Libft - 42 School Project

Libft is the first project in the 42 School curriculum's "Common Core." Its objective is to recreate a series of standard C library functions (including basic string, memory, and I/O operations) from scratch. This project acts as a fundamental building block for later projects, since students must rely on their own implementation (libft) rather than the standard C library. Through this exercise, we gained a deep understanding of how these functions work under the hood and became comfortable with low-level programming concepts.

Overview

Libft is a custom library that mirrors many functions from the standard C library (libc), including additional utility functions not found in libc. The project is divided into three main parts:

1. Reimplementation of Standard C Library Functions
2. Additional Utility Functions
3. Bonus: Linked List Functions

In addition, I have extended the library with implementations of functions from other key projects in the 42 curriculum: ft_printf (a printf-like function) and get_next_line (a function for reading input line by line).

Functions Implemented

Part 1: Standard C Library Functions

These are functions from the standard C library that are reimplemented to understand their workings in detail:

• Character Check Functions:

  • ft_isalpha - Checks for alphabetic characters.
  • ft_isdigit - Checks for digits (0-9).
  • ft_isalnum - Checks for alphanumeric characters.
  • ft_isascii - Checks if a character is ASCII.
  • ft_isprint - Checks for printable characters.

• String and Memory Manipulation Functions:

  • ft_strlen - Calculates the length of a string.
  • ft_memset - Fills a block of memory with a constant byte.
  • ft_bzero - Zeroes a block of memory.
  • ft_memcpy - Copies a block of memory.
  • ft_memmove - Moves a block of memory, handling overlapping memory areas.
  • ft_strlcpy - Copies a string to a destination buffer with size limitation.
  • ft_strlcat - Concatenates strings with size limitation.

• Character Case Conversion Functions:

  • ft_toupper - Converts a lowercase character to uppercase.
  • ft_tolower - Converts an uppercase character to lowercase.

• String Search and Comparison Functions:

  • ft_strchr - Locates the first occurrence of a character in a string.
  • ft_strrchr - Locates the last occurrence of a character in a string.
  • ft_strncmp - Compares two strings up to a specified number of characters.
  • ft_memchr - Scans memory for a specific byte.
  • ft_memcmp - Compares two memory areas.
  • ft_strnstr - Locates a substring in a string with a length limit.

• Conversion Functions:

  • ft_atoi - Converts a string to an integer.

• Memory Management Functions:

  • ft_calloc - Allocates and zeroes a block of memory.
  • ft_strdup - Duplicates a string.

Part 2: Additional Utility Functions

These functions are not part of the standard C library but are essential utilities for string manipulation and file handling:

• ft_substr - Extracts a substring from a string.
• ft_strjoin - Concatenates two strings into a new string.
• ft_strtrim - Trims leading and trailing whitespace (or specified characters) from a string.
• ft_split - Splits a string into an array of strings based on a delimiter.
• ft_itoa - Converts an integer to a string.
• ft_strmapi - Applies a function to each character of a string and returns a new string.
• ft_striteri - Applies a function to each character of a string in-place.
• ft_putchar_fd - Outputs a character to a file descriptor.
• ft_putstr_fd - Outputs a string to a file descriptor.
• ft_putendl_fd - Outputs a string to a file descriptor, followed by a newline.
• ft_putnbr_fd - Outputs an integer to a file descriptor.

Part 3: Bonus - Linked List Functions

This part of the project implements various functions for manipulating singly linked lists, which are not available in the standard C library:

• ft_lstnew - Creates a new list element.
• ft_lstadd_front - Adds an element at the beginning of a list.
• ft_lstsize - Returns the size of a list.
• ft_lstlast - Returns the last element of a list.
• ft_lstadd_back - Adds an element at the end of a list.
• ft_lstdelone - Deletes one element from a list.
• ft_lstclear - Deletes and frees an entire list.
• ft_lstiter - Iterates over a list and applies a function to each element.
• ft_lstmap - Applies a function to each element of a list and returns a new list.

Extended Features

In addition to the core Libft functions, I’ve incorporated two major functions from other 42 projects:

• ft_printf - A simplified version of the printf function. It formats and outputs data to the standard output, supporting various format specifiers such as %d, %s, %x, etc.
• get_next_line - A function that reads a line from a file descriptor, returning one line at a time. Useful for reading from files or standard input in a controlled manner.

How to Use

To compile the library, simply run the following command:

make

This will create a libft.a file, which can be linked with your other C projects.

To clean up object files after compilation, use:

make clean

To remove both object files and the compiled library, use:

make fclean

To recompile the library from scratch, use:

make re

Usage Example

Here’s an example of how you might use libft in your own C projects:

#include "libft.h"

int main(void)
{
    char *str = "Hello, World!";
    char *dup = ft_strdup(str);
    
    ft_putstr_fd(dup, 1); // Output: Hello, World!
    ft_putchar_fd('\n', 1);
    
    free(dup);
    return (0);
}

In this example, we use ft_strdup to duplicate a string, and ft_putstr_fd and ft_putchar_fd to print it to standard output.

Feel free to clone the repository and adapt the library for your own projects!