Class description
This class represents the current state of a checksum-process checksum calculation. It has an associated external console application running until it is disposed. You may call add-checksum-bytes multiple times to pipe data to the external utility. When finished, call get-checksum to receive the result and terminate the process, or dispose to discard the result and terminate the process. After the first get-checksum call the returned value is stored in the result slot, and subsequent calls return the same value.

It is not possible to add more data to the checksum after the first get-checksum call.

Most code should use with-checksum-state to make sure the external process is disposed of. Higher level words like checksum-bytes and checksum-stream use it to perform the disposal.