text: /**
   * Created by zhang on 2017/10/30.
   */
  
  // prng4.js - uses Arcfour as a PRNG
  
  function Arcfour() {
      this.i = 0;
      this.j = 0;
      this.S = new Array();
  }
  
  // Initialize arcfour context from key, an array of ints, each from [0..255]
  function ARC4init(key) {
      var i, j, t;
      for(i = 0; i < 256; ++i)
          this.S[i] = i;
      j = 0;
      for(i = 0; i < 256; ++i) {
          j = (j + this.S[i] + key[i % key.length]) & 255;
          t = this.S[i];
          this.S[i] = this.S[j];
          this.S[j] = t;
      }
      this.i = 0;
      this.j = 0;
  }
  
  function ARC4next() {
      var t;
      this.i = (this.i + 1) & 255;
      this.j = (this.j + this.S[this.i]) & 255;
      t = this.S[this.i];
      this.S[this.i] = this.S[this.j];
      this.S[this.j] = t;
      return this.S[(t + this.S[this.i]) & 255];
  }
  
  Arcfour.prototype.init = ARC4init;
  Arcfour.prototype.next = ARC4next;
  
  // Plug in your RNG constructor here
  function prng_newstate() {
      return new Arcfour();
  }
  
  // Pool size must be a multiple of 4 and greater than 32.
  // An array of bytes the size of the pool will be passed to init()
  var rng_psize = 256;