1296	/*
1297	* If all of the following conditions are true:
1298	*
1299	* - We're not about to write a symref.
1300	* - We're not about to write a log-only entry.
1301	* - Old and new object ID are different.
1302	*
1303	* Then we're essentially doing a no-op update that can be
1304	* skipped. This is not only for the sake of efficiency, but
1305	* also skips writing unneeded reflog entries.
1306	*/
1307	if ((u->type & REF_ISSYMREF) \|\|
1308	(u->flags & REF_LOG_ONLY) \|\|
1309	(u->flags & REF_HAVE_NEW && !oideq(&current_oid, &u->new_oid)))
1310	if (queue_transaction_update(refs, tx_data, u, &current_oid, err))
1311	return REF_TRANSACTION_ERROR_GENERIC;
1312
1313	return 0;
1314	}
1315
1316	static int reftable_be_transaction_prepare(struct ref_store *ref_store,
1317	struct ref_transaction *transaction,
1318	struct strbuf *err)
1319	{
1320	struct reftable_ref_store *refs =
1321	reftable_be_downcast(ref_store, REF_STORE_WRITE\|REF_STORE_MAIN, "ref_transaction_prepare");
1322	struct strbuf referent = STRBUF_INIT, head_referent = STRBUF_INIT;
1323	struct string_list refnames_to_check = STRING_LIST_INIT_NODUP;
1324	struct reftable_transaction_data *tx_data = NULL;
1325	struct reftable_backend *be;
1326	struct object_id head_oid;
1327	unsigned int head_type = 0;
1328	size_t i;
1329	int ret;
1330
1331	ret = refs->err;
1332	if (ret < 0)
1333	goto done;
1334
1335	tx_data = xcalloc(1, sizeof(*tx_data));
1336
1337	/*
1338	* Preprocess all updates. For one we check that there are no duplicate
1339	* reference updates in this transaction. Second, we lock all stacks
1340	* that will be modified during the transaction.
1341	*/
1342	for (i = 0; i < transaction->nr; i++) {
1343	ret = prepare_transaction_update(NULL, refs, tx_data,
1344	transaction->updates[i], err);
1345	if (ret)
1346	goto done;
1347	}
1348
1349	/*
1350	* Now that we have counted updates per stack we can preallocate their
1351	* arrays. This avoids having to reallocate many times.
1352	*/
1353	for (i = 0; i < tx_data->args_nr; i++) {
1354	CALLOC_ARRAY(tx_data->args[i].updates, tx_data->args[i].updates_expected);
1355	tx_data->args[i].updates_alloc = tx_data->args[i].updates_expected;
1356	}
1357
1358	/*
1359	* TODO: it's dubious whether we should reload the stack that "HEAD"
1360	* belongs to or not. In theory, it may happen that we only modify
1361	* stacks which are _not_ part of the "HEAD" stack. In that case we
1362	* wouldn't have prepared any transaction for its stack and would not
1363	* have reloaded it, which may mean that it is stale.
1364	*
1365	* On the other hand, reloading that stack without locking it feels
1366	* wrong, too, as the value of "HEAD" could be modified concurrently at
1367	* any point in time.
1368	*/
1369	ret = backend_for(&be, refs, "HEAD", NULL, 0);
1370	if (ret)
1371	goto done;
1372
1373	ret = reftable_backend_read_ref(be, "HEAD", &head_oid,
1374	&head_referent, &head_type);
1375	if (ret < 0)
1376	goto done;
1377	ret = 0;
1378
1379	for (i = 0; i < transaction->nr; i++) {
1380	ret = prepare_single_update(refs, tx_data, transaction, be,
1381	transaction->updates[i], i,
1382	&refnames_to_check, head_type,
1383	&head_referent, &referent, err);
1384	if (ret) {
1385	if (ref_transaction_maybe_set_rejected(transaction, i,
1386	ret, err)) {
1387	ret = 0;
1388	continue;
1389	}
1390	goto done;
1391	}
1392	}
1393
1394	ret = refs_verify_refnames_available(ref_store, &refnames_to_check,
1395	&transaction->refnames, NULL,
1396	transaction,
1397	transaction->flags & REF_TRANSACTION_FLAG_INITIAL,
1398	err);
1399	if (ret < 0)
1400	goto done;
1401
1402	transaction->backend_data = tx_data;
1403	transaction->state = REF_TRANSACTION_PREPARED;
1404
1405	done:
1406	if (ret < 0) {
1407	free_transaction_data(tx_data);
1408	transaction->state = REF_TRANSACTION_CLOSED;
1409	if (!err->len)
1410	strbuf_addf(err, _("reftable: transaction prepare: %s"),
1411	reftable_error_str(ret));
1412	}
1413	strbuf_release(&referent);
1414	strbuf_release(&head_referent);
1415	string_list_clear(&refnames_to_check, 1);
1416
1417	return ret;
1418	}
1419
1420	static int reftable_be_transaction_abort(struct ref_store *ref_store UNUSED,
1421	struct ref_transaction *transaction,
1422	struct strbuf *err UNUSED)
1423	{
1424	struct reftable_transaction_data *tx_data = transaction->backend_data;
1425	free_transaction_data(tx_data);
1426	transaction->state = REF_TRANSACTION_CLOSED;
1427	return 0;
1428	}
1429
1430	static int transaction_update_cmp(const void a, const void b)
1431	{
1432	struct reftable_transaction_update update_a = (struct reftable_transaction_update )a;
1433	struct reftable_transaction_update update_b = (struct reftable_transaction_update )b;
1434
1435	/*
1436	* If there is an index set, it should take preference (default is 0).
1437	* This ensures that updates with indexes are sorted amongst themselves.
1438	*/
1439	if (update_a->update->index \|\| update_b->update->index)
1440	return update_a->update->index - update_b->update->index;
1441
1442	return strcmp(update_a->update->refname, update_b->update->refname);
1443	}
1444
1445	static int should_write_log(struct reftable_ref_store refs, const char refname)
1446	{
1447	enum log_refs_config log_refs_cfg = reftable_be_write_options(refs)->log_all_ref_updates;
1448	if (log_refs_cfg == LOG_REFS_UNSET)
1449	log_refs_cfg = is_bare_repository(refs->base.repo) ? LOG_REFS_NONE : LOG_REFS_NORMAL;
1450
1451	switch (log_refs_cfg) {
1452	case LOG_REFS_NONE:
1453	return refs_reflog_exists(&refs->base, refname);
1454	case LOG_REFS_ALWAYS:
1455	return 1;
1456	case LOG_REFS_NORMAL:
1457	if (should_autocreate_reflog(log_refs_cfg, refname))
1458	return 1;
1459	return refs_reflog_exists(&refs->base, refname);
1460	default:
1461	BUG("unhandled core.logAllRefUpdates value %d", log_refs_cfg);
1462	}
1463	}
1464
1465	static int write_transaction_table(struct reftable_writer writer, void cb_data)
1466	{
1467	struct write_transaction_table_arg *arg = cb_data;
1468	uint64_t ts = reftable_stack_next_update_index(arg->be->stack);
1469	struct reftable_log_record *logs = NULL;
1470	struct ident_split committer_ident = {0};
1471	size_t logs_nr = 0, logs_alloc = 0, i;
1472	const char *committer_info;
1473	int ret = 0;
1474
1475	committer_info = git_committer_info(0);
1476	if (split_ident_line(&committer_ident, committer_info, strlen(committer_info)))
1477	BUG("failed splitting committer info");
1478
1479	QSORT(arg->updates, arg->updates_nr, transaction_update_cmp);
1480
1481	/*
1482	* During reflog migration, we add indexes for a single reflog with
1483	* multiple entries. Each entry will contain a different update_index,
1484	* so set the limits accordingly.
