diff options
Diffstat (limited to 'refs/reftable-backend.c')
| -rw-r--r-- | refs/reftable-backend.c | 2713 |
1 files changed, 2713 insertions, 0 deletions
diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c new file mode 100644 index 0000000000..8dae1e1112 --- /dev/null +++ b/refs/reftable-backend.c @@ -0,0 +1,2713 @@ +#define USE_THE_REPOSITORY_VARIABLE + +#include "../git-compat-util.h" +#include "../abspath.h" +#include "../chdir-notify.h" +#include "../config.h" +#include "../dir.h" +#include "../environment.h" +#include "../gettext.h" +#include "../hash.h" +#include "../hex.h" +#include "../iterator.h" +#include "../ident.h" +#include "../lockfile.h" +#include "../object.h" +#include "../path.h" +#include "../refs.h" +#include "../reftable/reftable-basics.h" +#include "../reftable/reftable-stack.h" +#include "../reftable/reftable-record.h" +#include "../reftable/reftable-error.h" +#include "../reftable/reftable-iterator.h" +#include "../repo-settings.h" +#include "../setup.h" +#include "../strmap.h" +#include "../trace2.h" +#include "../write-or-die.h" +#include "parse.h" +#include "refs-internal.h" + +/* + * Used as a flag in ref_update::flags when the ref_update was via an + * update to HEAD. + */ +#define REF_UPDATE_VIA_HEAD (1 << 8) + +struct reftable_backend { + struct reftable_stack *stack; + struct reftable_iterator it; +}; + +static void reftable_backend_on_reload(void *payload) +{ + struct reftable_backend *be = payload; + reftable_iterator_destroy(&be->it); +} + +static int reftable_backend_init(struct reftable_backend *be, + const char *path, + const struct reftable_write_options *_opts) +{ + struct reftable_write_options opts = *_opts; + opts.on_reload = reftable_backend_on_reload; + opts.on_reload_payload = be; + return reftable_new_stack(&be->stack, path, &opts); +} + +static void reftable_backend_release(struct reftable_backend *be) +{ + reftable_stack_destroy(be->stack); + be->stack = NULL; + reftable_iterator_destroy(&be->it); +} + +static int reftable_backend_read_ref(struct reftable_backend *be, + const char *refname, + struct object_id *oid, + struct strbuf *referent, + unsigned int *type) +{ + struct reftable_ref_record ref = {0}; + int ret; + + if (!be->it.ops) { + ret = reftable_stack_init_ref_iterator(be->stack, &be->it); + if (ret) + goto done; + } + + ret = reftable_iterator_seek_ref(&be->it, refname); + if (ret) + goto done; + + ret = reftable_iterator_next_ref(&be->it, &ref); + if (ret) + goto done; + + if (strcmp(ref.refname, refname)) { + ret = 1; + goto done; + } + + if (ref.value_type == REFTABLE_REF_SYMREF) { + strbuf_reset(referent); + strbuf_addstr(referent, ref.value.symref); + *type |= REF_ISSYMREF; + } else if (reftable_ref_record_val1(&ref)) { + unsigned int hash_id; + + switch (reftable_stack_hash_id(be->stack)) { + case REFTABLE_HASH_SHA1: + hash_id = GIT_HASH_SHA1; + break; + case REFTABLE_HASH_SHA256: + hash_id = GIT_HASH_SHA256; + break; + default: + BUG("unhandled hash ID %d", reftable_stack_hash_id(be->stack)); + } + + oidread(oid, reftable_ref_record_val1(&ref), + &hash_algos[hash_id]); + } else { + /* We got a tombstone, which should not happen. */ + BUG("unhandled reference value type %d", ref.value_type); + } + +done: + assert(ret != REFTABLE_API_ERROR); + reftable_ref_record_release(&ref); + return ret; +} + +struct reftable_ref_store { + struct ref_store base; + + /* + * The main backend refers to the common dir and thus contains common + * refs as well as refs of the main repository. + */ + struct reftable_backend main_backend; + /* + * The worktree backend refers to the gitdir in case the refdb is opened + * via a worktree. It thus contains the per-worktree refs. + */ + struct reftable_backend worktree_backend; + /* + * Map of worktree backends by their respective worktree names. The map + * is populated lazily when we try to resolve `worktrees/$worktree` refs. + */ + struct strmap worktree_backends; + struct reftable_write_options write_options; + + unsigned int store_flags; + enum log_refs_config log_all_ref_updates; + int err; +}; + +/* + * Downcast ref_store to reftable_ref_store. Die if ref_store is not a + * reftable_ref_store. required_flags is compared with ref_store's store_flags + * to ensure the ref_store has all required capabilities. "caller" is used in + * any necessary error messages. + */ +static struct reftable_ref_store *reftable_be_downcast(struct ref_store *ref_store, + unsigned int required_flags, + const char *caller) +{ + struct reftable_ref_store *refs; + + if (ref_store->be != &refs_be_reftable) + BUG("ref_store is type \"%s\" not \"reftables\" in %s", + ref_store->be->name, caller); + + refs = (struct reftable_ref_store *)ref_store; + + if ((refs->store_flags & required_flags) != required_flags) + BUG("operation %s requires abilities 0x%x, but only have 0x%x", + caller, required_flags, refs->store_flags); + + return refs; +} + +/* + * Some refs are global to the repository (refs/heads/{*}), while others are + * local to the worktree (eg. HEAD, refs/bisect/{*}). We solve this by having + * multiple separate databases (ie. multiple reftable/ directories), one for + * the shared refs, one for the current worktree refs, and one for each + * additional worktree. For reading, we merge the view of both the shared and + * the current worktree's refs, when necessary. + * + * This function also optionally assigns the rewritten reference name that is + * local to the stack. This translation is required when using worktree refs + * like `worktrees/$worktree/refs/heads/foo` as worktree stacks will store + * those references in their normalized form. + */ +static int backend_for(struct reftable_backend **out, + struct reftable_ref_store *store, + const char *refname, + const char **rewritten_ref, + int reload) +{ + struct reftable_backend *be; + const char *wtname; + int wtname_len; + + if (!refname) { + be = &store->main_backend; + goto out; + } + + switch (parse_worktree_ref(refname, &wtname, &wtname_len, rewritten_ref)) { + case REF_WORKTREE_OTHER: { + static struct strbuf wtname_buf = STRBUF_INIT; + struct strbuf wt_dir = STRBUF_INIT; + + /* + * We're using a static buffer here so that we don't need to + * allocate the worktree name whenever we look up a reference. + * This could be avoided if the strmap interface knew how to + * handle keys with a length. + */ + strbuf_reset(&wtname_buf); + strbuf_add(&wtname_buf, wtname, wtname_len); + + /* + * There is an edge case here: when the worktree references the + * current worktree, then we set up the stack once via + * `worktree_backends` and once via `worktree_backend`. This is + * wasteful, but in the reading case it shouldn't matter. And + * in the writing case we would notice that the stack is locked + * already and error out when trying to write a reference via + * both stacks. + */ + be = strmap_get(&store->worktree_backends, wtname_buf.buf); + if (!be) { + strbuf_addf(&wt_dir, "%s/worktrees/%s/reftable", + store->base.repo->commondir, wtname_buf.buf); + + CALLOC_ARRAY(be, 1); + store->err = reftable_backend_init(be, wt_dir.buf, + &store->write_options); + assert(store->err != REFTABLE_API_ERROR); + + strmap_put(&store->worktree_backends, wtname_buf.buf, be); + } + + strbuf_release(&wt_dir); + goto out; + } + case REF_WORKTREE_CURRENT: + /* + * If there is no worktree stack then we're currently in the + * main worktree. We thus return the main stack in that case. + */ + if (!store->worktree_backend.stack) + be = &store->main_backend; + else + be = &store->worktree_backend; + goto out; + case REF_WORKTREE_MAIN: + case REF_WORKTREE_SHARED: + be = &store->main_backend; + goto out; + default: + BUG("unhandled worktree reference type"); + } + +out: + if (reload) { + int ret = reftable_stack_reload(be->stack); + if (ret) + return ret; + } + *out = be; + + return 0; +} + +static int should_write_log(struct reftable_ref_store *refs, const char *refname) +{ + enum log_refs_config log_refs_cfg = refs->log_all_ref_updates; + if (log_refs_cfg == LOG_REFS_UNSET) + log_refs_cfg = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL; + + switch (log_refs_cfg) { + case LOG_REFS_NONE: + return refs_reflog_exists(&refs->base, refname); + case LOG_REFS_ALWAYS: + return 1; + case LOG_REFS_NORMAL: + if (should_autocreate_reflog(log_refs_cfg, refname)) + return 1; + return refs_reflog_exists(&refs->base, refname); + default: + BUG("unhandled core.logAllRefUpdates value %d", log_refs_cfg); + } +} + +static void fill_reftable_log_record(struct reftable_log_record *log, const struct ident_split *split) +{ + const char *tz_begin; + int sign = 1; + + reftable_log_record_release(log); + log->value_type = REFTABLE_LOG_UPDATE; + log->value.update.name = + xstrndup(split->name_begin, split->name_end - split->name_begin); + log->value.update.email = + xstrndup(split->mail_begin, split->mail_end - split->mail_begin); + log->value.update.time = atol(split->date_begin); + + tz_begin = split->tz_begin; + if (*tz_begin == '-') { + sign = -1; + tz_begin++; + } + if (*tz_begin == '+') { + sign = 1; + tz_begin++; + } + + log->value.update.tz_offset = sign * atoi(tz_begin); +} + +static int reftable_be_config(const char *var, const char *value, + const struct config_context *ctx, + void *_opts) +{ + struct reftable_write_options *opts = _opts; + + if (!strcmp(var, "reftable.blocksize")) { + unsigned long block_size = git_config_ulong(var, value, ctx->kvi); + if (block_size > 16777215) + die("reftable block size cannot exceed 16MB"); + opts->block_size = block_size; + } else if (!strcmp(var, "reftable.restartinterval")) { + unsigned long restart_interval = git_config_ulong(var, value, ctx->kvi); + if (restart_interval > UINT16_MAX) + die("reftable block size cannot exceed %u", (unsigned)UINT16_MAX); + opts->restart_interval = restart_interval; + } else if (!strcmp(var, "reftable.indexobjects")) { + opts->skip_index_objects = !git_config_bool(var, value); + } else if (!strcmp(var, "reftable.geometricfactor")) { + unsigned long factor = git_config_ulong(var, value, ctx->kvi); + if (factor > UINT8_MAX) + die("reftable geometric factor cannot exceed %u", (unsigned)UINT8_MAX); + opts->auto_compaction_factor = factor; + } else if (!strcmp(var, "reftable.locktimeout")) { + int64_t lock_timeout = git_config_int64(var, value, ctx->kvi); + if (lock_timeout > LONG_MAX) + die("reftable lock timeout cannot exceed %"PRIdMAX, (intmax_t)LONG_MAX); + if (lock_timeout < 0 && lock_timeout != -1) + die("reftable lock timeout does not support negative values other than -1"); + opts->lock_timeout_ms = lock_timeout; + } + + return 0; +} + +static int reftable_be_fsync(int fd) +{ + return fsync_component(FSYNC_COMPONENT_REFERENCE, fd); +} + +static struct ref_store *reftable_be_init(struct repository *repo, + const char *gitdir, + unsigned int store_flags) +{ + struct reftable_ref_store *refs = xcalloc(1, sizeof(*refs)); + struct strbuf path = STRBUF_INIT; + int is_worktree; + mode_t mask; + + mask = umask(0); + umask(mask); + + base_ref_store_init(&refs->base, repo, gitdir, &refs_be_reftable); + strmap_init(&refs->worktree_backends); + refs->store_flags = store_flags; + refs->log_all_ref_updates = repo_settings_get_log_all_ref_updates(repo); + + switch (repo->hash_algo->format_id) { + case GIT_SHA1_FORMAT_ID: + refs->write_options.hash_id = REFTABLE_HASH_SHA1; + break; + case GIT_SHA256_FORMAT_ID: + refs->write_options.hash_id = REFTABLE_HASH_SHA256; + break; + default: + BUG("unknown hash algorithm %d", repo->hash_algo->format_id); + } + refs->write_options.default_permissions = calc_shared_perm(the_repository, 0666 & ~mask); + refs->write_options.disable_auto_compact = + !git_env_bool("GIT_TEST_REFTABLE_AUTOCOMPACTION", 1); + refs->write_options.lock_timeout_ms = 100; + refs->write_options.fsync = reftable_be_fsync; + + repo_config(the_repository, reftable_be_config, &refs->write_options); + + /* + * It is somewhat unfortunate that we have to mirror the default block + * size of the reftable library here. But given that the write options + * wouldn't be updated by the library here, and given that we require + * the proper block size to trim reflog message so that they fit, we + * must set up a proper value here. + */ + if (!refs->write_options.block_size) + refs->write_options.block_size = 4096; + + /* + * Set up the main reftable stack that is hosted in GIT_COMMON_DIR. + * This stack contains both the shared and the main worktree refs. + * + * Note that we don't try to resolve the path in case we have a + * worktree because `get_common_dir_noenv()` already does it for us. + */ + is_worktree = get_common_dir_noenv(&path, gitdir); + if (!is_worktree) { + strbuf_reset(&path); + strbuf_realpath(&path, gitdir, 0); + } + strbuf_addstr(&path, "/reftable"); + refs->err = reftable_backend_init(&refs->main_backend, path.buf, + &refs->write_options); + if (refs->err) + goto done; + + /* + * If we're in a worktree we also need to set up the worktree reftable + * stack that is contained in the per-worktree GIT_DIR. + * + * Ideally, we would also add the stack to our worktree stack map. But + * we have no way to figure out the worktree name here and thus can't + * do it efficiently. + */ + if (is_worktree) { + strbuf_reset(&path); + strbuf_addf(&path, "%s/reftable", gitdir); + + refs->err = reftable_backend_init(&refs->worktree_backend, path.buf, + &refs->write_options); + if (refs->err) + goto done; + } + + chdir_notify_reparent("reftables-backend $GIT_DIR", &refs->base.gitdir); + +done: + assert(refs->err != REFTABLE_API_ERROR); + strbuf_release(&path); + return &refs->base; +} + +static void reftable_be_release(struct ref_store *ref_store) +{ + struct reftable_ref_store *refs = reftable_be_downcast(ref_store, 0, "release"); + struct strmap_entry *entry; + struct hashmap_iter iter; + + if (refs->main_backend.stack) + reftable_backend_release(&refs->main_backend); + if (refs->worktree_backend.stack) + reftable_backend_release(&refs->worktree_backend); + + strmap_for_each_entry(&refs->worktree_backends, &iter, entry) { + struct reftable_backend *be = entry->value; + reftable_backend_release(be); + free(be); + } + strmap_clear(&refs->worktree_backends, 0); +} + +static int reftable_be_create_on_disk(struct ref_store *ref_store, + int flags UNUSED, + struct strbuf *err UNUSED) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "create"); + struct strbuf sb = STRBUF_INIT; + + strbuf_addf(&sb, "%s/reftable", refs->base.gitdir); + safe_create_dir(the_repository, sb.buf, 1); + strbuf_reset(&sb); + + strbuf_addf(&sb, "%s/HEAD", refs->base.gitdir); + write_file(sb.buf, "ref: refs/heads/.invalid"); + adjust_shared_perm(the_repository, sb.buf); + strbuf_reset(&sb); + + strbuf_addf(&sb, "%s/refs", refs->base.gitdir); + safe_create_dir(the_repository, sb.buf, 1); + strbuf_reset(&sb); + + strbuf_addf(&sb, "%s/refs/heads", refs->base.gitdir); + write_file(sb.buf, "this repository uses the reftable format"); + adjust_shared_perm(the_repository, sb.buf); + + strbuf_release(&sb); + return 0; +} + +static int reftable_be_remove_on_disk(struct ref_store *ref_store, + struct strbuf *err) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "remove"); + struct strbuf sb = STRBUF_INIT; + int ret = 0; + + /* + * Release the ref store such that all stacks are closed. This is + * required so that the "tables.list" file is not open anymore, which + * would otherwise make it impossible to remove the file on Windows. + */ + reftable_be_release(ref_store); + + strbuf_addf(&sb, "%s/reftable", refs->base.gitdir); + if (remove_dir_recursively(&sb, 0) < 0) { + strbuf_addf(err, "could not delete reftables: %s", + strerror(errno)); + ret = -1; + } + strbuf_reset(&sb); + + strbuf_addf(&sb, "%s/HEAD", refs->base.gitdir); + if (unlink(sb.buf) < 0) { + strbuf_addf(err, "could not delete stub HEAD: %s", + strerror(errno)); + ret = -1; + } + strbuf_reset(&sb); + + strbuf_addf(&sb, "%s/refs/heads", refs->base.gitdir); + if (unlink(sb.buf) < 0) { + strbuf_addf(err, "could not delete stub heads: %s", + strerror(errno)); + ret = -1; + } + strbuf_reset(&sb); + + strbuf_addf(&sb, "%s/refs", refs->base.gitdir); + if (rmdir(sb.buf) < 0) { + strbuf_addf(err, "could not delete refs directory: %s", + strerror(errno)); + ret = -1; + } + + strbuf_release(&sb); + return ret; +} + +struct reftable_ref_iterator { + struct ref_iterator base; + struct reftable_ref_store *refs; + struct reftable_iterator iter; + struct reftable_ref_record ref; + struct object_id oid; + + char *prefix; + size_t prefix_len; + char **exclude_patterns; + size_t exclude_patterns_index; + size_t exclude_patterns_strlen; + unsigned int flags; + int err; +}; + +/* + * Handle exclude patterns. Returns either `1`, which tells the caller that the + * current reference shall not be shown. Or `0`, which indicates that it should + * be shown. + */ +static int should_exclude_current_ref(struct reftable_ref_iterator *iter) +{ + while (iter->exclude_patterns[iter->exclude_patterns_index]) { + const char *pattern = iter->exclude_patterns[iter->exclude_patterns_index]; + char *ref_after_pattern; + int cmp; + + /* + * Lazily cache the pattern length so that we don't have to + * recompute it every time this function is called. + */ + if (!iter->exclude_patterns_strlen) + iter->exclude_patterns_strlen = strlen(pattern); + + /* + * When the reference name is lexicographically bigger than the + * current exclude pattern we know that it won't ever match any + * of the following references, either. We thus advance to the + * next pattern and re-check whether it matches. + * + * Otherwise, if it's smaller, then we do not have a match and + * thus want to show the current reference. + */ + cmp = strncmp(iter->ref.refname, pattern, + iter->exclude_patterns_strlen); + if (cmp > 0) { + iter->exclude_patterns_index++; + iter->exclude_patterns_strlen = 0; + continue; + } + if (cmp < 0) + return 0; + + /* + * The reference shares a prefix with the exclude pattern and + * shall thus be omitted. We skip all references that match the + * pattern by seeking to the first reference after the block of + * matches. + * + * This is done by appending the highest possible character to + * the pattern. Consequently, all references that have the + * pattern as prefix and whose suffix starts with anything in + * the range [0x00, 0xfe] are skipped. And given that 0xff is a + * non-printable character that shouldn't ever be in a ref name, + * we'd not yield any such record, either. + * + * Note that the seeked-to reference may also be excluded. This + * is not handled here though, but the caller is expected to + * loop and re-verify the next reference for us. + */ + ref_after_pattern = xstrfmt("%s%c", pattern, 0xff); + iter->err = reftable_iterator_seek_ref(&iter->iter, ref_after_pattern); + iter->exclude_patterns_index++; + iter->exclude_patterns_strlen = 0; + trace2_counter_add(TRACE2_COUNTER_ID_REFTABLE_RESEEKS, 1); + + free(ref_after_pattern); + return 1; + } + + return 0; +} + +static int reftable_ref_iterator_advance(struct ref_iterator *ref_iterator) +{ + struct reftable_ref_iterator *iter = + (struct reftable_ref_iterator *)ref_iterator; + struct reftable_ref_store *refs = iter->refs; + const char *referent = NULL; + + while (!iter->err) { + int flags = 0; + + iter->err = reftable_iterator_next_ref(&iter->iter, &iter->ref); + if (iter->err) + break; + + /* + * The files backend only lists references contained in "refs/" unless + * the root refs are to be included. We emulate the same behaviour here. + */ + if (!starts_with(iter->ref.refname, "refs/") && + !