4. Write the Smalltalk Prim-Calling Method
This is the high-level method that will call the direct primitive method. It is generally part of one of your "application" classes. In class PrimMIDIPort, instance side, "primitives" protocol, I have the following,
"Read the data from the receiver into the argument (a MIDIPacket)."
| len | "reads packet header and data, answers amt. of data read"
len := self primReadPacket: packet data: packet data.
len >= 0
ifFalse: [...What to do on bad return value rather than failure...].
In Siren, this is called by a read loop that's triggered by a semaphore coming up from the VM, but that's outside of the scope here.
The actual primitive methods generally have names that start with "prim" as shown above.