reading file into buffer

Question

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I am reading the contents of a file into a bufer ready to populate a window in an MFC app.

My code is:

    //read file
CFile* pFile = new CFile(filePathAndName, CFile::modeRead);
ULONGLONG dwLength = pFile->GetLength();//I64u
char* buffer = new char[(int)dwLength];
UINT nActual = pFile->Read(buffer, dwLength);//sizeof(szBuffer));

However, I lways get about 10-12 characters of garbage right at the end of the buffer - it usually looks something like:
ýýýý««««««««îþîþ

Can anyone tell me where this comes from and how to remove it please. I even get it if the file is empty.

Posted 24-Oct-11 22:58pm

Jackie Lloyd

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CPallini 25-Oct-11 5:13am

Did you check 'nActual' value?

Jackie Lloyd 25-Oct-11 5:54am

nActual has the same value as dwLength - is this as it should be? Should I insert an eof character after the character with position nActual?

2 solutions

Solution 1

There is no null terminating character when reading like this - so you are adding the end of the buffer - what's the line when you set your string? You need to make sure you use nActual characters only - otherwise you'll get garbage at the end :)

Posted 24-Oct-11 23:43pm

Dave Kerr

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Jackie Lloyd 25-Oct-11 5:54am

nActual has the same value as dwLength - is this as it should be? Should I insert an eof character or null character \0 after the character with position nActual?

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Andrew Brock · Accepted Answer · 2011-10-25T03:32:00

Dave's answer is absolutely correct, however a better solution to the problem would be

C++

//read file
CFile* pFile = new CFile(filePathAndName, CFile::modeRead);
ULONGLONG dwLength = pFile->GetLength();//I64u
char* buffer = new char[(int)dwLength + 1]; //Notice the +1
buffer[dwLength] = 0; //This will make the last character a null terminator
UINT nActual = pFile->Read(buffer, dwLength);//sizeof(szBuffer));

This will allow you to use the file contents with any C++ function as a normal string