Extract Main CPU firmware from ICOM IC-R8600 firmware bundle (1.01-1.35 USA and non-USA versions)

MainCpuFirmwareExtract.cs

/// <summary>
/// Extract Main CPU firmware from ICOM IC-R8600 firmware bundle (1.01-1.35 USA and non-USA versions)
/// non-USA versions:
/// https://www.icomjapan.com/support/firmware_driver/?product=IC-R8600(EUR)&frm_type=Firmware&old=true
/// USA versions:
/// https://www.icomjapan.com/support/firmware_driver/?product=IC-R8600&frm_type=Firmware&old=true
/// </summary>
/// <param name="bundle">Firmware bundle</param>
/// <returns>Unpacked data</returns>
static byte[] MainCpuFirmwareExtract(byte[] bundle)
{
    const uint SIGNATURE = 0x88118833; // for r8600
    const int START_FIRMWARE_OFFSET = 0x10040; // for r8600
    const int START_DICTIONARY_OFFSET = 0xfee;

    var signature = BitConverter.ToUInt32(bundle, 0);
    if (signature != SIGNATURE)
        throw new Exception($"Wrong signature: 0x{signature:X}!");

    var dict = new byte[0x1000];
    var dictOffset = START_DICTIONARY_OFFSET;

    var dst = new byte[BitConverter.ToInt32(bundle, START_FIRMWARE_OFFSET)];
    var dstOffset = 0;

    var srcOffset = START_FIRMWARE_OFFSET + 4;

    try
    {
        while(true)
        {
            var cmdBits = (int)bundle[srcOffset++];
            for(var i=0; i<8; i++)
            {
                // raw data
                if ((cmdBits & 1) == 1)
                {
                    dst[dstOffset++] = bundle[srcOffset];
                    dict[dictOffset++] = bundle[srcOffset++];
                    dictOffset %= 0x1000;
                }
                // dict data
                else
                {
                    var index = (int)bundle[srcOffset++];
                    var len = (int)bundle[srcOffset++];
                    index = index | ((len & 0xf0) << 4);
                    len = (len & 0xf) + 2;
                    for(var j=0; j<=len; j++)
                    {
                        var value = dict[(index + j) % 0x1000];
                        dst[dstOffset++] = value;
                        dict[dictOffset++] = value;
                        dictOffset %=  0x1000;
                    }
                }
                cmdBits >>= 1;
            }
        }
    }
    catch(IndexOutOfRangeException)
    {
        return dstOffset != dst.Length+1 ? null : dst;
    }
}