1485	*/
1486	ret = reftable_writer_set_limits(writer, ts, ts + arg->max_index);
1487	if (ret < 0)
1488	goto done;
1489
1490	for (i = 0; i < arg->updates_nr; i++) {
1491	struct reftable_transaction_update *tx_update = &arg->updates[i];
1492	struct ref_update *u = tx_update->update;
1493
1494	if (u->rejection_err)
1495	continue;
1496
1497	/*
1498	* Write a reflog entry when updating a ref to point to
1499	* something new in either of the following cases:
1500	*
1501	* - The reference is about to be deleted. We always want to
1502	* delete the reflog in that case.
1503	* - REF_FORCE_CREATE_REFLOG is set, asking us to always create
1504	* the reflog entry.
1505	* - `core.logAllRefUpdates` tells us to create the reflog for
1506	* the given ref.
1507	*/
1508	if ((u->flags & REF_HAVE_NEW) &&
1509	!(u->type & REF_ISSYMREF) &&
1510	ref_update_has_null_new_value(u)) {
1511	struct reftable_log_record log = {0};
1512	struct reftable_iterator it = {0};
1513
1514	ret = reftable_stack_init_log_iterator(arg->be->stack, &it);
1515	if (ret < 0)
1516	goto done;
1517
1518	/*
1519	* When deleting refs we also delete all reflog entries
1520	* with them. While it is not strictly required to
1521	* delete reflogs together with their refs, this
1522	* matches the behaviour of the files backend.
1523	*
1524	* Unfortunately, we have no better way than to delete
1525	* all reflog entries one by one.
1526	*/
1527	ret = reftable_iterator_seek_log(&it, u->refname);
1528	while (ret == 0) {
1529	struct reftable_log_record *tombstone;
1530
1531	ret = reftable_iterator_next_log(&it, &log);
1532	if (ret < 0)
1533	break;
1534	if (ret > 0 \|\| strcmp(log.refname, u->refname)) {
1535	ret = 0;
1536	break;
1537	}
1538	if (reftable_log_record_is_deletion(&log))
1539	continue;
1540
1541	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1542	tombstone = &logs[logs_nr++];
1543	tombstone->refname = xstrdup(u->refname);
1544	tombstone->value_type = REFTABLE_LOG_DELETION;
1545	tombstone->update_index = log.update_index;
1546	}
1547
1548	reftable_log_record_release(&log);
1549	reftable_iterator_destroy(&it);
1550
1551	if (ret)
1552	goto done;
1553	} else if (!(u->flags & REF_SKIP_CREATE_REFLOG) &&
1554	(u->flags & REF_HAVE_NEW) &&
1555	(u->flags & REF_FORCE_CREATE_REFLOG \|\|
1556	should_write_log(arg->refs, u->refname))) {
1557	struct reftable_log_record *log;
1558	int create_reflog = 1;
1559
1560	if (u->new_target) {
1561	if (!refs_resolve_ref_unsafe(&arg->refs->base, u->new_target,
1562	RESOLVE_REF_READING, &u->new_oid, NULL)) {
1563	/*
1564	* TODO: currently we skip creating reflogs for dangling
1565	* symref updates. It would be nice to capture this as
1566	* zero oid updates however.
1567	*/
1568	create_reflog = 0;
1569	}
1570	}
1571
1572	if (create_reflog) {
1573	struct ident_split c;
1574
1575	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1576	log = &logs[logs_nr++];
1577	memset(log, 0, sizeof(*log));
1578
1579	if (u->committer_info) {
1580	if (split_ident_line(&c, u->committer_info,
1581	strlen(u->committer_info)))
1582	BUG("failed splitting committer info");
1583	} else {
1584	c = committer_ident;
1585	}
1586
1587	fill_reftable_log_record(log, &c);
1588
1589	/*
1590	* Updates are sorted by the writer. So updates for the same
1591	* refname need to contain different update indices.
1592	*/
1593	log->update_index = ts + u->index;
1594
1595	log->refname = xstrdup(u->refname);
1596	memcpy(log->value.update.new_hash,
1597	u->new_oid.hash, GIT_MAX_RAWSZ);
1598	memcpy(log->value.update.old_hash,
1599	tx_update->current_oid.hash, GIT_MAX_RAWSZ);
1600	log->value.update.message =
1601	xstrndup(u->msg, reftable_be_write_options(arg->refs)->opts.block_size / 2);
1602	}
1603	}
1604
1605	if (u->flags & REF_LOG_ONLY)
1606	continue;
1607
1608	if (u->new_target) {
1609	struct reftable_ref_record ref = {
1610	.refname = (char *)u->refname,
1611	.value_type = REFTABLE_REF_SYMREF,
1612	.value.symref = (char *)u->new_target,
1613	.update_index = ts,
1614	};
1615
1616	ret = reftable_writer_add_ref(writer, &ref);
1617	if (ret < 0)
1618	goto done;
1619	} else if ((u->flags & REF_HAVE_NEW) && ref_update_has_null_new_value(u)) {
1620	struct reftable_ref_record ref = {
1621	.refname = (char *)u->refname,
1622	.update_index = ts,
1623	.value_type = REFTABLE_REF_DELETION,
1624	};
1625
1626	ret = reftable_writer_add_ref(writer, &ref);
1627	if (ret < 0)
1628	goto done;
1629	} else if (u->flags & REF_HAVE_NEW) {
1630	struct reftable_ref_record ref = {0};
1631
1632	ref.refname = (char *)u->refname;
1633	ref.update_index = ts;
1634
1635	if (u->flags & REF_HAVE_PEELED) {
1636	ref.value_type = REFTABLE_REF_VAL2;
1637	memcpy(ref.value.val2.target_value, u->peeled.hash, GIT_MAX_RAWSZ);
1638	memcpy(ref.value.val2.value, u->new_oid.hash, GIT_MAX_RAWSZ);
1639	} else if (!is_null_oid(&u->new_oid)) {
1640	ref.value_type = REFTABLE_REF_VAL1;
1641	memcpy(ref.value.val1, u->new_oid.hash, GIT_MAX_RAWSZ);
1642	}
1643
1644	ret = reftable_writer_add_ref(writer, &ref);
1645	if (ret < 0)
1646	goto done;
1647	}
1648	}
1649
1650	/*
1651	* Logs are written at the end so that we do not have intermixed ref
1652	* and log blocks.
