This project has been created as part of the 42 curriculum by fjose-hi.

Description

A custom static C library developed as part of the 42 curriculum. This project recreates several standard C library functions while introducing additional utility functions and linked list management tools that can be reused throughout future projects.

Libft is one of the foundational projects in the 42 curriculum. The goal of the project is to deepen the understanding of low-level programming concepts in C by rebuilding commonly used standard library functions from scratch.

The project focuses on:

• Understanding memory management and pointer manipulation.
• Reimplementing functions from the standard C library.
• Creating reusable utility functions.
• Learning how static libraries work.
• Writing clean and maintainable code following the 42 Norm.

The final result is a static library called libft.a, which can be linked into future C projects.

This library includes:

• Character and string manipulation functions.
• Memory handling functions.
• Conversion utilities.
• File descriptor output functions.
• Linked list utilities (bonus part).

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Features

Mandatory Functions

Character Checks & Conversion

Function	Description
ft_isalpha	Checks if a character is alphabetic
ft_isdigit	Checks if a character is a digit
ft_isalnum	Checks if a character is alphanumeric
ft_isascii	Checks if a character is ASCII
ft_isprint	Checks if a character is printable
ft_toupper	Converts lowercase letters to uppercase
ft_tolower	Converts uppercase letters to lowercase

String Functions

Function	Description
ft_strlen	Calculates string length
ft_strlcpy	Copies strings safely
ft_strlcat	Concatenates strings safely
ft_strchr	Locates a character in a string
ft_strrchr	Locates the last occurrence of a character
ft_strncmp	Compares strings
ft_strnstr	Finds a substring in a string
ft_strdup	Duplicates a string
ft_substr	Extracts a substring
ft_strjoin	Concatenates two strings
ft_strtrim	Trims characters from a string
ft_split	Splits a string into an array
ft_strmapi	Applies a function to each character
ft_striteri	Iterates through a string applying a function

Memory Functions

Function	Description
ft_memset	Fills memory with a constant byte
ft_bzero	Sets bytes to zero
ft_memcpy	Copies memory areas
ft_memmove	Copies memory safely between overlapping areas
ft_memchr	Searches memory
ft_memcmp	Compares memory areas
ft_calloc	Allocates and initializes memory

Conversion Functions

Function	Description
ft_atoi	Converts a string to an integer
ft_itoa	Converts an integer to a string

File Descriptor Functions

Function	Description
ft_putchar_fd	Writes a character to a file descriptor
ft_putstr_fd	Writes a string to a file descriptor
ft_putendl_fd	Writes a string followed by a newline
ft_putnbr_fd	Writes a number to a file descriptor

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Bonus Part — Linked List Functions

The bonus section introduces a linked list API based on the t_list structure.

typedef struct s_list
{
    void            *content;
    struct s_list   *next;
}   t_list;

Function	Description
ft_lstnew	Creates a new list node
ft_lstadd_front	Adds a node at the beginning
ft_lstsize	Counts the number of nodes
ft_lstlast	Returns the last node
ft_lstadd_back	Adds a node at the end
ft_lstdelone	Deletes a single node
ft_lstclear	Clears an entire list
ft_lstiter	Iterates through the list
ft_lstmap	Creates a new list applying a function

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Project Structure

.
├── Makefile
├── libft.h
├── ft_*.c
└── bonus functions

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Instructions

Clone the Repository

git clone https://github.com/felipehillebrand-ops/Libft.git
cd Libft

Compilation

Compile mandatory functions:

make

Compile bonus functions:

make bonus

Cleaning Object Files

Remove object files:

make clean

Remove object files and library:

make fclean

Recompile everything:

make re

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Using the Library

Include the header in your project:

#include "libft.h"

Compile your program with the library:

cc main.c libft.a

Example:

#include "libft.h"
#include <stdio.h>

int main(void)
{
    printf("%d\n", ft_strlen("42"));
    return (0);
}

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Technical Choices

This project follows the requirements defined by the 42 subject:

• Written entirely in C.
• Compiled with the flags:

-Wall -Wextra -Werror

• No global variables are used.
• Fully compliant with the 42 Norm.
• Static library generated using ar.

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Testing

The project can be tested using:

• norminette
• Custom test cases
• Community Libft testers

Example:

norminette

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Resources

Documentation & References

• Linux Manual Pages (man pages)
• 42 Subject PDF for Libft

AI Usage Disclosure

AI tools were used during this project for:

• Reviewing README structure and formatting.
• Clarifying concepts related to memory management and linked lists.
• Improving documentation quality and wording.
• Verifying explanations of standard C library behavior.

All implementation, debugging, testing, and final validation of the code were completed manually.

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Learning Outcomes

Through this project, the following concepts were strengthened:

• Memory allocation and management.
• Pointer arithmetic.
• String manipulation in C.
• Static library creation.
• Linked list data structures.
• Defensive programming.
• Modular code organization.
• Writing reusable utility functions.

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License

This project was developed for educational purposes as part of the 42 curriculum.

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Author

Felipe José Hillebrand

GitHub: https://github.com/felipehillebrand-ops