var StringDecoder = exports.StringDecoder = function (encoding){ 
this.encoding = _AN_Call_replace('replace', (encoding || 'utf8').toLowerCase(), /[-_]/, ''); 
switch (this.encoding){ 
case 'utf8': this.surrogateSize = 3; 
break ; 
case 'ucs2': case 'utf16le': this.surrogateSize = 2; 
this.detectIncompleteChar = utf16DetectIncompleteChar; 
break ; 
default : { 
this.write = passThroughWrite; 
return ; 
} 
} 
this.charBuffer = new Buffer(6); 
this.charReceived = 0; 
this.charLength = 0; 
} 
; 
StringDecoder.prototype.write = function (buffer){ 
var charStr = ''; 
var offset = 0; 
while (this.charLength){ 
var i = (_AN_Read_length('length', buffer) >= this.charLength - this.charReceived)? this.charLength - this.charReceived: _AN_Read_length('length', buffer); 
buffer.copy(this.charBuffer, this.charReceived, offset, i); 
this.charReceived += (i - offset); 
offset = i; 
if (this.charReceived < this.charLength) { 
return ''; 
} 
charStr = this.charBuffer.slice(0, this.charLength).toString(this.encoding); 
var charCode = charStr.charCodeAt(_AN_Read_length('length', charStr) - 1); 
if (charCode >= 55296 && charCode <= 56319) { 
this.charLength += this.surrogateSize; 
charStr = ''; 
continue ; 
} 
this.charReceived = this.charLength = 0; 
if (i == _AN_Read_length('length', buffer)) return charStr; 
buffer = buffer.slice(i, _AN_Read_length('length', buffer)); 
break ; 
} 
var lenIncomplete = this.detectIncompleteChar(buffer); 
var end = _AN_Read_length('length', buffer); 
if (this.charLength) { 
buffer.copy(this.charBuffer, 0, _AN_Read_length('length', buffer) - lenIncomplete, end); 
this.charReceived = lenIncomplete; 
end -= lenIncomplete; 
} 
charStr += buffer.toString(this.encoding, 0, end); 
var end = _AN_Read_length('length', charStr) - 1; 
var charCode = charStr.charCodeAt(end); 
if (charCode >= 55296 && charCode <= 56319) { 
var size = this.surrogateSize; 
this.charLength += size; 
this.charReceived += size; 
this.charBuffer.copy(this.charBuffer, size, 0, size); 
_AN_Call_write('write', this.charBuffer, charStr.charAt(_AN_Read_length('length', charStr) - 1), this.encoding); 
return charStr.substring(0, end); 
} 
return charStr; 
} 
; 
StringDecoder.prototype.detectIncompleteChar = function (buffer){ 
var i = (_AN_Read_length('length', buffer) >= 3)? 3: _AN_Read_length('length', buffer); 
for (; i > 0; i-- ){ 
var c = buffer[_AN_Read_length('length', buffer) - i]; 
if (i == 1 && c >> 5 == 6) { 
this.charLength = 2; 
break ; 
} 
if (i <= 2 && c >> 4 == 14) { 
this.charLength = 3; 
break ; 
} 
if (i <= 3 && c >> 3 == 30) { 
this.charLength = 4; 
break ; 
} 
} 
return i; 
} 
; 
function passThroughWrite(buffer){ 
return buffer.toString(this.encoding); 
} 
function utf16DetectIncompleteChar(buffer){ 
var incomplete = this.charReceived = _AN_Read_length('length', buffer) % 2; 
this.charLength = incomplete? 2: 0; 
return incomplete; 
}