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typedef union{
unsigned long sum;
char _char[TypeSize];
}Left_Sum;

unsigned long checksum(void* pBuffer, int iLen)
{
Left_Sum leftsum;
unsigned long checksum;
unsigned long* pType = NULL;
char* pChar = NULL;
int iCount = iLen / sizeof(unsigned long);
int iLeft = iLen % sizeof(unsigned long);

if(NULL == pBuffer)
{
throw ;
}

pType = (type*)pBuffer;
pChar = (char*)pBuffer;

checksum = type(0);
leftsum.sum = type(0);

for(int i=0; i<iCount; ++i)
{
checksum += pType[i];
}

if(iLeft > 0)
{
memcpy(&leftsum._char[TypeSize-iLeft], &pChar[iLen-iLeft], iLeft);
}

return checksum + leftsum.sum;

}

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typedef union{
unsigned long sum;