IStream CopyTo

[Dontmindme]

I need help with the CopyTo method of ComTypes::IStream
I have the following code and there appears to be an issue where the original stream is left open.
Can someone please take a look and let me know what might be wrong with this code and if there is a better way to write this method?

Thanks!

const static int COPYTO_BUFFER_SIZE = 16384;
virtual void CopyTo(System::Runtime::InteropServices::ComTypes::IStream ^pstm, long long cb, System::IntPtr pcbRead, System::IntPtr pcbWritten)
{
array<unsigned char>^ buffer = gcnew array<unsigned char>(COPYTO_BUFFER_SIZE);
long long written = 0;

while(written < cb)
{
int count = min(COPYTO_BUFFER_SIZE, static_cast<int>(cb - written));

int read = stream->Read(buffer, 0, count);
if (read == 0) break;

pstm->Write(buffer, read, IntPtr::Zero);
written += read;
}

if (pcbRead != IntPtr::Zero) Marshal::WriteInt64(pcbRead, written);
if (pcbWritten != IntPtr::Zero) Marshal::WriteInt64(pcbWritten, written);
}

[o1vk4iN6]

You make want to consider actually learning C++ ISO standard instead of that .net crap. May as well stick with one standard and use C# instead if your going to be using .net.

[Dontmindme]

using .net is not option in this case

[webJose]

What do you mean "an issue"? I mean, why is it an issue for the stream to be left open? According to http://msdn.microsoft.com/en-us/library/windows/desktop/aa380038(v=vs.85).aspx , there is no specification that the original stream has to close after a call to CopyTo().

Also note that you should collect the actual number of bytes written in the destination stream (I think). Then use that value to increment your 'written' variable. Unless you know for sure that they are the same 100% of the time? I also think you should totalize the bytes read in a different variable so you don't "cheat" at the very end when you use 'written' for both output variables.

Other than that I don't think I see an issue, but then again, I don't know C++/CLI.

[o1vk4iN6]

Dontmindme wrote:

using .net is not option in this case

You are using .net though, none of the libraries you are using here are C++ but are Microsoft's .net framework which are also accessible using C#. Except C# does not conflict with any established standards.