diff options
Diffstat (limited to 'refs/packed-backend.c')
| -rw-r--r-- | refs/packed-backend.c | 991 |
1 files changed, 752 insertions, 239 deletions
diff --git a/refs/packed-backend.c b/refs/packed-backend.c index 3bc47ff..3279d42 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -2,53 +2,121 @@ #include "../config.h" #include "../refs.h" #include "refs-internal.h" -#include "ref-cache.h" #include "packed-backend.h" #include "../iterator.h" #include "../lockfile.h" -struct packed_ref_cache { - struct ref_cache *cache; +enum mmap_strategy { + /* + * Don't use mmap() at all for reading `packed-refs`. + */ + MMAP_NONE, /* - * Count of references to the data structure in this instance, - * including the pointer from files_ref_store::packed if any. - * The data will not be freed as long as the reference count - * is nonzero. + * Can use mmap() for reading `packed-refs`, but the file must + * not remain mmapped. This is the usual option on Windows, + * where you cannot rename a new version of a file onto a file + * that is currently mmapped. */ - unsigned int referrers; + MMAP_TEMPORARY, - /* The metadata from when this packed-refs cache was read */ - struct stat_validity validity; + /* + * It is OK to leave the `packed-refs` file mmapped while + * arbitrary other code is running. + */ + MMAP_OK }; -/* - * Increment the reference count of *packed_refs. - */ -static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs) -{ - packed_refs->referrers++; -} +#if defined(NO_MMAP) +static enum mmap_strategy mmap_strategy = MMAP_NONE; +#elif defined(MMAP_PREVENTS_DELETE) +static enum mmap_strategy mmap_strategy = MMAP_TEMPORARY; +#else +static enum mmap_strategy mmap_strategy = MMAP_OK; +#endif + +struct packed_ref_store; /* - * Decrease the reference count of *packed_refs. If it goes to zero, - * free *packed_refs and return true; otherwise return false. + * A `snapshot` represents one snapshot of a `packed-refs` file. + * + * Normally, this will be a mmapped view of the contents of the + * `packed-refs` file at the time the snapshot was created. However, + * if the `packed-refs` file was not sorted, this might point at heap + * memory holding the contents of the `packed-refs` file with its + * records sorted by refname. + * + * `snapshot` instances are reference counted (via + * `acquire_snapshot()` and `release_snapshot()`). This is to prevent + * an instance from disappearing while an iterator is still iterating + * over it. Instances are garbage collected when their `referrers` + * count goes to zero. + * + * The most recent `snapshot`, if available, is referenced by the + * `packed_ref_store`. Its freshness is checked whenever + * `get_snapshot()` is called; if the existing snapshot is obsolete, a + * new snapshot is taken. */ -static int release_packed_ref_cache(struct packed_ref_cache *packed_refs) -{ - if (!--packed_refs->referrers) { - free_ref_cache(packed_refs->cache); - stat_validity_clear(&packed_refs->validity); - free(packed_refs); - return 1; - } else { - return 0; - } -} +struct snapshot { + /* + * A back-pointer to the packed_ref_store with which this + * snapshot is associated: + */ + struct packed_ref_store *refs; + + /* Is the `packed-refs` file currently mmapped? */ + int mmapped; + + /* + * The contents of the `packed-refs` file. If the file was + * already sorted, this points at the mmapped contents of the + * file. If not, this points at heap-allocated memory + * containing the contents, sorted. If there were no contents + * (e.g., because the file didn't exist), `buf` and `eof` are + * both NULL. + */ + char *buf, *eof; + + /* The size of the header line, if any; otherwise, 0: */ + size_t header_len; + + /* + * What is the peeled state of the `packed-refs` file that + * this snapshot represents? (This is usually determined from + * the file's header.) + */ + enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled; + + /* + * Count of references to this instance, including the pointer + * from `packed_ref_store::snapshot`, if any. The instance + * will not be freed as long as the reference count is + * nonzero. + */ + unsigned int referrers; + + /* + * The metadata of the `packed-refs` file from which this + * snapshot was created, used to tell if the file has been + * replaced since we read it. + */ + struct stat_validity validity; +}; /* - * A container for `packed-refs`-related data. It is not (yet) a - * `ref_store`. + * A `ref_store` representing references stored in a `packed-refs` + * file. It implements the `ref_store` interface, though it has some + * limitations: + * + * - It cannot store symbolic references. + * + * - It cannot