1653	*/
1654	if (logs) {
1655	ret = reftable_writer_add_logs(writer, logs, logs_nr);
1656	if (ret < 0)
1657	goto done;
1658	}
1659
1660	done:
1661	assert(ret != REFTABLE_API_ERROR);
1662	for (i = 0; i < logs_nr; i++)
1663	reftable_log_record_release(&logs[i]);
1664	free(logs);
1665	return ret;
1666	}
1667
1668	static int reftable_be_transaction_finish(struct ref_store *ref_store UNUSED,
1669	struct ref_transaction *transaction,
1670	struct strbuf *err)
1671	{
1672	struct reftable_transaction_data *tx_data = transaction->backend_data;
1673	int ret = 0;
1674
1675	for (size_t i = 0; i < tx_data->args_nr; i++) {
1676	tx_data->args[i].max_index = transaction->max_index;
1677
1678	ret = reftable_addition_add(tx_data->args[i].addition,
1679	write_transaction_table, &tx_data->args[i]);
1680	if (ret < 0)
1681	goto done;
1682
1683	ret = reftable_addition_commit(tx_data->args[i].addition);
1684	if (ret < 0)
1685	goto done;
1686	}
1687
1688	done:
1689	assert(ret != REFTABLE_API_ERROR);
1690	free_transaction_data(tx_data);
1691	transaction->state = REF_TRANSACTION_CLOSED;
1692
1693	if (ret) {
1694	strbuf_addf(err, _("reftable: transaction failure: %s"),
1695	reftable_error_str(ret));
1696	return -1;
1697	}
1698	return ret;
1699	}
1700
1701	static int reftable_be_optimize(struct ref_store *ref_store,
1702	struct refs_optimize_opts *opts)
1703	{
1704	struct reftable_ref_store *refs =
1705	reftable_be_downcast(ref_store, REF_STORE_WRITE \| REF_STORE_ODB, "optimize_refs");
1706	struct reftable_stack *stack;
1707	int ret;
1708
1709	if (refs->err)
1710	return refs->err;
1711
1712	stack = refs->worktree_backend.stack;
1713	if (!stack)
1714	stack = refs->main_backend.stack;
1715
1716	if (opts->flags & REFS_OPTIMIZE_AUTO)
1717	ret = reftable_stack_auto_compact(stack, &reftable_be_write_options(refs)->opts);
1718	else
1719	ret = reftable_stack_compact_all(stack, &reftable_be_write_options(refs)->opts, NULL);
1720	if (ret < 0) {
1721	ret = error(_("unable to compact stack: %s"),
1722	reftable_error_str(ret));
1723	goto out;
1724	}
1725
1726	ret = reftable_stack_clean(stack);
1727	if (ret)
1728	goto out;
1729
1730	out:
1731	return ret;
1732	}
1733
1734	static int reftable_be_optimize_required(struct ref_store *ref_store,
1735	struct refs_optimize_opts *opts,
1736	bool *required)
1737	{
1738	struct reftable_ref_store *refs = reftable_be_downcast(ref_store, REF_STORE_READ,
1739	"optimize_refs_required");
1740	struct reftable_stack *stack;
1741	bool use_heuristics = false;
1742
1743	if (refs->err)
1744	return refs->err;
1745
1746	stack = refs->worktree_backend.stack;
1747	if (!stack)
1748	stack = refs->main_backend.stack;
1749
1750	if (opts->flags & REFS_OPTIMIZE_AUTO)
1751	use_heuristics = true;
1752
1753	return reftable_stack_compaction_required(stack, &reftable_be_write_options(refs)->opts,
1754	use_heuristics, required);
1755	}
1756
1757	struct write_create_symref_arg {
1758	struct reftable_ref_store *refs;
1759	struct reftable_stack *stack;
1760	struct strbuf *err;
1761	const char *refname;
1762	const char *target;
1763	const char *logmsg;
1764	};
1765
1766	struct write_copy_arg {
1767	struct reftable_ref_store *refs;
1768	struct reftable_backend *be;
1769	const char *oldname;
1770	const char *newname;
1771	const char *logmsg;
1772	int delete_old;
1773	};
1774
1775	static int write_copy_table(struct reftable_writer writer, void cb_data)
1776	{
1777	struct write_copy_arg *arg = cb_data;
1778	uint64_t deletion_ts, creation_ts;
1779	struct reftable_ref_record old_ref = {0}, refs[2] = {0};
1780	struct reftable_log_record old_log = {0}, *logs = NULL;
1781	struct reftable_iterator it = {0};
1782	struct string_list skip = STRING_LIST_INIT_NODUP;
1783	struct ident_split committer_ident = {0};
1784	struct strbuf errbuf = STRBUF_INIT;
1785	size_t logs_nr = 0, logs_alloc = 0, i;
1786	const char *committer_info;
1787	int ret;
1788
1789	committer_info = git_committer_info(0);
1790	if (split_ident_line(&committer_ident, committer_info, strlen(committer_info)))
1791	BUG("failed splitting committer info");
1792
1793	if (reftable_stack_read_ref(arg->be->stack, arg->oldname, &old_ref)) {
1794	ret = error(_("refname %s not found"), arg->oldname);
1795	goto done;
1796	}
1797	if (old_ref.value_type == REFTABLE_REF_SYMREF) {
1798	ret = error(_("refname %s is a symbolic ref, copying it is not supported"),
1799	arg->oldname);
1800	goto done;
1801	}
1802
1803	/*
1804	* There's nothing to do in case the old and new name are the same, so
1805	* we exit early in that case.
1806	*/
1807	if (!strcmp(arg->oldname, arg->newname)) {
1808	ret = 0;
1809	goto done;
1810	}
1811
1812	/*
1813	* Verify that the new refname is available.
1814	*/
1815	if (arg->delete_old)
1816	string_list_insert(&skip, arg->oldname);
1817	ret = refs_verify_refname_available(&arg->refs->base, arg->newname,
1818	NULL, &skip, 0, &errbuf);
1819	if (ret < 0) {
1820	error("%s", errbuf.buf);
1821	goto done;
1822	}
1823
1824	/*
1825	* When deleting the old reference we have to use two update indices:
1826	* once to delete the old ref and its reflog, and once to create the
1827	* new ref and its reflog. They need to be staged with two separate
1828	* indices because the new reflog needs to encode both the deletion of
1829	* the old branch and the creation of the new branch, and we cannot do
1830	* two changes to a reflog in a single update.
1831	*/
1832	deletion_ts = creation_ts = reftable_stack_next_update_index(arg->be->stack);
1833	if (arg->delete_old)
1834	creation_ts++;
1835	ret = reftable_writer_set_limits(writer, deletion_ts, creation_ts);
1836	if (ret < 0)
1837	goto done;
1838
1839	/*
1840	* Add the new reference. If this is a rename then we also delete the
1841	* old reference.
1842	*/
1843	refs[0] = old_ref;
1844	refs[0].refname = xstrdup(arg->newname);
1845	refs[0].update_index = creation_ts;
1846	if (arg->delete_old) {
1847	refs[1].refname = xstrdup(arg->oldname);
1848	refs[1].value_type = REFTABLE_REF_DELETION;
1849	refs[1].update_index = deletion_ts;
1850	}
1851	ret = reftable_writer_add_refs(writer, refs, arg->delete_old ? 2 : 1);
1852	if (ret < 0)
1853	goto done;
1854
1855	/*
1856	* When deleting the old branch we need to create a reflog entry on the
1857	* new branch name that indicates that the old branch has been deleted
1858	* and then recreated. This is a tad weird, but matches what the files
1859	* backend does.
1860	*/
1861	if (arg->delete_old) {
1862	struct strbuf head_referent = STRBUF_INIT;
1863	struct object_id head_oid;
1864	int append_head_reflog;
1865	unsigned head_type = 0;
1866
1867	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1868	memset(&logs[logs_nr], 0, sizeof(logs[logs_nr]));
1869	fill_reftable_log_record(&logs[logs_nr], &committer_ident);
1870	logs[logs_nr].refname = xstrdup(arg->newname);
1871	logs[logs_nr].update_index = deletion_ts;
1872	logs[logs_nr].value.update.message =
1873	xstrndup(arg->logmsg, reftable_be_write_options(arg->refs)->opts.block_size / 2);
1874	memcpy(logs[logs_nr].value.update.old_hash, old_ref.value.val1, GIT_MAX_RAWSZ);
1875	logs_nr++;
1876
1877	ret = reftable_backend_read_ref(arg->be, "HEAD", &head_oid,
1878	&head_referent, &head_type);
1879	if (ret < 0)
1880	goto done;
1881	append_head_reflog = (head_type & REF_ISSYMREF) && !strcmp(head_referent.buf, arg->oldname);
1882	strbuf_release(&head_referent);
1883
1884	/*
1885	* The files backend uses `refs_delete_ref()` to delete the old
1886	* branch name, which will append a reflog entry for HEAD in
1887	* case it points to the old branch.
