#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+ * `get_snapshot()` is called; if the existing snapshot is obsolete, a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;
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
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)
{
return refs;
}
-static void clear_packed_ref_cache(struct packed_ref_store *refs)
+static void clear_snapshot(struct packed_ref_store *refs)
+{
+ if (refs->snapshot) {
+ struct snapshot *snapshot = refs->snapshot;
+
+ refs->snapshot = NULL;
+ release_snapshot(snapshot);
+ }
+}
+
+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)
{
- if (refs->cache) {
- struct packed_ref_cache *cache = refs->cache;
+ 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++;
+ }
+}
+
+/*
+ * Compare a snapshot record at `rec` to the specified NUL-terminated
+ * refname.
+ */
+static int cmp_record_to_refname(const char *rec, const char *refname)
+{
+ 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++;
+ }
+}
+
+/*
+ * `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;
+
+ pos = snapshot->buf + snapshot->header_len;
+ eof = snapshot->eof;
+ len = eof - pos;
- refs->cache = NULL;
- release_packed_ref_cache(cache);
+ 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);
}
-/* The length of a peeled reference line in packed-refs, including EOL: */
-#define PEELED_LINE_LENGTH 42
+/*
+ * 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;
+}
/*
- * 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.
+ * 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 *parse_ref_line(struct strbuf *line, struct object_id *oid)
+static const char *find_end_of_record(const char *p, const char *end)
{
- const char *ref;
+ while (++p < end && (p[-1] != '\n' || p[0] == '^'))
+ ;
+ return p;
+}
- if (parse_oid_hex(line->buf, oid, &ref) < 0)
- return NULL;
- if (!isspace(*ref++))
- return NULL;
+/*
+ * 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 (isspace(*ref))
- return NULL;
+ if (buf == eof)
+ return;
- if (line->buf[line->len - 1] != '\n')
- return NULL;
- line->buf[--line->len] = 0;
+ 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);
+}
+
+/*
+ * 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;
+}
+
+/*
+ * 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;
+ }
+ }
- return ref;
+ if (mustexist)
+ return NULL;
+ else
+ return lo;
}
/*
- * 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.
+ * 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
* 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 (!line.len || line.buf[line.len - 1] != '\n')
- die("unterminated line in %s: %s", packed_refs_file, line.buf);
-
- 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;
- }
+ if (!load_contents(snapshot))
+ return snapshot;
- refname = parse_ref_line(&line, &oid);
- if (refname) {
- int flag = REF_ISPACKED;
+ /* 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 (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);
- }
+ eol = memchr(snapshot->buf, '\n',
+ snapshot->eof - snapshot->buf);
+ if (!eol)
+ die_unterminated_line(refs->path,
+ snapshot->buf,
+ snapshot->eof - snapshot->buf);
+
+ strbuf_add(&tmp, snapshot->buf, eol - snapshot->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);
+
+ if (!sorted) {
+ sort_snapshot(snapshot);
- return packed_refs;
+ /*
+ * 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);
-
- if (!refs->cache)
- refs->cache = read_packed_refs(refs->path);
-
- 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);
-}
+ validate_snapshot(refs);
-static struct ref_dir *get_packed_refs(struct packed_ref_store *refs)
-{
- return get_packed_ref_dir(get_packed_ref_cache(refs));
-}
+ if (!refs->snapshot)
+ refs->snapshot = create_snapshot(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,
{
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;
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)
(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;
}
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;
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);
+
+ if (prefix && *prefix)
+ start = find_reference_location(snapshot, prefix, 0);
+ else
+ start = snapshot->buf + snapshot->header_len;
- iter->cache = get_packed_ref_cache(refs);
- acquire_packed_ref_cache(iter->cache);
- iter->iter0 = cache_ref_iterator_begin(iter->cache->cache, prefix, 0);
+ 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;
}
/*
* 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;
}
}
/*
- * 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)
{
}
/*
- * 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.
*
}
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;
}
return -1;
}
+int is_packed_transaction_needed(struct ref_store *ref_store,
+ struct ref_transaction *transaction)
+{
+ struct packed_ref_store *refs = packed_downcast(
+ ref_store,
+ REF_STORE_READ,
+ "is_packed_transaction_needed");
+ struct strbuf referent = STRBUF_INIT;
+ size_t i;
+ int ret;
+
+ if (!is_lock_file_locked(&refs->lock))
+ BUG("is_packed_transaction_needed() called while unlocked");
+
+ /*
+ * We're only going to bother returning false for the common,
+ * trivial case that references are only being deleted, their
+ * old values are not being checked, and the old `packed-refs`
+ * file doesn't contain any of those reference(s). This gives
+ * false positives for some other cases that could
+ * theoretically be optimized away:
+ *
+ * 1. It could be that the old value is being verified without
+ * setting a new value. In this case, we could verify the
+ * old value here and skip the update if it agrees. If it
+ * disagrees, we could either let the update go through
+ * (the actual commit would re-detect and report the
+ * problem), or come up with a way of reporting such an
+ * error to *our* caller.
+ *
+ * 2. It could be that a new value is being set, but that it
+ * is identical to the current packed value of the
+ * reference.
+ *
+ * Neither of these cases will come up in the current code,
+ * because the only caller of this function passes to it a
+ * transaction that only includes `delete` updates with no
+ * `old_id`. Even if that ever changes, false positives only
+ * cause an optimization to be missed; they do not affect
+ * correctness.
+ */
+
+ /*
+ * Start with the cheap checks that don't require old
+ * reference values to be read:
+ */
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+
+ if (update->flags & REF_HAVE_OLD)
+ /* Have to check the old value -> needed. */
+ return 1;
+
+ if ((update->flags & REF_HAVE_NEW) && !is_null_oid(&update->new_oid))
+ /* Have to set a new value -> needed. */
+ return 1;
+ }
+
+ /*
+ * The transaction isn't checking any old values nor is it
+ * setting any nonzero new values, so it still might be able
+ * to be skipped. Now do the more expensive check: the update
+ * is needed if any of the updates is a delete, and the old
+ * `packed-refs` file contains a value for that reference.
+ */
+ ret = 0;
+ for (i = 0; i < transaction->nr; i++) {
+ struct ref_update *update = transaction->updates[i];
+ unsigned int type;
+ struct object_id oid;
+
+ if (!(update->flags & REF_HAVE_NEW))
+ /*
+ * This reference isn't being deleted -> not
+ * needed.
+ */
+ continue;
+
+ if (!refs_read_raw_ref(ref_store, update->refname,
+ oid.hash, &referent, &type) ||
+ errno != ENOENT) {
+ /*
+ * We have to actually delete that reference
+ * -> this transaction is needed.
+ */
+ ret = 1;
+ break;
+ }
+ }
+
+ strbuf_release(&referent);
+ return ret;
+}
+
struct packed_transaction_backend_data {
/* True iff the transaction owns the packed-refs lock. */
int own_lock;
/*
* 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));
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",
goto cleanup;
}
- clear_packed_ref_cache(refs);
ret = 0;
cleanup:
packed_initial_transaction_commit,
packed_pack_refs,
- packed_peel_ref,
packed_create_symref,
packed_delete_refs,
packed_rename_ref,