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1 | #include "git-compat-util.h" | |
2 | #include "base85.h" | |
3 | ||
4 | #undef DEBUG_85 | |
5 | ||
6 | #ifdef DEBUG_85 | |
7 | #define say(a) fprintf(stderr, a) | |
8 | #define say1(a,b) fprintf(stderr, a, b) | |
9 | #define say2(a,b,c) fprintf(stderr, a, b, c) | |
10 | #else | |
11 | #define say(a) do { /* nothing */ } while (0) | |
12 | #define say1(a,b) do { /* nothing */ } while (0) | |
13 | #define say2(a,b,c) do { /* nothing */ } while (0) | |
14 | #endif | |
15 | ||
16 | static const char en85[] = { | |
17 | '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', | |
18 | 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', | |
19 | 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', | |
20 | 'U', 'V', 'W', 'X', 'Y', 'Z', | |
21 | 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', | |
22 | 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', | |
23 | 'u', 'v', 'w', 'x', 'y', 'z', | |
24 | '!', '#', '$', '%', '&', '(', ')', '*', '+', '-', | |
25 | ';', '<', '=', '>', '?', '@', '^', '_', '`', '{', | |
26 | '|', '}', '~' | |
27 | }; | |
28 | ||
29 | static char de85[256]; | |
30 | static void prep_base85(void) | |
31 | { | |
32 | int i; | |
33 | if (de85['Z']) | |
34 | return; | |
35 | for (i = 0; i < ARRAY_SIZE(en85); i++) { | |
36 | int ch = en85[i]; | |
37 | de85[ch] = i + 1; | |
38 | } | |
39 | } | |
40 | ||
41 | int decode_85(char *dst, const char *buffer, int len) | |
42 | { | |
43 | prep_base85(); | |
44 | ||
45 | say2("decode 85 <%.*s>", len / 4 * 5, buffer); | |
46 | while (len) { | |
47 | unsigned acc = 0; | |
48 | int de, cnt = 4; | |
49 | unsigned char ch; | |
50 | do { | |
51 | ch = *buffer++; | |
52 | de = de85[ch]; | |
53 | if (--de < 0) | |
54 | return error("invalid base85 alphabet %c", ch); | |
55 | acc = acc * 85 + de; | |
56 | } while (--cnt); | |
57 | ch = *buffer++; | |
58 | de = de85[ch]; | |
59 | if (--de < 0) | |
60 | return error("invalid base85 alphabet %c", ch); | |
61 | /* Detect overflow. */ | |
62 | if (0xffffffff / 85 < acc || | |
63 | 0xffffffff - de < (acc *= 85)) | |
64 | return error("invalid base85 sequence %.5s", buffer-5); | |
65 | acc += de; | |
66 | say1(" %08x", acc); | |
67 | ||
68 | cnt = (len < 4) ? len : 4; | |
69 | len -= cnt; | |
70 | do { | |
71 | acc = (acc << 8) | (acc >> 24); | |
72 | *dst++ = acc; | |
73 | } while (--cnt); | |
74 | } | |
75 | say("\n"); | |
76 | ||
77 | return 0; | |
78 | } | |
79 | ||
80 | void encode_85(char *buf, const unsigned char *data, int bytes) | |
81 | { | |
82 | say("encode 85"); | |
83 | while (bytes) { | |
84 | unsigned acc = 0; | |
85 | int cnt; | |
86 | for (cnt = 24; cnt >= 0; cnt -= 8) { | |
87 | unsigned ch = *data++; | |
88 | acc |= ch << cnt; | |
89 | if (--bytes == 0) | |
90 | break; | |
91 | } | |
92 | say1(" %08x", acc); | |
93 | for (cnt = 4; cnt >= 0; cnt--) { | |
94 | int val = acc % 85; | |
95 | acc /= 85; | |
96 | buf[cnt] = en85[val]; | |
97 | } | |
98 | buf += 5; | |
99 | } | |
100 | say("\n"); | |
101 | ||
102 | *buf = 0; | |
103 | } | |
104 | ||
105 | #ifdef DEBUG_85 | |
106 | int main(int ac, char **av) | |
107 | { | |
108 | char buf[1024]; | |
109 | ||
110 | if (!strcmp(av[1], "-e")) { | |
111 | int len = strlen(av[2]); | |
112 | encode_85(buf, av[2], len); | |
113 | if (len <= 26) len = len + 'A' - 1; | |
114 | else len = len + 'a' - 26 - 1; | |
115 | printf("encoded: %c%s\n", len, buf); | |
116 | return 0; | |
117 | } | |
118 | if (!strcmp(av[1], "-d")) { | |
119 | int len = *av[2]; | |
120 | if ('A' <= len && len <= 'Z') len = len - 'A' + 1; | |
121 | else len = len - 'a' + 26 + 1; | |
122 | decode_85(buf, av[2]+1, len); | |
123 | printf("decoded: %.*s\n", len, buf); | |
124 | return 0; | |
125 | } | |
126 | if (!strcmp(av[1], "-t")) { | |
127 | char t[4] = { -1,-1,-1,-1 }; | |
128 | encode_85(buf, t, 4); | |
129 | printf("encoded: D%s\n", buf); | |
130 | return 0; | |
131 | } | |
132 | } | |
133 | #endif |