+ ssize_t base;
+ struct cookie *c = f->cookie;
+ if (whence>2U) {
+fail:
+ errno = EINVAL;
+ return -1;
+ }
+ base = (size_t [3]){0, c->pos, c->len}[whence];
+ if (off < -base || off > (ssize_t)c->size-base) goto fail;
+ return c->pos = base+off;
+}
+
+static size_t mread(FILE *f, unsigned char *buf, size_t len)
+{
+ struct cookie *c = f->cookie;
+ size_t rem = c->size - c->pos;
+ if (!len) return 0;