Javascript binary parser by Jonas Raoni Soares Silva

binary_parser.js

/**
 * Binary Parser.
 * Jonas Raoni Soares Silva
 * http://jsfromhell.com/classes/binary-parser [v1.0]
 */
var chr = String.fromCharCode;

var maxBits = [];
for (var i = 0; i < 64; i++) {
  maxBits[i] = Math.pow(2, i);
}

function BinaryParser (bigEndian, allowExceptions) {
  if(!(this instanceof BinaryParser)) return new BinaryParser(bigEndian, allowExceptions);
  
	this.bigEndian = bigEndian;
	this.allowExceptions = allowExceptions;
};

BinaryParser.warn = function warn (msg) {
	if (this.allowExceptions) {
		throw new Error(msg);
  }

	return 1;
};

BinaryParser.decodeFloat = function decodeFloat (data, precisionBits, exponentBits) {
	var b = new this.Buffer(this.bigEndian, data);

	b.checkBuffer(precisionBits + exponentBits + 1);

	var bias = maxBits[exponentBits - 1] - 1
    , signal = b.readBits(precisionBits + exponentBits, 1)
    , exponent = b.readBits(precisionBits, exponentBits)
    , significand = 0
    , divisor = 2
    , curByte = b.buffer.length + (-precisionBits >> 3) - 1;

	do {
		for (var byteValue = b.buffer[ ++curByte ], startBit = precisionBits % 8 || 8, mask = 1 << startBit; mask >>= 1; ( byteValue & mask ) && ( significand += 1 / divisor ), divisor *= 2 );
	} while (precisionBits -= startBit);

	return exponent == ( bias << 1 ) + 1 ? significand ? NaN : signal ? -Infinity : +Infinity : ( 1 + signal * -2 ) * ( exponent || significand ? !exponent ? Math.pow( 2, -bias + 1 ) * significand : Math.pow( 2, exponent - bias ) * ( 1 + significand ) : 0 );
};

BinaryParser.decodeInt = function decodeInt (data, bits, signed, forceBigEndian) {
  var b = new this.Buffer(this.bigEndian || forceBigEndian, data)
      , x = b.readBits(0, bits)
      , max = maxBits[bits]; //max = Math.pow( 2, bits );
  
  return signed && x >= max / 2
      ? x - max
      : x;
};

BinaryParser.encodeFloat = function encodeFloat (data, precisionBits, exponentBits) {
	var bias = maxBits[exponentBits - 1] - 1
    , minExp = -bias + 1
    , maxExp = bias
    , minUnnormExp = minExp - precisionBits
    , n = parseFloat(data)
    , status = isNaN(n) || n == -Infinity || n == +Infinity ? n : 0
    ,	exp = 0
    , len = 2 * bias + 1 + precisionBits + 3
    , bin = new Array(len)
    , signal = (n = status !== 0 ? 0 : n) < 0
    , intPart = Math.floor(n = Math.abs(n))
    , floatPart = n - intPart
    , lastBit
    , rounded
    , result
    , i
    , j;

	for (i = len; i; bin[--i] = 0);

	for (i = bias + 2; intPart && i; bin[--i] = intPart % 2, intPart = Math.floor(intPart / 2));

	for (i = bias + 1; floatPart > 0 && i; (bin[++i] = ((floatPart *= 2) >= 1) - 0 ) && --floatPart);

	for (i = -1; ++i < len && !bin[i];);

	if (bin[(lastBit = precisionBits - 1 + (i = (exp = bias + 1 - i) >= minExp && exp <= maxExp ? i + 1 : bias + 1 - (exp = minExp - 1))) + 1]) {
		if (!(rounded = bin[lastBit])) {
			for (j = lastBit + 2; !rounded && j < len; rounded = bin[j++]);
		}

		for (j = lastBit + 1; rounded && --j >= 0; (bin[j] = !bin[j] - 0) && (rounded = 0));
	}

	for (i = i - 2 < 0 ? -1 : i - 3; ++i < len && !bin[i];);

	if ((exp = bias + 1 - i) >= minExp && exp <= maxExp) {
		++i;
  } else if (exp < minExp) {
		exp != bias + 1 - len && exp < minUnnormExp && this.warn("encodeFloat::float underflow");
		i = bias + 1 - (exp = minExp - 1);
	}

	if (intPart || status !== 0) {
		this.warn(intPart ? "encodeFloat::float overflow" : "encodeFloat::" + status);
		exp = maxExp + 1;
		i = bias + 2;

		if (status == -Infinity) {
			signal = 1;
    } else if (isNaN(status)) {
			bin[i] = 1;
    }
	}

	for (n = Math.abs(exp + bias), j = exponentBits + 1, result = ""; --j; result = (n % 2) + result, n = n >>= 1);

	for (n = 0, j = 0, i = (result = (signal ? "1" : "0") + result + bin.slice(i, i + precisionBits).join("")).length, r = []; i; j = (j + 1) % 8) {
		n += (1 << j) * result.charAt(--i);
		if (j == 7) {
			r[r.length] = String.fromCharCode(n);
			n = 0;
		}
	}

	r[r.length] = n
    ? String.fromCharCode(n)
    : "";

	return (this.bigEndian ? r.reverse() : r).join("");
};

