node_core_bitop.js

class Bitop {
    constructor(buffer) {
      this.buffer = buffer;
      this.buflen = buffer.length;
      this.bufpos = 0;
      this.bufoff = 0;
      this.iserro = false;
    }
  
    read(n) {
      let v = 0;
      let d = 0;
      while (n) {
        if (n < 0 || this.bufpos >= this.buflen) {
          this.iserro = true;
          return 0;
        }
  
        this.iserro = false;
        d = this.bufoff + n > 8 ? 8 - this.bufoff : n;
  
        v <<= d;
        v += (this.buffer[this.bufpos] >> (8 - this.bufoff - d)) & (0xff >> (8 - d))
  
        this.bufoff += d;
        n -= d;
  
        if (this.bufoff == 8) {
          this.bufpos++;
          this.bufoff = 0;
        }
      }
      return v;
    }
  
    look(n) {
      let p = this.bufpos;
      let o = this.bufoff;
      let v = this.read(n);
      this.bufpos = p;
      this.bufoff = o;
      return v;
    }

    read_golomb() {
      let n;
      for (n = 0; this.read(1) == 0 && !this.iserro; n++);
      return (1 << n) + this.read(n) - 1;
    }
  }
  
  module.exports = Bitop;