1 #include <u.h>
2 #include <libc.h>
3 #include <bio.h>
4 
5 #define LB 2048
6 int	one;
7 int	two;
8 int	three;
9 
10 char	ldr[3][4] = { "", "\t", "\t\t" };
11 
12 Biobuf *ib1;
13 Biobuf *ib2;
14 Biobuf *openfil(char*);
15 int	rd(Biobuf*, char*);
16 void	wr(char*, int);
17 void	copy(Biobuf*, char*, int);
18 int	compare(char*, char*);
19 
20 void
21 main(int argc, char *argv[])
22 {
23 	int l;
24 	char	lb1[LB],lb2[LB];
25 
26 	l = 2;
27 	ARGBEGIN{
28 	case '1':
29 		if(!one) {
30 			one = 1;
31 			ldr[1][0] =
32 			ldr[2][l--] = '\0';
33 		}
34 		break;
35 
36 	case '2':
37 		if(!two) {
38 			two = 1;
39 			ldr[2][l--] = '\0';
40 		}
41 		break;
42 
43 	case '3':
44 		three = 1;
45 		break;
46 
47 	default:
48 		goto Usage;
49 
50 	}ARGEND
51 
52 	if(argc < 2) {
53     Usage:
54 		fprint(2, "usage: comm [-123] file1 file2\n");
55 		exits("usage");
56 	}
57 
58 	ib1 = openfil(argv[0]);
59 	ib2 = openfil(argv[1]);
60 
61 
62 	if(rd(ib1,lb1) < 0){
63 		if(rd(ib2,lb2) < 0)
64 			exits(0);
65 		copy(ib2,lb2,2);
66 	}
67 	if(rd(ib2,lb2) < 0)
68 		copy(ib1,lb1,1);
69 
70 	for(;;){
71 		switch(compare(lb1,lb2)) {
72 		case 0:
73 			wr(lb1,3);
74 			if(rd(ib1,lb1) < 0) {
75 				if(rd(ib2,lb2) < 0)
76 					exits(0);
77 				copy(ib2,lb2,2);
78 			}
79 			if(rd(ib2,lb2) < 0)
80 				copy(ib1,lb1,1);
81 			continue;
82 
83 		case 1:
84 			wr(lb1,1);
85 			if(rd(ib1,lb1) < 0)
86 				copy(ib2,lb2,2);
87 			continue;
88 
89 		case 2:
90 			wr(lb2,2);
91 			if(rd(ib2,lb2) < 0)
92 				copy(ib1,lb1,1);
93 			continue;
94 		}
95 	}
96 	exits(0);
97 }
98 
99 int
100 rd(Biobuf *file, char *buf)
101 {
102 	int i, c;
103 
104 	i = 0;
105 	while((c = Bgetc(file)) != Beof) {
106 		*buf = c;
107 		if(c == '\n' || i > LB-2) {
108 			*buf = '\0';
109 			return 0;
110 		}
111 		i++;
112 		buf++;
113 	}
114 	return -1;
115 }
116 
117 void
118 wr(char *str, int n)
119 {
120 
121 	switch(n){
122 		case 1:
123 			if(one)
124 				return;
125 			break;
126 
127 		case 2:
128 			if(two)
129 				return;
130 			break;
131 
132 		case 3:
133 			if(three)
134 				return;
135 	}
136 	print("%s%s\n", ldr[n-1],str);
137 }
138 
139 void
140 copy(Biobuf *ibuf, char *lbuf, int n)
141 {
142 	do
143 		wr(lbuf,n);
144 	while(rd(ibuf,lbuf) >= 0);
145 	exits(0);
146 }
147 
148 int
149 compare(char *a, char *b)
150 {
151 	while(*a == *b){
152 		if(*a == '\0')
153 			return 0;
154 		a++;
155 		b++;
156 	}
157 	if(*a < *b)
158 		return 1;
159 	return 2;
160 }
161 
162 Biobuf*
163 openfil(char *s)
164 {
165 	Biobuf *b;
166 
167 	if(s[0]=='-' && s[1]==0)
168 		s = "/fd/0";
169 	b = Bopen(s, OREAD);
170 	if(b)
171 		return b;
172 	fprint(2,"comm: cannot open %s: %r\n",s);
173 	exits("open");
174 	return 0;	/* shut up ken */
175 }