a85ct.d

   1 /* Invisible Vector Library
   2  * coded by Ketmar // Invisible Vector <ketmar@ketmar.no-ip.org>
   3  * Understanding is not required. Only obedience.
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, version 3 of the License ONLY.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  16  */
  17 // ASCII85 codec
  18 module iv.a85ct /*is aliced*/;
  19 import iv.alice;
  20
  21
  22 // very slow and enifficient ascii85 decoder
  23 string decodeAscii85(T) (const(T)[] src) {
  24   static immutable uint[5] pow85 = [85*85*85*85u, 85*85*85u, 85*85u, 85u, 1u];
  25   auto data = cast(const(ubyte)[])src;
  26   uint tuple = 0;
  27   int count = 0;
  28   string res = "";
  29
  30   void decodeTuple (int bytes) @safe nothrow {
  31     while (bytes-- > 0) {
  32       res ~= (tuple>>24)&0xff;
  33       tuple <<= 8;
  34     }
  35   }
  36
  37   foreach (immutable b; data) {
  38     if (b <= 32 || b > 126) continue; // skip blanks
  39     if (b == 'z') {
  40       // zero tuple
  41       if (count != 0) return null; // alas
  42       res ~= "\0\0\0\0";
  43     } else {
  44       if (b < '!' || b > 'u') return null; // alas
  45       tuple += (b-'!')*pow85[count++];
  46       if (count == 5) {
  47         decodeTuple(4);
  48         tuple = 0;
  49         count = 0;
  50       }
  51     }
  52   }
  53   // write last (possibly incomplete) tuple
  54   if (count > 1) {
  55     tuple += pow85[--count];
  56     decodeTuple(count);
  57   }
  58   return res;
  59 }
  60
  61
  62 string encodeAscii85(T) (const(T)[] src, int width=76) {
  63   auto data = cast(const(ubyte)[])src;
  64   uint tuple = 0;
  65   int count = 0, pos = 0;
  66   string res;
  67
  68   void encodeTuple () @safe nothrow {
  69     int tmp = 5;
  70     ubyte[5] buf;
  71     usize bpos = 0;
  72     do {
  73       buf[bpos++] = tuple%85;
  74       tuple /= 85;
  75     } while (--tmp > 0);
  76     tmp = count;
  77     do {
  78       if (width > 0 && pos >= width) { res ~= '\n'; pos = 0; }
  79       res ~= cast(char)(buf[--bpos]+'!');
  80       ++pos;
  81     } while (tmp-- > 0);
  82   }
  83
  84   foreach (immutable b; data) {
  85     switch (count++) {
  86       case 0: tuple |= b<<24; break;
  87       case 1: tuple |= b<<16; break;
  88       case 2: tuple |= b<<8; break;
  89       case 3:
  90         tuple |= b;
  91         if (tuple == 0) {
  92           // special case
  93           if (width > 0 && pos >= width) { res ~= '\n'; pos = 0; }
  94           res ~= 'z';
  95           ++pos;
  96         } else {
  97           encodeTuple();
  98         }
  99         tuple = 0;
 100         count = 0;
 101         break;
 102       default: assert(0);
 103     }
 104   }
 105   if (count > 0) encodeTuple();
 106   return res;
 107 }
 108
 109
 110 // for mixin
 111 template a85enc(string s) {
 112   private static enum qstr(string s) = s.stringof;
 113   enum a85enc = qstr!(encodeAscii85(s, 0));
 114 }
 115
 116
 117 // fox mixin
 118 template a85dec(string s) {
 119   private static enum qstr(string s) = s.stringof;
 120   enum a85dec = qstr!(decodeAscii85(s));
 121 }
 122
 123
 124 version(none) {
 125 enum e = encodeAscii85("One, two, Freddy's coming for you");
 126 enum s = decodeAscii85(`:Ms_p+EVgG/0IE&ARo=s-Z^D?Df'3+B-:f)EZfXGFT`);
 127
 128 void main () {
 129   import iv.writer;
 130   writeln(s);
 131   writeln(decodeAscii85(e) == s);
 132 }
 133 }