Convert C++ code to C#

Question

I have code wrote on C++:

    char szTempString[1500];
    DWORD dwDataLength = PacketBuffer.m_Length - (sizeof(ether_header) + pIpHeader->ip_hl*4 + pTcpHeader->th_off*4);
    PCHAR pData = (PCHAR)pEthHeader + (sizeof(ether_header) + pIpHeader->ip_hl*4 + pTcpHeader->th_off*4);

    // If packet contains any data - process it
    if (dwDataLength)
    {
        //
        // Copy packet payload into the temporary string
        //
        memcpy (szTempString, pData, dwDataLength);

C#:

char[] szTempString = new char[1500];
var dwDataLength = (int)PacketBuffer.m_Length -
(Marshal.SizeOf(typeof (ETHER_HEADER)) + (pIpHeader->IPLenVer & 0xF)*4 + (pTcpHeader->Off & 0xF)*4);

var pData = (IntPtr)pEthHeader + (Marshal.SizeOf(typeof(ETHER_HEADER)) +
(pIpHeader->IPLenVer & 0xF) * 4 + (pTcpHeader->Off & 0xF) * 4);

if(dwDataLength != 0)
{
    Marshal.Copy(pData,szTempString, 0, dwDataLength);
    Console.WriteLine(szTempString);
}

ehter_header, pIp_header and other is structs, they are converted to C#. The var szTempString contains strange data. Have I converted the pData and function memcpy properly?
Thanks.
PS. This is WinPkFilter library. Maybe somebody used it in C#?

Can you please look at this link . It talks about how to use Marshal.Copy correctly. Also this one might be useful too. — Sujay Ghosh
– Sujay Ghosh, Commented Apr 25, 2011 at 7:13
I don't know C# so this might be irrelevant, but pData in the C++ code is treated as a char*, and looks like it's treated as a int* in your C# code. That's two very different things when you do pointer arithmetics. — Mat
– Mat, Commented Apr 25, 2011 at 7:17

Simon Mourier · Accepted Answer · 2011-04-25 07:18:00Z

2

.NET's char is actually unicode, not like in c++. You should at least replace char by byte. Then, when you ultimately want a string from bytes, use the Encoding class, like this: Encoding.Default.GetString(bytes)...

answered Apr 25, 2011 at 7:18

Simon Mourier

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Comments

NickD · Accepted Answer · 2011-04-25 07:03:16Z

1

have you added a [StructLayout(LayoutKind.Sequential, Pack=1)] before your struct?

answered Apr 25, 2011 at 7:03

NickD

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2 Comments

user348173 Over a year ago

No, can you tell me more details

NickD Over a year ago

here is an example: sharperscience.blogspot.com/2008/11/…

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