Converting binary to signed decimal in Actionscript

Java

//  binary: 1111 1111 1111 0001
int hexValue = 0xFFF1;

short value = (short)(hexValue);
// value = -15 

to ActionScript

//  binary: 1111 1111 1111 0001
var hexValue:int = 0xFFF1;

// get everything except the signed bit "111 1111 1111 0001"
var unsignedValue:Number = (hexValue & 0x7FFF);  
// unsignedValue now equals 32,753

var signedValue:Number = unsignedValue;

// if the signed flag is set, flip the value
if ((hexValue >> 15) == 1) {
    signedValue = unsignedValue - 0x8000;   // 0x800 =  32,768 (maximum 15 bit number)
}

// signedValue = -15