private static uint CalcChecksum(ExecutableImage pe, out uint checkSumPos)
{
const uint checksum_pos_in_optional_headers = 64;
checkSumPos = (uint)pe.NTHeaders.OptionalHeader.Location.FileOffset + checksum_pos_in_optional_headers;
uint fileSize = (uint)pe.GetBytes().Length;
MemoryStream ms = new MemoryStream(pe.GetBytes());
byte[] bytes4 = new byte[4];
int pos = 0;
ulong calcSum = 0;
ulong top = (ulong)0xFFFFFFFF + 1;
while (ms.Read(bytes4, pos, 4) == 4)
{
uint dw = BitConverter.ToUInt32(bytes4, 0);
if (ms.Position == checkSumPos + 4)
{
continue;
}
calcSum = (calcSum & 0xFFFFFFFF) + dw + (calcSum >> 32);
if (calcSum > top)
{
calcSum = (calcSum & 0xFFFFFFFF) + (calcSum >> 32);
}
}
calcSum = (calcSum & 0xffff) + (calcSum >> 16);
calcSum = (calcSum) + (calcSum >> 16);
calcSum = calcSum & 0xffff;
calcSum += (uint)fileSize;
return((uint)calcSum);
}
