/*	Copyright 2001, 2002 Georges Menie (www.menie.org)    This program is free software; you can redistribute it and/or modify    it under the terms of the GNU Lesser General Public License as published by    the Free Software Foundation; either version 2 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 Lesser General Public License for more details.    You should have received a copy of the GNU Lesser General Public License    along with this program; if not, write to the Free Software    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA*/#include "baselib.h"#include "xmodem.h"#include "crc16.h"#include "xmodemdefs.h"static int check(int crc, const unsigned char *buf, int sz){	if (crc) {		unsigned short crc = crc16_ccitt(buf, sz);		unsigned short tcrc = (buf[sz]<<8)+buf[sz+1];		if (crc == tcrc)			return 1;	}	else {		int i;		unsigned char cks = 0;		for (i = 0; i < sz; ++i) {			cks += buf[i];		}		if (cks == buf[sz])		return 1;	}	return 0;}int xmodemReceive(unsigned char *dest, int destsz){	unsigned char xbuff[1030]; /* 1024 for XModem 1k + 3 head chars + 2 crc + nul */	unsigned char *p;	int bufsz, crc = 0;	unsigned char trychar = 'C';	unsigned char packetno = 1;	int i, c, len = 0;	int retry, retrans = MAXRETRANS;	for(;;) {		for( retry = 0; retry < 16; ++retry) {			if (trychar) _outbyte(trychar);			if ((c = _inbyte((DLY_1S)<<1)) >= 0) {				switch (c) {				case SOH:					bufsz = 128;					goto start_recv;				case STX:					bufsz = 1024;					goto start_recv;				case EOT:					FLUSHINPUT;					_outbyte(ACK);					return len; /* normal end */				case CAN:					if ((c = _inbyte(DLY_1S)) == CAN) {						FLUSHINPUT;						_outbyte(ACK);						return -1; /* canceled by remote */					}					break;				default:					break;				}			}		}		if (trychar == 'C') { trychar = NAK; continue; }		FLUSHINPUT;		_outbyte(CAN);		_outbyte(CAN);		_outbyte(CAN);		return -2; /* sync error */	start_recv:		if (trychar == 'C') crc = 1;		trychar = 0;		p = xbuff;		*p++ = c;		for (i = 0;  i < (bufsz+(crc?1:0)+3); ++i) {			if ((c = _inbyte(DLY_1S)) < 0) goto reject;			*p++ = c;		}		if (xbuff[1] == (unsigned char)(~xbuff[2]) && 			(xbuff[1] == packetno || xbuff[1] == (unsigned char)packetno-1) &&			check(crc, &xbuff[3], bufsz)) {			if (xbuff[1] == packetno)	{				register int count = destsz - len;				if (count > bufsz) count = bufsz;				if (count > 0) {					memcpy (&dest[len], &xbuff[3], count);					len += count;				}				++packetno;				retrans = MAXRETRANS+1;			}			if (--retrans <= 0) {				FLUSHINPUT;				_outbyte(CAN);				_outbyte(CAN);				_outbyte(CAN);				return -3; /* too many retry error */			}			_outbyte(ACK);			continue;		}	reject:		FLUSHINPUT;		_outbyte(NAK);	}}