bool IsAvailable(const ObjectReference &ref);
void UseObject(const ObjectReference& ref);
void SetSegmentChecksum(const std::string &segment, const std::string &path,
const std::string &checksum);
bool IsAvailable(const ObjectReference &ref);
void UseObject(const ObjectReference& ref);
void SetSegmentChecksum(const std::string &segment, const std::string &path,
const std::string &checksum);