/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include <u.h>#include <libc.h> enum {	Soh=	0x1,	Eot=	0x4,	Ack=	0x6,	Nak=	0x15,	Cancel=	0x18,}; int notifyf(void*, char*);int readupto(uchar*, int);int receive(int, uchar);void send(int); int debug, dfd; voidmain(int argc, char **argv){	int fd;	uchar seqno;	ulong bytes; 	ARGBEGIN {	case 'd':		dfd = 2;		debug = 1;		break;	} ARGEND 	if(argc != 1){		fprint(2, "usage: xmr filename\n");		exits("usage");	}	fd = open("/dev/consctl", OWRITE);	if(fd >= 0)		write(fd, "rawon", 5);	fd = create(argv[0], ORDWR, 0666);	if(fd < 0){		perror("xmr: create");		exits("create");	} 	atnotify(notifyf, 1);	send(Nak); 	/*	 *  keep receiving till the other side gives up	 */	bytes = 0;	for(seqno = 1; ; seqno++){		if(receive(fd, seqno) == -1)			break;		bytes += 128;	}	fprint(2, "xmr: received %ld bytes\n", bytes);	exits(0);} voidsend(int byte){	uchar c; 	c = byte;	if(write(1, &c, 1) != 1){		fprint(2, "xmr: hungup\n");		exits("hangup");	}} intreadupto(uchar *a, int len){	int n;	int sofar; 	for(sofar = 0; sofar < len; sofar += n){		n = read(0, a, len-sofar);		if(n <= 0){			send(Nak);			return sofar;		}		if(*a == Eot || *a == Cancel)			return sofar + n;		a += n;	}	return sofar; } intreceive(int fd, uchar seqno){	uchar buf[128+4];	uchar sum;	uchar *p;	int n;	int tries;	int have; 	for(have = 0, tries = 0;; tries++){		if(debug)			fprint(dfd, "have == %d\n", have);		if(tries > 10){			fprint(2, "xmr: timed out\n");			if(debug)				close(dfd);			exits("timeout");		} 		/* try to gather up a block */		alarm(15*1000);		n = readupto(&buf[have], 132-have);		alarm(0);		have += n;		if(have){			switch(buf[0]){			case Eot:				send(Ack);				return -1;			case Cancel:				fprint(2, "xmr: transfer aborted by sender\n");				exits("cancel");			}		}		if(have != 132)			continue; 		/* checksum */		for(p = buf, sum = 0; p < &buf[128+3]; p++)			sum += *p; 		/* If invalid block, resynchronize */		if(buf[0] != Soh || buf[2] != (255-buf[1]) || sum != buf[131]){			if(debug){				fprint(dfd, "resync %2.2ux %d %d %ux %ux\n", buf[0],					buf[1], buf[2], sum, buf[131]);				write(dfd, (char*)buf+3, 128);				fprint(dfd, "\n");			}			p = memchr(buf+1, Soh, 131);			if(p){				have = 132-(p-buf);				memmove(buf, p, have);			} else				have = 0;			continue;		} 		/* it's probably a real block, so dump it if there's an error */		have = 0; 		/* if this is the last block, ack */		if(buf[1] == seqno-1){			tries = 0;			send(Ack);		}else if(buf[1] == seqno){			if(debug)				fprint(dfd, "Ack\n");			send(Ack);			if(write(fd, buf+3, 128) != 128){				fprint(2, "xmr: abort, error writing file\n");				exits("write");			}			return 0;		} else {			send(Nak);		}	}} intnotifyf(void *a, char *msg){	USED(a);	if(strcmp(msg, "alarm") == 0)		return 1;	return 0;}