code: function Reader(buffer, offset, length, littleEndian) {
  
              var bufferLength = buffer.byteLength || buffer.length;
  
              this.offset = offset || 0;
              this.length = length || (bufferLength - this.offset);
              this.littleEndian = littleEndian || false;
  
              this.view = new DataView(buffer, this.offset, this.length);
          }
docs: 读取器
  
  @constructor
  @param {Array.<byte>} buffer 缓冲数组
  @param {number} offset 起始偏移
  @param {number} length 数组长度
  @param {boolean} littleEndian 是否小尾