(iter->flags & DO_FOR_EACH_INCLUDE_ROOT_REFS && + is_root_ref(iter->ref.refname))) { + continue; + } + + if (iter->prefix_len && + strncmp(iter->prefix, iter->ref.refname, iter->prefix_len)) { + iter->err = 1; + break; + } + + if (iter->exclude_patterns && should_exclude_current_ref(iter)) + continue; + + if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY && + parse_worktree_ref(iter->ref.refname, NULL, NULL, NULL) != + REF_WORKTREE_CURRENT) + continue; + + switch (iter->ref.value_type) { + case REFTABLE_REF_VAL1: + oidread(&iter->oid, iter->ref.value.val1, + refs->base.repo->hash_algo); + break; + case REFTABLE_REF_VAL2: + oidread(&iter->oid, iter->ref.value.val2.value, + refs->base.repo->hash_algo); + break; + case REFTABLE_REF_SYMREF: + referent = refs_resolve_ref_unsafe(&iter->refs->base, + iter->ref.refname, + RESOLVE_REF_READING, + &iter->oid, &flags); + if (!referent) + oidclr(&iter->oid, refs->base.repo->hash_algo); + break; + default: + BUG("unhandled reference value type %d", iter->ref.value_type); + } + + if (is_null_oid(&iter->oid)) + flags |= REF_ISBROKEN; + + if (check_refname_format(iter->ref.refname, REFNAME_ALLOW_ONELEVEL)) { + if (!refname_is_safe(iter->ref.refname)) + die(_("refname is dangerous: %s"), iter->ref.refname); + oidclr(&iter->oid, refs->base.repo->hash_algo); + flags |= REF_BAD_NAME | REF_ISBROKEN; + } + + if (iter->flags & DO_FOR_EACH_OMIT_DANGLING_SYMREFS && + flags & REF_ISSYMREF && + flags & REF_ISBROKEN) + continue; + + if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) && + !ref_resolves_to_object(iter->ref.refname, refs->base.repo, + &iter->oid, flags)) + continue; + + iter->base.refname = iter->ref.refname; + iter->base.referent = referent; + iter->base.oid = &iter->oid; + iter->base.flags = flags; + + break; + } + + if (iter->err > 0) + return ITER_DONE; + if (iter->err < 0) + return ITER_ERROR; + return ITER_OK; +} + +static int reftable_ref_iterator_seek(struct ref_iterator *ref_iterator, + const char *refname, unsigned int flags) +{ + struct reftable_ref_iterator *iter = + (struct reftable_ref_iterator *)ref_iterator; + + /* Unset any previously set prefix */ + FREE_AND_NULL(iter->prefix); + iter->prefix_len = 0; + + if (flags & REF_ITERATOR_SEEK_SET_PREFIX) { + iter->prefix = xstrdup_or_null(refname); + iter->prefix_len = refname ? strlen(refname) : 0; + } + iter->err = reftable_iterator_seek_ref(&iter->iter, refname); + + return iter->err; +} + +static int reftable_ref_iterator_peel(struct ref_iterator *ref_iterator, + struct object_id *peeled) +{ + struct reftable_ref_iterator *iter = + (struct reftable_ref_iterator *)ref_iterator; + + if (iter->ref.value_type == REFTABLE_REF_VAL2) { + oidread(peeled, iter->ref.value.val2.target_value, + iter->refs->base.repo->hash_algo); + return 0; + } + + return -1; +} + +static void reftable_ref_iterator_release(struct ref_iterator *ref_iterator) +{ + struct reftable_ref_iterator *iter = + (struct reftable_ref_iterator *)ref_iterator; + reftable_ref_record_release(&iter->ref); + reftable_iterator_destroy(&iter->iter); + if (iter->exclude_patterns) { + for (size_t i = 0; iter->exclude_patterns[i]; i++) + free(iter->exclude_patterns[i]); + free(iter->exclude_patterns); + } + free(iter->prefix); +} + +static struct ref_iterator_vtable reftable_ref_iterator_vtable = { + .advance = reftable_ref_iterator_advance, + .seek = reftable_ref_iterator_seek, + .peel = reftable_ref_iterator_peel, + .release = reftable_ref_iterator_release, +}; + +static int qsort_strcmp(const void *va, const void *vb) +{ + const char *a = *(const char **)va; + const char *b = *(const char **)vb; + return strcmp(a, b); +} + +static char **filter_exclude_patterns(const char **exclude_patterns) +{ + size_t filtered_size = 0, filtered_alloc = 0; + char **filtered = NULL; + + if (!exclude_patterns) + return NULL; + + for (size_t i = 0; ; i++) { + const char *exclude_pattern = exclude_patterns[i]; + int has_glob = 0; + + if (!exclude_pattern) + break; + + for (const char *p = exclude_pattern; *p; p++) { + has_glob = is_glob_special(*p); + if (has_glob) + break; + } + if (has_glob) + continue; + + ALLOC_GROW(filtered, filtered_size + 1, filtered_alloc); + filtered[filtered_size++] = xstrdup(exclude_pattern); + } + + if (filtered_size) { + QSORT(filtered, filtered_size, qsort_strcmp); + ALLOC_GROW(filtered, filtered_size + 1, filtered_alloc); + filtered[filtered_size++] = NULL; + } + + return filtered; +} + +static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_store *refs, + struct reftable_stack *stack, + const char *prefix, + const char **exclude_patterns, + int flags) +{ + struct reftable_ref_iterator *iter; + int ret; + + iter = xcalloc(1, sizeof(*iter)); + base_ref_iterator_init(&iter->base, &reftable_ref_iterator_vtable); + iter->base.oid = &iter->oid; + iter->flags = flags; + iter->refs = refs; + iter->exclude_patterns = filter_exclude_patterns(exclude_patterns); + + ret = refs->err; + if (ret) + goto done; + + ret = reftable_stack_reload(stack); + if (ret) + goto done; + + ret = reftable_stack_init_ref_iterator(stack, &iter->iter); + if (ret) + goto done; + + ret = reftable_ref_iterator_seek(&iter->base, prefix, + REF_ITERATOR_SEEK_SET_PREFIX); + if (ret) + goto done; + +done: + iter->err = ret; + return iter; +} + +static struct ref_iterator *reftable_be_iterator_begin(struct ref_store *ref_store, + const char *prefix, + const char **exclude_patterns, + unsigned int flags) +{ + struct reftable_ref_iterator *main_iter, *worktree_iter; + struct reftable_ref_store *refs; + unsigned int required_flags = REF_STORE_READ; + + if (!(flags & DO_FOR_EACH_INCLUDE_BROKEN)) + required_flags |= REF_STORE_ODB; + refs = reftable_be_downcast(ref_store, required_flags, "ref_iterator_begin"); + + main_iter = ref_iterator_for_stack(refs, refs->main_backend.stack, prefix, + exclude_patterns, flags); + + /* + * The worktree stack is only set when we're in an actual worktree + * right now. If we aren't, then we return the common reftable + * iterator, only. + */ + if (!refs->worktree_backend.stack) + return &main_iter->base; + + /* + * Otherwise we merge both the common and the per-worktree refs into a + * single iterator. + */ + worktree_iter = ref_iterator_for_stack(refs, refs->worktree_backend.stack, prefix, + exclude_patterns, flags); + return merge_ref_iterator_begin(&worktree_iter->base, &main_iter->base, + ref_iterator_select, NULL); +} + +static int reftable_be_read_raw_ref(struct ref_store *ref_store, + const char *refname, + struct object_id *oid, + struct strbuf *referent, + unsigned int *type, + int *failure_errno) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_READ, "read_raw_ref"); + struct reftable_backend *be; + int ret; + + if (refs->err < 0) + return refs->err; + + ret = backend_for(&be, refs, refname, &refname, 1); + if (ret) + return ret; + + ret = reftable_backend_read_ref(be, refname, oid, referent, type); + if (ret < 0) + return ret; + if (ret > 0) { + *failure_errno = ENOENT; + return -1; + } + + return 0; +} + +static int reftable_be_read_symbolic_ref(struct ref_store *ref_store, + const char *refname, + struct strbuf *referent) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_READ, "read_symbolic_ref"); + struct reftable_backend *be; + struct object_id oid; + unsigned int type = 0; + int ret; + + ret = backend_for(&be, refs, refname, &refname, 1); + if (ret) + return ret; + + ret = reftable_backend_read_ref(be, refname, &oid, referent, &type); + if (ret) + ret = -1; + else if (type == REF_ISSYMREF) + ; /* happy */ + else + ret = NOT_A_SYMREF; + return ret; +} + +struct reftable_transaction_update { + struct ref_update *update; + struct object_id current_oid; +}; + +struct write_transaction_table_arg { + struct reftable_ref_store *refs; + struct reftable_backend *be; + struct reftable_addition *addition; + struct reftable_transaction_update *updates; + size_t updates_nr; + size_t updates_alloc; + size_t updates_expected; + uint64_t max_index; +}; + +struct reftable_transaction_data { + struct write_transaction_table_arg *args; + size_t args_nr, args_alloc; +}; + +static void free_transaction_data(struct reftable_transaction_data *tx_data) +{ + if (!tx_data) + return; + for (size_t i = 0; i < tx_data->args_nr; i++) { + reftable_addition_destroy(tx_data->args[i].addition); + free(tx_data->args[i].updates); + } + free(tx_data->args); + free(tx_data); +} + +/* + * Prepare transaction update for the given reference update. This will cause + * us to lock the corresponding reftable stack for concurrent modification. + */ +static int prepare_transaction_update(struct write_transaction_table_arg **out, + struct reftable_ref_store *refs, + struct reftable_transaction_data *tx_data, + struct ref_update *update, + struct strbuf *err) +{ + struct write_transaction_table_arg *arg = NULL; + struct reftable_backend *be; + size_t i; + int ret; + + /* + * This function gets called in a loop, and we don't want to repeatedly + * reload the stack for every single ref update. Instead, we manually + * reload further down in the case where we haven't