binary diff: further updates.
[git/git.git] / base85.c
CommitLineData
0660626c
JH
1#include "cache.h"
2
3#undef DEBUG_85
4
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
14
15static 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 '|', '}', '~'
26};
27
28static char de85[256];
29static void prep_base85(void)
30{
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;
37 }
38}
39
40int decode_85(char *dst, char *buffer, int len)
41{
42 prep_base85();
43
44 say2("decode 85 <%.*s>", len/4*5, buffer);
45 while (len) {
46 unsigned acc = 0;
47 int cnt;
48 for (cnt = 0; cnt < 5; cnt++, buffer++) {
49 int ch = *((unsigned char *)buffer);
50 int de = de85[ch];
51 if (!de)
52 return error("invalid base85 alphabet %c", ch);
53 de--;
54 if (cnt == 4) {
55 /*
56 * Detect overflow. The largest
57 * 5-letter possible is "|NsC0" to
58 * encode 0xffffffff, and "|NsC" gives
59 * 0x03030303 at this point (i.e.
60 * 0xffffffff = 0x03030303 * 85).
61 */
62 if (0x03030303 < acc ||
63 (0x03030303 == acc && de))
64 error("invalid base85 sequence %.5s",
65 buffer-3);
66 }
67 acc = acc * 85 + de;
68 say1(" <%08x>", acc);
69 }
70 say1(" %08x", acc);
71 for (cnt = 0; cnt < 4 && len; cnt++, len--) {
72 *dst++ = (acc >> 24) & 0xff;
73 acc = acc << 8;
74 }
75 }
76 say("\n");
77
78 return 0;
79}
80
81void encode_85(char *buf, unsigned char *data, int bytes)
82{
83 prep_base85();
84
85 say("encode 85");
86 while (bytes) {
87 unsigned acc = 0;
88 int cnt;
89 for (cnt = 0; cnt < 4 && bytes; cnt++, bytes--) {
90 int ch = *data++;
91 acc |= ch << ((3-cnt)*8);
92 }
93 say1(" %08x", acc);
94 for (cnt = 0; cnt < 5; cnt++) {
95 int val = acc % 85;
96 acc /= 85;
97 buf[4-cnt] = en85[val];
98 }
99 buf += 5;
100 }
101 say("\n");
102
103 *buf = 0;
104}
105
106#ifdef DEBUG_85
107int main(int ac, char **av)
108{
109 char buf[1024];
110
111 if (!strcmp(av[1], "-e")) {
112 int len = strlen(av[2]);
113 encode_85(buf, av[2], len);
114 if (len <= 26) len = len + 'A' - 1;
115 else len = len + 'a' - 26 + 1;
116 printf("encoded: %c%s\n", len, buf);
117 return 0;
118 }
119 if (!strcmp(av[1], "-d")) {
120 int len = *av[2];
121 if ('A' <= len && len <= 'Z') len = len - 'A' + 1;
122 else len = len - 'a' + 26 + 1;
123 decode_85(buf, av[2]+1, len);
124 printf("decoded: %.*s\n", len, buf);
125 return 0;
126 }
127 if (!strcmp(av[1], "-t")) {
128 char t[4] = { -1,-1,-1,-1 };
129 encode_85(buf, t, 4);
130 printf("encoded: D%s\n", buf);
131 return 0;
132 }
133}
134#endif