+static char *pack_revindex_filename(struct packed_git *p)
+{
+ size_t len;
+ if (!strip_suffix(p->pack_name, ".pack", &len))
+ BUG("pack_name does not end in .pack");
+ return xstrfmt("%.*s.rev", (int)len, p->pack_name);
+}
+
+#define RIDX_HEADER_SIZE (12)
+#define RIDX_MIN_SIZE (RIDX_HEADER_SIZE + (2 * the_hash_algo->rawsz))
+
+struct revindex_header {
+ uint32_t signature;
+ uint32_t version;
+ uint32_t hash_id;
+};
+
+static int load_revindex_from_disk(char *revindex_name,
+ uint32_t num_objects,
+ const uint32_t **data_p, size_t *len_p)
+{
+ int fd, ret = 0;
+ struct stat st;
+ void *data = NULL;
+ size_t revindex_size;
+ struct revindex_header *hdr;
+
+ fd = git_open(revindex_name);
+
+ if (fd < 0) {
+ ret = -1;
+ goto cleanup;
+ }
+ if (fstat(fd, &st)) {
+ ret = error_errno(_("failed to read %s"), revindex_name);
+ goto cleanup;
+ }
+
+ revindex_size = xsize_t(st.st_size);
+
+ if (revindex_size < RIDX_MIN_SIZE) {
+ ret = error(_("reverse-index file %s is too small"), revindex_name);
+ goto cleanup;
+ }
+
+ if (revindex_size - RIDX_MIN_SIZE != st_mult(sizeof(uint32_t), num_objects)) {
+ ret = error(_("reverse-index file %s is corrupt"), revindex_name);
+ goto cleanup;
+ }
+
+ data = xmmap(NULL, revindex_size, PROT_READ, MAP_PRIVATE, fd, 0);
+ hdr = data;
+
+ if (ntohl(hdr->signature) != RIDX_SIGNATURE) {
+ ret = error(_("reverse-index file %s has unknown signature"), revindex_name);
+ goto cleanup;
+ }
+ if (ntohl(hdr->version) != 1) {
+ ret = error(_("reverse-index file %s has unsupported version %"PRIu32),
+ revindex_name, ntohl(hdr->version));
+ goto cleanup;
+ }
+ if (!(ntohl(hdr->hash_id) == 1 || ntohl(hdr->hash_id) == 2)) {
+ ret = error(_("reverse-index file %s has unsupported hash id %"PRIu32),
+ revindex_name, ntohl(hdr->hash_id));
+ goto cleanup;
+ }
+
+cleanup:
+ if (ret) {
+ if (data)
+ munmap(data, revindex_size);
+ } else {
+ *len_p = revindex_size;
+ *data_p = (const uint32_t *)data;
+ }
+
+ close(fd);
+ return ret;
+}
+
+static int load_pack_revindex_from_disk(struct packed_git *p)
+{
+ char *revindex_name;
+ int ret;
+ if (open_pack_index(p))
+ return -1;
+
+ revindex_name = pack_revindex_filename(p);
+
+ ret = load_revindex_from_disk(revindex_name,
+ p->num_objects,
+ &p->revindex_map,
+ &p->revindex_size);
+ if (ret)
+ goto cleanup;
+
+ p->revindex_data = (const uint32_t *)((const char *)p->revindex_map + RIDX_HEADER_SIZE);
+
+cleanup:
+ free(revindex_name);
+ return ret;
+}
+
+int load_pack_revindex(struct packed_git *p)
+{
+ if (p->revindex || p->revindex_data)
+ return 0;
+
+ if (!load_pack_revindex_from_disk(p))
+ return 0;
+ else if (!create_pack_revindex_in_memory(p))
+ return 0;
+ return -1;
+}
+
+int offset_to_pack_pos(struct packed_git *p, off_t ofs, uint32_t *pos)