1888	*/
1889	if (append_head_reflog) {
1890	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1891	logs[logs_nr] = logs[logs_nr - 1];
1892	logs[logs_nr].refname = xstrdup("HEAD");
1893	logs[logs_nr].value.update.name =
1894	xstrdup(logs[logs_nr].value.update.name);
1895	logs[logs_nr].value.update.email =
1896	xstrdup(logs[logs_nr].value.update.email);
1897	logs[logs_nr].value.update.message =
1898	xstrdup(logs[logs_nr].value.update.message);
1899	logs_nr++;
1900	}
1901	}
1902
1903	/*
1904	* Create the reflog entry for the newly created branch.
1905	*/
1906	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1907	memset(&logs[logs_nr], 0, sizeof(logs[logs_nr]));
1908	fill_reftable_log_record(&logs[logs_nr], &committer_ident);
1909	logs[logs_nr].refname = xstrdup(arg->newname);
1910	logs[logs_nr].update_index = creation_ts;
1911	logs[logs_nr].value.update.message =
1912	xstrndup(arg->logmsg, reftable_be_write_options(arg->refs)->opts.block_size / 2);
1913	memcpy(logs[logs_nr].value.update.new_hash, old_ref.value.val1, GIT_MAX_RAWSZ);
1914	logs_nr++;
1915
1916	/*
1917	* In addition to writing the reflog entry for the new branch, we also
1918	* copy over all log entries from the old reflog. Last but not least,
1919	* when renaming we also have to delete all the old reflog entries.
1920	*/
1921	ret = reftable_stack_init_log_iterator(arg->be->stack, &it);
1922	if (ret < 0)
1923	goto done;
1924
1925	ret = reftable_iterator_seek_log(&it, arg->oldname);
1926	if (ret < 0)
1927	goto done;
1928
1929	while (1) {
1930	ret = reftable_iterator_next_log(&it, &old_log);
1931	if (ret < 0)
1932	goto done;
1933	if (ret > 0 \|\| strcmp(old_log.refname, arg->oldname)) {
1934	ret = 0;
1935	break;
1936	}
1937	if (reftable_log_record_is_deletion(&old_log))
1938	continue;
1939
1940	free(old_log.refname);
1941
1942	/*
1943	* Copy over the old reflog entry with the new refname.
1944	*/
1945	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1946	logs[logs_nr] = old_log;
1947	logs[logs_nr].refname = xstrdup(arg->newname);
1948	logs_nr++;
1949
1950	/*
1951	* Delete the old reflog entry in case we are renaming.
1952	*/
1953	if (arg->delete_old) {
1954	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
1955	memset(&logs[logs_nr], 0, sizeof(logs[logs_nr]));
1956	logs[logs_nr].refname = xstrdup(arg->oldname);
1957	logs[logs_nr].value_type = REFTABLE_LOG_DELETION;
1958	logs[logs_nr].update_index = old_log.update_index;
1959	logs_nr++;
1960	}
1961
1962	/*
1963	* Transfer ownership of the log record we're iterating over to
1964	* the array of log records. Otherwise, the pointers would get
1965	* free'd or reallocated by the iterator.
1966	*/
1967	memset(&old_log, 0, sizeof(old_log));
1968	}
1969
1970	ret = reftable_writer_add_logs(writer, logs, logs_nr);
1971	if (ret < 0)
1972	goto done;
1973
1974	done:
1975	assert(ret != REFTABLE_API_ERROR);
1976	reftable_iterator_destroy(&it);
1977	string_list_clear(&skip, 0);
1978	strbuf_release(&errbuf);
1979	for (i = 0; i < logs_nr; i++)
1980	reftable_log_record_release(&logs[i]);
1981	free(logs);
1982	for (i = 0; i < ARRAY_SIZE(refs); i++)
1983	reftable_ref_record_release(&refs[i]);
1984	reftable_ref_record_release(&old_ref);
1985	reftable_log_record_release(&old_log);
1986	return ret;
1987	}
1988
1989	static int reftable_be_rename_ref(struct ref_store *ref_store,
1990	const char *oldrefname,
1991	const char *newrefname,
1992	const char *logmsg)
1993	{
1994	struct reftable_ref_store *refs =
1995	reftable_be_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
1996	struct write_copy_arg arg = {
1997	.refs = refs,
1998	.oldname = oldrefname,
1999	.newname = newrefname,
2000	.logmsg = logmsg,
2001	.delete_old = 1,
2002	};
2003	int ret;
2004
2005	ret = refs->err;
2006	if (ret < 0)
2007	goto done;
2008
2009	ret = backend_for(&arg.be, refs, newrefname, &newrefname, 1);
2010	if (ret)
2011	goto done;
2012	ret = reftable_stack_add(arg.be->stack, &write_copy_table, &arg,
2013	&reftable_be_write_options(refs)->opts,
2014	REFTABLE_STACK_NEW_ADDITION_RELOAD);
2015
2016	done:
2017	assert(ret != REFTABLE_API_ERROR);
2018	return ret;
2019	}
2020
2021	static int reftable_be_copy_ref(struct ref_store *ref_store,
2022	const char *oldrefname,
2023	const char *newrefname,
2024	const char *logmsg)
2025	{
2026	struct reftable_ref_store *refs =
2027	reftable_be_downcast(ref_store, REF_STORE_WRITE, "copy_ref");
2028	struct write_copy_arg arg = {
2029	.refs = refs,
2030	.oldname = oldrefname,
2031	.newname = newrefname,
2032	.logmsg = logmsg,
2033	};
2034	int ret;
2035
2036	ret = refs->err;
2037	if (ret < 0)
2038	goto done;
2039
2040	ret = backend_for(&arg.be, refs, newrefname, &newrefname, 1);
2041	if (ret)
2042	goto done;
2043	ret = reftable_stack_add(arg.be->stack, &write_copy_table, &arg,
2044	&reftable_be_write_options(refs)->opts,
2045	REFTABLE_STACK_NEW_ADDITION_RELOAD);
2046
2047	done:
2048	assert(ret != REFTABLE_API_ERROR);
2049	return ret;
2050	}
2051
2052	struct reftable_reflog_iterator {
2053	struct ref_iterator base;
2054	struct reftable_ref_store *refs;
2055	struct reftable_iterator iter;
2056	struct reftable_log_record log;
2057	struct strbuf last_name;
2058	int err;
2059	};
2060
2061	static int reftable_reflog_iterator_advance(struct ref_iterator *ref_iterator)
2062	{
2063	struct reftable_reflog_iterator *iter =
2064	(struct reftable_reflog_iterator *)ref_iterator;
2065
2066	while (!iter->err) {
2067	iter->err = reftable_iterator_next_log(&iter->iter, &iter->log);
2068	if (iter->err)
2069	break;
2070
2071	if (reftable_log_record_is_deletion(&iter->log))
2072	continue;
2073
2074	/*
2075	* We want the refnames that we have reflogs for, so we skip if
2076	* we've already produced this name. This could be faster by
2077	* seeking directly to reflog@update_index==0.
