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, either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 // ASCII85 codec
  19 module iv.a85ct /*is aliced*/;
  20 import iv.alice;
  21
  22
  23 // very slow and enifficient ascii85 decoder
  24 string decodeAscii85(T) (const(T)[] src) {
  25   static immutable uint[5] pow85 = [85*85*85*85u, 85*85*85u, 85*85u, 85u, 1u];
  26   auto data = cast(const(ubyte)[])src;
  27   uint tuple = 0;
  28   int count = 0;
  29   string res = "";
  30
  31   void decodeTuple (int bytes) @safe nothrow {
  32     while (bytes-- > 0) {
  33       res ~= (tuple>>24)&0xff;
  34       tuple <<= 8;
  35     }
  36   }
  37
  38   foreach (immutable b; data) {
  39     if (b <= 32 || b > 126) continue; // skip blanks
  40     if (b == 'z') {
  41       // zero tuple
  42       if (count != 0) return null; // alas
  43       res ~= "\0\0\0\0";
  44     } else {
  45       if (b < '!' || b > 'u') return null; // alas
  46       tuple += (b-'!')*pow85[count++];
  47       if (count == 5) {
  48         decodeTuple(4);
  49         tuple = 0;
  50         count = 0;
  51       }
  52     }
  53   }
  54   // write last (possibly incomplete) tuple
  55   if (count > 1) {
  56     tuple += pow85[--count];
  57     decodeTuple(count);
  58   }
  59   return res;
  60 }
  61
  62
  63 string encodeAscii85(T) (const(T)[] src, int width=76) {
  64   auto data = cast(const(ubyte)[])src;
  65   uint tuple = 0;
  66   int count = 0, pos = 0;
  67   string res;
  68
  69   void encodeTuple () @safe nothrow {
  70     int tmp = 5;
  71     ubyte[5] buf;
  72     usize bpos = 0;
  73     do {
  74       buf[bpos++] = tuple%85;
  75       tuple /= 85;
  76     } while (--tmp > 0);
  77     tmp = count;
  78     do {
  79       if (width > 0 && pos >= width) { res ~= '\n'; pos = 0; }
  80       res ~= cast(char)(buf[--bpos]+'!');
  81       ++pos;
  82     } while (tmp-- > 0);
  83   }
  84
  85   foreach (immutable b; data) {
  86     switch (count++) {
  87       case 0: tuple |= b<<24; break;
  88       case 1: tuple |= b<<16; break;
  89       case 2: tuple |= b<<8; break;
  90       case 3:
  91         tuple |= b;
  92         if (tuple == 0) {
  93           // special case
  94           if (width > 0 && pos >= width) { res ~= '\n'; pos = 0; }
  95           res ~= 'z';
  96           ++pos;
  97         } else {
  98           encodeTuple();
  99         }
 100         tuple = 0;
 101         count = 0;
 102         break;
 103       default: assert(0);
 104     }
 105   }
 106   if (count > 0) encodeTuple();
 107   return res;
 108 }
 109
 110
 111 // for mixin
 112 template a85enc(string s) {
 113   private static enum qstr(string s) = s.stringof;
 114   enum a85enc = qstr!(encodeAscii85(s, 0));
 115 }
 116
 117
 118 // fox mixin
 119 template a85dec(string s) {
 120   private static enum qstr(string s) = s.stringof;
 121   enum a85dec = qstr!(decodeAscii85(s));
 122 }
 123
 124
 125 version(none) {
 126 enum e = encodeAscii85("One, two, Freddy's coming for you");
 127 enum s = decodeAscii85(`:Ms_p+EVgG/0IE&ARo=s-Z^D?Df'3+B-:f)EZfXGFT`);
 128
 129 void main () {
 130   import iv.writer;
 131   writeln(s);
 132   writeln(decodeAscii85(e) == s);
 133 }
 134 }