sys/src/libc/port/u64.c

   1 #include <u.h>
   2 #include <libc.h>
   3
   4 #define between(x,min,max)      (((min-1-x) & (x-max-1))>>8)
   5
   6 int
   7 enc64chr(int o)
   8 {
   9         int c;
  10
  11         c  = between(o,  0, 25) & ('A'+o);
  12         c |= between(o, 26, 51) & ('a'+(o-26));
  13         c |= between(o, 52, 61) & ('0'+(o-52));
  14         c |= between(o, 62, 62) & ('+');
  15         c |= between(o, 63, 63) & ('/');
  16         return c;
  17 }
  18
  19 int
  20 dec64chr(int c)
  21 {
  22         int o;
  23
  24         o  = between(c, 'A', 'Z') & (1+(c-'A'));
  25         o |= between(c, 'a', 'z') & (1+26+(c-'a'));
  26         o |= between(c, '0', '9') & (1+52+(c-'0'));
  27         o |= between(c, '+', '+') & (1+62);
  28         o |= between(c, '/', '/') & (1+63);
  29         return o-1;
  30 }
  31
  32 int
  33 dec64x(uchar *out, int lim, char *in, int n, int (*chr)(int))
  34 {
  35         ulong b24;
  36         uchar *start = out;
  37         uchar *e = out + lim;
  38         int i, c;
  39
  40         b24 = 0;
  41         i = 0;
  42         while(n-- > 0){
  43                 c = chr(*in++);
  44                 if(c < 0)
  45                         continue;
  46                 switch(i){
  47                 case 0:
  48                         b24 = c<<18;
  49                         break;
  50                 case 1:
  51                         b24 |= c<<12;
  52                         break;
  53                 case 2:
  54                         b24 |= c<<6;
  55                         break;
  56                 case 3:
  57                         if(out + 3 > e)
  58                                 goto exhausted;
  59
  60                         b24 |= c;
  61                         *out++ = b24>>16;
  62                         *out++ = b24>>8;
  63                         *out++ = b24;
  64                         i = 0;
  65                         continue;
  66                 }
  67                 i++;
  68         }
  69         switch(i){
  70         case 2:
  71                 if(out + 1 > e)
  72                         goto exhausted;
  73                 *out++ = b24>>16;
  74                 break;
  75         case 3:
  76                 if(out + 2 > e)
  77                         goto exhausted;
  78                 *out++ = b24>>16;
  79                 *out++ = b24>>8;
  80                 break;
  81         }
  82 exhausted:
  83         return out - start;
  84 }
  85
  86 int
  87 enc64x(char *out, int lim, uchar *in, int n, int (*chr)(int))
  88 {
  89         int i;
  90         ulong b24;
  91         char *start = out;
  92         char *e = out + lim;
  93
  94         for(i = n/3; i > 0; i--){
  95                 b24 = *in++<<16;
  96                 b24 |= *in++<<8;
  97                 b24 |= *in++;
  98                 if(out + 4 >= e)
  99                         goto exhausted;
 100                 *out++ = chr(b24>>18);
 101                 *out++ = chr((b24>>12)&0x3f);
 102                 *out++ = chr((b24>>6)&0x3f);
 103                 *out++ = chr(b24&0x3f);
 104         }
 105
 106         switch(n%3){
 107         case 2:
 108                 b24 = *in++<<16;
 109                 b24 |= *in<<8;
 110                 if(out + 4 >= e)
 111                         goto exhausted;
 112                 *out++ = chr(b24>>18);
 113                 *out++ = chr((b24>>12)&0x3f);
 114                 *out++ = chr((b24>>6)&0x3f);
 115                 *out++ = '=';
 116                 break;
 117         case 1:
 118                 b24 = *in<<16;
 119                 if(out + 4 >= e)
 120                         goto exhausted;
 121                 *out++ = chr(b24>>18);
 122                 *out++ = chr((b24>>12)&0x3f);
 123                 *out++ = '=';
 124                 *out++ = '=';
 125                 break;
 126         }
 127 exhausted:
 128         *out = 0;
 129         return out - start;
 130 }
 131
 132 int
 133 enc64(char *out, int lim, uchar *in, int n)
 134 {
 135         return enc64x(out, lim, in, n, enc64chr);
 136 }
 137
 138 int
 139 dec64(uchar *out, int lim, char *in, int n)
 140 {
 141         return dec64x(out, lim, in, n, dec64chr);
 142 }