yet prepared the + * specific `reftable_backend`. + */ + ret = backend_for(&be, refs, update->refname, NULL, 0); + if (ret) + return ret; + + /* + * Search for a preexisting stack update. If there is one then we add + * the update to it, otherwise we set up a new stack update. + */ + for (i = 0; !arg && i < tx_data->args_nr; i++) + if (tx_data->args[i].be == be) + arg = &tx_data->args[i]; + + if (!arg) { + struct reftable_addition *addition; + + ret = reftable_stack_reload(be->stack); + if (ret) + return ret; + + ret = reftable_stack_new_addition(&addition, be->stack, + REFTABLE_STACK_NEW_ADDITION_RELOAD); + if (ret) { + if (ret == REFTABLE_LOCK_ERROR) + strbuf_addstr(err, "cannot lock references"); + return ret; + } + + ALLOC_GROW(tx_data->args, tx_data->args_nr + 1, + tx_data->args_alloc); + arg = &tx_data->args[tx_data->args_nr++]; + arg->refs = refs; + arg->be = be; + arg->addition = addition; + arg->updates = NULL; + arg->updates_nr = 0; + arg->updates_alloc = 0; + arg->updates_expected = 0; + arg->max_index = 0; + } + + arg->updates_expected++; + + if (out) + *out = arg; + + return 0; +} + +/* + * Queue a reference update for the correct stack. We potentially need to + * handle multiple stack updates in a single transaction when it spans across + * multiple worktrees. + */ +static int queue_transaction_update(struct reftable_ref_store *refs, + struct reftable_transaction_data *tx_data, + struct ref_update *update, + struct object_id *current_oid, + struct strbuf *err) +{ + struct write_transaction_table_arg *arg = NULL; + int ret; + + if (update->backend_data) + BUG("reference update queued more than once"); + + ret = prepare_transaction_update(&arg, refs, tx_data, update, err); + if (ret < 0) + return ret; + + ALLOC_GROW(arg->updates, arg->updates_nr + 1, + arg->updates_alloc); + arg->updates[arg->updates_nr].update = update; + oidcpy(&arg->updates[arg->updates_nr].current_oid, current_oid); + update->backend_data = &arg->updates[arg->updates_nr++]; + + return 0; +} + +static enum ref_transaction_error prepare_single_update(struct reftable_ref_store *refs, + struct reftable_transaction_data *tx_data, + struct ref_transaction *transaction, + struct reftable_backend *be, + struct ref_update *u, + size_t update_idx, + struct string_list *refnames_to_check, + unsigned int head_type, + struct strbuf *head_referent, + struct strbuf *referent, + struct strbuf *err) +{ + enum ref_transaction_error ret = 0; + struct object_id current_oid = {0}; + const char *rewritten_ref; + + /* + * There is no need to reload the respective backends here as + * we have already reloaded them when preparing the transaction + * update. And given that the stacks have been locked there + * shouldn't have been any concurrent modifications of the + * stack. + */ + ret = backend_for(&be, refs, u->refname, &rewritten_ref, 0); + if (ret) + return REF_TRANSACTION_ERROR_GENERIC; + + /* Verify that the new object ID is valid. */ + if ((u->flags & REF_HAVE_NEW) && !is_null_oid(&u->new_oid) && + !(u->flags & REF_SKIP_OID_VERIFICATION) && + !(u->flags & REF_LOG_ONLY)) { + struct object *o = parse_object(refs->base.repo, &u->new_oid); + if (!o) { + strbuf_addf(err, + _("trying to write ref '%s' with nonexistent object %s"), + u->refname, oid_to_hex(&u->new_oid)); + return REF_TRANSACTION_ERROR_INVALID_NEW_VALUE; + } + + if (o->type != OBJ_COMMIT && is_branch(u->refname)) { + strbuf_addf(err, _("trying to write non-commit object %s to branch '%s'"), + oid_to_hex(&u->new_oid), u->refname); + return REF_TRANSACTION_ERROR_INVALID_NEW_VALUE; + } + } + + /* + * When we update the reference that HEAD points to we enqueue + * a second log-only update for HEAD so that its reflog is + * updated accordingly. + */ + if (head_type == REF_ISSYMREF && + !(u->flags & REF_LOG_ONLY) && + !(u->flags & REF_UPDATE_VIA_HEAD) && + !strcmp(rewritten_ref, head_referent->buf)) { + /* + * First make sure that HEAD is not already in the + * transaction. This check is O(lg N) in the transaction + * size, but it happens at most once per transaction. + */ + if (string_list_has_string(&transaction->refnames, "HEAD")) { + /* An entry already existed */ + strbuf_addf(err, + _("multiple updates for 'HEAD' (including one " + "via its referent '%s') are not allowed"), + u->refname); + return REF_TRANSACTION_ERROR_NAME_CONFLICT; + } + + ref_transaction_add_update( + transaction, "HEAD", + u->flags | REF_LOG_ONLY | REF_NO_DEREF, + &u->new_oid, &u->old_oid, NULL, NULL, NULL, + u->msg); + } + + ret = reftable_backend_read_ref(be, rewritten_ref, + ¤t_oid, referent, &u->type); + if (ret < 0) + return REF_TRANSACTION_ERROR_GENERIC; + if (ret > 0 && !ref_update_expects_existing_old_ref(u)) { + struct string_list_item *item; + /* + * The reference does not exist, and we either have no + * old object ID or expect the reference to not exist. + * We can thus skip below safety checks as well as the + * symref splitting. But we do want to verify that + * there is no conflicting reference here so that we + * can output a proper error message instead of failing + * at a later point. + */ + item = string_list_append(refnames_to_check, u->refname); + item->util = xmalloc(sizeof(update_idx)); + memcpy(item->util, &update_idx, sizeof(update_idx)); + + /* + * There is no need to write the reference deletion + * when the reference in question doesn't exist. + */ + if ((u->flags & REF_HAVE_NEW) && !ref_update_has_null_new_value(u)) { + ret = queue_transaction_update(refs, tx_data, u, + ¤t_oid, err); + if (ret) + return REF_TRANSACTION_ERROR_GENERIC; + } + + return 0; + } + if (ret > 0) { + /* The reference does not exist, but we expected it to. */ + strbuf_addf(err, _("cannot lock ref '%s': " + + + "unable to resolve reference '%s'"), + ref_update_original_update_refname(u), u->refname); + return REF_TRANSACTION_ERROR_NONEXISTENT_REF; + } + + if (u->type & REF_ISSYMREF) { + /* + * The reftable stack is locked at this point already, + * so it is safe to call `refs_resolve_ref_unsafe()` + * here without causing races. + */ + const char *resolved = refs_resolve_ref_unsafe(&refs->base, u->refname, 0, + ¤t_oid, NULL); + + if (u->flags & REF_NO_DEREF) { + if (u->flags & REF_HAVE_OLD && !resolved) { + strbuf_addf(err, _("cannot lock ref '%s': " + "error reading reference"), u->refname); + return REF_TRANSACTION_ERROR_GENERIC; + } + } else { + struct ref_update *new_update; + int new_flags; + + new_flags = u->flags; + if (!strcmp(rewritten_ref, "HEAD")) + new_flags |= REF_UPDATE_VIA_HEAD; + + if (string_list_has_string(&transaction->refnames, referent->buf)) { + strbuf_addf(err, + _("multiple updates for '%s' (including one " + "via symref '%s') are not allowed"), + referent->buf, u->refname); + return REF_TRANSACTION_ERROR_NAME_CONFLICT; + } + + /* + * If we are updating a symref (eg. HEAD), we should also + * update the branch that the symref points to. + * + * This is generic functionality, and would be better + * done in refs.c, but the current implementation is + * intertwined with the locking in files-backend.c. + */ + new_update = ref_transaction_add_update( + transaction, referent->buf, new_flags, + u->new_target ? NULL : &u->new_oid, + u->old_target ? NULL : &u->old_oid, + u->new_target, u->old_target, + u->committer_info, u->msg); + + new_update->parent_update = u; + + /* + * Change the symbolic ref update to log only. Also, it + * doesn't need to check its old OID value, as that will be + * done when new_update is processed. + */ + u->flags |= REF_LOG_ONLY | REF_NO_DEREF; + u->flags &= ~REF_HAVE_OLD; + } + } + + /* + * Verify that the old object matches our expectations. Note + * that the error messages here do not make a lot of sense in + * the context of the reftable backend as we never lock + * individual refs. But the error messages match what the files + * backend returns, which keeps our tests happy. + */ + if (u->old_target) { + if (!(u->type & REF_ISSYMREF)) { + strbuf_addf(err, _("cannot lock ref '%s': " + "expected symref with target '%s': " + "but is a regular ref"), + ref_update_original_update_refname(u), + u->old_target); + return REF_TRANSACTION_ERROR_EXPECTED_SYMREF; + } + + ret = ref_update_check_old_target(referent->buf, u, err); + if (ret) + return ret; + } else if ((u->flags & REF_HAVE_OLD) && !oideq(¤t_oid, &u->old_oid)) { + if (is_null_oid(&u->old_oid)) { + strbuf_addf(err, _("cannot lock ref '%s': " + "reference already exists"), + ref_update_original_update_refname(u)); + return REF_TRANSACTION_ERROR_CREATE_EXISTS; + } else if (is_null_oid(¤t_oid)) { + strbuf_addf(err, _("cannot lock ref '%s': " + "reference is missing but expected %s"), + ref_update_original_update_refname(u), + oid_to_hex(&u->old_oid)); + return REF_TRANSACTION_ERROR_NONEXISTENT_REF; + } else { + strbuf_addf(err, _("cannot lock ref '%s': " + "is at %s but expected %s"), + ref_update_original_update_refname(u), + oid_to_hex(¤t_oid), + oid_to_hex(&u->old_oid)); + return REF_TRANSACTION_ERROR_INCORRECT_OLD_VALUE; + } + } + + /* + * If all of the following conditions are true: + * + * - We're not about to write a symref. + * - We're not about to write a log-only entry. + * - Old and new object ID are different. + * + * Then we're essentially doing a no-op update that can be + * skipped. This is not only for the sake of efficiency, but + * also skips writing unneeded reflog entries. + */ + if ((u->type & REF_ISSYMREF) || + (u->flags & REF_LOG_ONLY) || + (u->flags & REF_HAVE_NEW && !oideq(¤t_oid, &u->new_oid))) + if (queue_transaction_update(refs, tx_data, u, ¤t_oid, err)) + return