2078	*/
2079	if (!strcmp(iter->log.refname, iter->last_name.buf))
2080	continue;
2081
2082	if (check_refname_format(iter->log.refname,
2083	REFNAME_ALLOW_ONELEVEL))
2084	continue;
2085
2086	strbuf_reset(&iter->last_name);
2087	strbuf_addstr(&iter->last_name, iter->log.refname);
2088	iter->base.ref.name = iter->log.refname;
2089
2090	break;
2091	}
2092
2093	if (iter->err > 0)
2094	return ITER_DONE;
2095	if (iter->err < 0)
2096	return ITER_ERROR;
2097	return ITER_OK;
2098	}
2099
2100	static int reftable_reflog_iterator_seek(struct ref_iterator *ref_iterator UNUSED,
2101	const char *refname UNUSED,
2102	unsigned int flags UNUSED)
2103	{
2104	BUG("reftable reflog iterator cannot be seeked");
2105	return -1;
2106	}
2107
2108	static void reftable_reflog_iterator_release(struct ref_iterator *ref_iterator)
2109	{
2110	struct reftable_reflog_iterator *iter =
2111	(struct reftable_reflog_iterator *)ref_iterator;
2112	reftable_log_record_release(&iter->log);
2113	reftable_iterator_destroy(&iter->iter);
2114	strbuf_release(&iter->last_name);
2115	}
2116
2117	static struct ref_iterator_vtable reftable_reflog_iterator_vtable = {
2118	.advance = reftable_reflog_iterator_advance,
2119	.seek = reftable_reflog_iterator_seek,
2120	.release = reftable_reflog_iterator_release,
2121	};
2122
2123	static struct reftable_reflog_iterator reflog_iterator_for_stack(struct reftable_ref_store refs,
2124	struct reftable_stack *stack)
2125	{
2126	struct reftable_reflog_iterator *iter;
2127	int ret;
2128
2129	iter = xcalloc(1, sizeof(*iter));
2130	base_ref_iterator_init(&iter->base, &reftable_reflog_iterator_vtable);
2131	strbuf_init(&iter->last_name, 0);
2132	iter->refs = refs;
2133
2134	ret = refs->err;
2135	if (ret)
2136	goto done;
2137
2138	ret = reftable_stack_reload(stack);
2139	if (ret < 0)
2140	goto done;
2141
2142	ret = reftable_stack_init_log_iterator(stack, &iter->iter);
2143	if (ret < 0)
2144	goto done;
2145
2146	ret = reftable_iterator_seek_log(&iter->iter, "");
2147	if (ret < 0)
2148	goto done;
2149
2150	done:
2151	iter->err = ret;
2152	return iter;
2153	}
2154
2155	static struct ref_iterator reftable_be_reflog_iterator_begin(struct ref_store ref_store)
2156	{
2157	struct reftable_ref_store *refs =
2158	reftable_be_downcast(ref_store, REF_STORE_READ, "reflog_iterator_begin");
2159	struct reftable_reflog_iterator main_iter, worktree_iter;
2160
2161	main_iter = reflog_iterator_for_stack(refs, refs->main_backend.stack);
2162	if (!refs->worktree_backend.stack)
2163	return &main_iter->base;
2164
2165	worktree_iter = reflog_iterator_for_stack(refs, refs->worktree_backend.stack);
2166
2167	return merge_ref_iterator_begin(&worktree_iter->base, &main_iter->base,
2168	ref_iterator_select, NULL);
2169	}
2170
2171	static int yield_log_record(struct reftable_ref_store *refs,
2172	struct reftable_log_record *log,
2173	each_reflog_ent_fn fn,
2174	void *cb_data)
2175	{
2176	struct object_id old_oid, new_oid;
2177	const char *full_committer;
2178
2179	oidread(&old_oid, log->value.update.old_hash, refs->base.repo->hash_algo);
2180	oidread(&new_oid, log->value.update.new_hash, refs->base.repo->hash_algo);
2181
2182	/*
2183	* When both the old object ID and the new object ID are null
2184	* then this is the reflog existence marker. The caller must
2185	* not be aware of it.
2186	*/
2187	if (is_null_oid(&old_oid) && is_null_oid(&new_oid))
2188	return 0;
2189
2190	full_committer = fmt_ident(log->value.update.name, log->value.update.email,
2191	WANT_COMMITTER_IDENT, NULL, IDENT_NO_DATE);
2192	return fn(log->refname, &old_oid, &new_oid, full_committer,
2193	log->value.update.time, log->value.update.tz_offset,
2194	log->value.update.message, cb_data);
2195	}
2196
2197	static int reftable_be_for_each_reflog_ent_reverse(struct ref_store *ref_store,
2198	const char *refname,
2199	each_reflog_ent_fn fn,
2200	void *cb_data)
2201	{
2202	struct reftable_ref_store *refs =
2203	reftable_be_downcast(ref_store, REF_STORE_READ, "for_each_reflog_ent_reverse");
2204	struct reftable_log_record log = {0};
2205	struct reftable_iterator it = {0};
2206	struct reftable_backend *be;
2207	int ret;
2208
2209	if (refs->err < 0)
2210	return refs->err;
2211
2212	/*
2213	* TODO: we should adapt this callsite to reload the stack. There is no
2214	* obvious reason why we shouldn't.
2215	*/
2216	ret = backend_for(&be, refs, refname, &refname, 0);
2217	if (ret)
2218	goto done;
2219
2220	ret = reftable_stack_init_log_iterator(be->stack, &it);
2221	if (ret < 0)
2222	goto done;
2223
2224	ret = reftable_iterator_seek_log(&it, refname);
2225	while (!ret) {
2226	ret = reftable_iterator_next_log(&it, &log);
2227	if (ret < 0)
2228	break;
2229	if (ret > 0 \|\| strcmp(log.refname, refname)) {
2230	ret = 0;
2231	break;
2232	}
2233	if (reftable_log_record_is_deletion(&log))
2234	continue;
2235
2236	ret = yield_log_record(refs, &log, fn, cb_data);
2237	if (ret)
2238	break;
2239	}
2240
2241	done:
2242	reftable_log_record_release(&log);
2243	reftable_iterator_destroy(&it);
2244	return ret;
2245	}
2246
2247	static int reftable_be_for_each_reflog_ent(struct ref_store *ref_store,
2248	const char *refname,
2249	each_reflog_ent_fn fn,
2250	void *cb_data)
2251	{
2252	struct reftable_ref_store *refs =
2253	reftable_be_downcast(ref_store, REF_STORE_READ, "for_each_reflog_ent");
2254	struct reftable_log_record *logs = NULL;
2255	struct reftable_iterator it = {0};
2256	struct reftable_backend *be;
2257	size_t logs_alloc = 0, logs_nr = 0, i;
2258	int ret;
2259
2260	if (refs->err < 0)
2261	return refs->err;
2262
2263	/*
2264	* TODO: we should adapt this callsite to reload the stack. There is no
2265	* obvious reason why we shouldn't.
