Achieving Reuse Through Design Patterns A Case Study of Evolving Object-Oriented System Software Across OS Platforms

Building system software that is reusable across OS platforms presents developers with many challenges. It is often difficult to reuse existing interfaces and implementations directly due to portability, functionality, and efficiency constraints imposed by different platforms and applications. It may still be possible, however, to leverage prior development effort by reusing design patterns. Design patterns embody recurring architectural themes that underlie solutions to requirements in particular problem domains. This paper presents a case study of an object-oriented framework written in C++ that was ported from several UNIX platforms to the Windows NT platform. The framework supports concurrent event demultiplexing and event handler dispatching. Fundamental differences in the event demultiplexing and I/O mechanisms on the UNIX and Windows NT platforms precluded direct reuse of many algorithms and interfaces in the framework. However, it was possible to reuse the underlying design patterns, which greatly reduced development effort and project