Werner's Miscellanea
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Werner's Miscellanea Commit Details
Date: | 2011-08-17 11:59:05 (12 years 7 months ago) |
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Author: | Werner Almesberger |
Commit: | 08a13cd9759451ccf298000448ad52513a451dfe |
Message: | bitcmp/: little utility to find which bits differ between two files |
Files: |
bitcmp/Makefile (1 diff) bitcmp/bitcmp.c (1 diff) |
Change Details
bitcmp/Makefile | ||
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1 | CFLAGS=-Wall | |
2 | ||
3 | all: bitcmp |
bitcmp/bitcmp.c | ||
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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 | } |
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