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/*++
Copyright (c) 1993 Microsoft Corporation
Module Name:
chksum.c
Abstract:
This module implements checksum functions.
Author:
David N. Cutler (davec) 11-Mar-1993
Revision History:
--*/
#include "windows.h"
#ifdef __cplusplus
extern "C"
#endif
USHORT
ChkSum(
ULONG PartialSum,
PUSHORT Source,
ULONG Length
)
/*++
Routine Description:
This function initializes a kernel process object. The base priority,
affinity, and page frame numbers for the process page table directory
and hyper space are stored in the process object.
Arguments:
PartialSum - Supplies the initial checksum value.
Sources - Supplies a pointer to the array of words for which the
checksum is computed.
Length - Supplies the length of the array in words.
Return Value:
The computed checksum value is returned as the function value.
--*/
{
//
// Compute the word wise checksum allowing carries to occur into the
// high order half of the checksum longword.
//
while (Length--) {
PartialSum += *Source++;
PartialSum = (PartialSum >> 16) + (PartialSum & 0xffff);
}
//
// Fold final carry into a single word result and return the resultant
// value.
//
return (USHORT)(((PartialSum >> 16) + PartialSum) & 0xffff);
}
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