学步园

USHORT checksum(USHORT *buffer, int size)
{
unsigned long cksum=0;
while(size >1)
{
cksum+=*buffer++;
size -=sizeof(USHORT);
}
if(size )
{

cksum += *(UCHAR*)buffer;
}
cksum = (cksum >> 16) + (cksum & 0xffff);//这两行是否可以不要呢？不行是long
cksum += (cksum >>16);                            //
return (USHORT)(~cksum);
}