BinaryParser.encodeInt = function encodeInt (data, bits, signed, forceBigEndian) {
	var max = maxBits[bits];

  if (data >= max || data < -(max / 2)) {
    this.warn("encodeInt::overflow");
    data = 0;
  }

	if (data < 0) {
    data += max;
  }

	for (var r = []; data; r[r.length] = String.fromCharCode(data % 256), data = Math.floor(data / 256));

	for (bits = -(-bits >> 3) - r.length; bits--; r[r.length] = "\0");

  return ((this.bigEndian || forceBigEndian) ? r.reverse() : r).join("");
};

BinaryParser.toSmall    = function( data ){ return this.decodeInt( data,  8, true  ); };
BinaryParser.fromSmall  = function( data ){ return this.encodeInt( data,  8, true  ); };
BinaryParser.toByte     = function( data ){ return this.decodeInt( data,  8, false ); };
BinaryParser.fromByte   = function( data ){ return this.encodeInt( data,  8, false ); };
BinaryParser.toShort    = function( data ){ return this.decodeInt( data, 16, true  ); };
BinaryParser.fromShort  = function( data ){ return this.encodeInt( data, 16, true  ); };
BinaryParser.toWord     = function( data ){ return this.decodeInt( data, 16, false ); };
BinaryParser.fromWord   = function( data ){ return this.encodeInt( data, 16, false ); };
BinaryParser.toInt      = function( data ){ return this.decodeInt( data, 32, true  ); };
BinaryParser.fromInt    = function( data ){ return this.encodeInt( data, 32, true  ); };
BinaryParser.toLong     = function( data ){ return this.decodeInt( data, 64, true  ); };
BinaryParser.fromLong   = function( data ){ return this.encodeInt( data, 64, true  ); };
BinaryParser.toDWord    = function( data ){ return this.decodeInt( data, 32, false ); };
BinaryParser.fromDWord  = function( data ){ return this.encodeInt( data, 32, false ); };
BinaryParser.toQWord    = function( data ){ return this.decodeInt( data, 64, true ); };
BinaryParser.fromQWord  = function( data ){ return this.encodeInt( data, 64, true ); };
BinaryParser.toFloat    = function( data ){ return this.decodeFloat( data, 23, 8   ); };
BinaryParser.fromFloat  = function( data ){ return this.encodeFloat( data, 23, 8   ); };
BinaryParser.toDouble   = function( data ){ return this.decodeFloat( data, 52, 11  ); };
BinaryParser.fromDouble = function( data ){ return this.encodeFloat( data, 52, 11  ); };

// Factor out the encode so it can be shared by add_header and push_int32
BinaryParser.encode_int32 = function encode_int32 (number, asArray) {
  var a, b, c, d, unsigned;
  unsigned = (number < 0) ? (number + 0x100000000) : number;
  a = Math.floor(unsigned / 0xffffff);
  unsigned &= 0xffffff;
  b = Math.floor(unsigned / 0xffff);
  unsigned &= 0xffff;
  c = Math.floor(unsigned / 0xff);
  unsigned &= 0xff;
  d = Math.floor(unsigned);
  return asArray ? [chr(a), chr(b), chr(c), chr(d)] : chr(a) + chr(b) + chr(c) + chr(d);
};

BinaryParser.encode_int64 = function encode_int64 (number) {
  var a, b, c, d, e, f, g, h, unsigned;
  unsigned = (number < 0) ? (number + 0x10000000000000000) : number;
  a = Math.floor(unsigned / 0xffffffffffffff);
  unsigned &= 0xffffffffffffff;
  b = Math.floor(unsigned / 0xffffffffffff);
  unsigned &= 0xffffffffffff;
  c = Math.floor(unsigned / 0xffffffffff);
  unsigned &= 0xffffffffff;
  d = Math.floor(unsigned / 0xffffffff);
  unsigned &= 0xffffffff;
  e = Math.floor(unsigned / 0xffffff);
  unsigned &= 0xffffff;
  f = Math.floor(unsigned / 0xffff);
  unsigned &= 0xffff;
  g = Math.floor(unsigned / 0xff);
  unsigned &= 0xff;
  h = Math.floor(unsigned);
  return chr(a) + chr(b) + chr(c) + chr(d) + chr(e) + chr(f) + chr(g) + chr(h);
};

/**
 * UTF8 methods
 */

// Take a raw binary string and return a utf8 string
BinaryParser.decode_utf8 = function decode_utf8 (binaryStr) {
  var len = binaryStr.length
    , decoded = ''
    , i = 0
    , c = 0
    , c1 = 0
    , c2 = 0
    , c3;

  while (i < len) {
    c = binaryStr.charCodeAt(i);
    if (c < 128) {
      decoded += String.fromCharCode(c);
      i++;
    } else if ((c > 191) && (c < 224)) {
	    c2 = binaryStr.charCodeAt(i+1);
      decoded += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
      i += 2;
    } else {
	    c2 = binaryStr.charCodeAt(i+1);
	    c3 = binaryStr.charCodeAt(i+2);
      decoded += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
      i += 3;
    }
  }

  return decoded;
};

