Jméno a příjmení: Matúš Ďurica
Login: xduric06
Script is divided into multiple source files, which contain definitions of various functions (most importantly parse_src_file()), interfaces and classes. Main file parse.php checks command-line arguments and either displays help to stdout if --help argument was used or calls the aforementioned function parse_src_file() to parse the source IPPcode23 code if no arguments were inputted. Combination of --help argument and source code on stdin displays help and exits with code 0. Unknown arguments or incorrect amount of arguments lead to error code 10.
I decided to use OOP for this part of the project. I used Visitor pattern, because I felt, it suited this project really well. Details of my implementation of the Visitor pattern can be seen in the diagram below.
Visitor pattern allows adding new functions without needing to modify the classes (e.g., implementing another Visitor sub-class which would parse into different language). Visitor pattern also allows programmers to follow open/closed principle (open for extension, closed for modification). This leads to easily extensible and reusable code.
Script utilizes one cycle to check the whole source code file. First thing being checked is the header .IPPcode23. Only after header_flag variable is set to true, script continues with parsing the rest of the file. Missing header or incorrect header leads to error code 21.
Checking instructions is done using switch statement, where unknown instructions lead to error code 22. Arguments are checked using check_var(), check_label() and check_symb() functions. All of them utilize regular expressions to check arguments of the instructions. Incorrect argument leads to error code 23.
After IPPcode23 instruction is checked for its arguments using functions descibed above, Visitable object (depending on number of arguments) is created and then parse() function is called. This function then calls visit_no_arg(), visit_1_arg(), visit_2_arg() or visit_3_arg() depending on the Visitable object from which it was called, which generates XML with the data of the arguments to stdout.