Problems writing to a stream

[dbridle]

Hi all,

I'm back again with more i/o issues! Everything I read suggests that this should work, but I said that last time and the answer was relatively simple, hopefully this goes the same way!

Here is my code:

                 	LPVOID lpData = NULL;
                        LPSTREAM lpAttachStream;

for(int i = 6; (i < text_file.size()); i++)
			{
				ULONG ulAttachNum = 0;
				LPSTREAM lpAttachStream;

				hr = lpMessage->CreateAttach(NULL, 0, &ulAttachNum, &attachment);
				if (FAILED(hr))
					break;

				hr =   lpMessage->OpenProperty(PR_ATTACH_DATA_BIN, &IID_IStream, 0, MAPI_CREATE | MAPI_MODIFY, (LPUNKNOWN *)&lpAttachStream);
				CreateStreamOnHGlobal(NULL, TRUE, &lpAttachStream);
                                HANDLE hFile = CreateFile(text_file[i].c_str(), GENERIC_READ, 0, NULL, OPEN_EXISTING, 0,NULL);
				
		   	
	
			// Free the buffer.
			// LocalFree( lpMsgBuf );

				if ( hFile != INVALID_HANDLE_VALUE) 
				{
					 //alocate memory on global
					nBytes = GetFileSize( hFile, NULL);
					if ( ( hMem = GlobalAlloc( GMEM_MOVEABLE, nBytes)) != NULL) 
					{
						//read file content in global allocated mem
						if ( ( lpData = GlobalLock( hMem)) != NULL) 
						{
							ReadFile( hFile, lpData, nBytes, &nBytes, NULL);
							GlobalUnlock( hMem);
						}
					}
					::CloseHandle( hFile);
				}
				
				ULONG ulBytesWritten = 0;
				ULONG ulSize = 0;

				// Write the body to the stream
				hr = lpAttachStream->Write((const void*)lpData, (ULONG)&ulSize, (ULONG*)&ulBytesWritten);

// Commit the stream
				hr = lpAttachStream->Commit(NULL);
	
				if (FAILED(hr))
				{
					MessageBox(NULL,"Unable to commit stream",NULL,MB_OK);
		
				}

				// Release the memory
				hr = lpAttachStream->Release();
	
				// free global alocated memory
				if ( hMem) 
					GlobalFree( hMem);
	
				if (FAILED(hr))
				{
					MessageBox(NULL,"Unable to release memory",NULL,MB_OK);
					// goto cleanup;
				}

				// Save the changes to the message
				lpMessage->SaveChanges(KEEP_OPEN_READWRITE);

The problem is with the last line. I just get access violation, which suggest I have an issue with my streams but I can't figure it out. Everything previous to that statement, appears to go ok during debugging, its just this one line.

Any thoughts?

Thanks in advance,

Darren

[kooth]

Hi Darren,

I don't see where you initialize lpAttachStream, which is a huge problem as you can imagine.

I don't see a definition for hFile, nBytes, or hMem (but you may have left them out of your post.)

Also, if hFile does equal INVALID_HANDLE_VALUE, lpData will never be initialized, causing another huge problem occuring on the last line.

I hope that helps!

Kooth

[dbridle]

Hi Kooth,

Thanks very much for your response. The code is quite large, which is the main reason why I did not paste it all in, however I am happy to if it helps. Otherwise, here is some answers to your questions.

lpAttachStream, is an LPSTREAM, its defined at the top of the code I pasted in (LPSTREAM lpAttachStream;). hFile is also defined in the code as a handle ( HANDLE hFile = CreateFile(text_file[i].c_str(), GENERIC_READ, 0, NULL, OPEN_EXISTING, 0,NULL); ).

nBytes is a DWORD, its defined at the top. hMem also defined at the top is HGLOBAL.

I checked the return code by doing GetLastError() and its returning fine, saying successful. Whether lpData has the correct data in it, I have no idea as I don't know enough about streams to know if that is right.

Is my code for the write() routine ok? The interface that the write is being performed on is LPSTREAM, I checked the syntax, and it should be (const void *pv, ULONG cb, ULONG *pcbWritten). Is this a problem with the lpData portion, am I not casting it correctly etc?

THanks for your help!

Darren

[kooth]

Thanks for your update. You still need to initialize lpAttachStream: It is pointing nowhere and that is causing your access violation.

[dbridle]

Hi Kooth,

The following code initializes lpAttachStream:

hr = lpMessage->OpenProperty(PR_ATTACH_DATA_BIN, &IID_IStream, 0, MAPI_CREATE | MAPI_MODIFY, (LPUNKNOWN *)&lpAttachStream);

I'm going to edit the first post and put the entire loop in so it makes it more readable.

[kooth]

That helps alot! My guess is you should do some more error checking (like the return from OpenProperty() for example), as this might point to the error.

[dbridle]

Hi Kooth,

Right now, I'm running everything through Debug and watching the return codes. For all of hte code except the last function's, the return codes are S_OK. I do need to add error checking, and will add it after I get the code right.

So from that I think I can assume the functions are working right? Or do I need some different error checking going on?

[dbridle]

I think I found the issue. For some reason I was thinking that the ulSize parameter was an OUT, that was given to me after the stream was written. It is in fact an input.

Write((const void*)lpData, (ULONG)&ulSize, (ULONG*)&ulBytesWritten);

I have done a sizeof(lpData) but its still bombing on that line. lpData is an LPVOID that contains a stream of bytes read from a file. I'm wondering how I get the size of the stream? Here is the parameter from MSDN:

"The number of bytes of data to attempt to write into the stream. This value can be zero."

Any help please?

Darren

[dbridle]

The problem was the function CreateStreamOnHGlobal it was completely unneccesary! Thanks for all your help :)