0x0F-function_pointers

C - Function pointers

In this project, I learned about function pointers in C - what they hold, where they point in virtual memory, and how to use them.

Header Files 📁

• function_pointers.h: Header file containing prototypes for all functions written for programs 0-2 of the project.

File	Prototype
0-print_name.c	void print_name(char *name, void (*f)(char *));
1-array_iterator.c	void array_iterator(int *array, size_t size, void (*action)(int));
2-int_index.c	int int_index(int *array, int size, int (*cmp)(int));

• 3-calc.h: Header file containing definitions and prototypes for all types and function written for the program 3-main.c.

Type/File	Definition/Prototypes
struct op	char *op int (*f)(int a, int b)
typedef op_t	struct op
3-op_functions.c	int op_add(int a, int b); int op_sub(int a, int b); int op_mul(int a, int b); int op_div(int a, int b); int op_mod(int a, int b);
3-get_op_func.c	int (*get_op_func(char *s))(int, int);

Tasks 📃

• 0. What's my name

  • 0-print_name.c: C function that prints a name.

• 1. If you spend too much time thinking about a thing, you'll never get it done

  • 1-array_iterator.c: C function that executes a function given as a parameter on each element of an array.

• 2. To hell with circumstances; I create opportunities

  • 2-int_index.c: C function that searches for an integer.
    • Returns the index of the first element for which the cmp function does not return 0.
    • If no element is matched or size <= 0, the function returns -1.

• 3. A goal is not always meant to be reached, it often serves simply as something to aim at

  • 3-op_functions.c: File containing the following five functions:

    • op_add: Returns the sum of a and b.
    • op_sub: Returns the difference of a and b.
    • op_mul: Returns the product of a and b.
    • op_div: Returns the division of a by b.
    • op_mod: Returns the remainder of the division of a by b.

  • 3-get_op_func.c: C function that selects the correct function from 3-op_functions.c to perform the operation asked by the user.

    • If the operator argument s does not match any of the five expected operators (+, -, *, /, %), the function returns NULL.

  • 3-main.c: C program that performs simple mathematical operations.

    • Prints the result of the operation, followed by a new line.
    • Usage ./a.out num1 operator num2
    • The program assumes num1 and num2 are integers that can be converted from string input to int using atoi.
    • The program assumes that the result of all operations can be stored in an int.
    • operator is one of either + (addition), - (subtraction), * (multiplication), / (division), or % (modulo).
    • If the number of arguments is incorrect, the program prints Error followed by a new line and exits with a status value of 98.
    • If the operator is none of the above, the program prints Error followed by a new line and exits with a status value of 99.
    • If the user tries to divide (/ or %) by 0, the program prints Error followed by a new line and exits with a status value of 100.

• 4. Most hackers are young because young people tend to be adaptable. As long as you remain adaptable, you can always be a good hacker

  • 100-main_opcodes.c: C program that prints the opcodes of its own main function, followed by a new line.
    • Usage: ./main number_of_bytes
    • Opcodes are printed two-decimal long in hexadecimal, lowercase.
    • If the number of arguments is incorrect, the program prints Error followed by a new line and exits with a status value of 2.