// 
// Cforall Version 1.0.0 Copyright (C) 2017 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
// 
// devicedriver.cfa -- 
// 
// Author           : Peter A. Buhr
// Created On       : Sat Mar 16 15:30:34 2019
// Last Modified By : Peter A. Buhr
// Last Modified On : Tue Mar 19 15:59:06 2019
// Update Count     : 87
// 

#include <fstream.hfa>
#include <coroutine.hfa>

enum Status { CONT, MSG, ESTX, ELNTH, ECRC };
coroutine Driver {
	Status status;
	char * msg, byte;
}; // Driver

void ?{}( Driver & d, char * m ) { d.msg = m; }
Status next( Driver & d, char b ) with( d ) {
	byte = b; resume( d ); return status;
} // next

void checkCRC( Driver & d, unsigned int sum ) with( d ) {
	suspend();
	unsigned short int crc = byte << 8;					// sign extension over written
	suspend();
	// prevent sign extension for signed char
	status = (crc | (unsigned char)byte) == sum ? MSG : ECRC;
} // checkCRC

void main( Driver & d ) with( d ) {
	enum { STX = '\002', ESC = '\033', ETX = '\003', MaxMsg = 64 };
  msg: for () {											// parse message
		status = CONT;
		unsigned int lnth = 0, sum = 0;
		while ( byte != STX ) suspend();
	  emsg: for () {
			suspend();
			choose ( byte ) {							// process byte
			  case STX:
				status = ESTX; suspend(); continue msg;
			  case ETX:
				break emsg;
			  case ESC:
				suspend();
			} // choose
			if ( lnth >= MaxMsg ) {						// buffer full ?
				status = ELNTH; suspend(); continue msg;
			} // if
			msg[lnth++] = byte;
			sum += byte;
		} // for
		msg[lnth] = '\0';								// terminate string
		checkCRC( d, sum );								// refactor CRC check
		suspend();
	} // for
} // main

int main() {
	char msg[65], byte;
	Driver driver = { msg };
  eof: for () {											// read until end of file
		sin | byte;										// read one character
	  if ( eof( sin ) ) break eof;						// eof ?
		choose( next( driver, byte ) ) {				// analyse character
		  case MSG:
			sout | "msg:" | msg;
		  case ESTX:
			sout | "STX in message";
		  case ELNTH:
			sout | "message too long";
		  case ECRC:
			sout | "CRC failure";
		  default: ;
		} // choose
	} // for
} // main

// Local Variables: //
// tab-width: 4 //
// compile-command: "cfa -g -Wall -Wextra devicedriver.cfa" //
// End: //