/// <summary>
/// Calculate the CRC-32 of a memory pointer.
/// </summary>
/// <param name="data">Pointer containing the bytes to calculate.</param>
/// <param name="length">Specify the length, in bytes, of the data to be checked.</param>
/// <param name="crc">Input CRC value for ongoing calculations (default is FFFFFFFFh).</param>
/// <param name="bufflen">Specify the size, in bytes, of the marshaling buffer to be used (default is 1k).</param>
/// <returns>A 32-bit unsigned integer representing the calculated CRC.</returns>
/// <remarks></remarks>
public static uint Calculate(IntPtr data, IntPtr length, uint crc = 0xFFFFFFFFU, int bufflen = 1024)
{
uint CalculateRet = default;
if (length.ToInt64() <= 0L)
{
throw new ArgumentOutOfRangeException("length", "length must be a positive number.");
}
if (data == IntPtr.Zero)
{
throw new ArgumentNullException("data", "data cannot be equal to null.");
}
// ' our working marshal buffer will be 1k, this is a good compromise between eating up memory and efficiency.
int blen = bufflen;
byte[] b;
var mm = new MemPtr(data);
long i;
long l = length.ToInt64();
long c = l - 1L;
int e;
int j;
b = new byte[blen];
var loopTo = c;
for (i = 0L; (long)blen >= 0 ? i <= loopTo : i >= loopTo; i += blen)
{
if (l - i > blen)
{
e = blen;
}
else
{
e = (int)(l - i);
}
mm.GrabBytes((IntPtr)i, e, ref b);
e -= 1;
var loopTo1 = e;
for (j = 0; j <= loopTo1; j++)
{
crc = Crc32Table[(int)((crc ^ b[j]) & 0xFFL)] ^ crc >> 8;
}
}
CalculateRet = crc ^ 0xFFFFFFFFU;
return(CalculateRet);
}
