dpack/packer_rle.js

   1 /*
   2  * simple RLE packer
   3  * 1st char: code of rep prefix, then:
   4  * char or
   5  * repprefix,count,code
   6  */
   7 function RLEPack (s) {
   8   var f, res = "", used = [], ch;
   9   /* find least used char */
  10   for (f = 0; f <= 255; f++) used[f] = 0;
  11   for (f = 0; f < s.length; f++) {
  12     ch = s[f];
  13     /*if (!used[ch]) {
  14       if (ch >= 32 && ch <= 126) print('"'+String.fromCharCode(ch)+'"');
  15       else print("0x"+ch.toString(16).toUpperCase());
  16     }*/
  17     used[ch]++;
  18   }
  19
  20   var repChar = 35, repCnt = used[repChar], repASCII = true;
  21   for (f = 0; f <= 255; f++) {
  22     var uc = used[f];
  23     if (uc < repCnt || (!repASCII && uc <= repCnt)) {
  24       repChar = f; repCnt = uc;
  25       repASCII = (f >= 32 && f <= 126 && f != 34 && f != 92);
  26     }
  27   }
  28   /*
  29   print("----------");
  30   if (repASCII) print('"'+String.fromCharCode(repChar)+'"');
  31   else print("0x"+repChar.charCodeAt(0).toString(16).toUpperCase());
  32   print("cnt: "+repCnt);
  33   print("used: "+used[repChar]);
  34   */
  35   function AddCode (c, isRep) {
  36     if (!isRep && c == repChar) {
  37       /* 'repeat' once */
  38       /*print("fuck!");*/
  39       AddCode(repChar, true);
  40       AddCode(0, true);
  41     }
  42     if (c >= 32 && c <= 126) {
  43       if (c == 34 || c == 92) res += '\\';
  44       res += String.fromCharCode(c);
  45     } else {
  46       var h = c.toString(16).toLowerCase();
  47       while (h.length < 2) h = "0"+h;
  48       res += "\\x"+h;
  49     }
  50   }
  51
  52   AddCode(repChar, true); /* repchar */
  53   for (f = 0; f < s.length; ) {
  54     var c = s[f];
  55     if (f >= s.length-2) { AddCode(c); f++; continue; }
  56     if (s[f+1] == c && (c == repChar || s[f+2] == c)) {
  57       /* repeats */
  58       AddCode(repChar, true);
  59       var cnt = -1; /* 0 means at least one repeat */
  60       while (cnt < 255 && f < s.length && s[f] == c) { cnt++; f++; }
  61       AddCode(cnt, true); /* repcount */
  62       AddCode(c, true); /* char */
  63       /*print("rep "+(cnt+1)+"; char: "+c);*/
  64     } else { AddCode(c); f++; }
  65   }
  66   return res;
  67 }
  68
  69
  70 /*
  71  * simple RLE unpacker
  72  * 1st char: code of rep prefix, then:
  73  * char or
  74  * repprefix,count,code
  75  */
  76 function RLEUnpack (s) {
  77   var res = [], rc = s.charCodeAt(0);
  78   /*print(rc);*/
  79   for (var f = 1; f < s.length; ) {
  80     var cc = s.charCodeAt(f++);
  81     if (cc == rc) {
  82       var cnt = s.charCodeAt(f++);
  83       cc = s.charCodeAt(f++);
  84       /*print("pos: "+(f-3)+"; rep "+(cnt+1)+"; char: "+cc+"; npos: "+f+"; nchar: "+s.charCodeAt(f));*/
  85       while (cnt-- > 0) res.push(cc);
  86     }
  87     res.push(cc);
  88   }
  89   return res;
  90 }
  91
  92
  93 function PackArray (arr) {
  94   return RLEPack(arr);
  95 }
  96
  97
  98 function DUnpackStr (s) {
  99   return RLEUnpack(s);
 100 }