/*
 *  UCBOOT -- UC Boot for Receive-Only
 *	UCBOOT is a minimum program which receives a file via FTP 3,
 *		converts it into UNIX text file format from CP/M text file
 *		format, and stores it under the name ucboot.txt
 *	Version 1.0
 *	by Richard Conn
 */
#define	FALSE	0
#define	TRUE	~FALSE

/*  ASCII Characters  */
#define	SOH	001
#define	EOT	004
#define	ACK	006
#define	CR	015
#define	NAK	025
#define	CAN	030
#define	CTRLZ	032

/*  UC Constants  */
#define	TO	-1		/* Timeout Flag */
#define	ERRMAX	10		/* Max errors tolerated */
#define	BLOCKSZ	128		/* Size of transmission block */
#define	CREATE	0644		/* Mode for New Files */
#define	DEST	"ucboot.txt"	/* Log File */

/*  Library Utilities  */
#include	<stdio.h>
#include	<sys/types.h>
#include	<sys/stat.h>
#include	<sgtty.h>
#include	<signal.h>
#include	<ctype.h>

main ()
{
	int fd;			/* file descriptor */
	int blocknum;		/* next block to receive */
	int rbcnt;		/* total number of received blocks */
	int errorcnt;		/* number of errors on current block */
	int receiving;		/* continuation flag */
	int char1;		/* first char received in block */
	int rcode;		/* received block code */

	if (!access(DEST,2))
		printf("File %s Exists -- Deleting", DEST);
	unlink(DEST);
	if ((fd = creat(DEST, CREATE)) == -1) {
		printf("Can't Create %s\n", DEST);
		return;
	}

	printf("UCBOOT Receiving File %s via FTP 3\n", DEST);
	printf("Ready to Receive\n");

	blocknum = 1;
	rbcnt = 0;
	errorcnt = 0;
	receiving = TRUE;

	binary(TRUE);

	sendbyte(NAK);

	while (receiving) {
		do {
			char1 = recvbyte(6);
		} 
		while ((char1 != SOH) && (char1 != EOT) && (char1 != TO));
		switch (char1) {
		case TO :
			if (++errorcnt == ERRMAX) {
				close(fd);
				sleep(3);
				binary(FALSE);
				receiving = FALSE;
			}
			sendbyte(NAK);
			break;
		case EOT :
			sendbyte(ACK);
			while (recvbyte(3) != TO);
			close(fd);
			sleep(3);
			binary(FALSE);
			receiving = FALSE;
			break;
		case SOH :
			rcode = getblock(fd,blocknum);
			switch (rcode) {
			case 0 :
				errorcnt = 0;
				blocknum = ++blocknum & 0xff;
				rbcnt++;
				sendbyte(ACK);
				break;
			case 1 :
				if (++errorcnt < ERRMAX) { 
					sendbyte(NAK);
					break;
				}
			default :
				close(fd);
				sendbyte(CAN);
				binary(FALSE);
				while (recvbyte(3) != TO);
				receiving = FALSE;
				break;
			}
			break;
		}
	}
}

getblock(fd,blocknum)
int fd, blocknum;
{
	int curblock, cmpblock, delay;
	int recdone, checksum, inchecksum, byte, bufcnt, c;
	int errflg, errchr;
	char buff[BLOCKSZ];

	curblock = recvbyte(3);
	if (curblock == TO) return(1);
	cmpblock = recvbyte(3);
	if (curblock == TO) return(1);
	if ((curblock + cmpblock) != 0xff) {
		while (recvbyte(3) != TO);
		return(1);
	}
	checksum = 0;
	byte = 0;
	recdone = FALSE;
	for (bufcnt=0; bufcnt<BLOCKSZ; bufcnt++) {
		c = recvbyte(3);
		if (c == TO) return(1);
		buff[byte] = c;
		checksum = (checksum + c) & 0xff;
		if (c == CR) continue;
		if (c == CTRLZ) {
			recdone = TRUE;
			continue;
		}
		if (!recdone) byte++;
	}
	inchecksum = recvbyte(3);
	if (inchecksum == TO) return(1);
	if (checksum != inchecksum) return(1);
	if (curblock != blocknum) {
		if (curblock == (blocknum+1)&0xff) return(2);
		return(0);
	}
	if (write(fd,buff,byte) < 0) return(2);
	return(0);
}

sendbyte(data)
char data;
{
	write (1, &data, 1);
}

recvbyte(seconds)
unsigned seconds;
{
	char c;
	int alarmfunc();

	signal(SIGALRM,alarmfunc);
	alarm(seconds);	
	if (read (0, &c, 1) < 0) return(TO);
	alarm(0);
	return (c&0xff);
}

alarmfunc()
{
	return;
}

binary(setflg)
int setflg;
{
	static struct sgttyb ttys, ttysold;
	static struct stat statbuf;

	if (setflg) {
		if (gtty (0, &ttys) < 0) return(FALSE);
		ttysold.sg_ispeed = ttys.sg_ispeed;
		ttysold.sg_ospeed = ttys.sg_ospeed;
		ttysold.sg_erase = ttys.sg_erase;
		ttysold.sg_kill = ttys.sg_kill;
		ttysold.sg_flags = ttys.sg_flags;
		ttys.sg_flags |= RAW;
		ttys.sg_flags &= ~ECHO;
		ttys.sg_flags &= ~XTABS;
		ttys.sg_flags &= ~LCASE;
		ttys.sg_flags |= ANYP;
		ttys.sg_flags &= ~NL3;
		ttys.sg_flags &= ~TAB0;
		ttys.sg_flags &= ~TAB1;
		ttys.sg_flags &= ~CR3;
		ttys.sg_flags &= ~FF1;
		ttys.sg_flags &= ~BS1;
		if (stty (0, &ttys) < 0) return(FALSE);
		return(TRUE);
	}
	else {
		if (stty (0, &ttysold) < 0) return (FALSE);
		return(TRUE);
	}
}