Non-MFC String Class for ATL

Introduction

When writing ATL components, I have found that one of the hardest things for Windows programmers to overcome is the dependency on the MFC library. For dates and strings, MFC simplifies the programmer's job by handling memory allocations and type conversions within its class encapsulation. However, with that simplification comes the price of having to distribute the MFC DLL's with your component.

This article focuses on the issues surrounding the use of strings in an ATL component. If you don't include MFC support in your ATL component, you obviously won't have the CString available to use. There have been several articles published that address this issue. Several of the ones that I have read are:

• NonMFC:CString (posted on www.worldofatl.com) - This article provides a new CString class based on the standard template library (STL).
• Add MFC's CString to ATL w/ No MFC dependencies (by K. Shane Triem (www.codeguru.com) - This article illustrates how to use a Visual Studio macro to extract the CString class source code from the MFC library and then use this class in your ATL component.

CCOMString

While both of these articles are viable alternatives to the MFC CString class, I wanted a class that would compile under both ANSI and Unicode and had no dependencies whatsoever: neither MFC or STL. My alternative was to write a string handling class entitled CCOMString which is based entirely on Visual C++'s TCHAR datatype.

The TCHAR datatype is defined as follows:

• As a char when _MBCS is defined in your program.
• As a wchar_t when _UNICODE is defined in your program.
• As a char when neither _MBCS or _UNICODE is defined in your program.

Therefore, by using the TCHAR datatype, CCOMString is compatible with both ANSI and Unicode compile modes. Please note that there is one caveat to this class in its present state of development: it does not currently include exception handling for the memory allocation functions. I am currently trapping any memory allocation errors with the ATLASSERT macro, but these will compile away in Release mode (I'm still researching a way to handle these errors without adding the exception handling overhead to the class).

The current version of the CCOMString includes the following functionality. Please note, if there are any functions in the CCOMString class that you download that are not listed in the text below, they are considered to be undocumented and, therefore, possibly untest as well:

Constructors

Assignment Operations

Concatenation

Accessors for the String as an Array

Conversions

Searching

Extraction

Replacing

Comparison

Formatting

History

28 June 2000 - memory leak fix in source

12 August 2000 - updated source ZIP file

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