REF_TRANSACTION_ERROR_GENERIC; + + return 0; +} + +static int reftable_be_transaction_prepare(struct ref_store *ref_store, + struct ref_transaction *transaction, + struct strbuf *err) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE|REF_STORE_MAIN, "ref_transaction_prepare"); + struct strbuf referent = STRBUF_INIT, head_referent = STRBUF_INIT; + struct string_list refnames_to_check = STRING_LIST_INIT_NODUP; + struct reftable_transaction_data *tx_data = NULL; + struct reftable_backend *be; + struct object_id head_oid; + unsigned int head_type = 0; + size_t i; + int ret; + + ret = refs->err; + if (ret < 0) + goto done; + + tx_data = xcalloc(1, sizeof(*tx_data)); + + /* + * Preprocess all updates. For one we check that there are no duplicate + * reference updates in this transaction. Second, we lock all stacks + * that will be modified during the transaction. + */ + for (i = 0; i < transaction->nr; i++) { + ret = prepare_transaction_update(NULL, refs, tx_data, + transaction->updates[i], err); + if (ret) + goto done; + } + + /* + * Now that we have counted updates per stack we can preallocate their + * arrays. This avoids having to reallocate many times. + */ + for (i = 0; i < tx_data->args_nr; i++) { + CALLOC_ARRAY(tx_data->args[i].updates, tx_data->args[i].updates_expected); + tx_data->args[i].updates_alloc = tx_data->args[i].updates_expected; + } + + /* + * TODO: it's dubious whether we should reload the stack that "HEAD" + * belongs to or not. In theory, it may happen that we only modify + * stacks which are _not_ part of the "HEAD" stack. In that case we + * wouldn't have prepared any transaction for its stack and would not + * have reloaded it, which may mean that it is stale. + * + * On the other hand, reloading that stack without locking it feels + * wrong, too, as the value of "HEAD" could be modified concurrently at + * any point in time. + */ + ret = backend_for(&be, refs, "HEAD", NULL, 0); + if (ret) + goto done; + + ret = reftable_backend_read_ref(be, "HEAD", &head_oid, + &head_referent, &head_type); + if (ret < 0) + goto done; + ret = 0; + + for (i = 0; i < transaction->nr; i++) { + ret = prepare_single_update(refs, tx_data, transaction, be, + transaction->updates[i], i, + &refnames_to_check, head_type, + &head_referent, &referent, err); + if (ret) { + if (ref_transaction_maybe_set_rejected(transaction, i, ret)) { + strbuf_reset(err); + ret = 0; + + continue; + } + goto done; + } + } + + ret = refs_verify_refnames_available(ref_store, &refnames_to_check, + &transaction->refnames, NULL, + transaction, + transaction->flags & REF_TRANSACTION_FLAG_INITIAL, + err); + if (ret < 0) + goto done; + + transaction->backend_data = tx_data; + transaction->state = REF_TRANSACTION_PREPARED; + +done: + if (ret < 0) { + free_transaction_data(tx_data); + transaction->state = REF_TRANSACTION_CLOSED; + if (!err->len) + strbuf_addf(err, _("reftable: transaction prepare: %s"), + reftable_error_str(ret)); + } + strbuf_release(&referent); + strbuf_release(&head_referent); + string_list_clear(&refnames_to_check, 1); + + return ret; +} + +static int reftable_be_transaction_abort(struct ref_store *ref_store UNUSED, + struct ref_transaction *transaction, + struct strbuf *err UNUSED) +{ + struct reftable_transaction_data *tx_data = transaction->backend_data; + free_transaction_data(tx_data); + transaction->state = REF_TRANSACTION_CLOSED; + return 0; +} + +static int transaction_update_cmp(const void *a, const void *b) +{ + struct reftable_transaction_update *update_a = (struct reftable_transaction_update *)a; + struct reftable_transaction_update *update_b = (struct reftable_transaction_update *)b; + + /* + * If there is an index set, it should take preference (default is 0). + * This ensures that updates with indexes are sorted amongst themselves. + */ + if (update_a->update->index || update_b->update->index) + return update_a->update->index - update_b->update->index; + + return strcmp(update_a->update->refname, update_b->update->refname); +} + +static int write_transaction_table(struct reftable_writer *writer, void *cb_data) +{ + struct write_transaction_table_arg *arg = cb_data; + uint64_t ts = reftable_stack_next_update_index(arg->be->stack); + struct reftable_log_record *logs = NULL; + struct ident_split committer_ident = {0}; + size_t logs_nr = 0, logs_alloc = 0, i; + const char *committer_info; + int ret = 0; + + committer_info = git_committer_info(0); + if (split_ident_line(&committer_ident, committer_info, strlen(committer_info))) + BUG("failed splitting committer info"); + + QSORT(arg->updates, arg->updates_nr, transaction_update_cmp); + + /* + * During reflog migration, we add indexes for a single reflog with + * multiple entries. Each entry will contain a different update_index, + * so set the limits accordingly. + */ + ret = reftable_writer_set_limits(writer, ts, ts + arg->max_index); + if (ret < 0) + goto done; + + for (i = 0; i < arg->updates_nr; i++) { + struct reftable_transaction_update *tx_update = &arg->updates[i]; + struct ref_update *u = tx_update->update; + + if (u->rejection_err) + continue; + + /* + * Write a reflog entry when updating a ref to point to + * something new in either of the following cases: + * + * - The reference is about to be deleted. We always want to + * delete the reflog in that case. + * - REF_FORCE_CREATE_REFLOG is set, asking us to always create + * the reflog entry. + * - `core.logAllRefUpdates` tells us to create the reflog for + * the given ref. + */ + if ((u->flags & REF_HAVE_NEW) && + !(u->type & REF_ISSYMREF) && + ref_update_has_null_new_value(u)) { + struct reftable_log_record log = {0}; + struct reftable_iterator it = {0}; + + ret = reftable_stack_init_log_iterator(arg->be->stack, &it); + if (ret < 0) + goto done; + + /* + * When deleting refs we also delete all reflog entries + * with them. While it is not strictly required to + * delete reflogs together with their refs, this + * matches the behaviour of the files backend. + * + * Unfortunately, we have no better way than to delete + * all reflog entries one by one. + */ + ret = reftable_iterator_seek_log(&it, u->refname); + while (ret == 0) { + struct reftable_log_record *tombstone; + + ret = reftable_iterator_next_log(&it, &log); + if (ret < 0) + break; + if (ret > 0 || strcmp(log.refname, u->refname)) { + ret = 0; + break; + } + + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + tombstone = &logs[logs_nr++]; + tombstone->refname = xstrdup(u->refname); + tombstone->value_type = REFTABLE_LOG_DELETION; + tombstone->update_index = log.update_index; + } + + reftable_log_record_release(&log); + reftable_iterator_destroy(&it); + + if (ret) + goto done; + } else if (!(u->flags & REF_SKIP_CREATE_REFLOG) && + (u->flags & REF_HAVE_NEW) && + (u->flags & REF_FORCE_CREATE_REFLOG || + should_write_log(arg->refs, u->refname))) { + struct reftable_log_record *log; + int create_reflog = 1; + + if (u->new_target) { + if (!refs_resolve_ref_unsafe(&arg->refs->base, u->new_target, + RESOLVE_REF_READING, &u->new_oid, NULL)) { + /* + * TODO: currently we skip creating reflogs for dangling + * symref updates. It would be nice to capture this as + * zero oid updates however. + */ + create_reflog = 0; + } + } + + if (create_reflog) { + struct ident_split c; + + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + log = &logs[logs_nr++]; + memset(log, 0, sizeof(*log)); + + if (u->committer_info) { + if (split_ident_line(&c, u->committer_info, + strlen(u->committer_info))) + BUG("failed splitting committer info"); + } else { + c = committer_ident; + } + + fill_reftable_log_record(log, &c); + + /* + * Updates are sorted by the writer. So updates for the same + * refname need to contain different update indices. + */ + log->update_index = ts + u->index; + + log->refname = xstrdup(u->refname); + memcpy(log->value.update.new_hash, + u->new_oid.hash, GIT_MAX_RAWSZ); + memcpy(log->value.update.old_hash, + tx_update->current_oid.hash, GIT_MAX_RAWSZ); + log->value.update.message = + xstrndup(u->msg, arg->refs->write_options.block_size / 2); + } + } + + if (u->flags & REF_LOG_ONLY) + continue; + + if (u->new_target) { + struct reftable_ref_record ref = { + .refname = (char *)u->refname, + .value_type = REFTABLE_REF_SYMREF, + .value.symref = (char *)u->new_target, + .update_index = ts, + }; + + ret = reftable_writer_add_ref(writer, &ref); + if (ret < 0) + goto done; + } else if ((u->flags & REF_HAVE_NEW) && ref_update_has_null_new_value(u)) { + struct reftable_ref_record ref = { + .refname = (char *)u->refname, + .update_index = ts, + .value_type = REFTABLE_REF_DELETION, + }; + + ret = reftable_writer_add_ref(writer, &ref); + if (ret < 0) + goto done; + } else if (u->flags & REF_HAVE_NEW) { + struct reftable_ref_record ref = {0}; + struct object_id peeled; + int peel_error; + + ref.refname = (char *)u->refname; + ref.update_index = ts; + + peel_error = peel_object(arg->refs->base.repo, &u->new_oid, &peeled); + if (!peel_error) { + ref.value_type = REFTABLE_REF_VAL2; + memcpy(ref.value.val2.target_value, peeled.hash, GIT_MAX_RAWSZ); + memcpy(ref.value.val2.value, u->new_oid.hash, GIT_MAX_RAWSZ); + } else if (!is_null_oid(&u->new_oid)) { + ref.value_type = REFTABLE_REF_VAL1; + memcpy(ref.value.val1, u->new_oid.hash, GIT_MAX_RAWSZ); + } + + ret = reftable_writer_add_ref(writer, &ref); + if (ret < 0) + goto done; + } + } + + /* + * Logs are written at the end so that we do not have intermixed ref + * and log blocks. + */ + if (logs) { + ret = reftable_writer_add_logs(writer, logs, logs_nr); + if (ret < 0) + goto done; + } + +done: + assert(ret != REFTABLE_API_ERROR); + for (i = 0; i < logs_nr; i++) + reftable_log_record_release(&logs[i]); + free(logs); + return ret; +} + +static int reftable_be_transaction_finish(struct ref_store *ref_store UNUSED, + struct ref_transaction *transaction, + struct strbuf *err) +{ + struct reftable_transaction_data *tx_data = transaction->backend_data; + int ret = 0; + + for (size_t i = 0; i < tx_data->args_nr; i++) { + tx_data->args[i].max_index = transaction->max_index; + + ret = reftable_addition_add(tx_data->args[i].addition, + write_transaction_table, &tx_data->args[i]); + if (ret < 0) + goto done; + + ret = reftable_addition_commit(tx_data->args[i].addition); + if (ret < 0) + goto done; + } + +done: + assert(ret != REFTABLE_API_ERROR); + free_transaction_data(tx_data); + transaction->state = REF_TRANSACTION_CLOSED; + + if (ret) { + strbuf_addf(err, _("reftable: transaction failure: %s"), + reftable_error_str(ret)); + return -1; + } + return ret; +} + +static int reftable_be_pack_refs(struct ref_store *ref_store, + struct pack_refs_opts *opts) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB, "pack_refs"); + struct reftable_stack *stack; + int ret; + + if (refs->err) + return refs->err; + + stack = refs->worktree_backend.stack; + if (!stack) + stack = refs->main_backend.stack; + + if (opts->flags & PACK_REFS_AUTO) + ret = reftable_stack_auto_compact(stack); + else + ret = reftable_stack_compact_all(stack, NULL); + if (ret < 0) { + ret = error(_("unable to compact stack: %s"), + reftable_error_str(ret)); + goto out; + } + + ret = reftable_stack_clean(stack); + if (ret) + goto out; + +out: + return ret; +} + +struct write_create_symref_arg { + struct reftable_ref_store *refs; + struct reftable_stack *stack; + struct strbuf *err; + const char *refname; + const char *target; + const char *logmsg; +}; + +struct write_copy_arg { + struct reftable_ref_store *refs; + struct reftable_backend *be; + const char *oldname; + const char *newname; + const char *logmsg; + int delete_old; +}; + +static int write_copy_table(struct reftable_writer *writer, void *cb_data) +{ + struct write_copy_arg *arg = cb_data; + uint64_t deletion_ts, creation_ts; + struct reftable_ref_record old_ref = {0}, refs[2] = {0}; + struct reftable_log_record old_log = {0}, *logs = NULL; + struct reftable_iterator it = {0}; + struct string_list skip = STRING_LIST_INIT_NODUP; + struct ident_split committer_ident = {0}; + struct strbuf errbuf = STRBUF_INIT; + size_t logs_nr = 0, logs_alloc = 0, i; + const char *committer_info; + int ret; + + committer_info = git_committer_info(0); + if (split_ident_line(&committer_ident, committer_info, strlen(committer_info))) + BUG("failed splitting committer info"); + + if (reftable_stack_read_ref(arg->be->stack, arg->oldname, &old_ref)) { + ret = error(_("refname %s not found"), arg->oldname); + goto done; + } + if (old_ref.value_type == REFTABLE_REF_SYMREF) { + ret = error(_("refname %s is a symbolic ref, copying it is not supported"), + arg->oldname); + goto done; + } + + /* + * There's nothing to do in case the old and new name are the same, so + * we exit early in that case. + */ + if (!strcmp(arg->oldname, arg->newname)) { + ret = 0; + goto done; + } + + /* + * Verify that the new refname is available. + */ + if (arg->delete_old) + string_list_insert(&skip, arg->oldname); + ret = refs_verify_refname_available(&arg->refs->base, arg->newname, + NULL, &skip, 0, &errbuf); + if (ret < 0) { + error("%s", errbuf.buf); + goto done; + } + + /* + * When deleting the old reference we have to use two update indices: + * once to delete the old ref and its reflog, and once to create the + * new ref and its reflog. They need to be staged with two separate + * indices because the new reflog needs to encode both the deletion of + * the old branch and the creation of the new branch, and we cannot do + * two changes to a reflog in a single update. + */ + deletion_ts = creation_ts = reftable_stack_next_update_index(arg->be->stack); + if (arg->delete_old) + creation_ts++; + ret = reftable_writer_set_limits(writer, deletion_ts, creation_ts); + if (ret < 0) + goto done; + + /* + * Add the new reference. If this is a rename then we also delete the + * old reference. + */ + refs[0] = old_ref; + refs[0].refname = xstrdup(arg->newname); + refs[0].update_index = creation_ts; + if (arg->delete_old) { + refs[1].refname = xstrdup(arg->oldname); + refs[1].value_type = REFTABLE_REF_DELETION; + refs[1].update_index = deletion_ts; + } + ret = reftable_writer_add_refs(writer, refs, arg->delete_old ? 2 : 1); + if (ret < 0) + goto done; + + /* + * When deleting the old branch we need to create a reflog entry on the + * new branch name that indicates that the old branch has been deleted + * and then recreated. This is a tad weird, but matches what the files + * backend does. + */ + if (arg->delete_old) { + struct strbuf head_referent = STRBUF_INIT; + struct object_id head_oid; + int append_head_reflog; + unsigned head_type = 0; + + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + memset(&logs[logs_nr], 0, sizeof(logs[logs_nr])); + fill_reftable_log_record(&logs[logs_nr], &committer_ident); + logs[logs_nr].refname = xstrdup(arg->newname); + logs[logs_nr].update_index = deletion_ts; + logs[logs_nr].value.update.message = + xstrndup(arg->logmsg, arg->refs->write_options.block_size / 2); + memcpy(logs[logs_nr].value.update.old_hash, old_ref.value.val1, GIT_MAX_RAWSZ); + logs_nr++; + + ret = reftable_backend_read_ref(arg->be, "HEAD", &head_oid, + &head_referent, &head_type); + if (ret < 0) + goto done; + append_head_reflog = (head_type & REF_ISSYMREF) && !strcmp(head_referent.buf, arg->oldname); + strbuf_release(&head_referent); + + /* + * The files backend uses `refs_delete_ref()` to delete the old + * branch name, which will append a reflog entry for HEAD in + * case it points to the old branch. + */ + if (append_head_reflog) { + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + logs[logs_nr] = logs[logs_nr - 1]; + logs[logs_nr].refname = xstrdup("HEAD"); + logs[logs_nr].value.update.name = + xstrdup(logs[logs_nr].value.update.name); + logs[logs_nr].value.update.email = + xstrdup(logs[logs_nr].value.update.email); + logs[logs_nr].value.update.message = + xstrdup(logs[logs_nr].value.update.message); + logs_nr++; + } + } + + /* + * Create the reflog entry for the newly created branch. + */ + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + memset(&logs[logs_nr], 0, sizeof(logs[logs_nr])); + fill_reftable_log_record(&logs[logs_nr], &committer_ident); + logs[logs_nr].refname = xstrdup(arg->newname); + logs[logs_nr].update_index = creation_ts; + logs[logs_nr].value.update.message = + xstrndup(arg->logmsg, arg->refs->write_options.block_size / 2); + memcpy(logs[logs_nr].value.update.new_hash, old_ref.value.val1, GIT_MAX_RAWSZ); + logs_nr++; + + /* + * In addition to writing the reflog entry for the new branch, we also + * copy over all log entries from the old reflog. Last but not least, + * when renaming we also have to delete all the old reflog entries. + */ + ret = reftable_stack_init_log_iterator(arg->be->stack, &it); + if (ret < 0) + goto done; + + ret = reftable_iterator_seek_log(&it, arg->oldname); + if (ret < 0) + goto done; + + while (1) { + ret = reftable_iterator_next_log(&it, &old_log); + if (ret < 0) + goto done; + if (ret > 0 || strcmp(old_log.refname, arg->oldname)) { + ret = 0; + break; + } + + free(old_log.refname); + + /* + * Copy over the old reflog entry with the new refname. + */ + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + logs[logs_nr] = old_log; + logs[logs_nr].refname = xstrdup(arg->newname); + logs_nr++; + + /* + * Delete the old reflog entry in case we are renaming. + */ + if (arg->delete_old) { + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + memset(&logs[logs_nr], 0, sizeof(logs[logs_nr])); + logs[logs_nr].refname = xstrdup(arg->oldname); + logs[logs_nr].value_type = REFTABLE_LOG_DELETION; + logs[logs_nr].update_index = old_log.update_index; + logs_nr++; + } + + /* + * Transfer ownership of the log record we're iterating over to + * the array of log records. Otherwise, the pointers would get + * free'd or reallocated by the iterator. + */ + memset(&old_log, 0, sizeof(old_log)); + } + + ret = reftable_writer_add_logs(writer, logs, logs_nr); + if (ret < 0) + goto done; + +done: + assert(ret != REFTABLE_API_ERROR); + reftable_iterator_destroy(&it); + string_list_clear(&skip, 0); + strbuf_release(&errbuf); + for (i = 0; i < logs_nr; i++) + reftable_log_record_release(&logs[i]); + free(logs); + for (i = 0; i < ARRAY_SIZE(refs); i++) + reftable_ref_record_release(&refs[i]); + reftable_ref_record_release(&old_ref); + reftable_log_record_release(&old_log); + return ret; +} + +static int reftable_be_rename_ref(struct ref_store *ref_store, + const char *oldrefname, + const char *newrefname, + const char *logmsg) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "rename_ref"); + struct write_copy_arg arg = { + .refs = refs, + .oldname = oldrefname, + .newname = newrefname, + .logmsg = logmsg, + .delete_old = 1, + }; + int ret; + + ret = refs->err; + if (ret < 0) + goto done; + + ret = backend_for(&arg.be, refs, newrefname, &newrefname, 1); + if (ret) + goto done; + ret = reftable_stack_add(arg.be->stack, &write_copy_table, &arg); + +done: + assert(ret != REFTABLE_API_ERROR); + return ret; +} + +static int reftable_be_copy_ref(struct ref_store *ref_store, + const char *oldrefname, + const char *newrefname, + const char *logmsg) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "copy_ref"); + struct write_copy_arg arg = { + .refs = refs, + .oldname = oldrefname, + .newname = newrefname, + .logmsg = logmsg, + }; + int ret; + + ret = refs->err; + if (ret < 0) + goto done; + + ret = backend_for(&arg.be, refs, newrefname, &newrefname, 1); + if (ret) + goto done; + ret = reftable_stack_add(arg.be->stack, &write_copy_table, &arg); + +done: + assert(ret != REFTABLE_API_ERROR); + return ret; +} + +struct reftable_reflog_iterator { + struct ref_iterator base; + struct reftable_ref_store *refs; + struct reftable_iterator iter; + struct reftable_log_record log; + struct strbuf last_name; + int err; +}; + +static int reftable_reflog_iterator_advance(struct ref_iterator *ref_iterator) +{ + struct reftable_reflog_iterator *iter = + (struct reftable_reflog_iterator *)ref_iterator; + + while (!iter->err) { + iter->err = reftable_iterator_next_log(&iter->iter, &iter->log); + if (iter->err) + break; + + /* + * We want the refnames that we have reflogs for, so we skip if + * we've already produced this name. This could be faster by + * seeking directly to reflog@update_index==0. + */ + if (!strcmp(iter->log.refname, iter->last_name.buf)) + continue; + + if (check_refname_format(iter->log.refname, + REFNAME_ALLOW_ONELEVEL)) + continue; + + strbuf_reset(&iter->last_name); + strbuf_addstr(&iter->last_name, iter->log.refname); + iter->base.refname = iter->log.refname; + + break; + } + + if (iter->err > 0) + return ITER_DONE; + if (iter->err < 0) + return ITER_ERROR; + return ITER_OK; +} + +static int reftable_reflog_iterator_seek(struct ref_iterator *ref_iterator UNUSED, + const char *refname UNUSED, + unsigned int flags UNUSED) +{ + BUG("reftable reflog iterator cannot be seeked"); + return -1; +} + +static int reftable_reflog_iterator_peel(struct ref_iterator *ref_iterator UNUSED, + struct object_id *peeled UNUSED) +{ + BUG("reftable reflog iterator cannot be peeled"); + return -1; +} + +static void reftable_reflog_iterator_release(struct ref_iterator *ref_iterator) +{ + struct reftable_reflog_iterator *iter = + (struct reftable_reflog_iterator *)ref_iterator; + reftable_log_record_release(&iter->log); + reftable_iterator_destroy(&iter->iter); + strbuf_release(&iter->last_name); +} + +static struct ref_iterator_vtable reftable_reflog_iterator_vtable = { + .advance = reftable_reflog_iterator_advance, + .seek = reftable_reflog_iterator_seek, + .peel = reftable_reflog_iterator_peel, + .release = reftable_reflog_iterator_release, +}; + +static struct reftable_reflog_iterator *reflog_iterator_for_stack(struct reftable_ref_store *refs, + struct reftable_stack *stack) +{ + struct reftable_reflog_iterator *iter; + int ret; + + iter = xcalloc(1, sizeof(*iter)); + base_ref_iterator_init(&iter->base, &reftable_reflog_iterator_vtable); + strbuf_init(&iter->last_name, 0); + iter->refs = refs; + + ret = refs->err; + if (ret) + goto done; + + ret = reftable_stack_reload(stack); + if (ret < 0) + goto done; + + ret = reftable_stack_init_log_iterator(stack, &iter->iter); + if (ret < 0) + goto done; + + ret = reftable_iterator_seek_log(&iter->iter, ""); + if (ret < 0) + goto done; + +done: + iter->err = ret; + return iter; +} + +static struct ref_iterator *reftable_be_reflog_iterator_begin(struct ref_store *ref_store) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_READ, "reflog_iterator_begin"); + struct reftable_reflog_iterator *main_iter, *worktree_iter; + + main_iter = reflog_iterator_for_stack(refs, refs->main_backend.stack); + if (!refs->worktree_backend.stack) + return &main_iter->base; + + worktree_iter = reflog_iterator_for_stack(refs, refs->worktree_backend.stack); + + return merge_ref_iterator_begin(&worktree_iter->base, &main_iter->base, + ref_iterator_select, NULL); +} + +static int yield_log_record(struct reftable_ref_store *refs, + struct reftable_log_record *log, + each_reflog_ent_fn fn, + void *cb_data) +{ + struct object_id old_oid, new_oid; + const char *full_committer; + + oidread(&old_oid, log->value.update.old_hash, refs->base.repo->hash_algo); + oidread(&new_oid, log->value.update.new_hash, refs->base.repo->hash_algo); + + /* + * When both the old object ID and the new object ID are null + * then this is the reflog existence marker. The caller must + * not be aware of it. + */ + if (is_null_oid(&old_oid) && is_null_oid(&new_oid)) + return 0; + + full_committer = fmt_ident(log->value.update.name, log->value.update.email, + WANT_COMMITTER_IDENT, NULL, IDENT_NO_DATE); + return fn(&old_oid, &new_oid, full_committer, + log->value.update.time, log->value.update.tz_offset, + log->value.update.message, cb_data); +} + +static int reftable_be_for_each_reflog_ent_reverse(struct ref_store *ref_store, + const char *refname, + each_reflog_ent_fn fn, + void *cb_data) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_READ, "for_each_reflog_ent_reverse"); + struct reftable_log_record log = {0}; + struct reftable_iterator it = {0}; + struct reftable_backend *be; + int ret; + + if (refs->err < 0) + return refs->err; + + /* + * TODO: we should adapt this callsite to reload the stack. There is no + * obvious reason why we shouldn't. + */ + ret = backend_for(&be, refs, refname, &refname, 0); + if (ret) + goto done; + + ret = reftable_stack_init_log_iterator(be->stack, &it); + if (ret < 0) + goto done; + + ret = reftable_iterator_seek_log(&it, refname); + while (!ret) { + ret = reftable_iterator_next_log(&it, &log); + if (ret < 0) + break; + if (ret > 0 || strcmp(log.refname, refname)) { + ret = 0; + break; + } + + ret = yield_log_record(refs, &log, fn, cb_data); + if (ret) + break; + } + +done: + reftable_log_record_release(&log); + reftable_iterator_destroy(&it); + return ret; +} + +static int reftable_be_for_each_reflog_ent(struct ref_store *ref_store, + const char *refname, + each_reflog_ent_fn fn, + void *cb_data) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_READ, "for_each_reflog_ent"); + struct reftable_log_record *logs = NULL; + struct reftable_iterator it = {0}; + struct reftable_backend *be; + size_t logs_alloc = 0, logs_nr = 0, i; + int ret; + + if (refs->err < 0) + return refs->err; + + /* + * TODO: we should adapt this callsite to reload the stack. There is no + * obvious reason why we shouldn't. + */ + ret = backend_for(&be, refs, refname, &refname, 0); + if (ret) + goto done; + + ret = reftable_stack_init_log_iterator(be->stack, &it); + if (ret < 0) + goto done; + + ret = reftable_iterator_seek_log(&it, refname); + while (!ret) { + struct reftable_log_record log = {0}; + + ret = reftable_iterator_next_log(&it, &log); + if (ret < 0) + goto done; + if (ret > 0 || strcmp(log.refname, refname)) { + reftable_log_record_release(&log); + ret = 0; + break; + } + + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + logs[logs_nr++] = log; + } + + for (i = logs_nr; i--;) { + ret = yield_log_record(refs, &logs[i], fn, cb_data); + if (ret) + goto done; + } + +done: + reftable_iterator_destroy(&it); + for (i = 0; i < logs_nr; i++) + reftable_log_record_release(&logs[i]); + free(logs); + return ret; +} + +static int reftable_be_reflog_exists(struct ref_store *ref_store, + const char *refname) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_READ, "reflog_exists"); + struct reftable_log_record log = {0}; + struct reftable_iterator it = {0}; + struct reftable_backend *be; + int ret; + + ret = refs->err; + if (ret < 0) + goto done; + + ret = backend_for(&be, refs, refname, &refname, 1); + if (ret < 0) + goto done; + + ret = reftable_stack_init_log_iterator(be->stack, &it); + if (ret < 0) + goto done; + + ret = reftable_iterator_seek_log(&it, refname); + if (ret < 0) + goto done; + + /* + * Check whether we get at least one log record for the given ref name. + * If so, the reflog exists, otherwise it doesn't. + */ + ret = reftable_iterator_next_log(&it, &log); + if (ret < 0) + goto done; + if (ret > 0) { + ret = 0; + goto done; + } + + ret = strcmp(log.refname, refname) == 0; + +done: + reftable_iterator_destroy(&it); + reftable_log_record_release(&log); + if (ret < 0) + ret = 0; + return ret; +} + +struct write_reflog_existence_arg { + struct reftable_ref_store *refs; + const char *refname; + struct reftable_stack *stack; +}; + +static int write_reflog_existence_table(struct reftable_writer *writer, + void *cb_data) +{ + struct write_reflog_existence_arg *arg = cb_data; + uint64_t ts = reftable_stack_next_update_index(arg->stack); + struct reftable_log_record log = {0}; + int ret; + + ret = reftable_stack_read_log(arg->stack, arg->refname, &log); + if (ret <= 0) + goto done; + + ret = reftable_writer_set_limits(writer, ts, ts); + if (ret < 0) + goto done; + + /* + * The existence entry has both old and new object ID set to the + * null object ID. Our iterators are aware of this and will not present + * them to their callers. + */ + log.refname = xstrdup(arg->refname); + log.update_index = ts; + log.value_type = REFTABLE_LOG_UPDATE; + ret = reftable_writer_add_log(writer, &log); + +done: + assert(ret != REFTABLE_API_ERROR); + reftable_log_record_release(&log); + return ret; +} + +static int reftable_be_create_reflog(struct ref_store *ref_store, + const char *refname, + struct strbuf *errmsg UNUSED) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "create_reflog"); + struct reftable_backend *be; + struct write_reflog_existence_arg arg = { + .refs = refs, + .refname = refname, + }; + int ret; + + ret = refs->err; + if (ret < 0) + goto done; + + ret = backend_for(&be, refs, refname, &refname, 1); + if (ret) + goto done; + arg.stack = be->stack; + + ret = reftable_stack_add(be->stack, &write_reflog_existence_table, &arg); + +done: + return ret; +} + +struct write_reflog_delete_arg { + struct reftable_stack *stack; + const char *refname; +}; + +static int write_reflog_delete_table(struct reftable_writer *writer, void *cb_data) +{ + struct write_reflog_delete_arg *arg = cb_data; + struct reftable_log_record log = {0}, tombstone = {0}; + struct reftable_iterator it = {0}; + uint64_t ts = reftable_stack_next_update_index(arg->stack); + int ret; + + ret = reftable_writer_set_limits(writer, ts, ts); + if (ret < 0) + goto out; + + ret = reftable_stack_init_log_iterator(arg->stack, &it); + if (ret < 0) + goto out; + + /* + * In order to delete a table we need to delete all reflog entries one + * by one. This is inefficient, but the reftable format does not have a + * better marker right now. + */ + ret = reftable_iterator_seek_log(&it, arg->refname); + while (ret == 0) { + ret = reftable_iterator_next_log(&it, &log); + if (ret < 0) + break; + if (ret > 0 || strcmp(log.refname, arg->refname)) { + ret = 0; + break; + } + + tombstone.refname = (char *)arg->refname; + tombstone.value_type = REFTABLE_LOG_DELETION; + tombstone.update_index = log.update_index; + + ret = reftable_writer_add_log(writer, &tombstone); + } + +out: + reftable_log_record_release(&log); + reftable_iterator_destroy(&it); + return ret; +} + +static int reftable_be_delete_reflog(struct ref_store *ref_store, + const char *refname) +{ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "delete_reflog"); + struct reftable_backend *be; + struct write_reflog_delete_arg arg = { + .refname = refname, + }; + int ret; + + ret = backend_for(&be, refs, refname, &refname, 1); + if (ret) + return ret; + arg.stack = be->stack; + + ret = reftable_stack_add(be->stack, &write_reflog_delete_table, &arg); + + assert(ret != REFTABLE_API_ERROR); + return ret; +} + +struct reflog_expiry_arg { + struct reftable_ref_store *refs; + struct reftable_stack *stack; + struct reftable_log_record *records; + struct object_id update_oid; + const char *refname; + size_t len; +}; + +static int write_reflog_expiry_table(struct reftable_writer *writer, void *cb_data) +{ + struct reflog_expiry_arg *arg = cb_data; + uint64_t ts = reftable_stack_next_update_index(arg->stack); + uint64_t live_records = 0; + size_t i; + int ret; + + for (i = 0; i < arg->len; i++) + if (arg->records[i].value_type == REFTABLE_LOG_UPDATE) + live_records++; + + ret = reftable_writer_set_limits(writer, ts, ts); + if (ret < 0) + return ret; + + if (!is_null_oid(&arg->update_oid)) { + struct reftable_ref_record ref = {0}; + struct object_id peeled; + + ref.refname = (char *)arg->refname; + ref.update_index = ts; + + if (!peel_object(arg->refs->base.repo, &arg->update_oid, &peeled)) { + ref.value_type = REFTABLE_REF_VAL2; + memcpy(ref.value.val2.target_value, peeled.hash, GIT_MAX_RAWSZ); + memcpy(ref.value.val2.value, arg->update_oid.hash, GIT_MAX_RAWSZ); + } else { + ref.value_type = REFTABLE_REF_VAL1; + memcpy(ref.value.val1, arg->update_oid.hash, GIT_MAX_RAWSZ); + } + + ret = reftable_writer_add_ref(writer, &ref); + if (ret < 0) + return ret; + } + + /* + * When there are no more entries left in the reflog we empty it + * completely, but write a placeholder reflog entry that indicates that + * the reflog still exists. + */ + if (!live_records) { + struct reftable_log_record log = { + .refname = (char *)arg->refname, + .value_type = REFTABLE_LOG_UPDATE, + .update_index = ts, + }; + + ret = reftable_writer_add_log(writer, &log); + if (ret) + return ret; + } + + for (i = 0; i < arg->len; i++) { + ret = reftable_writer_add_log(writer, &arg->records[i]); + if (ret) + return ret; + } + + return 0; +} + +static int reftable_be_reflog_expire(struct ref_store *ref_store, + const char *refname, + unsigned int flags, + reflog_expiry_prepare_fn prepare_fn, + reflog_expiry_should_prune_fn should_prune_fn, + reflog_expiry_cleanup_fn cleanup_fn, + void *policy_cb_data) +{ + /* + * For log expiry, we write tombstones for every single reflog entry + * that is to be expired. This means that the entries are still + * retrievable by delving into the stack, and expiring entries + * paradoxically takes extra memory. This memory is only reclaimed when + * compacting the reftable stack. + * + * It would be better if the refs backend supported an API that sets a + * criterion for all refs, passing the criterion to pack_refs(). + * + * On the plus side, because we do the expiration per ref, we can easily + * insert the reflog existence dummies. + */ + struct reftable_ref_store *refs = + reftable_be_downcast(ref_store, REF_STORE_WRITE, "reflog_expire"); + struct reftable_log_record *logs = NULL; + struct reftable_log_record *rewritten = NULL; + struct reftable_iterator it = {0}; + struct reftable_addition *add = NULL; + struct reflog_expiry_arg arg = {0}; + struct reftable_backend *be; + struct object_id oid = {0}; + struct strbuf referent = STRBUF_INIT; + uint8_t *last_hash = NULL; + size_t logs_nr = 0, logs_alloc = 0, i; + unsigned int type = 0; + int ret; + + if (refs->err < 0) + return refs->err; + + ret = backend_for(&be, refs, refname, &refname, 1); + if (ret < 0) + goto done; + + ret = reftable_stack_init_log_iterator(be->stack, &it); + if (ret < 0) + goto done; + + ret = reftable_iterator_seek_log(&it, refname); + if (ret < 0) + goto done; + + ret = reftable_stack_new_addition(&add, be->stack, 0); + if (ret < 0) + goto done; + + ret = reftable_backend_read_ref(be, refname, &oid, &referent, &type); + if (ret < 0) + goto done; + prepare_fn(refname, &oid, policy_cb_data); + + while (1) { + struct reftable_log_record log = {0}; + struct object_id old_oid, new_oid; + + ret = reftable_iterator_next_log(&it, &log); + if (ret < 0) + goto done; + if (ret > 0 || strcmp(log.refname, refname)) { + reftable_log_record_release(&log); + break; + } + + oidread(&old_oid, log.value.update.old_hash, + ref_store->repo->hash_algo); + oidread(&new_oid, log.value.update.new_hash, + ref_store->repo->hash_algo); + + /* + * Skip over the reflog existence marker. We will add it back + * in when there are no live reflog records. + */ + if (is_null_oid(&old_oid) && is_null_oid(&new_oid)) { + reftable_log_record_release(&log); + continue; + } + + ALLOC_GROW(logs, logs_nr + 1, logs_alloc); + logs[logs_nr++] = log; + } + + /* + * We need to rewrite all reflog entries according to the pruning + * callback function: + * + * - If a reflog entry shall be pruned we mark the record for + * deletion. + * + * - Otherwise we may have to rewrite the chain of reflog entries so + * that gaps created by just-deleted records get backfilled. + */ + CALLOC_ARRAY(rewritten, logs_nr); + for (i = logs_nr; i--;) { + struct reftable_log_record *dest = &rewritten[i]; + struct object_id old_oid, new_oid; + + *dest = logs[i]; + oidread(&old_oid, logs[i].value.update.old_hash, + ref_store->repo->hash_algo); + oidread(&new_oid, logs[i].value.update.new_hash, + ref_store->repo->hash_algo); + + if (should_prune_fn(&old_oid, &new_oid, logs[i].value.update.email, + (timestamp_t)logs[i].value.update.time, + logs[i].value.update.tz_offset, + logs[i].value.update.message, + policy_cb_data)) { + dest->value_type = REFTABLE_LOG_DELETION; + } else { + if ((flags & EXPIRE_REFLOGS_REWRITE) && last_hash) + memcpy(dest->value.update.old_hash, last_hash, GIT_MAX_RAWSZ); + last_hash = logs[i].value.update.new_hash; + } + } + + if (flags & EXPIRE_REFLOGS_UPDATE_REF && last_hash && !is_null_oid(&oid)) + oidread(&arg.update_oid, last_hash, ref_store->repo->hash_algo); + + arg.refs = refs; + arg.records = rewritten; + arg.len = logs_nr; + arg.stack = be->stack; + arg.refname = refname; + + ret = reftable_addition_add(add, &write_reflog_expiry_table, &arg); + if (ret < 0) + goto done; + + /* + * Future improvement: we could skip writing records that were + * not changed. + */ + if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) + ret = reftable_addition_commit(add); + +done: + if (add) + cleanup_fn(policy_cb_data); + assert(ret != REFTABLE_API_ERROR); + + reftable_iterator_destroy(&it); + reftable_addition_destroy(add); + for (i = 0; i < logs_nr; i++) + reftable_log_record_release(&logs[i]); + strbuf_release(&referent); + free(logs); + free(rewritten); + return ret; +} + +static int reftable_be_fsck(struct ref_store *ref_store UNUSED, + struct fsck_options *o UNUSED, + struct worktree *wt UNUSED) +{ + return 0; +} + +struct ref_storage_be refs_be_reftable = { + .name = "reftable", + .init = reftable_be_init, + .release = reftable_be_release, + .create_on_disk = reftable_be_create_on_disk, + .remove_on_disk = reftable_be_remove_on_disk, + + .transaction_prepare = reftable_be_transaction_prepare, + .transaction_finish = reftable_be_transaction_finish, + .transaction_abort = reftable_be_transaction_abort, + + .pack_refs = reftable_be_pack_refs, + .rename_ref = reftable_be_rename_ref, + .copy_ref = reftable_be_copy_ref, + + .iterator_begin = reftable_be_iterator_begin, + .read_raw_ref = reftable_be_read_raw_ref, + .read_symbolic_ref = reftable_be_read_symbolic_ref, + + .reflog_iterator_begin = reftable_be_reflog_iterator_begin, + .for_each_reflog_ent = reftable_be_for_each_reflog_ent, + .for_each_reflog_ent_reverse = reftable_be_for_each_reflog_ent_reverse, + .reflog_exists = reftable_be_reflog_exists, + .create_reflog = reftable_be_create_reflog, + .delete_reflog = reftable_be_delete_reflog, + .reflog_expire = reftable_be_reflog_expire, + + .fsck = reftable_be_fsck, +}; |