bprovider

type Segment interface {
	//Returns the address of the first free word in the segment when it was locked
	BaseAddress() uint64

	//Unlocks the segment for the StorageProvider to give to other consumers
	//Implies a flush
	Unlock()

	//Writes a slice to the segment, returns immediately
	//Returns nil if op is OK, otherwise ErrNoSpace or ErrInvalidArgument
	//It is up to the implementer to work out how to report no space immediately
	//The uint64 is the address to be used for the next write
	Write(uuid []byte, address uint64, data []byte) (uint64, error)

	//Block until all writes are complete. Note this does not imply a flush of the underlying files.
	Flush()
}

type StorageProvider interface {

	//Called at startup of a normal run
	Initialize(configprovider.Configuration, *rez.RezManager)

	//Called to create the database for the first time
	//Note that initialize is not called before this function call
	//and you can assume the program will exit shortly after this
	//function call
	CreateDatabase(cfg configprovider.Configuration, overwrite bool) error

	// Lock a segment, or block until a segment can be locked
	// Returns a Segment struct
	LockCoreSegment(uuid []byte) Segment
	LockVectorSegment(uuid []byte) Segment

	// Read the blob into the given buffer
	Read(ctx context.Context, uuid []byte, address uint64, buffer []byte) ([]byte, error)

	// Read the given version of superblock into the buffer.
	ReadSuperBlock(ctx context.Context, uuid []byte, version uint64, buffer []byte) ([]byte, error)

	// Writes a superblock of the given version
	// TODO I think the storage will need to chunk this, because sb logs of gigabytes are possible
	WriteSuperBlock(uuid []byte, version uint64, buffer []byte)

	// Sets the version of a stream. If it is in the past, it is essentially a rollback,
	// and although no space is freed, the consecutive version numbers can be reused
	// note to self: you must make sure not to call ReadSuperBlock on versions higher
	// than you get from GetStreamVersion because they might succeed
	SetStreamVersion(uuid []byte, version uint64)

	// A subset of the above, but just gets version
	GetStreamVersion(ctx context.Context, uuid []byte) (uint64, error)

	// Tombstones a uuid
	ObliterateStreamMetadata(uuid []byte)

	// Perform a background cleanup iteration. This could take a long time.
	// If it returns no error, the given uuids no longer exist (assuming they
	// were not written to while the bg task was active)
	BackgroundCleanup(uuids [][]byte) error
}