2266	*/
2267	ret = backend_for(&be, refs, refname, &refname, 0);
2268	if (ret)
2269	goto done;
2270
2271	ret = reftable_stack_init_log_iterator(be->stack, &it);
2272	if (ret < 0)
2273	goto done;
2274
2275	ret = reftable_iterator_seek_log(&it, refname);
2276	while (!ret) {
2277	struct reftable_log_record log = {0};
2278
2279	ret = reftable_iterator_next_log(&it, &log);
2280	if (ret < 0)
2281	goto done;
2282	if (ret > 0 \|\| strcmp(log.refname, refname)) {
2283	reftable_log_record_release(&log);
2284	ret = 0;
2285	break;
2286	}
2287	if (reftable_log_record_is_deletion(&log)) {
2288	reftable_log_record_release(&log);
2289	continue;
2290	}
2291
2292	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
2293	logs[logs_nr++] = log;
2294	}
2295
2296	for (i = logs_nr; i--;) {
2297	ret = yield_log_record(refs, &logs[i], fn, cb_data);
2298	if (ret)
2299	goto done;
2300	}
2301
2302	done:
2303	reftable_iterator_destroy(&it);
2304	for (i = 0; i < logs_nr; i++)
2305	reftable_log_record_release(&logs[i]);
2306	free(logs);
2307	return ret;
2308	}
2309
2310	static int reftable_be_reflog_exists(struct ref_store *ref_store,
2311	const char *refname)
2312	{
2313	struct reftable_ref_store *refs =
2314	reftable_be_downcast(ref_store, REF_STORE_READ, "reflog_exists");
2315	struct reftable_log_record log = {0};
2316	struct reftable_iterator it = {0};
2317	struct reftable_backend *be;
2318	int ret;
2319
2320	ret = refs->err;
2321	if (ret < 0)
2322	goto done;
2323
2324	ret = backend_for(&be, refs, refname, &refname, 1);
2325	if (ret < 0)
2326	goto done;
2327
2328	ret = reftable_stack_init_log_iterator(be->stack, &it);
2329	if (ret < 0)
2330	goto done;
2331
2332	ret = reftable_iterator_seek_log(&it, refname);
2333	if (ret < 0)
2334	goto done;
2335
2336	/*
2337	* Check whether we get at least one non-deleted log record for the
2338	* given ref name. If so, the reflog exists, otherwise it doesn't.
2339	*/
2340	while (1) {
2341	ret = reftable_iterator_next_log(&it, &log);
2342	if (ret < 0)
2343	goto done;
2344	if (ret > 0) {
2345	ret = 0;
2346	goto done;
2347	}
2348	if (strcmp(log.refname, refname)) {
2349	ret = 0;
2350	goto done;
2351	}
2352	if (!reftable_log_record_is_deletion(&log))
2353	break;
2354	}
2355
2356	ret = 1;
2357
2358	done:
2359	reftable_iterator_destroy(&it);
2360	reftable_log_record_release(&log);
2361	if (ret < 0)
2362	ret = 0;
2363	return ret;
2364	}
2365
2366	struct write_reflog_existence_arg {
2367	struct reftable_ref_store *refs;
2368	const char *refname;
2369	struct reftable_stack *stack;
2370	};
2371
2372	static int write_reflog_existence_table(struct reftable_writer *writer,
2373	void *cb_data)
2374	{
2375	struct write_reflog_existence_arg *arg = cb_data;
2376	uint64_t ts = reftable_stack_next_update_index(arg->stack);
2377	struct reftable_log_record log = {0};
2378	int ret;
2379
2380	ret = reftable_stack_read_log(arg->stack, arg->refname, &log);
2381	if (ret <= 0)
2382	goto done;
2383
2384	ret = reftable_writer_set_limits(writer, ts, ts);
2385	if (ret < 0)
2386	goto done;
2387
2388	/*
2389	* The existence entry has both old and new object ID set to the
2390	* null object ID. Our iterators are aware of this and will not present
2391	* them to their callers.
2392	*/
2393	log.refname = xstrdup(arg->refname);
2394	log.update_index = ts;
2395	log.value_type = REFTABLE_LOG_UPDATE;
2396	ret = reftable_writer_add_log(writer, &log);
2397
2398	done:
2399	assert(ret != REFTABLE_API_ERROR);
2400	reftable_log_record_release(&log);
2401	return ret;
2402	}
2403
2404	static int reftable_be_create_reflog(struct ref_store *ref_store,
2405	const char *refname,
2406	struct strbuf *errmsg UNUSED)
2407	{
2408	struct reftable_ref_store *refs =
2409	reftable_be_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
2410	struct reftable_backend *be;
2411	struct write_reflog_existence_arg arg = {
2412	.refs = refs,
2413	.refname = refname,
2414	};
2415	int ret;
2416
2417	ret = refs->err;
2418	if (ret < 0)
2419	goto done;
2420
2421	ret = backend_for(&be, refs, refname, &refname, 1);
2422	if (ret)
2423	goto done;
2424	arg.stack = be->stack;
2425
2426	ret = reftable_stack_add(be->stack, &write_reflog_existence_table, &arg,
2427	&reftable_be_write_options(refs)->opts,
2428	REFTABLE_STACK_NEW_ADDITION_RELOAD);
2429
2430	done:
2431	return ret;
2432	}
2433
2434	struct write_reflog_delete_arg {
2435	struct reftable_stack *stack;
2436	const char *refname;
2437	};
2438
2439	static int write_reflog_delete_table(struct reftable_writer writer, void cb_data)
2440	{
2441	struct write_reflog_delete_arg *arg = cb_data;
2442	struct reftable_log_record log = {0}, tombstone = {0};
2443	struct reftable_iterator it = {0};
2444	uint64_t ts = reftable_stack_next_update_index(arg->stack);
2445	int ret;
2446
2447	ret = reftable_writer_set_limits(writer, ts, ts);
2448	if (ret < 0)
2449	goto out;
2450
2451	ret = reftable_stack_init_log_iterator(arg->stack, &it);
2452	if (ret < 0)
2453	goto out;
2454
2455	/*
2456	* In order to delete a table we need to delete all reflog entries one
2457	* by one. This is inefficient, but the reftable format does not have a
2458	* better marker right now.
