C + + Computing ICMP header checksum instance _c language

This article describes the C + + computing ICMP header checksum method, share for everyone to reference. The specific implementation code is as follows:

Copy Code code as follows:

USHORT Checksum (ushort* buff, int nsize)
{
unsigned long cksum=0;
Add the data to the cksum in Word units
while (Nsize > 1)
{
Cksum + = *buff++;
Nsize-= sizeof (USHORT);
}

If it is odd, extend the last word to two words, then add
if (nsize)
{
Cksum + = * (uchar*) buff;
}
Add the high 16 bits of the cksum to the lower 16 bits, and get the checksum after the inverse
Cksum = (cksum>>16) + (CKSUM&&0XFFFF);
Cksum + = (cksum>>16);
Return (USHORT) (~cksum);
}

I hope this article will help you with the C + + program design.