func (mem *cache) UncompressedDigest(anyDigest digest.Digest) digest.Digest {
	mem.mutex.Lock()
	defer mem.mutex.Unlock()
	return mem.uncompressedDigestLocked(anyDigest)
}
func (mem *cache) UncompressedDigest(anyDigest digest.Digest) digest.Digest {
	mem.mutex.Lock()
	defer mem.mutex.Unlock()
	return mem.uncompressedDigestLocked(anyDigest)
}
// UncompressedDigest returns an uncompressed digest corresponding to anyDigest.
// May return anyDigest if it is known to be uncompressed.
// Returns "" if nothing is known about the digest (it may be compressed or uncompressed).