2459	*/
2460	ret = reftable_iterator_seek_log(&it, arg->refname);
2461	while (ret == 0) {
2462	ret = reftable_iterator_next_log(&it, &log);
2463	if (ret < 0)
2464	break;
2465	if (ret > 0 \|\| strcmp(log.refname, arg->refname)) {
2466	ret = 0;
2467	break;
2468	}
2469	if (reftable_log_record_is_deletion(&log))
2470	continue;
2471
2472	tombstone.refname = (char *)arg->refname;
2473	tombstone.value_type = REFTABLE_LOG_DELETION;
2474	tombstone.update_index = log.update_index;
2475
2476	ret = reftable_writer_add_log(writer, &tombstone);
2477	}
2478
2479	out:
2480	reftable_log_record_release(&log);
2481	reftable_iterator_destroy(&it);
2482	return ret;
2483	}
2484
2485	static int reftable_be_delete_reflog(struct ref_store *ref_store,
2486	const char *refname)
2487	{
2488	struct reftable_ref_store *refs =
2489	reftable_be_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
2490	struct reftable_backend *be;
2491	struct write_reflog_delete_arg arg = {
2492	.refname = refname,
2493	};
2494	int ret;
2495
2496	ret = backend_for(&be, refs, refname, &refname, 1);
2497	if (ret)
2498	return ret;
2499	arg.stack = be->stack;
2500
2501	ret = reftable_stack_add(be->stack, &write_reflog_delete_table, &arg,
2502	&reftable_be_write_options(refs)->opts,
2503	REFTABLE_STACK_NEW_ADDITION_RELOAD);
2504
2505	assert(ret != REFTABLE_API_ERROR);
2506	return ret;
2507	}
2508
2509	struct reflog_expiry_arg {
2510	struct reftable_ref_store *refs;
2511	struct reftable_stack *stack;
2512	struct reftable_log_record *records;
2513	struct object_id update_oid;
2514	const char *refname;
2515	size_t len;
2516	};
2517
2518	static int write_reflog_expiry_table(struct reftable_writer writer, void cb_data)
2519	{
2520	struct reflog_expiry_arg *arg = cb_data;
2521	uint64_t ts = reftable_stack_next_update_index(arg->stack);
2522	uint64_t live_records = 0;
2523	size_t i;
2524	int ret;
2525
2526	for (i = 0; i < arg->len; i++)
2527	if (arg->records[i].value_type == REFTABLE_LOG_UPDATE)
2528	live_records++;
2529
2530	ret = reftable_writer_set_limits(writer, ts, ts);
2531	if (ret < 0)
2532	return ret;
2533
2534	if (!is_null_oid(&arg->update_oid)) {
2535	struct reftable_ref_record ref = {0};
2536	struct object_id peeled;
2537
2538	ref.refname = (char *)arg->refname;
2539	ref.update_index = ts;
2540
2541	if (!peel_object(arg->refs->base.repo, &arg->update_oid, &peeled, 0)) {
2542	ref.value_type = REFTABLE_REF_VAL2;
2543	memcpy(ref.value.val2.target_value, peeled.hash, GIT_MAX_RAWSZ);
2544	memcpy(ref.value.val2.value, arg->update_oid.hash, GIT_MAX_RAWSZ);
2545	} else {
2546	ref.value_type = REFTABLE_REF_VAL1;
2547	memcpy(ref.value.val1, arg->update_oid.hash, GIT_MAX_RAWSZ);
2548	}
2549
2550	ret = reftable_writer_add_ref(writer, &ref);
2551	if (ret < 0)
2552	return ret;
2553	}
2554
2555	/*
2556	* When there are no more entries left in the reflog we empty it
2557	* completely, but write a placeholder reflog entry that indicates that
2558	* the reflog still exists.
2559	*/
2560	if (!live_records) {
2561	struct reftable_log_record log = {
2562	.refname = (char *)arg->refname,
2563	.value_type = REFTABLE_LOG_UPDATE,
2564	.update_index = ts,
2565	};
2566
2567	ret = reftable_writer_add_log(writer, &log);
2568	if (ret)
2569	return ret;
2570	}
2571
2572	for (i = 0; i < arg->len; i++) {
2573	ret = reftable_writer_add_log(writer, &arg->records[i]);
2574	if (ret)
2575	return ret;
2576	}
2577
2578	return 0;
2579	}
2580
2581	static int reftable_be_reflog_expire(struct ref_store *ref_store,
2582	const char *refname,
2583	unsigned int flags,
2584	reflog_expiry_prepare_fn prepare_fn,
2585	reflog_expiry_should_prune_fn should_prune_fn,
2586	reflog_expiry_cleanup_fn cleanup_fn,
2587	void *policy_cb_data)
2588	{
2589	/*
2590	* For log expiry, we write tombstones for every single reflog entry
2591	* that is to be expired. This means that the entries are still
2592	* retrievable by delving into the stack, and expiring entries
2593	* paradoxically takes extra memory. This memory is only reclaimed when
2594	* compacting the reftable stack.
2595	*
2596	* It would be better if the refs backend supported an API that sets a
2597	* criterion for all refs, passing the criterion to pack_refs().
2598	*
2599	* On the plus side, because we do the expiration per ref, we can easily
2600	* insert the reflog existence dummies.
2601	*/
2602	struct reftable_ref_store *refs =
2603	reftable_be_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
2604	struct reftable_log_record *logs = NULL;
2605	struct reftable_log_record *rewritten = NULL;
2606	struct reftable_iterator it = {0};
2607	struct reftable_addition *add = NULL;
2608	struct reflog_expiry_arg arg = {0};
2609	struct reftable_backend *be;
2610	struct object_id oid = {0};
2611	struct strbuf referent = STRBUF_INIT;
2612	uint8_t *last_hash = NULL;
2613	size_t logs_nr = 0, logs_alloc = 0, i;
2614	unsigned int type = 0;
2615	int ret;
2616
2617	if (refs->err < 0)
2618	return refs->err;
2619
2620	ret = backend_for(&be, refs, refname, &refname, 1);
2621	if (ret < 0)
2622	goto done;
2623
2624	ret = reftable_stack_new_addition(&add, be->stack,
2625	&reftable_be_write_options(refs)->opts,
2626	REFTABLE_STACK_NEW_ADDITION_RELOAD);
2627	if (ret < 0)
2628	goto done;
2629
2630	ret = reftable_stack_init_log_iterator(be->stack, &it);
2631	if (ret < 0)
2632	goto done;
2633
2634	ret = reftable_iterator_seek_log(&it, refname);
2635	if (ret < 0)
2636	goto done;
2637
2638	ret = reftable_backend_read_ref(be, refname, &oid, &referent, &type);
2639	if (ret < 0)
2640	goto done;
2641	prepare_fn(refname, &oid, policy_cb_data);
2642
2643	while (1) {
2644	struct reftable_log_record log = {0};
2645	struct object_id old_oid, new_oid;
2646
2647	ret = reftable_iterator_next_log(&it, &log);
2648	if (ret < 0)
2649	goto done;
2650	if (ret > 0 \|\| strcmp(log.refname, refname)) {
2651	reftable_log_record_release(&log);
2652	break;
2653	}
2654	if (reftable_log_record_is_deletion(&log)) {
2655	reftable_log_record_release(&log);
2656	continue;
2657	}
2658
2659	oidread(&old_oid, log.value.update.old_hash,
2660	ref_store->repo->hash_algo);
2661	oidread(&new_oid, log.value.update.new_hash,
2662	ref_store->repo->hash_algo);
2663
2664	/*
2665	* Skip over the reflog existence marker. We will add it back
2666	* in when there are no live reflog records.
2667	*/
2668	if (is_null_oid(&old_oid) && is_null_oid(&new_oid)) {
2669	reftable_log_record_release(&log);
2670	continue;
2671	}
2672
2673	ALLOC_GROW(logs, logs_nr + 1, logs_alloc);
2674	logs[logs_nr++] = log;
2675	}
2676
2677	/*
2678	* We need to rewrite all reflog entries according to the pruning
2679	* callback function:
2680	*
2681	* - If a reflog entry shall be pruned we mark the record for
2682	* deletion.
2683	*
2684	* - Otherwise we may have to rewrite the chain of reflog entries so
2685	* that gaps created by just-deleted records get backfilled.
2686	*/
2687	CALLOC_ARRAY(rewritten, logs_nr);
2688	for (i = logs_nr; i--;) {
2689	struct reftable_log_record *dest = &rewritten[i];
2690	struct object_id old_oid, new_oid;
2691
2692	*dest = logs[i];
2693	oidread(&old_oid, logs[i].value.update.old_hash,
2694	ref_store->repo->hash_algo);
2695	oidread(&new_oid, logs[i].value.update.new_hash,
2696	ref_store->repo->hash_algo);
2697
2698	if (should_prune_fn(&old_oid, &new_oid, logs[i].value.update.email,
2699	(timestamp_t)logs[i].value.update.time,
2700	logs[i].value.update.tz_offset,
2701	logs[i].value.update.message,
2702	policy_cb_data)) {
2703	dest->value_type = REFTABLE_LOG_DELETION;
2704	} else {
2705	if ((flags & EXPIRE_REFLOGS_REWRITE) && last_hash)
2706	memcpy(dest->value.update.old_hash, last_hash, GIT_MAX_RAWSZ);
2707	last_hash = logs[i].value.update.new_hash;
2708	}
2709	}
2710
2711	if (flags & EXPIRE_REFLOGS_UPDATE_REF && last_hash && !is_null_oid(&oid))
2712	oidread(&arg.update_oid, last_hash, ref_store->repo->hash_algo);
2713
2714	arg.refs = refs;
2715	arg.records = rewritten;
2716	arg.len = logs_nr;
2717	arg.stack = be->stack;
2718	arg.refname = refname;
2719
2720	ret = reftable_addition_add(add, &write_reflog_expiry_table, &arg);
2721	if (ret < 0)
2722	goto done;
2723
2724	/*
2725	* Future improvement: we could skip writing records that were
2726	* not changed.
