Werner's Miscellanea
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Source at commit 08a13cd9759451ccf298000448ad52513a451dfe created 12 years 7 months ago. By Werner Almesberger, bitcmp/: little utility to find which bits differ between two files | |
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1 | #include <stdint.h> |
2 | #include <stdlib.h> |
3 | #include <stdio.h> |
4 | #include <unistd.h> |
5 | #include <string.h> |
6 | #include <fcntl.h> |
7 | |
8 | |
9 | #define BUFFER 4096 |
10 | |
11 | |
12 | static int do_open(const char *name) |
13 | { |
14 | int fd; |
15 | |
16 | fd = open(name, O_RDONLY); |
17 | if (fd >= 0) |
18 | return fd; |
19 | |
20 | perror(name); |
21 | exit(1); |
22 | } |
23 | |
24 | |
25 | static void usage(const char *name) |
26 | { |
27 | fprintf(stderr, |
28 | "usage: %s [-w|-l] [-B] file1 file2\n" |
29 | " -w compare words (16 bits; default is bytes)\n" |
30 | " -l compare long words (32 bits; default is bytes)\n" |
31 | " -B use big-endian (default: little-endian)\n" |
32 | , name); |
33 | exit(1); |
34 | } |
35 | |
36 | |
37 | int main(int argc, char *const *argv) |
38 | { |
39 | int little = 1; |
40 | int bytes = 1; |
41 | int c; |
42 | int fd1, fd2; |
43 | const char *name1, *name2; |
44 | uint8_t buf1[BUFFER], buf2[BUFFER]; |
45 | ssize_t got1, got2, len; |
46 | uint32_t diff; |
47 | int i, j; |
48 | static unsigned bin[32]; |
49 | |
50 | while ((c = getopt(argc, argv, "Blw")) != EOF) { |
51 | switch (c) { |
52 | case 'B': |
53 | little = 0; |
54 | break; |
55 | case 'l': |
56 | bytes = 4; |
57 | break; |
58 | case 'w': |
59 | bytes = 2; |
60 | break; |
61 | default: |
62 | usage(*argv); |
63 | } |
64 | } |
65 | if (argc-optind != 2) |
66 | usage(*argv); |
67 | |
68 | name1 = argv[optind]; |
69 | name2 = argv[optind+1]; |
70 | |
71 | fd1 = do_open(name1); |
72 | fd2 = do_open(name2); |
73 | |
74 | while (1) { |
75 | memset(buf1, 0, BUFFER); |
76 | memset(buf2, 0, BUFFER); |
77 | got1 = read(fd1, buf1, BUFFER); |
78 | if (got1 < 0) { |
79 | perror(name1); |
80 | return 1; |
81 | } |
82 | got2 = read(fd2, buf2, BUFFER); |
83 | if (got2 < 0) { |
84 | perror(name2); |
85 | return 1; |
86 | } |
87 | if (got1 != got2) |
88 | fprintf(stderr, "%s < %s\n", |
89 | got1 < got2 ? name1 : name2, |
90 | got1 < got2 ? name2 : name1); |
91 | len = got1 < got2 ? got1 : got2; |
92 | if (!len) |
93 | break; |
94 | for (i = 0; i <= len; i += bytes) { |
95 | diff = 0; |
96 | switch (bytes) { |
97 | case 4: |
98 | diff |= (buf1[i+2] ^ buf2[i+2]) << 16; |
99 | diff |= (buf1[i+3] ^ buf2[i+3]) << 24; |
100 | /* fall through */ |
101 | case 2: |
102 | diff |= (buf1[i+1] ^ buf2[i+1]) << 8; |
103 | /* fall through */ |
104 | case 1: |
105 | diff |= buf1[i] ^ buf2[i]; |
106 | break; |
107 | default: |
108 | abort(); |
109 | } |
110 | for (j = 0; j != 32; j++) |
111 | if (diff & (1 << j)) |
112 | bin[j]++; |
113 | } |
114 | } |
115 | |
116 | for (j = 0; j != 8*bytes; j++) { |
117 | if (little) |
118 | i = j; |
119 | else |
120 | i = 8*(bytes-1-(j >> 3))+(j & 7); |
121 | if (bin[i]) |
122 | printf("%2d: %u\n", j, bin[i]); |
123 | } |
124 | return 0; |
125 | } |
126 |
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