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// BinaryReader
// Refactored by Vjeux <vjeuxx@gmail.com>
// http://blog.vjeux.com/2010/javascript/javascript-binary-reader.html
// Original
//+ Jonas Raoni Soares Silva
//@ http://jsfromhell.com/classes/binary-parser [rev. #1]
BinaryReader = function (data) {
this._buffer = data;
this._pos = 0;
};
BinaryReader.prototype = {
/* Public */
readInt8: function (){ return this._decodeInt(8, true); },
readUInt8: function (){ return this._decodeInt(8, false); },
readInt16: function (){ return this._decodeInt(16, true); },
readUInt16: function (){ return this._decodeInt(16, false); },
readInt32: function (){ return this._decodeInt(32, true); },
readUInt32: function (){ return this._decodeInt(32, false); },
readFloat: function (){ return this._decodeFloat(23, 8); },
readDouble: function (){ return this._decodeFloat(52, 11); },
readChar: function () { return this.readString(1); },
readString: function (length) {
this._checkSize(length * 8);
var result = this._buffer.substr(this._pos, length);
this._pos += length;
return result;
},
seek: function (pos) {
this._pos = pos;
this._checkSize(0);
},
getPosition: function () {
return this._pos;
},
getSize: function () {
return this._buffer.length;
},
/* Private */
_decodeFloat: function(precisionBits, exponentBits){
var length = precisionBits + exponentBits + 1;
var size = length >> 3;
this._checkSize(length);
var bias = Math.pow(2, exponentBits - 1) - 1;
var signal = this._readBits(precisionBits + exponentBits, 1, size);
var exponent = this._readBits(precisionBits, exponentBits, size);
var significand = 0;
var divisor = 2;
// var curByte = length + (-precisionBits >> 3) - 1;
var curByte = 0;
do {
var byteValue = this._readByte(++curByte, size);
var startBit = precisionBits % 8 || 8;
var mask = 1 << startBit;
while (mask >>= 1) {
if (byteValue & mask) {
significand += 1 / divisor;
}
divisor *= 2;
}
} while (precisionBits -= startBit);
this._pos += size;
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);
},
_decodeInt: function(bits, signed){
var x = this._readBits(0, bits, bits / 8), max = Math.pow(2, bits);
var result = signed && x >= max / 2 ? x - max : x;
this._pos += bits / 8;
return result;
},
//shl fix: Henri Torgemane ~1996 (compressed by Jonas Raoni)
_shl: function (a, b){
for (++b; --b; a = ((a %= 0x7fffffff + 1) & 0x40000000) == 0x40000000 ? a * 2 : (a - 0x40000000) * 2 + 0x7fffffff + 1);
return a;
},
_readByte: function (i, size) {
return this._buffer.charCodeAt(this._pos + size - i - 1) & 0xff;
},
_readBits: function (start, length, size) {
var offsetLeft = (start + length) % 8;
var offsetRight = start % 8;
var curByte = size - (start >> 3) - 1;
var lastByte = size + (-(start + length) >> 3);
var diff = curByte - lastByte;
var sum = (this._readByte(curByte, size) >> offsetRight) & ((1 << (diff ? 8 - offsetRight : length)) - 1);
if (diff && offsetLeft) {
sum += (this._readByte(lastByte++, size) & ((1 << offsetLeft) - 1)) << (diff-- << 3) - offsetRight;
}
while (diff) {
sum += this._shl(this._readByte(lastByte++, size), (diff-- << 3) - offsetRight);
}
return sum;
},
_checkSize: function (neededBits) {
if (!(this._pos + Math.ceil(neededBits / 8) < this._buffer.length)) {
throw new Error("Index out of bound");
}
}
};
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