XModem.cpp

// This code was taken from: https://github.com/mgk/arduino-xmodem
// (https://code.google.com/archive/p/arduino-xmodem)
// which was released under GPL V3:
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation,
// Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
// -----------------------------------------------------------------------------

#include <stdio.h>
#include <string.h>

#include "XModem.h"
#ifdef UTEST
#include "CppUTestExt/MockSupport.h"
#endif
const unsigned char XModem::NACK = 21;
const unsigned char XModem::ACK =  6;

const unsigned char XModem::SOH =  1;
const unsigned char XModem::EOT =  4;
const unsigned char XModem::CAN =  0x18;

const int XModem::receiveDelay=7000;
const int XModem::rcvRetryLimit = 10;




XModem::XModem(int (*recvChar)(int msDelay),
               void (*sendData)(const char *data, int len))
{
	this->sendData = sendData;
	this->recvChar = recvChar;
	this->dataHandler = NULL;
	
}
XModem::XModem(int (*recvChar)(int msDelay),
               void (*sendData)(const char *data, int len),
               bool (*dataHandler)(unsigned long number, char *buffer, int len))
{
	this->sendData = sendData;
	this->recvChar = recvChar;
	this->dataHandler = dataHandler;
	
}

bool XModem::dataAvail(int delay)
{
	if (this->byte != -1)
		return true;
	if ((this->byte = this->recvChar(delay)) != -1)
		return true;
	else
		return false;
		
}
int XModem::dataRead(int delay)
{
	int b;
	if(this->byte != -1)
	{
		b = this->byte;
		this->byte = -1;
		return b;
	}
	return this->recvChar(delay);
}
void XModem::dataWrite(char symbol)
{
  this->sendData(&symbol, 1);
}
bool XModem::receiveFrameNo()
{
	unsigned char num = 
		(unsigned char)this->dataRead(XModem::receiveDelay);
	unsigned char invnum = 
		(unsigned char)this->dataRead(XModem::receiveDelay);
	this->repeatedBlock = false;
	//check for repeated block
	if (invnum == (255-num) && num == this->blockNo-1) {
		this->repeatedBlock = true;
		return true;	
	}
	
	if(num != this-> blockNo || invnum != (255-num))
		return false;
	else
		return true;
}
bool XModem::receiveData()
{
	for(int i = 0; i < 128; i++) {
		int byte = this->dataRead(XModem::receiveDelay);
		if(byte != -1)
			this->buffer[i] = (unsigned char)byte;
		else
			return false;
	}
	return true;	
}
bool XModem::checkCrc()
{
	unsigned short frame_crc = ((unsigned char)this->
				dataRead(XModem::receiveDelay)) << 8;
	
	frame_crc |= (unsigned char)this->dataRead(XModem::receiveDelay);
	//now calculate crc on data
	unsigned short crc = this->crc16_ccitt(this->buffer, 128);
	
	if(frame_crc != crc)
		return false;
	else
		return true;
	
}
bool XModem::checkChkSum()
{
	unsigned char frame_chksum = (unsigned char)this->
						dataRead(XModem::receiveDelay);
	//calculate chksum
	unsigned char chksum = 0;
	for(int i = 0; i< 128; i++) {
		chksum += this->buffer[i];
	}
	if(frame_chksum == chksum)
		return true;
	else
		return false;
}
bool XModem::sendNack()
{
	this->dataWrite(XModem::NACK);	
	this->retries++;
	if(this->retries < XModem::rcvRetryLimit)
		return true;
	else
		return false;
	
}
bool XModem::receiveFrames(transfer_t transfer)
{
	this->blockNo = 1;
	this->blockNoExt = 1;
	this->retries = 0;
	while (1) {
		char cmd = this->dataRead(1000);
		switch(cmd){
			case XModem::SOH:
				if (!this->receiveFrameNo()) {
					if (this->sendNack())
						break;
					else
						return false;
				}
				if (!this->receiveData()) {	
					if (this->sendNack())
						break;
					else
						return false;
					
