gitweb: use new Git::Repo API, and add optional caching
[git/gitweb-caching.git] / base85.c
blobb88270f90844095b3d352cc4213cbebd95a7f420
1 #include "cache.h"
3 #undef DEBUG_85
5 #ifdef DEBUG_85
6 #define say(a) fprintf(stderr, a)
7 #define say1(a,b) fprintf(stderr, a, b)
8 #define say2(a,b,c) fprintf(stderr, a, b, c)
9 #else
10 #define say(a) do {} while(0)
11 #define say1(a,b) do {} while(0)
12 #define say2(a,b,c) do {} while(0)
13 #endif
15 static const char en85[] = {
16 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
17 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
18 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
19 'U', 'V', 'W', 'X', 'Y', 'Z',
20 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
21 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
22 'u', 'v', 'w', 'x', 'y', 'z',
23 '!', '#', '$', '%', '&', '(', ')', '*', '+', '-',
24 ';', '<', '=', '>', '?', '@', '^', '_', '`', '{',
25 '|', '}', '~'
28 static char de85[256];
29 static void prep_base85(void)
31 int i;
32 if (de85['Z'])
33 return;
34 for (i = 0; i < ARRAY_SIZE(en85); i++) {
35 int ch = en85[i];
36 de85[ch] = i + 1;
40 int decode_85(char *dst, const char *buffer, int len)
42 prep_base85();
44 say2("decode 85 <%.*s>", len/4*5, buffer);
45 while (len) {
46 unsigned acc = 0;
47 int de, cnt = 4;
48 unsigned char ch;
49 do {
50 ch = *buffer++;
51 de = de85[ch];
52 if (--de < 0)
53 return error("invalid base85 alphabet %c", ch);
54 acc = acc * 85 + de;
55 } while (--cnt);
56 ch = *buffer++;
57 de = de85[ch];
58 if (--de < 0)
59 return error("invalid base85 alphabet %c", ch);
61 * Detect overflow. The largest
62 * 5-letter possible is "|NsC0" to
63 * encode 0xffffffff, and "|NsC" gives
64 * 0x03030303 at this point (i.e.
65 * 0xffffffff = 0x03030303 * 85).
67 if (0x03030303 < acc ||
68 0xffffffff - de < (acc *= 85))
69 return error("invalid base85 sequence %.5s", buffer-5);
70 acc += de;
71 say1(" %08x", acc);
73 cnt = (len < 4) ? len : 4;
74 len -= cnt;
75 do {
76 acc = (acc << 8) | (acc >> 24);
77 *dst++ = acc;
78 } while (--cnt);
80 say("\n");
82 return 0;
85 void encode_85(char *buf, const unsigned char *data, int bytes)
87 prep_base85();
89 say("encode 85");
90 while (bytes) {
91 unsigned acc = 0;
92 int cnt;
93 for (cnt = 24; cnt >= 0; cnt -= 8) {
94 int ch = *data++;
95 acc |= ch << cnt;
96 if (--bytes == 0)
97 break;
99 say1(" %08x", acc);
100 for (cnt = 4; cnt >= 0; cnt--) {
101 int val = acc % 85;
102 acc /= 85;
103 buf[cnt] = en85[val];
105 buf += 5;
107 say("\n");
109 *buf = 0;
112 #ifdef DEBUG_85
113 int main(int ac, char **av)
115 char buf[1024];
117 if (!strcmp(av[1], "-e")) {
118 int len = strlen(av[2]);
119 encode_85(buf, av[2], len);
120 if (len <= 26) len = len + 'A' - 1;
121 else len = len + 'a' - 26 + 1;
122 printf("encoded: %c%s\n", len, buf);
123 return 0;
125 if (!strcmp(av[1], "-d")) {
126 int len = *av[2];
127 if ('A' <= len && len <= 'Z') len = len - 'A' + 1;
128 else len = len - 'a' + 26 + 1;
129 decode_85(buf, av[2]+1, len);
130 printf("decoded: %.*s\n", len, buf);
131 return 0;
133 if (!strcmp(av[1], "-t")) {
134 char t[4] = { -1,-1,-1,-1 };
135 encode_85(buf, t, 4);
136 printf("encoded: D%s\n", buf);
137 return 0;
140 #endif