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#include <u.h>
2 
#include <libc.h>
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4 
enum {
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	Soh=	0x1,
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	Eot=	0x4,
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	Ack=	0x6,
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	Nak=	0x15,
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	Cancel=	0x18,
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};
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int notifyf(void*, char*);
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int readupto(uchar*, int);
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int receive(int, uchar);
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void send(int);
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17 
int debug, dfd;
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void
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main(int argc, char **argv)
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{
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	int fd;
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	uchar seqno;
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	ulong bytes;
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	ARGBEGIN {
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	case 'd':
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		dfd = 2;
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		debug = 1;
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		break;
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	} ARGEND
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	if(argc != 1){
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		fprint(2, "usage: xmr filename\n");
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		exits("usage");
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	}
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	fd = open("/dev/consctl", OWRITE);
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	if(fd >= 0)
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		write(fd, "rawon", 5);
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	fd = create(argv[0], ORDWR, 0666);
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	if(fd < 0){
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		perror("xmr: create");
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		exits("create");
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	}
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	atnotify(notifyf, 1);
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	send(Nak);
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	/*
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	 *  keep receiving till the other side gives up
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	 */
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	bytes = 0;
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	for(seqno = 1; ; seqno++){
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		if(receive(fd, seqno) == -1)
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			break;
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		bytes += 128;
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	}
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	fprint(2, "xmr: received %ld bytes\n", bytes);
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	exits(0);
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}
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void
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send(int byte)
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{
65 
	uchar c;
66 
 
67 
	c = byte;
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	if(write(1, &c, 1) != 1){
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		fprint(2, "xmr: hungup\n");
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		exits("hangup");
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	}
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}
73 
 
74 
int
75 
readupto(uchar *a, int len)
76 
{
77 
	int n;
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	int sofar;
79 
 
80 
	for(sofar = 0; sofar < len; sofar += n){
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		n = read(0, a, len-sofar);
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		if(n <= 0){
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			send(Nak);
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			return sofar;
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		}
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		if(*a == Eot || *a == Cancel)
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			return sofar + n;
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		a += n;
89 
	}
90 
	return sofar;
91 
 
92 
}
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int
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receive(int fd, uchar seqno)
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{
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	uchar buf[128+4];
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	uchar sum;
99 
	uchar *p;
100 
	int n;
101 
	int tries;
102 
	int have;
103 
 
104 
	for(have = 0, tries = 0;; tries++){
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		if(debug)
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			fprint(dfd, "have == %d\n", have);
107 
		if(tries > 10){
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			fprint(2, "xmr: timed out\n");
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			if(debug)
110 
				close(dfd);
111 
			exits("timeout");
112 
		}
113 
 
114 
		/* try to gather up a block */
115 
		alarm(15*1000);
116 
		n = readupto(&buf[have], 132-have);
117 
		alarm(0);
118 
		have += n;
119 
		if(have){
120 
			switch(buf[0]){
121 
			case Eot:
122 
				send(Ack);
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				return -1;
124 
			case Cancel:
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				fprint(2, "xmr: transfer aborted by sender\n");
126 
				exits("cancel");
127 
			}
128 
		}
129 
		if(have != 132)
130 
			continue;
131 
 
132 
		/* checksum */
133 
		for(p = buf, sum = 0; p < &buf[128+3]; p++)
134 
			sum += *p;
135 
 
136 
		/* If invalid block, resynchronize */
137 
		if(buf[0] != Soh || buf[2] != (255-buf[1]) || sum != buf[131]){
138 
			if(debug){
139 
				fprint(dfd, "resync %2.2ux %d %d %ux %ux\n", buf[0],
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					buf[1], buf[2], sum, buf[131]);
141 
				write(dfd, (char*)buf+3, 128);
142 
				fprint(dfd, "\n");
143 
			}
144 
			p = memchr(buf+1, Soh, 131);
145 
			if(p){
146 
				have = 132-(p-buf);
147 
				memmove(buf, p, have);
148 
			} else
149 
				have = 0;
150 
			continue;
151 
		}
152 
 
153 
		/* it's probably a real block, so dump it if there's an error */
154 
		have = 0;
155 
 
156 
		/* if this is the last block, ack */
157 
		if(buf[1] == seqno-1){
158 
			tries = 0;
159 
			send(Ack);
160 
		}else if(buf[1] == seqno){
161 
			if(debug)
162 
				fprint(dfd, "Ack\n");
163 
			send(Ack);
164 
			if(write(fd, buf+3, 128) != 128){
165 
				fprint(2, "xmr: abort, error writing file\n");
166 
				exits("write");
167 
			}
168 
			return 0;
169 
		} else {
170 
			send(Nak);
171 
		}
172 
	}
173 
}
174 
 
175 
int
176 
notifyf(void *a, char *msg)
177 
{
178 
	USED(a);
179 
	if(strcmp(msg, "alarm") == 0)
180 
		return 1;
181 
	return 0;
182 
}