				};
				if (transfer == Crc) {
					if (!this->checkCrc()) {
						if (this->sendNack())
							break;
						else
							return false;
					}
				} else {
					if(!this->checkChkSum()) {
						if (this->sendNack())
							break;
						else
							return false;
					}
				}
				//callback
				if(this->dataHandler != NULL && 
				   this->repeatedBlock == false)
					if(!this->dataHandler(this->blockNoExt, 
							  this->buffer, 128)) {
						return false;
					}
				//ack
				this->dataWrite(XModem::ACK);
				if(this->repeatedBlock == false)
				{
					this->blockNo++;
					this->blockNoExt++;
				}
                                this->retries = 0;
				break;
			case XModem::EOT:
				this->dataWrite(XModem::ACK);
				return true;
			case XModem::CAN:
				//wait second CAN
				if(this->dataRead(XModem::receiveDelay) ==
						XModem::CAN) {
					this->dataWrite(XModem::ACK);
					//this->flushInput();
					return false;
				}
				//something wrong
				this->dataWrite(XModem::CAN);
				this->dataWrite(XModem::CAN);
				this->dataWrite(XModem::CAN);
				return false;
			default:
				//something wrong
				this->dataWrite(XModem::CAN);
				this->dataWrite(XModem::CAN);
				this->dataWrite(XModem::CAN);
				return false;
		}
		
	}
}
void XModem::init()
{
	//set preread byte  	
	this->byte = -1;
}
bool XModem::receive()
{
	this->init();
	
	for (int i =0; i <  128; i++)
	{
		this->dataWrite('C');	
		if (this->dataAvail(1000)) 
			return receiveFrames(Crc);
	
	}
	for (int i =0; i <  128; i++)
	{
		this->dataWrite(XModem::NACK);	
		if (this->dataAvail(1000)) 
			return receiveFrames(ChkSum);
	}
  return false;
}
unsigned short XModem::crc16_ccitt(char *buf, int size)
{
	unsigned short crc = 0;
	while (--size >= 0) {
		int i;
		crc ^= (unsigned short) *buf++ << 8;
		for (i = 0; i < 8; i++)
			if (crc & 0x8000)
				crc = crc << 1 ^ 0x1021;
			else
				crc <<= 1;
	}
	return crc;
}
unsigned char XModem::generateChkSum(const char *buf, int len)
{
	//calculate chksum
	unsigned char chksum = 0;
	for(int i = 0; i< len; i++) {
		chksum += buf[i];
	}
	return chksum;
	
}

bool XModem::transmitFrames(transfer_t transfer)
{
	this->blockNo = 1;
	this->blockNoExt = 1;
	// use this only in unit tetsing
	//memset(this->buffer, 'A', 128);
	while(1)
	{
		//get data
		if (this->dataHandler != NULL)
		{
			if( false == 
			    this->dataHandler(this->blockNoExt, this->buffer+3, 
			    128))
			{
				//end of transfer
				this->dataWrite(XModem::EOT);
				//wait ACK
				if (this->dataRead(XModem::receiveDelay) == 
					XModem::ACK)
					return true;
				else
					return false;

			}			
			
		}
		else
		{
			//cancel transfer - send CAN twice
			this->dataWrite(XModem::CAN);
			this->dataWrite(XModem::CAN);
			//wait ACK
			if (this->dataRead(XModem::receiveDelay) == 
				XModem::ACK)
				return true;
			else
				return false;
		}
		//SOH
                buffer[0] = XModem::SOH;
		//frame number
		buffer[1] = this->blockNo;
		//inv frame number
		buffer[2] = (unsigned char)(255-(this->blockNo));
		//(data is already in buffer starting at byte 3)
		//checksum or crc
		if (transfer == ChkSum) {
                  buffer[3+128] = this->generateChkSum(buffer+3, 128);
                  this->sendData(buffer, 3+128+1);
		} else {
                  unsigned short crc;
                  crc = this->crc16_ccitt(this->buffer+3, 128);
                  buffer[3+128+0] = (unsigned char)(crc >> 8);
                  buffer[3+128+1] = (unsigned char)(crc);;
                  this->sendData(buffer, 3+128+2);
		}

		//TO DO - wait NACK or CAN or ACK
		int ret = this->dataRead(XModem::receiveDelay);
		switch(ret)
		{
			case XModem::ACK: //data is ok - go to next chunk
				this->blockNo++;
				this->blockNoExt++;
				continue;
			case XModem::NACK: //resend data
				continue;
			case XModem::CAN: //abort transmision
				return false;

		}
	
	}
	return false;
}
bool XModem::transmit()
{
	int retry = 0;
	int sym;
	this->init();
	
	//wait for CRC transfer
	while(retry < 256)
	{
		if(this->dataAvail(1000))
		{
			sym = this->dataRead(1); //data is here - no delay
			if(sym == 'C')	
				return this->transmitFrames(Crc);
			if(sym == XModem::NACK)
				return this->transmitFrames(ChkSum);
		}
		retry++;
	}	
	return false;
}