Reddy - API Design for C++

I should begin by confessing that I do not consider myself a world-class API designer or software engineer. I do, however, consider myself an expert researcher in the areas of computer graphics and geometric modeling. It was in this line of work that I first met Martin at Pixar Animation Studios.

As a graphics researcher I was accustomed to writing mathematically sophisticated papers. I was also formally trained as a computer scientist at a major university and had written my share of code. Armed with this background, when I was presented with the opportunity to lead a group of software engineers working on a new generation of animation software for Pixar, I figured that it couldnt be any more difficult than research. After all, research is, by definition, the creation of the unknown, whereas engineering is the implementation of well-understood subjects. I could not have been more wrong.

I came to realize that software engineering was, without a doubt, the most difficult challenge I had ever been presented with. After more years than I care to admit, I eventually gave up and went back to graphics research.

I cant tell you how much I would have benefitted from a book such as API Design for C++. Many of the lessons we learned the hard way have been captured by Martin in this insightful, easy-to-use book. Martin approaches the subject not from the perspective of an academic software researcher (although he draws heavily from results and insights gained there), but from the perspective of an in-the-trenches software engineer and manager. He has experienced firsthand the importance of good software design and has emerged as an articulate voice of what good means. In this book he presents effective strategies for achieving that goal.

I particularly like that Martin is not focusing just on API design, but more broadly on software life cycles, allowing him to cover topics such as versioning, strategies for backward compatibility, and branching methodologies.

In short, this book should be of great value to those creating or managing software activities. It is a comprehensive collection of best practices that have proven themselves time and time again.

Tony DeRose, Senior Scientist and Research Group Lead, Pixar Animation Studios

Writing large applications in C++ is a complex and tricky business. However, designing reusable C++ interfaces that are robust, stable, easy to use, and durable is even more difficult. The best way to succeed in this endeavor is to adhere to the tenets of good Application Programming Interface (API) design.

An API presents a logical interface to a software component and hides the internal details required to implement that component. It offers a high-level abstraction for a module and promotes code reuse by allowing multiple applications to share the same functionality.

Modern software development has become highly dependent on APIs, from low-level application frameworks to data format APIs and graphical user interface (GUI) frameworks. In fact, common software engineering terms such as modular development, code reuse, componentization, dynamic link library or DLL, software frameworks, distributed computing, and service-oriented architecture all imply the need for strong API design skills.

Some popular C and C++ APIs that you may already be aware of include the Standard Template Library (STL), Boost, the Microsoft Windows API (Win32), Microsoft Foundation Classes (MFC), libtiff, libpng, zlib, libxml++, OpenGL, MySQL++, Nokias Qt, wxWidgets, GTK++, KDE, SkypeKit, POSIX pthreads, Intels Threading Building Blocks, the Netscape Plugin API, and the Apache module API. In addition, many of Googles open-source projects are C++, as is much of the code on the sourceforge.net , bitbucket.org , and freshmeat.net Web sites.

APIs such as these are used in all facets of software development, from desktop applications, to mobile computing and embedded systems, to Web development. For example, the Mozilla Firefox Web browser is built on top of more than 80 dynamic libraries, each of which provides the implementation for one or more APIs.

Elegant and robust API design is therefore a critical aspect of contemporary software development. One important way in which this differs from standard application development is the far greater need for change management. As we all know, change is an inevitable factor in software development; new requirements, feature requests, and bug fixes cause software to evolve in ways that were never anticipated when it was first devised. However, changes to an API thats shared by hundreds of end-user applications can cause major upheaval and ultimately may cause clients to abandon an API. The primary goal of good API design is therefore to provide your clients with the functionality they need while also causing minimal impact to their codeideally zero impactwhen you release a new version.