NewBuilder with finalizer of itself.

NewWriterF from https://github.com/Mrs4s/MiraiGo/blob/master/binary/writer.go.

OpenWriterF must call func cl to close from https://github.com/Mrs4s/MiraiGo/blob/master/binary/writer.go.

PutBuilder 将 Builder 放回池中.

SelectBuilder 从池中取出一个 Builder.

ToBytes from https://github.com/Mrs4s/MiraiGo/blob/master/binary/writer.go.