store reflogs. + * + * - It does not support reference renaming (though it could). + * + * On the other hand, it can be locked outside of a reference + * transaction. In that case, it remains locked even after the + * transaction is done and the new `packed-refs` file is activated. */ struct packed_ref_store { struct ref_store base; @@ -59,10 +127,10 @@ struct packed_ref_store { char *path; /* - * A cache of the values read from the `packed-refs` file, if - * it might still be current; otherwise, NULL. + * A snapshot of the values read from the `packed-refs` file, + * if it might still be current; otherwise, NULL. */ - struct packed_ref_cache *cache; + struct snapshot *snapshot; /* * Lock used for the "packed-refs" file. Note that this (and @@ -78,6 +146,49 @@ struct packed_ref_store { struct tempfile *tempfile; }; +/* + * Increment the reference count of `*snapshot`. + */ +static void acquire_snapshot(struct snapshot *snapshot) +{ + snapshot->referrers++; +} + +/* + * If the buffer in `snapshot` is active, then either munmap the + * memory and close the file, or free the memory. Then set the buffer + * pointers to NULL. + */ +static void clear_snapshot_buffer(struct snapshot *snapshot) +{ + if (snapshot->mmapped) { + if (munmap(snapshot->buf, snapshot->eof - snapshot->buf)) + die_errno("error ummapping packed-refs file %s", + snapshot->refs->path); + snapshot->mmapped = 0; + } else { + free(snapshot->buf); + } + snapshot->buf = snapshot->eof = NULL; + snapshot->header_len = 0; +} + +/* + * Decrease the reference count of `*snapshot`. If it goes to zero, + * free `*snapshot` and return true; otherwise return false. + */ +static int release_snapshot(struct snapshot *snapshot) +{ + if (!--snapshot->referrers) { + stat_validity_clear(&snapshot->validity); + clear_snapshot_buffer(snapshot); + free(snapshot); + return 1; + } else { + return 0; + } +} + struct ref_store *packed_ref_store_create(const char *path, unsigned int store_flags) { @@ -116,64 +227,369 @@ static struct packed_ref_store *packed_downcast(struct ref_store *ref_store, return refs; } -static void clear_packed_ref_cache(struct packed_ref_store *refs) +static void clear_snapshot(struct packed_ref_store *refs) { - if (refs->cache) { - struct packed_ref_cache *cache = refs->cache; + if (refs->snapshot) { + struct snapshot *snapshot = refs->snapshot; - refs->cache = NULL; - release_packed_ref_cache(cache); + refs->snapshot = NULL; + release_snapshot(snapshot); } } -/* The length of a peeled reference line in packed-refs, including EOL: */ -#define PEELED_LINE_LENGTH 42 +static NORETURN void die_unterminated_line(const char *path, + const char *p, size_t len) +{ + if (len < 80) + die("unterminated line in %s: %.*s", path, (int)len, p); + else + die("unterminated line in %s: %.75s...", path, p); +} + +static NORETURN void die_invalid_line(const char *path, + const char *p, size_t len) +{ + const char *eol = memchr(p, '\n', len); + + if (!eol) + die_unterminated_line(path, p, len); + else if (eol - p < 80) + die("unexpected line in %s: %.*s", path, (int)(eol - p), p); + else + die("unexpected line in %s: %.75s...", path, p); + +} + +struct snapshot_record { + const char *start; + size_t len; +}; + +static int cmp_packed_ref_records(const void *v1, const void *v2) +{ + const struct snapshot_record *e1 = v1, *e2 = v2; + const char *r1 = e1->start + GIT_SHA1_HEXSZ + 1; + const char *r2 = e2->start + GIT_SHA1_HEXSZ + 1; + + while (1) { + if (*r1 == '\n') + return *r2 == '\n' ? 0 : -1; + if (*r1 != *r2) { + if (*r2 == '\n') + return 1; + else + return (unsigned char)*r1 < (unsigned char)*r2 ? -1 : +1; + } + r1++; + r2++; + } +} /* - * Parse one line from a packed-refs file. Write the SHA1 to sha1. - * Return a pointer to the refname within the line (null-terminated), - * or NULL if there was a problem. + * Compare a snapshot record at `rec` to the specified NUL-terminated + * refname. */ -static const char *parse_ref_line(struct strbuf *line, struct object_id *oid) +static int cmp_record_to_refname(const char *rec, const char *refname) { - const char *ref; + const char *r1 = rec + GIT_SHA1_HEXSZ + 1; + const char *r2 = refname; + + while (1) { + if (*r1 == '\n') + return *r2 ? -1 : 0; + if (!