pkg/blobinfocache/memory/memory.go
func (mem *cache) uncompressedDigestLocked(anyDigest digest.Digest) digest.Digest {
	if d, ok := mem.uncompressedDigests[anyDigest]; ok {
		return d
	}
	// Presence in digestsByUncompressed implies that anyDigest must already refer to an uncompressed digest.
	// This way we don't have to waste storage space with trivial (uncompressed, uncompressed) mappings
	// when we already record a (compressed, uncompressed) pair.
	if m, ok := mem.digestsByUncompressed[anyDigest]; ok && len(m) > 0 {
		return anyDigest
	}
	return ""
}
func (mem *cache) uncompressedDigestLocked(anyDigest digest.Digest) digest.Digest {
	if d, ok := mem.uncompressedDigests[anyDigest]; ok {
		return d
	}
	// Presence in digestsByUncompressed implies that anyDigest must already refer to an uncompressed digest.
	// This way we don't have to waste storage space with trivial (uncompressed, uncompressed) mappings
	// when we already record a (compressed, uncompressed) pair.
	if m, ok := mem.digestsByUncompressed[anyDigest]; ok && len(m) > 0 {
		return anyDigest
	}
	return ""
}
// uncompressedDigestLocked implements types.BlobInfoCache.UncompressedDigest, but must be called only with mem.mutex held.