gistfile1.js

var encodeUint8 = (function() {
  var arr = new Uint8Array( 1 );
  return function( number ) {
    // If we assume that the number passed in
    // valid, we can just use it directly.
    // return String.fromCharCode( number );
    arr[0] = number;
    return String.fromCharCode( arr[0] );
  };
}());

var encodeFloat32 = (function() {
  var arr  = new Float32Array( 1 );
  var char = new Uint8Array( arr.buffer );
  return function( number ) {
    arr[0] = number;
    // In production code, please pay
    // attention to endianness here.
    return String.fromCharCode( char[0], char[1], char[2], char[3] );
  };
}());

var encodeState = function( state ) {
  var msg = '';
  for ( var i = 0; i < state.length; ++i ) {
    var player = state[i];

    // Encode id
    msg += encodeUint8( player.id );

    // Encode transform
    msg += ( encodeFloat32( player.transform.position.x ) +
             encodeFloat32( player.transform.position.y ) +
             encodeFloat32( player.transform.position.z ) +
             encodeFloat32( player.transform.rotation.x ) +
             encodeFloat32( player.transform.rotation.y ) +
             encodeFloat32( player.transform.rotation.z ) +
             encodeFloat32( player.transform.rotation.w ) );
  }
  return msg;
};

var impreciseMsg = encodeState( state );


// Decode
var decodeUint8 = function( str, offset, obj, propName ) {
  obj[ propName ] = str.charCodeAt( offset );

  // Number of bytes (characters) read.
  return 1;
};

var decodeFloat32 = (function() {
  var arr  = new Float32Array( 1 );
  var char = new Uint8Array( arr.buffer );
  return function( str, offset, obj, propName ) {
    // Again, pay attention to endianness
    // here in production code.
    for ( var i = 0; i < 4; ++i ) {
      char[i] = str.charCodeAt( offset + i );
    }

    obj[ propName ] = arr[0];

    // Number of bytes (characters) read.
    return 4;
  };
}());

var decodeState = function( str ) {
  var charsRead = 0;

  var state = [];
  while ( charsRead < str.length ) {
    // GC performance suffers here. Read Martin Wells’
    // article about writing GC-friendly code, here
    // on BuildNewGames.com
    var player = { transform: {} };
    var position = player.transform.position = {};
    var rotation = player.transform.rotation = {};

    // !!!: The order of decode is same as encode!

    // Decode id
    charsRead += decodeUint8( str, charsRead, player, 'id' );

    // Decode transform
    charsRead += decodeFloat32( str, charsRead, position, 'x' );
    charsRead += decodeFloat32( str, charsRead, position, 'y' );
    charsRead += decodeFloat32( str, charsRead, position, 'z' );
    charsRead += decodeFloat32( str, charsRead, rotation, 'x' );
    charsRead += decodeFloat32( str, charsRead, rotation, 'y' );
    charsRead += decodeFloat32( str, charsRead, rotation, 'z' );
    charsRead += decodeFloat32( str, charsRead, rotation, 'w' );

    state.push( player );
  }
  return state;
};

var decodedState = decodeState( impreciseMsg );