*r2) + return 1; + if (*r1 != *r2) + return (unsigned char)*r1 < (unsigned char)*r2 ? -1 : +1; + r1++; + r2++; + } +} - if (parse_oid_hex(line->buf, oid, &ref) < 0) - return NULL; - if (!isspace(*ref++)) - return NULL; +/* + * `snapshot->buf` is not known to be sorted. Check whether it is, and + * if not, sort it into new memory and munmap/free the old storage. + */ +static void sort_snapshot(struct snapshot *snapshot) +{ + struct snapshot_record *records = NULL; + size_t alloc = 0, nr = 0; + int sorted = 1; + const char *pos, *eof, *eol; + size_t len, i; + char *new_buffer, *dst; - if (isspace(*ref)) - return NULL; + pos = snapshot->buf + snapshot->header_len; + eof = snapshot->eof; + len = eof - pos; - if (line->buf[line->len - 1] != '\n') - return NULL; - line->buf[--line->len] = 0; + if (!len) + return; + + /* + * Initialize records based on a crude estimate of the number + * of references in the file (we'll grow it below if needed): + */ + ALLOC_GROW(records, len / 80 + 20, alloc); + + while (pos < eof) { + eol = memchr(pos, '\n', eof - pos); + if (!eol) + /* The safety check should prevent this. */ + BUG("unterminated line found in packed-refs"); + if (eol - pos < GIT_SHA1_HEXSZ + 2) + die_invalid_line(snapshot->refs->path, + pos, eof - pos); + eol++; + if (eol < eof && *eol == '^') { + /* + * Keep any peeled line together with its + * reference: + */ + const char *peeled_start = eol; + + eol = memchr(peeled_start, '\n', eof - peeled_start); + if (!eol) + /* The safety check should prevent this. */ + BUG("unterminated peeled line found in packed-refs"); + eol++; + } + + ALLOC_GROW(records, nr + 1, alloc); + records[nr].start = pos; + records[nr].len = eol - pos; + nr++; + + if (sorted && + nr > 1 && + cmp_packed_ref_records(&records[nr - 2], + &records[nr - 1]) >= 0) + sorted = 0; + + pos = eol; + } + + if (sorted) + goto cleanup; + + /* We need to sort the memory. First we sort the records array: */ + QSORT(records, nr, cmp_packed_ref_records); + + /* + * Allocate a new chunk of memory, and copy the old memory to + * the new in the order indicated by `records` (not bothering + * with the header line): + */ + new_buffer = xmalloc(len); + for (dst = new_buffer, i = 0; i < nr; i++) { + memcpy(dst, records[i].start, records[i].len); + dst += records[i].len; + } + + /* + * Now munmap the old buffer and use the sorted buffer in its + * place: + */ + clear_snapshot_buffer(snapshot); + snapshot->buf = new_buffer; + snapshot->eof = new_buffer + len; + snapshot->header_len = 0; + +cleanup: + free(records); +} + +/* + * Return a pointer to the start of the record that contains the + * character `*p` (which must be within the buffer). If no other + * record start is found, return `buf`. + */ +static const char *find_start_of_record(const char *buf, const char *p) +{ + while (p > buf && (p[-1] != '\n' || p[0] == '^')) + p--; + return p; +} + +/* + * Return a pointer to the start of the record following the record + * that contains `*p`. If none is found before `end`, return `end`. + */ +static const char *find_end_of_record(const char *p, const char *end) +{ + while (++p < end && (p[-1] != '\n' || p[0] == '^')) + ; + return p; +} + +/* + * We want to be able to compare mmapped reference records quickly, + * without totally parsing them. We can do so because the records are + * LF-terminated, and the refname should start exactly (GIT_SHA1_HEXSZ + * + 1) bytes past the beginning of the record. + * + * But what if the `packed-refs` file contains garbage? We're willing + * to tolerate not detecting the problem, as long as we don't produce + * totally garbled output (we can't afford to check the integrity of + * the whole file during every Git invocation). But we do want to be + * sure that we never read past the end of the buffer in memory and + * perform an illegal memory access. + * + * Guarantee that minimum level of safety by verifying that the last + * record in the file is LF-terminated, and that it has at least + * (GIT_SHA1_HEXSZ + 1) characters before the LF. Die if either of + * these checks fails. + */ +static void verify_buffer_safe(struct snapshot *snapshot) +{ + const char *buf = snapshot->buf + snapshot->header_len; + const char *eof = snapshot->eof; + const char *last_line; + + if (buf == eof) + return; + + last_line = find_start_of_record(buf, eof - 1); + if (*(eof - 1) != '\n' || eof - last_line < GIT_SHA1_HEXSZ + 2) + die_invalid_line(snapshot->refs->path, + last_line, eof - last_line); +} - return ref; +/* + * Depending on `mmap_strategy`, either mmap or read the contents of + * the `packed-refs` file into the snapshot. Return 1 if the file + * existed and was read, or 0 if the file was absent. Die on errors. + */ +static int load_contents(struct snapshot *snapshot) +{ + int fd; + struct stat st; + size_t size; + ssize_t bytes_read; + + fd = open(snapshot->refs->path, O_RDONLY); + if (fd < 0) { + if (errno == ENOENT) { + /* + * This is OK; it just means that no + * "packed-refs" file has been written yet, + * which is equivalent to it being empty, + * which is its state