Code Syntax-Comparison Algorithm Based on Type-Redefinition-Preprocessing and Rehash Classification

The code comparison technology plays an important role in the fields of software security protection and plagiarism detection. Nowadays, there are mainly FIVE approaches of plagiarism detection, file-attribute-based, text-based, token-based, syntax-based and semantic-based. The prior three approaches have their own limitations, while the technique based on syntax has its shortage of detection ability and low efficiency that all of these approaches cannot meet the requirements on large-scale software plagiarism detection. Based on our prior research, we propose an algorithm on type redefinition plagiarism detection, which could detect the level of simple type redefinition, repeating pattern redefinition, and the redefinition of type with pointer. Besides, this paper also proposes a code syntax-comparison algorithm based on rehash classification, which enhances the node storage structure of the syntax tree, and greatly improves the efficiency.