Reads a txdata integer from buf at the specified offset
Buffer object from where the number will be read
Number of bytes to skip before starting to read
Size of the serialized data
the bytes size of a serialized txData
Writes value to buf at the specified offset
Buffer object where the number will be written
Number of bytes to skip before starting to write. Must satisfy
Offset plus the number of bytes that has been written
Class to handle the protocol TxData type http://dev.nuls.io/protocol/index.html#Transaction