Nodejs String from Ascii85 fromAscii85()

Method Source Code

String.prototype.fromAscii85 = function() {
  var str = this.slice(2, -2).replace(/z/g, '!!!!!').replace(/\s/g, '');
  var decoded = '';
  
  
  for(var i = 0, len = str.length; i < len; i+=5) {
    var n = 0;/*from   w w  w  . j ava2s. com*/
    var us = 0;
    for(var j = 4; j >= 0; j--) {
      var c = str[j+i] || (us++, 'u'),
          code = c.charCodeAt(0) - 33;

      n += code * Math.pow(85, Math.abs(j-4));
    }
    
    var bin = stretch(n.toString(2), 32);
    
    for(var j = 0; j < 32; j+=8) {
      var char = parseInt(bin.slice(j, j+8), 2);
      decoded += String.fromCharCode(char);
    }
    decoded = decoded.slice(0, us > 0 ? -us : undefined);
  }
  
  return decoded;
}

function to8bit(n) {
  var bin = stretch(n.toString(2), 8);
  
  return bin;
}

function stretch(s, n) {
  var r = s;
  while(r.length < n) {
    r = '0' + r;
  }
  
  return r;
}

Related

1. fromAscii85()

   String.prototype.fromAscii85 = function() {
     var str = this.slice(2, -2).replace(/\s/g, ''), result = ''
     while (str.length) {
       if (str[0] == 'z') {
         result += '\u0000\u0000\u0000\u0000'
         str = str.substr(1)
       } else {
         let num = 0, j = 5, i = 4
         while (j--) {
   ...
   

2. fromAscii85()

   String.prototype.fromAscii85 = function() {
     var ret = "";
     var str = this.replace(/\s+/g, "").replace("z", "!!!!!").slice(2, -2);
     for(var i=0; i<str.length; i+=5){
       var deficit = Math.max(0, 5+i-str.length);
       var nnn = 0;
       for(var j=0; j<5; j++){
         nnn = nnn*85 + (str.charCodeAt(i+j) || 117) - 33;
       var codes = [];
       for(var j=0; j<4; j++){
         codes.push(nnn%256);
         nnn = nnn/256 | 0;
       codes.reverse();
       var chunk = String.fromCharCode.apply(undefined, codes).slice(0, 4-deficit);
       ret+= chunk;
     return ret;
   

3. fromAscii85()

   String.prototype.fromAscii85 = function() {
       console.log(this)
       let pad = 'u', addnum = 0, s = this.substring(2, this.length - 2).replace(/\s/g, ''), str = '', res = '';
       for (let i = 0; i < s.length; i++)
           str += s[i] === 'z' ? '!!!!!' : s[i];
       while (str.length % 5 !== 0)
           str += pad;
           addnum ++;
   ...