2727	*/
2728	if (!(flags & EXPIRE_REFLOGS_DRY_RUN))
2729	ret = reftable_addition_commit(add);
2730
2731	done:
2732	if (add)
2733	cleanup_fn(policy_cb_data);
2734	assert(ret != REFTABLE_API_ERROR);
2735
2736	reftable_iterator_destroy(&it);
2737	reftable_addition_destroy(add);
2738	for (i = 0; i < logs_nr; i++)
2739	reftable_log_record_release(&logs[i]);
2740	strbuf_release(&referent);
2741	free(logs);
2742	free(rewritten);
2743	return ret;
2744	}
2745
2746	static void reftable_fsck_verbose_handler(const char msg, void cb_data)
2747	{
2748	struct fsck_options *o = cb_data;
2749
2750	if (o->verbose)
2751	fprintf_ln(stderr, "%s", msg);
2752	}
2753
2754	static const enum fsck_msg_id fsck_msg_id_map[] = {
2755	[REFTABLE_FSCK_ERROR_TABLE_NAME] = FSCK_MSG_BAD_REFTABLE_TABLE_NAME,
2756	};
2757
2758	static int reftable_fsck_error_handler(struct reftable_fsck_info *info,
2759	void *cb_data)
2760	{
2761	struct fsck_ref_report report = { .path = info->path };
2762	struct fsck_options *o = cb_data;
2763	enum fsck_msg_id msg_id;
2764
2765	if (info->error < 0 \|\| info->error >= REFTABLE_FSCK_MAX_VALUE)
2766	BUG("unknown fsck error: %d", (int)info->error);
2767
2768	msg_id = fsck_msg_id_map[info->error];
2769
2770	if (!msg_id)
2771	BUG("fsck_msg_id value missing for reftable error: %d", (int)info->error);
2772
2773	return fsck_report_ref(o, &report, msg_id, "%s", info->msg);
2774	}
2775
2776	static int reftable_be_fsck(struct ref_store ref_store, struct fsck_options o,
2777	struct worktree *wt)
2778	{
2779	struct reftable_ref_store *refs =
2780	reftable_be_downcast(ref_store, REF_STORE_READ, "fsck");
2781	struct reftable_ref_iterator *iter = NULL;
2782	struct reftable_ref_record ref = { 0 };
2783	struct fsck_ref_report report = { 0 };
2784	struct strbuf refname = STRBUF_INIT;
2785	struct reftable_backend *backend;
2786	int ret, errors = 0;
2787
2788	if (is_main_worktree(wt)) {
2789	backend = &refs->main_backend;
2790	} else {
2791	ret = backend_for_worktree(&backend, refs, wt->id);
2792	if (ret < 0) {
2793	ret = error(_("reftable stack for worktree '%s' is broken"),
2794	wt->id);
2795	goto out;
2796	}
2797	}
2798
2799	errors \|= reftable_fsck_check(backend->stack, reftable_fsck_error_handler,
2800	reftable_fsck_verbose_handler, o);
2801
2802	iter = ref_iterator_for_stack(refs, backend->stack, "", NULL, 0);
2803	if (!iter) {
2804	ret = error(_("could not create iterator for worktree '%s'"), wt->id);
2805	goto out;
2806	}
2807
2808	while (1) {
2809	ret = reftable_iterator_next_ref(&iter->iter, &ref);
2810	if (ret > 0)
2811	break;
2812	if (ret < 0) {
2813	ret = error(_("could not read record for worktree '%s'"), wt->id);
2814	goto out;
2815	}
2816
2817	strbuf_reset(&refname);
2818	if (!is_main_worktree(wt))
2819	strbuf_addf(&refname, "worktrees/%s/", wt->id);
2820	strbuf_addstr(&refname, ref.refname);
2821	report.path = refname.buf;
2822
2823	switch (ref.value_type) {
2824	case REFTABLE_REF_DELETION:
2825	continue;
2826	case REFTABLE_REF_VAL1:
2827	case REFTABLE_REF_VAL2: {
2828	struct object_id oid;
2829	unsigned hash_id;
2830
2831	switch (reftable_stack_hash_id(backend->stack)) {
2832	case REFTABLE_HASH_SHA1:
2833	hash_id = GIT_HASH_SHA1;
2834	break;
2835	case REFTABLE_HASH_SHA256:
2836	hash_id = GIT_HASH_SHA256;
2837	break;
2838	default:
2839	BUG("unhandled hash ID %d",
2840	reftable_stack_hash_id(backend->stack));
2841	}
2842
2843	oidread(&oid, reftable_ref_record_val1(&ref),
2844	&hash_algos[hash_id]);
2845
2846	errors \|= refs_fsck_ref(ref_store, o, &report, ref.refname, &oid);
2847	break;
2848	}
2849	case REFTABLE_REF_SYMREF:
2850	errors \|= refs_fsck_symref(ref_store, o, &report, ref.refname,
2851	ref.value.symref);
2852	break;
2853	default:
2854	BUG("unhandled reference value type %d", ref.value_type);
2855	}
2856	}
2857
2858	ret = errors ? -1 : 0;
2859
2860	out:
2861	if (iter)
2862	ref_iterator_free(&iter->base);
2863	reftable_ref_record_release(&ref);
2864	strbuf_release(&refname);
2865	return ret;
2866	}
2867
2868	struct ref_storage_be refs_be_reftable = {
2869	.name = "reftable",
2870	.init = reftable_be_init,
2871	.release = reftable_be_release,
2872	.create_on_disk = reftable_be_create_on_disk,
2873	.remove_on_disk = reftable_be_remove_on_disk,
2874
2875	.transaction_prepare = reftable_be_transaction_prepare,
2876	.transaction_finish = reftable_be_transaction_finish,
2877	.transaction_abort = reftable_be_transaction_abort,
2878
2879	.optimize = reftable_be_optimize,
2880	.optimize_required = reftable_be_optimize_required,
2881
2882	.rename_ref = reftable_be_rename_ref,
2883	.copy_ref = reftable_be_copy_ref,
2884
2885	.iterator_begin = reftable_be_iterator_begin,
2886	.read_raw_ref = reftable_be_read_raw_ref,
2887	.read_symbolic_ref = reftable_be_read_symbolic_ref,
2888
2889	.reflog_iterator_begin = reftable_be_reflog_iterator_begin,
2890	.for_each_reflog_ent = reftable_be_for_each_reflog_ent,
2891	.for_each_reflog_ent_reverse = reftable_be_for_each_reflog_ent_reverse,
2892	.reflog_exists = reftable_be_reflog_exists,
2893	.create_reflog = reftable_be_create_reflog,
2894	.delete_reflog = reftable_be_delete_reflog,
2895	.reflog_expire = reftable_be_reflog_expire,
2896
2897	.fsck = reftable_be_fsck,
2898	};