A Dynamic Loading Mechanism Based On .COM Files

The wide application of the embedded system needs good software system to support .the systematic expansile ability become one basic demand already with embedded system deep to develop, system needs urgently one mechanism that can dispose system at runtime, that is to say system at runtime may add dynamically the module, this kind of mechanism is dynamic loading mechanism that this thesis will study. Dynamic loading mechanism in this thesis is that application starts from scratch. So system only needs a dynamic loading mechanism, which can load dynamically the module and dispose the embedded systems which suit different uses.We have analyzed several kinds of loading mode existing at present in this thesis: the java_based dynamic loading mode, the dynamic loading mode of embedded Linux and the principle of the dynamic linking library in windows. On this basis we have put forward the principle and the process of dynamic loading mechanism under the general meaning. The principle of dynamic loading mechanism requires the ability of dynamic loading and dynamic analyzing. Dynamic loading mechanism use dynamic linking principle and the module is linked to system only while be called and carried out. Dynamic loading can be divided into three operation: download, load and unload. Download finishes download module from long-distance to native. Load operation is to finish to read module into memory, then to analyze unresolved reference outside module. Unload the module from memory when it is no longer used.Based on the general principle of dynamic loading and the key problems of dynamic loading in-depth analysis and study, this dissertation brings forward a dynamic loading mechanism based on .COM Files (This thesis called DLoader). After analysing some key problems in-depth as a dynamically loading module—.COM module format , .COM module name space management and .COM module loading, and so on,we presents the dynamic loading system prototype program design of the special environment.The program uses the real-time kernel ofμC/OS-Ⅱto manage tasks of the dynamic loading system, and using the dynamic loading mechanism to load dynamically loaded modules.Despite the dynamic loading system is not totally from scratch on the dynamic allocation of the system, but, it can provide us to the eventual realization of the dynamic loading mechanism a theoretical and technical experience on the accumulation, and it can provide a good reference for our ultimate realization of the dynamic loading mechanism. Finally, we let the dynamic loading mechanism work on remote automatic control system,and it can work well.In this paper, the dynamic loading system can ensure real-time and embedded security, and at the same time it makes the system with a high degree of flexibility and scalability. The entire system has smaller fixed framework, which can be dynamically loaded modules to meet the needs of different applications, and there is a great value to the real-time updating and software upgrading...