TwenteResearchandEducationonSoftwareEngineering,
                     DepartmentofComputerScience,
            Faculty of Electrical Engineering, Mathematics and Computer Science,
                        University of Twente
          Performingtransformations on .NET
              Intermediate Language code
                       S.R. Boschman
                       Enschede, August23, 2006
                                     Prof. dr. ir. M. Aksit
                                   Dr. ir. L.M.J. Bergmans
                                                  ¨
                                         Ir. P.E.A. Durr
                                            Abstract
       To express crosscutting concerns in a clear manner, the aspect-oriented programming (AOP)
       paradigm was introduced. In AOP languages, crosscutting concerns are defined in aspects.
       Theseaspects are composed, or woven, with components. These components encapsulate func-
       tionality expressed in traditional object-oriented languages.
       As the aspect language and component language can be separated, an AOP solution can be
       implemented independent of the component language. A suitable platform for such an AOP
       solution is the .NET Framework, since, in principle, this platform can support a wide range of
       different component languages (i.e. programming languages).
       This thesis will describe the development of a tool that can weave the aspects with the com-
       ponents in the .NET Framework environment. The first step is to discuss the Common Inter-
       mediateLanguage(CIL)inmoredetail,asallprogramminglanguagesinthe.NETFramework
       maptothisCIL.ThesecondstepistocreateamappingfromAOPconstructstoCILcodestruc-
       tures. The third step provides an overview of possible approaches to perform the weaving of
       aspects and base components. One of the weaving approaches is based on modifying the CIL
       code stored in binary files, called assemblies. The fourth, and last, step is the discussion of the
       creation of the weaver tool.
       Theresultis the CIL Weaving Tool, which consists of two parts. The first part is the PE Weaver,
       responsible for creating textual IL files from the assemblies and recreating the assemblies after
       weaving. The second part is the IL Weaver, which performs the actual weaving on the textual
       IL files. To define the weave operations that have to be performed by the IL Weaver, a weave
       specification file has to be supplied. This weave specification file allows the definition of weave
       points, which are based on AOP constructs.