+static struct sha1_size_cache {
+ unsigned char sha1[20];
+ unsigned long size;
+} **sha1_size_cache;
+static int sha1_size_cache_nr, sha1_size_cache_alloc;
+
+static struct sha1_size_cache *locate_size_cache(unsigned char *sha1,
+ int find_only,
+ unsigned long size)
+{
+ int first, last;
+ struct sha1_size_cache *e;
+
+ first = 0;
+ last = sha1_size_cache_nr;
+ while (last > first) {
+ int cmp, next = (last + first) >> 1;
+ e = sha1_size_cache[next];
+ cmp = memcmp(e->sha1, sha1, 20);
+ if (!cmp)
+ return e;
+ if (cmp < 0) {
+ last = next;
+ continue;
+ }
+ first = next+1;
+ }
+ /* not found */
+ if (find_only)
+ return NULL;
+ /* insert to make it at "first" */
+ if (sha1_size_cache_alloc <= sha1_size_cache_nr) {
+ sha1_size_cache_alloc = alloc_nr(sha1_size_cache_alloc);
+ sha1_size_cache = xrealloc(sha1_size_cache,
+ sha1_size_cache_alloc *
+ sizeof(*sha1_size_cache));
+ }
+ sha1_size_cache_nr++;
+ if (first < sha1_size_cache_nr)
+ memmove(sha1_size_cache + first + 1, sha1_size_cache + first,
+ (sha1_size_cache_nr - first - 1) *
+ sizeof(*sha1_size_cache));
+ e = xmalloc(sizeof(struct sha1_size_cache));
+ sha1_size_cache[first] = e;
+ memcpy(e->sha1, sha1, 20);
+ e->size = size;
+ return e;
+}
+
+/*
+ * While doing rename detection and pickaxe operation, we may need to
+ * grab the data for the blob (or file) for our own in-core comparison.
+ * diff_filespec has data and size fields for this purpose.
+ */
+int diff_populate_filespec(struct diff_filespec *s, int size_only)
+{
+ int err = 0;
+ if (!DIFF_FILE_VALID(s))
+ die("internal error: asking to populate invalid file.");
+ if (S_ISDIR(s->mode))
+ return -1;
+
+ if (!use_size_cache)
+ size_only = 0;
+
+ if (s->data)
+ return err;
+ if (!s->sha1_valid ||
+ work_tree_matches(s->path, s->sha1)) {
+ struct stat st;
+ int fd;
+ if (lstat(s->path, &st) < 0) {
+ if (errno == ENOENT) {
+ err_empty:
+ err = -1;
+ empty:
+ s->data = "";
+ s->size = 0;
+ return err;
+ }
+ }
+ s->size = st.st_size;
+ if (!s->size)
+ goto empty;
+ if (size_only)
+ return 0;
+ if (S_ISLNK(st.st_mode)) {
+ int ret;
+ s->data = xmalloc(s->size);
+ s->should_free = 1;
+ ret = readlink(s->path, s->data, s->size);
+ if (ret < 0) {
+ free(s->data);
+ goto err_empty;
+ }
+ return 0;
+ }
+ fd = open(s->path, O_RDONLY);
+ if (fd < 0)
+ goto err_empty;
+ s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
+ s->should_munmap = 1;
+ close(fd);
+ }
+ else {
+ char type[20];
+ struct sha1_size_cache *e;
+
+ if (size_only) {
+ e = locate_size_cache(s->sha1, 1, 0);
+ if (e) {
+ s->size = e->size;
+ return 0;
+ }
+ if (!sha1_object_info(s->sha1, type, &s->size))
+ locate_size_cache(s->sha1, 0, s->size);
+ }
+ else {
+ s->data = read_sha1_file(s->sha1, type, &s->size);
+ s->should_free = 1;
+ }
+ }
+ return 0;
+}
+
+void diff_free_filespec_data(struct diff_filespec *s)
+{
+ if (s->should_free)
+ free(s->data);
+ else if (s->should_munmap)
+ munmap(s->data, s->size);
+ s->should_free = s->should_munmap = 0;
+ s->data = NULL;
+}
+