when initialized with + * zeros. + */ + return 0; + } else { + die_errno("couldn't read %s", snapshot->refs->path); + } + } + + stat_validity_update(&snapshot->validity, fd); + + if (fstat(fd, &st) < 0) + die_errno("couldn't stat %s", snapshot->refs->path); + size = xsize_t(st.st_size); + + switch (mmap_strategy) { + case MMAP_NONE: + snapshot->buf = xmalloc(size); + bytes_read = read_in_full(fd, snapshot->buf, size); + if (bytes_read < 0 || bytes_read != size) + die_errno("couldn't read %s", snapshot->refs->path); + snapshot->eof = snapshot->buf + size; + snapshot->mmapped = 0; + break; + case MMAP_TEMPORARY: + case MMAP_OK: + snapshot->buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0); + snapshot->eof = snapshot->buf + size; + snapshot->mmapped = 1; + break; + } + close(fd); + + return 1; } /* - * Read from `packed_refs_file` into a newly-allocated - * `packed_ref_cache` and return it. The return value will already - * have its reference count incremented. + * Find the place in `snapshot->buf` where the start of the record for + * `refname` starts. If `mustexist` is true and the reference doesn't + * exist, then return NULL. If `mustexist` is false and the reference + * doesn't exist, then return the point where that reference would be + * inserted. In the latter mode, `refname` doesn't have to be a proper + * reference name; for example, one could search for "refs/replace/" + * to find the start of any replace references. + * + * The record is sought using a binary search, so `snapshot->buf` must + * be sorted. + */ +static const char *find_reference_location(struct snapshot *snapshot, + const char *refname, int mustexist) +{ + /* + * This is not *quite* a garden-variety binary search, because + * the data we're searching is made up of records, and we + * always need to find the beginning of a record to do a + * comparison. A "record" here is one line for the reference + * itself and zero or one peel lines that start with '^'. Our + * loop invariant is described in the next two comments. + */ + + /* + * A pointer to the character at the start of a record whose + * preceding records all have reference names that come + * *before* `refname`. + */ + const char *lo = snapshot->buf + snapshot->header_len; + + /* + * A pointer to a the first character of a record whose + * reference name comes *after* `refname`. + */ + const char *hi = snapshot->eof; + + while (lo < hi) { + const char *mid, *rec; + int cmp; + + mid = lo + (hi - lo) / 2; + rec = find_start_of_record(lo, mid); + cmp = cmp_record_to_refname(rec, refname); + if (cmp < 0) { + lo = find_end_of_record(mid, hi); + } else if (cmp > 0) { + hi = rec; + } else { + return rec; + } + } + + if (mustexist) + return NULL; + else + return lo; +} + +/* + * Create a newly-allocated `snapshot` of the `packed-refs` file in + * its current state and return it. The return value will already have + * its reference count incremented. * * A comment line of the form "# pack-refs with: " may contain zero or * more traits. We interpret the traits as follows: * - * No traits: + * Neither `peeled` nor `fully-peeled`: * * Probably no references are peeled. But if the file contains a * peeled value for a reference, we will use it. * - * peeled: + * `peeled`: * * References under "refs/tags/", if they *can* be peeled, *are* * peeled in this file. References outside of "refs/tags/" are * probably not peeled even if they could have been, but if we find * a peeled value for such a reference we will use it. * - * fully-peeled: + * `fully-peeled`: * * All references in the file that can be peeled are peeled. * Inversely (and this is more important), any references in the @@ -181,141 +597,122 @@ static const char *parse_ref_line(struct strbuf *line, struct object_id *oid) * trait should typically be written alongside "peeled" for * compatibility with older clients, but we do not require it * (i.e., "peeled" is a no-op if "fully-peeled" is set). + * + * `sorted`: + * + * The references in this file are known to be sorted by refname. */ -static struct packed_ref_cache *read_packed_refs(const char *packed_refs_file) +static struct snapshot *create_snapshot(struct packed_ref_store *refs) { - FILE *f; - struct packed_ref_cache *packed_refs = xcalloc(1, sizeof(*packed_refs)); - struct ref_entry *last = NULL; - struct strbuf line = STRBUF_INIT; - enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE; - struct ref_dir *dir; - - acquire_packed_ref_cache(packed_refs); - packed_refs->cache = create_ref_cache(NULL, NULL); - packed_refs->cache->root->flag &= ~REF_INCOMPLETE; - - f = fopen(packed_refs_file, "r"); - if (!f) { - if (errno == ENOENT) { - /* - * This is OK; it just means that no - * "packed-refs" file has been written yet, - * which is equivalent to it being empty. - */ - return packed_refs; - } else { - die_errno("couldn't read %s", packed_refs_file); - } - } + struct snapshot *snapshot = xcalloc(1, sizeof(*snapshot)); + int sorted = 0; - stat_validity_update(&packed_refs->validity, fileno(f)); + snapshot->refs = refs; + acquire_snapshot(snapshot); + snapshot->peeled = PEELED_NONE; - dir = get_ref_dir(packed_refs->cache->root); - while (strbuf_getwholeline(&line, f, '\n') != EOF) { - struct object_id oid; - const char *refname; - const char *traits; + if (!load_contents(snapshot)) + return snapshot; - if (!line.len || line.buf[line.len - 1] != '\n') - die("unterminated line in %s: %s", packed_refs_file, line.buf); + /* If the file has a header line, process it: */ + if (snapshot->buf < snapshot->eof && *snapshot->buf == '#') { + struct strbuf tmp = STRBUF_INIT; + char *p; + const char *eol; + struct string_list traits = STRING_LIST_INIT_NODUP; - if (skip_prefix(line.buf, "# pack-refs with:", &traits)) { - if (strstr(traits, " fully-peeled ")) - peeled = PEELED_FULLY; - else if (strstr(traits, " peeled ")) - peeled = PEELED_TAGS; - /* perhaps other traits later as well */ - continue; - } + eol = memchr(snapshot->buf, '\n', + snapshot->eof - snapshot->buf); + if (!eol) + die_unterminated_line(refs->path, + snapshot->buf, + snapshot->eof - snapshot->buf); - refname = parse_ref_line(&line, &oid); - if (refname) { - int flag = REF_ISPACKED; + strbuf_add(&tmp, snapshot->buf, eol - snapshot->buf); - if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) { - if (!refname_is_safe(refname)) - die("packed refname is dangerous: %s", refname); - oidclr(&oid); - flag |= REF_BAD_NAME | REF_ISBROKEN; - } - last = create_ref_entry(refname, &oid, flag); - if (peeled == PEELED_FULLY || - (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/"))) - last->flag |= REF_KNOWS_PEELED; - add_ref_entry(dir, last); - } else if (last && - line.buf[0] == '^' && - line.len == PEELED_LINE_LENGTH && - line.buf[PEELED_LINE_LENGTH - 1] == '\n' && - !get_oid_hex(line.buf + 1, &oid)) { - oidcpy(&last->u.value.peeled, &oid); - /* - * Regardless of what the file header said, - * we definitely know the value of *this* - * reference: - */ - last->flag |= REF_KNOWS_PEELED; - } else { - strbuf_setlen(&line, line.len - 1); - die("unexpected line in %s: %s", packed_refs_file, line.buf); - } + if (!skip_prefix(tmp.buf, "# pack-refs with:", (const char **)&p)) + die_invalid_line(refs->path, + snapshot->buf, + snapshot->eof - snapshot->buf); + + string_list_split_in_place(&traits, p, ' ', -1); + + if (unsorted_string_list_has_string(&traits, "fully-peeled")) + snapshot->peeled = PEELED_FULLY; + else if (unsorted_string_list_has_string(&traits, "peeled")) + snapshot->peeled = PEELED_TAGS; + + sorted = unsorted_string_list_has_string(&traits, "sorted"); + + /* perhaps other traits later as well */ + + /* The "+ 1" is for the LF character. */ + snapshot->header_len = eol + 1 - snapshot->buf; + + string_list_clear(&traits, 0); + strbuf_release(&tmp); } - fclose(f); - strbuf_release(&line); + verify_buffer_safe(snapshot); - return packed_refs; + if (!sorted) { + sort_snapshot(snapshot); + + /* + * Reordering the records might have moved a short one + * to the end of the buffer, so verify the buffer's + * safety again: + */ + verify_buffer_safe(snapshot); + } + + if (mmap_strategy != MMAP_OK && snapshot->mmapped) { + /* + * We don't want to leave the file mmapped, so we are + * forced to make a copy now: + */ + size_t size = snapshot->eof - + (snapshot->buf + snapshot->header_len); + char *buf_copy = xmalloc(size); + + memcpy(buf_copy, snapshot->buf + snapshot->header_len, size); + clear_snapshot_buffer(snapshot); + snapshot->buf = buf_copy; + snapshot->eof = buf_copy + size; + } + + return snapshot; } /* - * Check that the packed refs cache (if any) still reflects the - * contents of the file. If not, clear the cache. + * Check that `refs->snapshot` (if present) still reflects the + * contents of the `packed-refs` file. If not, clear the snapshot. */ -static void validate_packed_ref_cache(struct packed_ref_store *refs) +static void validate_snapshot(struct packed_ref_store *refs) { - if (refs->cache && - !stat_validity_check(&refs->cache->validity, refs->path)) - clear_packed_ref_cache(refs); + if (refs->snapshot && + !stat_validity_check(&refs->snapshot->validity, refs->path)) + clear_snapshot(refs); } /* - * Get the packed_ref_cache for the specified packed_ref_store, - * creating and populating it if it hasn't been read before or