// Encode a cstring
BinaryParser.encode_cstring = function encode_cstring (s) {
  return unescape(encodeURIComponent(s)) + BinaryParser.fromByte(0);
};

// Take a utf8 string and return a binary string
BinaryParser.encode_utf8 = function encode_utf8 (s) {
  var a = ""
    , c;

  for (var n = 0, len = s.length; n < len; n++) {
    c = s.charCodeAt(n);

    if (c < 128) {
	    a += String.fromCharCode(c);
    } else if ((c > 127) && (c < 2048)) {
	    a += String.fromCharCode((c>>6) | 192) ;
	    a += String.fromCharCode((c&63) | 128);
    } else {
      a += String.fromCharCode((c>>12) | 224);
      a += String.fromCharCode(((c>>6) & 63) | 128);
      a += String.fromCharCode((c&63) | 128);
    }
  }

  return a;
};

BinaryParser.hprint = function hprint (s) {
  var number;

  for (var i = 0, len = s.length; i < len; i++) {
    if (s.charCodeAt(i) < 32) {
      number = s.charCodeAt(i) <= 15
        ? "0" + s.charCodeAt(i).toString(16)
        : s.charCodeAt(i).toString(16);        
      process.stdout.write(number + " ")
    } else {
      number = s.charCodeAt(i) <= 15
        ? "0" + s.charCodeAt(i).toString(16)
        : s.charCodeAt(i).toString(16);
        process.stdout.write(number + " ")
    }
  }
  
  process.stdout.write("\n\n");
};

BinaryParser.ilprint = function hprint (s) {
  var number;

  for (var i = 0, len = s.length; i < len; i++) {
    if (s.charCodeAt(i) < 32) {
      number = s.charCodeAt(i) <= 15
        ? "0" + s.charCodeAt(i).toString(10)
        : s.charCodeAt(i).toString(10);

      require('util').debug(number+' : ');
    } else {
      number = s.charCodeAt(i) <= 15
        ? "0" + s.charCodeAt(i).toString(10)
        : s.charCodeAt(i).toString(10);
      require('util').debug(number+' : '+ s.charAt(i));
    }
  }
};

BinaryParser.hlprint = function hprint (s) {
  var number;

  for (var i = 0, len = s.length; i < len; i++) {
    if (s.charCodeAt(i) < 32) {
      number = s.charCodeAt(i) <= 15
        ? "0" + s.charCodeAt(i).toString(16)
        : s.charCodeAt(i).toString(16);
      require('util').debug(number+' : ');
    } else {
      number = s.charCodeAt(i) <= 15
        ? "0" + s.charCodeAt(i).toString(16)
        : s.charCodeAt(i).toString(16);
      require('util').debug(number+' : '+ s.charAt(i));
    }
  }
};

/**
 * BinaryParser buffer constructor.
 */
function BinaryParserBuffer (bigEndian, buffer) {
  this.bigEndian = bigEndian || 0;
  this.buffer = [];
  this.setBuffer(buffer);
};

BinaryParserBuffer.prototype.setBuffer = function setBuffer (data) {
  var l, i, b;

	if (data) {
    i = l = data.length;
    b = this.buffer = new Array(l);
		for (; i; b[l - i] = data.charCodeAt(--i));
		this.bigEndian && b.reverse();
	}
};

BinaryParserBuffer.prototype.hasNeededBits = function hasNeededBits (neededBits) {
	return this.buffer.length >= -(-neededBits >> 3);
};

BinaryParserBuffer.prototype.checkBuffer = function checkBuffer (neededBits) {
	if (!this.hasNeededBits(neededBits)) {
		throw new Error("checkBuffer::missing bytes");
  }
};

BinaryParserBuffer.prototype.readBits = function readBits (start, length) {
	//shl fix: Henri Torgemane ~1996 (compressed by Jonas Raoni)

	function shl (a, b) {
		for (; b--; a = ((a %= 0x7fffffff + 1) & 0x40000000) == 0x40000000 ? a * 2 : (a - 0x40000000) * 2 + 0x7fffffff + 1);
		return a;
	}

	if (start < 0 || length <= 0) {
		return 0;
  }

	this.checkBuffer(start + length);

  var offsetLeft
    , offsetRight = start % 8
    , curByte = this.buffer.length - ( start >> 3 ) - 1
    , lastByte = this.buffer.length + ( -( start + length ) >> 3 )
    , diff = curByte - lastByte
    , sum = ((this.buffer[ curByte ] >> offsetRight) & ((1 << (diff ? 8 - offsetRight : length)) - 1)) + (diff && (offsetLeft = (start + length) % 8) ? (this.buffer[lastByte++] & ((1 << offsetLeft) - 1)) << (diff-- << 3) - offsetRight : 0);

	for(; diff; sum += shl(this.buffer[lastByte++], (diff-- << 3) - offsetRight));

	return sum;
};

/**
 * Expose.
 */
BinaryParser.Buffer = BinaryParserBuffer;

exports.BinaryParser = BinaryParser;