func newWriter(ctx context.Context, objC obj.Client, prefix string) *Writer {
	// Initialize buzhash64 with WindowSize window.
	hash := buzhash64.New()
	hash.Write(make([]byte, WindowSize))
	return &Writer{
		ctx:       ctx,
		objC:      objC,
		prefix:    prefix,
		cbs:       []func([]*DataRef) error{},
		buf:       &bytes.Buffer{},
		hash:      hash,
		splitMask: (1 << uint64(AverageBits)) - 1,
	}
}
func newWriter(ctx context.Context, objC obj.Client, prefix string) *Writer {
	// Initialize buzhash64 with WindowSize window.
	hash := buzhash64.New()
	hash.Write(make([]byte, WindowSize))
	return &Writer{
		ctx:       ctx,
		objC:      objC,
		prefix:    prefix,
		cbs:       []func([]*DataRef) error{},
		buf:       &bytes.Buffer{},
		hash:      hash,
		splitMask: (1 << uint64(AverageBits)) - 1,
	}
}
// newWriter creates a new Writer.