if the - * file has been changed (according to its `validity` field) since it - * was last read. On the other hand, if we hold the lock, then assume - * that the file hasn't been changed out from under us, so skip the - * extra `stat()` call in `stat_validity_check()`. + * Get the `snapshot` for the specified packed_ref_store, creating and + * populating it if it hasn't been read before or if the file has been + * changed (according to its `validity` field) since it was last read. + * On the other hand, if we hold the lock, then assume that the file + * hasn't been changed out from under us, so skip the extra `stat()` + * call in `stat_validity_check()`. This function does *not* increase + * the snapshot's reference count on behalf of the caller. */ -static struct packed_ref_cache *get_packed_ref_cache(struct packed_ref_store *refs) +static struct snapshot *get_snapshot(struct packed_ref_store *refs) { if (!is_lock_file_locked(&refs->lock)) - validate_packed_ref_cache(refs); + validate_snapshot(refs); - if (!refs->cache) - refs->cache = read_packed_refs(refs->path); + if (!refs->snapshot) + refs->snapshot = create_snapshot(refs); - return refs->cache; -} - -static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache) -{ - return get_ref_dir(packed_ref_cache->cache->root); -} - -static struct ref_dir *get_packed_refs(struct packed_ref_store *refs) -{ - return get_packed_ref_dir(get_packed_ref_cache(refs)); -} - -/* - * Return the ref_entry for the given refname from the packed - * references. If it does not exist, return NULL. - */ -static struct ref_entry *get_packed_ref(struct packed_ref_store *refs, - const char *refname) -{ - return find_ref_entry(get_packed_refs(refs), refname); + return refs->snapshot; } static int packed_read_raw_ref(struct ref_store *ref_store, @@ -324,69 +721,147 @@ static int packed_read_raw_ref(struct ref_store *ref_store, { struct packed_ref_store *refs = packed_downcast(ref_store, REF_STORE_READ, "read_raw_ref"); - - struct ref_entry *entry; + struct snapshot *snapshot = get_snapshot(refs); + const char *rec; *type = 0; - entry = get_packed_ref(refs, refname); - if (!entry) { + rec = find_reference_location(snapshot, refname, 1); + + if (!rec) { + /* refname is not a packed reference. */ errno = ENOENT; return -1; } - hashcpy(sha1, entry->u.value.oid.hash); + if (get_sha1_hex(rec, sha1)) + die_invalid_line(refs->path, rec, snapshot->eof - rec); + *type = REF_ISPACKED; return 0; } -static int packed_peel_ref(struct ref_store *ref_store, - const char *refname, unsigned char *sha1) -{ - struct packed_ref_store *refs = - packed_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB, - "peel_ref"); - struct ref_entry *r = get_packed_ref(refs, refname); - - if (!r || peel_entry(r, 0)) - return -1; - - hashcpy(sha1, r->u.value.peeled.hash); - return 0; -} +/* + * This value is set in `base.flags` if the peeled value of the + * current reference is known. In that case, `peeled` contains the + * correct peeled value for the reference, which might be `null_sha1` + * if the reference is not a tag or if it is broken. + */ +#define REF_KNOWS_PEELED 0x40 +/* + * An iterator over a snapshot of a `packed-refs` file. + */ struct packed_ref_iterator { struct ref_iterator base; - struct packed_ref_cache *cache; - struct ref_iterator *iter0; + struct snapshot *snapshot; + + /* The current position in the snapshot's buffer: */ + const char *pos; + + /* The end of the part of the buffer that will be iterated over: */ + const char *eof; + + /* Scratch space for current values: */ + struct object_id oid, peeled; + struct strbuf refname_buf; + unsigned int flags; }; +/* + * Move the iterator to the next record in the snapshot, without + * respect for whether the record is actually required by the current + * iteration. Adjust the fields in `iter` and return `ITER_OK` or + * `ITER_DONE`. This function does not free the iterator in the case + * of `ITER_DONE`. + */ +static int next_record(struct packed_ref_iterator *iter) +{ + const char *p = iter->pos, *eol; + + strbuf_reset(&iter->refname_buf); + + if (iter->pos == iter->eof) + return ITER_DONE; + + iter->base.flags = REF_ISPACKED; + + if (iter->eof - p < GIT_SHA1_HEXSZ + 2 || + parse_oid_hex(p, &iter->oid, &p) || + !isspace(*p++)) + die_invalid_line(iter->snapshot->refs->path, + iter->pos, iter->eof - iter->pos); + + eol = memchr(p, '\n', iter->eof - p); + if (!eol) + die_unterminated_line(iter->snapshot->refs->path, + iter->pos, iter->eof - iter->pos); + + strbuf_add(&iter->refname_buf, p, eol - p); + iter->base.refname = iter->refname_buf.buf; + + if (check_refname_format(iter->base.refname, REFNAME_ALLOW_ONELEVEL)) { + if (!refname_is_safe(iter->base.refname)) + die("packed refname is dangerous: %s", + iter->base.refname); + oidclr(&iter->oid); + iter->base.flags |= REF_BAD_NAME | REF_ISBROKEN; + } + if (iter->snapshot->peeled == PEELED_FULLY || + (iter->snapshot->peeled == PEELED_TAGS && + starts_with(iter->base.refname, "refs/tags/"))) + iter->base.flags |= REF_KNOWS_PEELED; + + iter->pos = eol + 1; + + if (iter->pos < iter->eof && *iter->pos == '^') { + p = iter->pos + 1; + if (iter->eof - p < GIT_SHA1_HEXSZ + 1 || + parse_oid_hex(p, &iter->peeled, &p) || + *p++ != '\n') + die_invalid_line(iter->snapshot->refs->path, + iter->pos, iter->eof - iter->pos); + iter->pos = p; + + /* + * Regardless of what the file header said, we + * definitely know the value of *this* reference. But + * we suppress it if the reference is broken: + */ + if ((iter->base.flags & REF_ISBROKEN)) { + oidclr(&iter->peeled); + iter->base.flags &= ~REF_KNOWS_PEELED; + } else { + iter->base.flags |= REF_KNOWS_PEELED; + } + } else { + oidclr(&iter->peeled); + } + + return ITER_OK; +} + static int packed_ref_iterator_advance(struct ref_iterator *ref_iterator) { struct packed_ref_iterator *iter = (struct packed_ref_iterator *)ref_iterator; int ok; - while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) { + while ((ok = next_record(iter)) == ITER_OK) { if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY && - ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE) + ref_type(iter->base.refname) != REF_TYPE_PER_WORKTREE) continue; if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) && - !ref_resolves_to_object(iter->iter0->refname, - iter->iter0->oid, - iter->iter0->flags)) + !ref_resolves_to_object(iter->base.refname, &iter->oid, + iter->flags)) continue; - iter->base.refname = iter->iter0->refname; - iter->base.oid = iter->iter0->oid; - iter->base.flags = iter->iter0->flags; return ITER_OK; } - iter->iter0 = NULL; if (ref_iterator_abort(ref_iterator) != ITER_DONE) ok = ITER_ERROR; @@ -399,7 +874,14 @@ static int packed_ref_iterator_peel(struct ref_iterator *ref_iterator, struct packed_ref_iterator *iter = (struct packed_ref_iterator *)ref_iterator; - return ref_iterator_peel(iter->iter0, peeled); + if ((iter->base.flags & REF_KNOWS_PEELED)) { + oidcpy(peeled, &iter->peeled); + return is_null_oid(&iter->peeled) ? -1 : 0; + } else if ((iter->base.flags & (REF_ISBROKEN | REF_ISSYMREF))) { + return -1; + } else { + return !!peel_object(iter->oid.hash, peeled->hash); + } } static int packed_ref_iterator_abort(struct ref_iterator *ref_iterator) @@ -408,10 +890,8 @@ static int packed_ref_iterator_abort(struct ref_iterator *ref_iterator) (struct packed_ref_iterator *)ref_iterator; int ok = ITER_DONE; - if (iter->iter0) - ok = ref_iterator_abort(iter->iter0); - - release_packed_ref_cache(iter->cache); + strbuf_release(&iter->refname_buf); + release_snapshot(iter->snapshot); base_ref_iterator_free(ref_iterator); return ok; } @@ -427,6 +907,8 @@ static struct ref_iterator *packed_ref_iterator_begin( const char *prefix, unsigned int flags) { struct packed_ref_store *refs; + struct snapshot *snapshot; + const char *start; struct packed_ref_iterator *iter; struct ref_iterator *ref_iterator; unsigned int required_flags = REF_STORE_READ; @@ -435,22 +917,40 @@ static struct ref_iterator *packed_ref_iterator_begin( required_flags |= REF_STORE_ODB; refs = packed_downcast(ref_store, required_flags, "ref_iterator_begin"); + /* + * Note that `get_snapshot()` internally checks whether the + * snapshot is up to date with what is on disk, and re-reads + * it if not. + */ + snapshot = get_snapshot(refs); + + if (!snapshot->buf) + return empty_ref_iterator_begin(); + iter = xcalloc(1, sizeof(*iter)); ref_iterator = &iter->base; - base_ref_iterator_init(ref_iterator, &packed_ref_iterator_vtable); + base_ref_iterator_init(ref_iterator, &packed_ref_iterator_vtable, 1); - /* - * Note that get_packed_ref_cache() internally checks whether - * the packed-ref cache is up to date with what is on disk, - * and re-reads it if not. - */ + iter->snapshot = snapshot; + acquire_snapshot(snapshot); - iter->cache = get_packed_ref_cache(refs); - acquire_packed_ref_cache(iter->cache); - iter->iter0 = cache_ref_iterator_begin(iter->cache->cache, prefix, 0); + if (prefix && *prefix) + start = find_reference_location(snapshot, prefix, 0); + else + start = snapshot->buf + snapshot->header_len; + + iter->pos = start; + iter->eof = snapshot->eof; + strbuf_init(&iter->refname_buf, 0); + + iter->base.oid = &iter->oid; iter->flags = flags; + if (prefix && *prefix) + /* Stop iteration after we've gone *past* prefix: */ + ref_iterator = prefix_ref_iterator_begin(ref_iterator, prefix, 0); + return ref_iterator; } @@ -505,19 +1005,19 @@ int packed_refs_lock(struct ref_store *ref_store, int flags, struct strbuf *err) /* * Now that we hold the `packed-refs` lock, make sure that our - * cache matches the current version of the file. Normally - * `get_packed_ref_cache()` does that for us, but that - * function assumes that when the file is locked, any existing - * cache is still valid. We've just locked the file, but it - * might have changed the moment *before* we locked it. + * snapshot matches the current version of the file. Normally + * `get_snapshot()` does that for us, but that function + * assumes that when the file is locked, any existing snapshot + * is still valid. We've just locked the file, but it might + * have changed the moment *before* we locked it. */ - validate_packed_ref_cache(refs); + validate_snapshot(refs); /* * Now make sure that the packed-refs file as it exists in the - * locked state is loaded into the cache: + * locked state is loaded into the snapshot: */ - get_packed_ref_cache(refs); + get_snapshot(refs); return 0; } @@ -544,11 +1044,15 @@ int packed_refs_is_locked(struct ref_store *ref_store) } /* - * The packed-refs header line that we write out. Perhaps other - * traits will be added later. The trailing space is required. + * The packed-refs header line that we write out. Perhaps other traits + * will be added later. + * + * Note that earlier versions of Git used to parse these traits by + * looking for " trait " in the line. For this reason, the space after + * the colon and the trailing space are required. */ static const char PACKED_REFS_HEADER[] = - "# pack-refs with: peeled fully-peeled \n"; + "# pack-refs with: peeled fully-peeled sorted \n"; static int packed_init_db(struct ref_store *ref_store, struct strbuf *err) { @@ -557,9 +1061,9 @@ static int packed_init_db(struct ref_store *ref_store, struct strbuf *err) } /* - * Write the packed-refs from the cache to the packed-refs tempfile, - * incorporating any changes from `updates`. `updates` must be a - * sorted string list whose keys are the refnames and whose util + * Write the packed refs from the current snapshot to the packed-refs + * tempfile, incorporating any changes from `updates`. `updates` must + * be a sorted string list whose keys are the refnames and whose util * values are `struct ref_update *`. On error, rollback the tempfile, * write an error message to `err`, and return a nonzero value. * @@ -729,8 +1233,8 @@ static int write_with_updates(struct packed_ref_store *refs, } if (ok != ITER_DONE) { - strbuf_addf(err, "unable to write packed-refs file: " - "error iterating over old contents"); + strbuf_addstr(err, "unable to write packed-refs file: " + "error iterating over old contents"); goto error; } @@ -802,9 +1306,10 @@ static int packed_transaction_prepare(struct ref_store *ref_store, /* * Note that we *don't* skip transactions with zero updates, * because such a transaction might be executed for the side - * effect of ensuring that all of the references are peeled. - * If the caller wants to optimize away empty transactions, it - * should do so itself. + * effect of ensuring that all of the references are peeled or + * ensuring that the `packed-refs` file is sorted. If the + * caller wants to optimize away empty transactions, it should + * do so itself. */ data = xcalloc(1, sizeof(*data)); @@ -870,6 +1375,8 @@ static int packed_transaction_finish(struct ref_store *ref_store, int ret = TRANSACTION_GENERIC_ERROR; char *packed_refs_path; + clear_snapshot(refs); + packed_refs_path = get_locked_file_path(&refs->lock); if (rename_tempfile(&refs->tempfile, packed_refs_path)) { strbuf_addf(err, "error replacing %s: %s", @@ -877,7 +1384,6 @@ static int packed_transaction_finish(struct ref_store *ref_store, goto cleanup; } - clear_packed_ref_cache(refs); ret = 0; cleanup: @@ -966,6 +1472,13 @@ static int packed_rename_ref(struct ref_store *ref_store, die("BUG: packed reference store does not support renaming references"); } +static int packed_copy_ref(struct ref_store *ref_store, + const char *oldrefname, const char *newrefname, + const char *logmsg) +{ + die("BUG: packed reference store does not support copying references"); +} + static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_store) { return empty_ref_iterator_begin(); @@ -1027,10 +1540,10 @@ struct ref_storage_be refs_be_packed = { packed_initial_transaction_commit, packed_pack_refs, - packed_peel_ref, packed_create_symref, packed_delete_refs, packed_rename_ref, + packed_copy_ref, packed_ref_iterator_begin, packed_read_raw_ref, |