File: base85.c

package info (click to toggle)
git 1:2.20.1-2+deb10u3
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 45,676 kB
  • sloc: ansic: 210,769; sh: 180,432; perl: 29,102; tcl: 21,663; python: 6,143; makefile: 3,700; sed: 189; php: 120; asm: 98; csh: 45; ruby: 24; lisp: 12
file content (132 lines) | stat: -rw-r--r-- 2,825 bytes parent folder | download | duplicates (18)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
#include "cache.h"

#undef DEBUG_85

#ifdef DEBUG_85
#define say(a) fprintf(stderr, a)
#define say1(a,b) fprintf(stderr, a, b)
#define say2(a,b,c) fprintf(stderr, a, b, c)
#else
#define say(a) do { /* nothing */ } while (0)
#define say1(a,b) do { /* nothing */ } while (0)
#define say2(a,b,c) do { /* nothing */ } while (0)
#endif

static const char en85[] = {
	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
	'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
	'U', 'V', 'W', 'X', 'Y', 'Z',
	'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
	'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
	'u', 'v', 'w', 'x', 'y', 'z',
	'!', '#', '$', '%', '&', '(', ')', '*', '+', '-',
	';', '<', '=', '>', '?', '@', '^', '_',	'`', '{',
	'|', '}', '~'
};

static char de85[256];
static void prep_base85(void)
{
	int i;
	if (de85['Z'])
		return;
	for (i = 0; i < ARRAY_SIZE(en85); i++) {
		int ch = en85[i];
		de85[ch] = i + 1;
	}
}

int decode_85(char *dst, const char *buffer, int len)
{
	prep_base85();

	say2("decode 85 <%.*s>", len / 4 * 5, buffer);
	while (len) {
		unsigned acc = 0;
		int de, cnt = 4;
		unsigned char ch;
		do {
			ch = *buffer++;
			de = de85[ch];
			if (--de < 0)
				return error("invalid base85 alphabet %c", ch);
			acc = acc * 85 + de;
		} while (--cnt);
		ch = *buffer++;
		de = de85[ch];
		if (--de < 0)
			return error("invalid base85 alphabet %c", ch);
		/* Detect overflow. */
		if (0xffffffff / 85 < acc ||
		    0xffffffff - de < (acc *= 85))
			return error("invalid base85 sequence %.5s", buffer-5);
		acc += de;
		say1(" %08x", acc);

		cnt = (len < 4) ? len : 4;
		len -= cnt;
		do {
			acc = (acc << 8) | (acc >> 24);
			*dst++ = acc;
		} while (--cnt);
	}
	say("\n");

	return 0;
}

void encode_85(char *buf, const unsigned char *data, int bytes)
{
	say("encode 85");
	while (bytes) {
		unsigned acc = 0;
		int cnt;
		for (cnt = 24; cnt >= 0; cnt -= 8) {
			unsigned ch = *data++;
			acc |= ch << cnt;
			if (--bytes == 0)
				break;
		}
		say1(" %08x", acc);
		for (cnt = 4; cnt >= 0; cnt--) {
			int val = acc % 85;
			acc /= 85;
			buf[cnt] = en85[val];
		}
		buf += 5;
	}
	say("\n");

	*buf = 0;
}

#ifdef DEBUG_85
int main(int ac, char **av)
{
	char buf[1024];

	if (!strcmp(av[1], "-e")) {
		int len = strlen(av[2]);
		encode_85(buf, av[2], len);
		if (len <= 26) len = len + 'A' - 1;
		else len = len + 'a' - 26 - 1;
		printf("encoded: %c%s\n", len, buf);
		return 0;
	}
	if (!strcmp(av[1], "-d")) {
		int len = *av[2];
		if ('A' <= len && len <= 'Z') len = len - 'A' + 1;
		else len = len - 'a' + 26 + 1;
		decode_85(buf, av[2]+1, len);
		printf("decoded: %.*s\n", len, buf);
		return 0;
	}
	if (!strcmp(av[1], "-t")) {
		char t[4] = { -1,-1,-1,-1 };
		encode_85(buf, t, 4);
		printf("encoded: D%s\n", buf);
		return 0;
	}
}
#endif