Problem using C++ CString for file i/o

Stugots · 11-10-2006 01:11PM #1

I'm rebuilding a text file editing application which I originally wrote under Visual C++ 6.0 in the Visual C++ .NET environment. An exception has popped up when using the following code to allocate a CString buffer for the data read from the file. The code in question is as follows:

LPTSTR pszBuffer = m_szDataBuffer.GetBuffer(ar.GetFile()->GetLength());
m_nBufferLength = ar.Read( pszBuffer, ar.GetFile()->GetLength() );
m_szDataBuffer.ReleaseBuffer();

The call to m_szDataBuffer.ReleaseBuffer() throws an exception because the size of the buffer to be released is greater than the allocated buffer => ReleaseBuffer() calls SetLength(nLength) with nLength == the size of data from the file. The following Assert fails in SetLength:

ATLASSERT( nLength <= GetData()->nAllocLength );

GetData()->nAllocLength is less than half the size that should be allocated in the buffer.

Any suggestions on how to proceed?

Tobias Greeshman · 12-10-2006 03:51PM

As far as I recall the GetBuffer ( ) function can throw exceptions as well. Have you tried placing the call to GetBuffer in a try/catch block to see if any exception is being thrown. If only half of the desired length is being allocated, I'd say this function might be the cause.

Stugots · 16-10-2006 04:19PM

Thanks for your help. Turns out the problem was that I was not specifying the buffer length when releasing the buffer.

Problem using C++ CString for file i/o

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