+/*
+ * 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 err = 0;
+ if (!s->file_valid)
+ die("internal error: asking to populate invalid file.");
+ if (S_ISDIR(s->mode))
+ return -1;
+
+ 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 (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];
+ 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 = 0;
+}
+