CartoDB-SQL-API/app/models/bin_encoder.js

function ArrayBufferSer(type, data, options) {
  if(type === undefined) {
      throw "ArrayBufferSer should be created with a type";
  }
  this.options = options || {};
  this._initFunctions();
  this.headerSize = 8;
  this.data = data;
  this.type = type = Math.min(type, ArrayBufferSer.BUFFER);
  var size = this._sizeFor(this.headerSize, data);
  this.buffer = new Buffer(this.headerSize + size);
  this.buffer.writeUInt32BE(type, 0); // this could be one byte but for byte padding is better to be 4 bytes
  this.buffer.writeUInt32BE(size, 4);
  this.offset = this.headerSize;

  var w = this.writeFn[type];

  var i;
  if(!this.options.delta) {
    for(i = 0; i < data.length; ++i) {
      this[w](data[i]);
    }
  } else {
    this[w](data[0]);
    for(i = 1; i < data.length; ++i) {
      this[w](data[i] - data[i - 1]);
    }
  }
}

//
// constants
//
ArrayBufferSer.INT8 = 1;
ArrayBufferSer.UINT8 = 2;
ArrayBufferSer.UINT8_CLAMP = 3;
ArrayBufferSer.INT16 = 4;
ArrayBufferSer.UINT16 = 5;
ArrayBufferSer.INT32 = 6;
ArrayBufferSer.UINT32 = 7;
ArrayBufferSer.FLOAT32 = 8;
//ArrayBufferSer.FLOAT64 = 9; not supported
ArrayBufferSer.STRING = 10;
ArrayBufferSer.BUFFER = 11;

ArrayBufferSer.MAX_PADDING = ArrayBufferSer.INT32;


ArrayBufferSer.typeNames = {
  'int8': ArrayBufferSer.INT8,
  'uint8': ArrayBufferSer.UINT8,
  'uintclamp': ArrayBufferSer.UINT8_CLAMP,
  'int16': ArrayBufferSer.INT16,
  'uint16': ArrayBufferSer.UINT16,
  'int32': ArrayBufferSer.INT32,
  'uint32': ArrayBufferSer.UINT32,
  'float32': ArrayBufferSer.FLOAT32,
  'string': ArrayBufferSer.STRING,
  'buffer': ArrayBufferSer.BUFFER
};

ArrayBufferSer.prototype = {

  // 0 not used
  sizes: [NaN, 1, 1, 1, 2, 2, 4, 4, 4, 8],

  _paddingFor: function(off, type) {
    var s = this.sizes[type];
    if(s) {
      var r = off % s;
      return r === 0 ? 0 : s - r;
    }
    return 0;
  },

  _sizeFor: function(offset, t) {
    var self = this;
    var s = this.sizes[this.type];
    if(s) {
      return s*t.length;
    }
    s = 0;
    if(this.type === ArrayBufferSer.STRING) {
      // calculate size with padding
      t.forEach(function(arr) { 
        var pad = self._paddingFor(offset, ArrayBufferSer.MAX_PADDING);
        s += pad;
        offset += pad;
        var len = (self.headerSize + arr.length*2);
        s += len;
        offset += len;
      });
    } else {
      t.forEach(function(arr) {
        var pad = self._paddingFor(offset, ArrayBufferSer.MAX_PADDING);
        s += pad;
        offset += pad;
        s += arr.getSize();
        offset += arr.getSize();
      });
    }
    return s;
  },

  getDataSize: function() {
    return this._sizeFor(0, this.data);
  },

  getSize: function() {
    return this.headerSize + this._sizeFor(this.headerSize, this.data);
  },

  writeFn: [
      '',
      'writeInt8',
      'writeUInt8',
      'writeUInt8Clamp',
      'writeInt16LE',
      'writeUInt16LE',
      'writeUInt32LE',
      'writeUInt32LE',
      'writeFloatLE',
      'writeDoubleLE',
      'writeString',
      'writteBuffer'
  ],

  _initFunctions: function() {
    var self = this;
    this.writeFn.forEach(function(fn) {
      if(self[fn] === undefined) {
        self[fn] = function(d) {
          self.buffer[fn](d, self.offset);
          self.offset += self.sizes[self.type];
        };
      }
    });
  },

  writeUInt8Clamp: function(c) {
    this.buffer.writeUInt8(Math.min(255, c), this.offset);
    this.offset += 1;
  },

  writeString: function(s) {
    var arr = [];
    for(var i = 0, len = s.length; i < len; ++i) {
      arr.push(s.charCodeAt(i));
    }
    var str = new ArrayBufferSer(ArrayBufferSer.UINT16, arr);
    this.writteBuffer(str);
  },

  writteBuffer: function(b) {
    this.offset += this._paddingFor(this.offset, ArrayBufferSer.MAX_PADDING);
    // copy header
    b.buffer.copy(this.buffer, this.offset);
    this.offset += b.buffer.length;
  }

};


module.exports = ArrayBufferSer;