function hexStringToUint8Array(hexString)
{
    if (hexString.length % 2 != 0)
        throw "Invalid hexString";
    var arrayBuffer = new Uint8Array(hexString.length / 2);

    for (var i = 0; i < hexString.length; i += 2) {
        var byteValue = parseInt(hexString.substr(i, 2), 16);
        if (byteValue == NaN)
            throw "Invalid hexString";
        arrayBuffer[i/2] = byteValue;
    }

    return arrayBuffer;
}

function asciiToUint8Array(str)
{
    var chars = [];
    for (var i = 0; i < str.length; ++i)
        chars.push(str.charCodeAt(i));
    return new Uint8Array(chars);
}