+// ReadAt returns data from the cache, first retrieving it from Keep if
+// necessary.
+func (c *BlockCache) ReadAt(kc *KeepClient, locator string, p []byte, off int) (int, error) {
+ buf, err := c.Get(kc, locator)
+ if err != nil {
+ return 0, err
+ }
+ if off > len(buf) {
+ return 0, io.ErrUnexpectedEOF
+ }
+ return copy(p, buf[off:]), nil
+}
+