0x19. C - Stacks, Queues - LIFO, FIFO

Monty Interpreter

Creating an Interpreter for Monty Bytecodes Using C Programming Language

Monty 0.98 is a scripting language that is first compiled into Monty byte codes (Just like Python).
It relies on a unique stack, with specific instructions to manipulate it.
The goal of this project is to create an interpreter for Monty ByteCodes files.

• What do LIFO and FIFO mean
• What is a stack, and when to use it
• What is a queue, and when to use it
• What are the common implementations of stacks and queues
• What are the most common use cases of stacks and queues
• What is the proper way to use global variables

Data structures

Please use the following data structures for this project. Don’t forget to include them in your header file.

/**
 * struct stack_s - doubly linked list representation of a stack (or queue)
 * @n: integer
 * @prev: points to the previous element of the stack (or queue)
 * @next: points to the next element of the stack (or queue)
 *
 * Description: doubly linked list node structure
 * for stack, queues, LIFO, FIFO
 */
typedef struct stack_s
{
        int n;
        struct stack_s *prev;
        struct stack_s *next;
} stack_t;

/**
 * struct instruction_s - opcode and its function
 * @opcode: the opcode
 * @f: function to handle the opcode
 *
 * Description: opcode and its function
 * for stack, queues, LIFO, FIFO
 */
typedef struct instruction_s
{
        char *opcode;
        void (*f)(stack_t **stack, unsigned int line_number);
} instruction_t;

Compilation & Output

• Your code will be compiled this way:

$ gcc -Wall -Werror -Wextra -pedantic -std=c89 *.c -o monty

• Any output must be printed on stdout
• Any error message must be printed on stderr
• Here is a link to a GitHub repository that could help you making sure your errors are printed on stderr

The monty program

• Usage: monty file

  • where file is the path to the file containing Monty byte code

• If the user does not give any file or more than one argument to your program, print the error message USAGE: monty file, followed by a new line, and exit with the status EXIT_FAILURE

• If, for any reason, it’s not possible to open the file, print the error message Error: Can't open file <file>, followed by a new line, and exit with the status EXIT_FAILURE

  • where <file> is the name of the file

• If the file contains an invalid instruction, print the error message L<line_number>: unknown instruction <opcode>, followed by a new line, and exit with the status EXIT_FAILURE

• where is the line number where the instruction appears.

  • Line numbers always start at 1

• The monty program runs the bytecodes line by line and stop if either:

  • it executed properly every line of the file
  • it finds an error in the file
  • an error occured

• If you can’t malloc anymore, print the error message Error: malloc failed, followed by a new line, and exit with status EXIT_FAILURE.

• You have to use malloc and free and are not allowed to use any other function from man malloc (realloc, calloc, …)