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

Libft

Description

Libft is the first project in the 42 curriculum.

The objective of this project is to recreate a selection of standard C library functions and develop a deeper understanding of fundamental programming concepts such as memory management, pointers, strings, dynamic allocation, and linked lists.

By building this library from scratch, I created a reusable collection of functions that can be used throughout future 42 projects and personal C development.

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Instructions

Compilation

Compile the library by running:

make

This generates the static library:

libft.a

Cleaning

Remove object files:

make clean

Remove object files and the library:

make fclean

Rebuild everything:

make re

Using the Library

Include the header file in your source code:

#include "libft.h"

Compile your project while linking against the library:

cc main.c libft.a

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Library Description

The library is divided into three main sections:

1. Reimplementation of standard libc functions
2. Additional utility functions
3. Bonus linked list functions

All function prototypes are available in libft.h.

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Part 1 - Libc Functions

The first section consists of recreating commonly used functions from the standard C library while preserving their original behavior whenever possible.

Character Classification

• ft_isalpha
• ft_isdigit
• ft_isalnum
• ft_isascii
• ft_isprint

These functions return:

• 1 if the condition is true
• 0 if the condition is false

String Functions

• ft_strlen
• ft_strlcpy
• ft_strlcat
• ft_strchr
• ft_strrchr
• ft_strncmp
• ft_strnstr
• ft_strdup

Memory Functions

• ft_memset
• ft_bzero
• ft_memcpy
• ft_memmove
• ft_memchr
• ft_memcmp
• ft_calloc

Character Conversion

• ft_toupper
• ft_tolower

Conversion

• ft_atoi

Notes

Some functions intentionally preserve the behavior and limitations of the original libc implementation. For example, ft_memcpy should not be used when memory regions overlap.

For ft_calloc, when either nmemb or size is zero, the function returns a unique pointer that can safely be passed to free().

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Part 2 - Additional Functions

The second section contains utility functions that are not part of the standard C library but are frequently useful in future projects.

String Manipulation

ft_substr

Allocates and returns a substring from a given string.

ft_strjoin

Allocates and returns a new string resulting from the concatenation of two strings.

ft_strtrim

Allocates and returns a copy of a string with specified characters removed from both ends.

ft_split

Splits a string using a delimiter character and returns an array of newly allocated strings.

String Iteration

ft_striteri

Applies a function to each character of a string.

ft_strmapi

Creates a new string by applying a function to every character of the original string.

Conversion

ft_itoa

Converts an integer into its string representation.

File Descriptor Output

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 followed by a newline to a file descriptor.

ft_putnbr_fd

Outputs an integer to a file descriptor.

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Part 3 - Bonus: Linked Lists

The bonus section introduces singly linked lists and dynamic data structures.

Node Creation

ft_lstnew

Allocates and returns a new list node. The content is initialized with the provided parameter and the next pointer is set to NULL.

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List Operations

ft_lstadd_front

Adds a node to the beginning of a list.

ft_lstadd_back

Adds a node to the end of a list.

ft_lstlast

Returns the last node of a list.

ft_lstsize

Returns the total number of nodes in a list.

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Memory Management

ft_lstdelone

Deletes a single node using a specified delete function and frees the node itself.

ft_lstclear

Deletes and frees an entire list and sets the list pointer to NULL.

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Iteration and Mapping

ft_lstiter

Iterates through a list and applies a function to each node's content.

ft_lstmap

Creates a new list by applying a function to every node's content while preserving the original list.

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Features

• Reimplementation of standard libc functions
• Dynamic memory allocation utilities
• String manipulation helpers
• Integer/string conversion functions
• File descriptor output functions
• Linked list implementation
• Static library generation through Makefile
• Reusable codebase for future 42 projects

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Testing

The library was tested through:

• Custom test programs
• Comparison with the behavior of the original libc functions
• Edge case validation
• Manual debugging
• Memory leak checking using Valgrind

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Resources

The following resources were helpful during the development of this project:

• The C Programming Language — Brian W. Kernighan & Dennis M. Ritchie
• 42 School documentation and subject PDF
• Linux manual pages (man)
• GeeksforGeeks
• Stack Overflow
• Various educational YouTube channels
• Discussions with classmates and fellow developers

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AI Usage

Artificial Intelligence was only used to help write and format this README file.

The project implementation was completed by the author.

Learning Outcomes

Through this project I gained practical experience with:

• Memory management
• Pointer arithmetic
• String manipulation
• Dynamic allocation
• Static libraries
• Makefiles
• Linked lists
• Modular programming
• Defensive coding practices
• Unit tests

Libft serves as the foundation for future projects in the 42 curriculum and provides a personal standard library that can be reused and expanded over time.