Andrew's git - gitweb.git/blob

   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, const 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 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);
  60                /*
  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).
  66                 */
  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);
  72
  73                cnt = (len < 4) ? len : 4;
  74                len -= cnt;
  75                do {
  76                        acc = (acc << 8) | (acc >> 24);
  77                        *dst++ = acc;
  78                } while (--cnt);
  79        }
  80        say("\n");
  81
  82        return 0;
  83}
  84
  85void encode_85(char *buf, const unsigned char *data, int bytes)
  86{
  87        prep_base85();
  88
  89        say("encode 85");
  90        while (bytes) {
  91                unsigned acc = 0;
  92                int cnt;
  93                for (cnt = 24; cnt >= 0; cnt -= 8) {
  94                        unsigned ch = *data++;
  95                        acc |= ch << cnt;
  96                        if (--bytes == 0)
  97                                break;
  98                }
  99                say1(" %08x", acc);
 100                for (cnt = 4; cnt >= 0; cnt--) {
 101                        int val = acc % 85;
 102                        acc /= 85;
 103                        buf[cnt] = en85[val];
 104                }
 105                buf += 5;
 106        }
 107        say("\n");
 108
 109        *buf = 0;
 110}
 111
 112#ifdef DEBUG_85
 113int main(int ac, char **av)
 114{
 115        char buf[1024];
 116
 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;
 124        }
 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;
 132        }
 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;
 138        }
 139}
 140#endif