Dr. Dobb's Electronic Review of Computer Books
ATL Internalsby Brent E. Rector
"This book is the definitive reference for ATL programmers. The chapter on CComObject is worth the price alone."--Don Box, COM guy, DevelopMentor "Brent and Chris are always technically accurate and present the information in a well written, easy to understand manner... I bought it and I'm the ATL Development Lead!"--Christian Beaumont, ATL/blockquote>… See more details below
"This book is the definitive reference for ATL programmers. The chapter on CComObject is worth the price alone."--Don Box, COM guy, DevelopMentor "Brent and Chris are always technically accurate and present the information in a well written, easy to understand manner... I bought it and I'm the ATL Development Lead!"--Christian Beaumont, ATL Development Lead, Microsoft Corporation
The Active Template Library (ATL) is a set of small, efficient, and flexible classes that facilitate the creation of interoperable COM components. Written for experienced COM and Visual C++ programmers, this book provides in-depth coverage of ATL's inner workings. It offers insight into the rationale behind ATL design, explains its architectural underpinnings, shows how ATL maps to COM, and describes important implementation details.
With coverage current through ATL version 3.0, ATL Internals includes an overview of the Wizards but then goes well beyond the basics. The authors provide the detailed information needed to utilize ATL to its greatest advantage and work around its shortcomings. You will find detailed coverage of such topics as:
- ATL Smart Types, such as CComPtr, CComVariant, and CComBSTR
- Objects in ATL, covering COM object responsibilities and ATL threading model support
- Servers in ATL, including ATL's class object implementations, managing server lifetime, self-registration, and server build optimizations
- Interface maps, focusing on the techniques C++ programmers can use to implement COM interfaces and how ATL supports these techniques
- Persistence and connection points
- Enumeration, covering both pre-calculatedand dynamic data sets, and enumerating over an STL container
- ATL windowing classes
- Controls and Control Containment
If you want to optimize ATL by learning effective techniques that reduce the time you spend writing boilerplate COM code, there is no better resource than this book.
Dr. Dobb's Electronic Review of Computer Books
Read an Excerpt
C is a framework for generating assembly language code (ASM). Most ASM programmers shifting to C spent a lot of time examining and replacing the compiler-generated code because they didn't trust the compiler to create correct code. As time went on and C compilers got better, ASM programmers gradually learned to trust the compiler to generate not only correct code, but also efficient code. Of course, talented C programmers never forget that the compiler is generating ASM. They know that they can still reach into selected areas and dictate the generated code when their needs exceed the capabilities of the language.
Microsoft's Active Template Library (ATL) is a framework for generating C++/COM code. Most C++ programmers shifting to ATL seem to fear examining, let alone replacing, ATL-generated code. They don't trust ATL any more than ASM programmers trusted their C compilers, because the source for ATL is fairly inscrutable to the casual observer. However, ATL is performing the same services for the C++/COM programmer that the C compiler performed for ASM programmers, namely, providing a simpler way to generate boilerplate code correctly and efficiently. Of course, talented ATL programmers never forget that ATL is generating C++/COM code. They know that they can still reach into selected areas and dictate the generated code when their needs exceed the capabilities of ATL. Our goal in writing this book is to turn you into an ATL programmer, unafraid to reach into it and bend it to your will.
This book is for the C++/COM programmer shifting to ATL 3.0, as provided with Visual C++ 6.0. Because ATL was built with a set of assumptions, to be aneffective ATL programmer you need to understand not only how ATL is built but also why. Of course, to understand the why of ATL, you'll have to understand the environment in which ATL was developed, that is, COM. Instead of attempting to compress all required COM knowledge into one or two chapters, this book assumes you already know COM and shows you the design, usage, and internals of ATL. Don Box's Essential COM (Addison-Wesley, 1998) is a good source of COM knowledge, if you'd like to brush up before diving into ATL.
With the exception of the first chapter, this book was arranged from the lowest levels of ATL to the highest, each chapter building on knowledge in previous chapters. The first chapter is a brief overview of some of the more common uses for ATL, and the wizards (if they exist) that aid in these uses. Whenever things get too detailed in the first chapter, however, we refer you to a subsequent chapter that will provide more in-depth coverage. Chapters 2 through 5 present the core of ATL. Chapter 2 covers the ATL smart types, such as CComPtr, CComQIPtr, CComBSTR, and CComVariant. Chapter 3 discusses how objects are implemented in ATL, concentrating on the great range of choices you have when implementing IUnknown. Chapter 4 discusses the glue code required to expose COM objects from COM servers. Chapter 5 delves into the implementation of IUnknown again, this time concentrating on how to implement QueryInterface, showing techniques such as tear-off interfaces and aggregation. Chapters 6, 7, and 8 discuss canned interface implementations that ATL provides to support object persistence, connection points, and COM collections and enumerators, respectively. These services can be used by components that may or may not provide their own user interface. Chapters 9, 10, and 11, on the other hand, concentrate on building both standalone applications and user interface components. These chapters cover the ATL window classes, controls, and control containment, respectively. Because much of what makes the ATL source difficult to read is its advanced use of templates, Appendix A provides a set of examples meant to illustrate how templates are used and built. If you've seen ATL source code before and wondered why you can pass the name of a deriving class to a base class template, you may find Appendix A useful. Appendix B provides a list of the important ATL classes and the header files in which they are declared (and often implemented).
When writing these chapters, it became necessary not only to show diagrams and sample usage code, but also internal ATL implementation code. In fact, this book often becomes your personal tour guide through the ATL source code.
Because the ATL team didn't write their code to be published in book form, it was often necessary to reformat it or even to abbreviate it. Every effort has been made to retain the essence of the original code, but, as always, the ATL source code is the final arbiter. You might find Appendix B useful when tracking down the actual implementation.
If there are any errors in the sample source or in any part of this book, you may contact Brent Rector at ...
Meet the Author
Brent E. Rector is President of Wise Owl Consulting, Inc., a firm that specializes in Windows/COM development and consulting. He also teaches classes on COM, ATL, and MTS for DevelopMentor, a leading COM education firm. He received the Microsoft Annual MVP (Most Valuable Professional) award for his contributions to CompuServe's Windows forums.
Chris Sells is a content strategist on the Microsoft MSDN content team. Previously, he was the director of software engineering at DevelopMentor. Chris is the author of Windows Telephony Programming (Addison-Wesley, 1998) and Windows Forms Programming in Visual Basic .NET (Addison-Wesley, 2004), and coauthor of Effective COM (Addison-Wesley, 1999), ATL Internals (Addison-Wesley, 1999), and Essential .NET, Volume 1 (Addison-Wesley, 2003).
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