[C/VB6/VB.Net]IP/TCP/UDP头部校验和的计算函数

RFC里面的C源代码

//计算校验和USHORT checksum(USHORT *buffer,int size){ unsigned long cksum = 0; while(size>1) { cksum += *buffer++; size -= sizeof(USHORT); } if (size) { cksum += *(UCHAR *)buffer; } //将32位数转换成16 while (cksum>>16) cksum=(cksum >> 16) + (cksum & 0xffff); return (USHORT) (~cksum);}

VB.Net的

''' <summary> ''' 计算校验和 ''' </summary> ''' <param name="arrHeader">要计算校验和的头部字节数组</param> ''' <param name="HeaderSize">头部长度，单位：字节</param> Private Function CalcCheckSum(ByVal arrHeader() As Byte, ByVal HeaderSize As Integer) As UInt16 '若包头长度不是 2 字节的倍数 '则用 0 比特填充到 2 字节的倍数 Dim CkSum As UInt32, arrTmp() As UInt16 ReDim arrTmp(IIf(HeaderSize Mod 2, (HeaderSize - 1) / 2, HeaderSize / 2 - 1)) Dim GCH As GCHandle = GCHandle.Alloc(arrTmp, GCHandleType.Pinned) Dim tPtr As IntPtr = GCH.AddrOfPinnedObject Marshal.Copy(arrHeader, 0, tPtr, HeaderSize) For i As Integer = 0 To arrTmp.GetUpperBound(0) CkSum += arrTmp(i) Next While (CkSum >> 16) CkSum = (CkSum >> 16) + (CkSum And &HFFFF) End While Return (Not CkSum) And &HFFFF End Function

VB6的

Private Function CalcCheckSum(srcIPP() As Byte, ByVal IPSize As Long) As IntegerDim CkSum As Long, i As Long, IPTmp() As Integer'若包头长度不是 16 比特的倍数'则用 0 比特填充到 16 比特的倍数ReDim IPTmp(IIf(IPSize Mod 2, (IPSize - 1) / 2, IPSize / 2 - 1))CopyMemory IPTmp(0), srcIPP(0), IPSizeFor i = 0 To UBound(IPTmp) CkSum = CkSum + IPTmp(i) + (IPTmp(i) And &H8000&) * 2NextWhile (CkSum And &HFFFF0000) CkSum = (CkSum And &HFFFF0000) / &H10000 + CkSum And &HFFFF&WendCkSum = (Not CkSum) And &HFFFF&CalcCheckSum = CkSum - (CkSum And &H8000&) * 2End Function