dns2/lib/reader.js

A DNS Server and Client Implementation in Pure JavaScript with no dependencies.

/**
 * [Reader description]
 * @param {[type]} buffer [description]
 * @param {[type]} offset [description]
 */
function BufferReader(buffer, offset) {
  this.buffer = buffer;
  this.offset = offset || 0;
  return this;
}

/**
 * [read description]
 * @param  {[type]} buffer [description]
 * @param  {[type]} offset [description]
 * @param  {[type]} length [description]
 * @return {[type]}        [description]
 */
BufferReader.read = function(buffer, offset, length) {
  let a = [];
  let c = Math.ceil(length / 8);
  let l = Math.floor(offset / 8);
  const m = offset % 8;
  function t(n) {
    const r = [ 0, 0, 0, 0, 0, 0, 0, 0 ];
    for (let i = 7; i >= 0; i--) {
      r[7 - i] = n & Math.pow(2, i) ? 1 : 0;
    }
    a = a.concat(r);
  }
  function p(a) {
    let n = 0;
    const f = a.length - 1;
    for (let i = f; i >= 0; i--) { if (a[f - i]) n += Math.pow(2, i); }
    return n;
  }
  while (c--) t(buffer.readUInt8(l++));
  return p(a.slice(m, m + length));
};

/**
 * [read description]
 * @param  {[type]} size [description]
 * @return {[type]}      [description]
 */
BufferReader.prototype.read = function(size) {
  const val = BufferReader.read(this.buffer, this.offset, size);
  this.offset += size;
  return val;
};

module.exports = BufferReader;