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

Libft

Description

The Libft project is my very first project at 42. The goal is to re-code a set of standard C library functions, learning in this process how memory management, pointers, and string manipulation work under the surface.

Library Description

This library will contain basic functions for:

• Checking characters (like checking if a character is a letter or a number).
• Manipulating strings (like counting the length of a text or copying a text).
• Managing memory (allocating, clearing and moving chunks of bytes).
• Utility functions (number-to-string conversion, printing to specific file descriptors).
• Linked lists handling (dynamically create, navigate, map and clear node structures).

1. Character Classification & Manipulation

• ft_isalpha - Checks if the character is an alphabetic letter.
• ft_isdigit - Checks if the character is a digit (0 through 9).
• ft_isalnum - Checks if the character is alphanumeric (either a letter or a digit).
• ft_isascii - Checks if the character fits into the ASCII character set.
• ft_isprint - Checks if the character is printable (including space).
• ft_toupper - Converts a lowercase letter to uppercase.
• ft_tolower - Converts an uppercase letter to lowercase.

2. Raw Memory Management

• ft_memset - Fills the first n bytes of a memory area with a constant byte.
• ft_bzero - Erases the data in a memory area by writing zeros to it.
• ft_memcpy - Copies n bytes from one memory area to another (areas must not overlap).
• ft_memmove - Copies n bytes from one memory area to another safely (handles overlapping areas).
• ft_memchr - Scans a memory area for the first instance of a specific character.
• ft_memcmp - Compares two different memory areas byte by byte.

3. String Manipulation

• ft_strlen - Calculates the total length of a string, excluding the terminating null byte.
• ft_strlcpy - Copies a string into a bounded buffer, ensuring proper null-termination.
• ft_strlcat - Appends a string into a bounded buffer, ensuring proper null-termination.
• ft_strchr - Finds the first occurrence of a specific character in a string.
• ft_strrchr - Finds the last occurrence of a specific character in a string.
• ft_strncmp - Compares the first n characters of two strings.
• ft_strnstr - Locates a substring inside a main string within a length limit.
• ft_strdup - Duplicates a string by allocating dynamic memory for the copy using malloc.
• ft_substr - Creates and returns a specific substring from a larger string.
• ft_strjoin - Concatenates two strings together into a newly allocated string.
• ft_strtrim - Removes specified character sets from the beginning and end of a string.
• ft_split - Splits a single string into an array of strings using a character delimiter.
• ft_strmapi - Applies a function to each character of a string to create a new modified copy.
• ft_striteri - Applies a function to each character of a string, modifying the original in place.

4. Data Conversion

• ft_atoi - Converts the initial portion of a string into an integer value.
• ft_itoa - Converts an integer value into a newly allocated null-terminated string.

5. Dynamic Memory Allocation

• ft_calloc - Allocates memory for an array, initializes all its bytes to zero, and returns a pointer.

6. Output Functions

• ft_putchar_fd - Outputs a single character to the given file descriptor.
• ft_putstr_fd - Outputs a string to the given file descriptor.
• ft_putendl_fd - Outputs a string followed by a newline character to the given file descriptor.
• ft_putnbr_fd - Outputs an integer as text to the given file descriptor.

7. Linked Lists

• ft_lstnew - Allocates and returns a new node initialized with content.
• ft_lstadd_front - Adds a new node to the very beginning of the linked list.
• ft_lstsize - Counts and returns the total number of nodes currently in the linked list.
• ft_lstlast - Navigates to and returns a pointer to the last node of the linked list.
• ft_lstadd_back - Appends a new node to the very end of the linked list.
• ft_lstdelone - Frees the memory of a node's content using a custom function, then frees the node itself.
• ft_lstclear - Deletes and frees an entire linked list node by node, setting the original pointer to NULL.
• ft_lstiter - Iterates through a list and applies a function to the content of each individual node.
• ft_lstmap - Iterates a list, applies a function to create a new list, and handles cleanups safely if an allocation fails.

Instructions

The library is compiled into a libft.a static library using a Makefile with the cc compiler and strict flags (-Wall -Wextra -Werror).

Compilation

Clone the repository and run make in the project root:

git clone https://github.com/palenki/libft.git
cd libft
make

This will generate the libft.a static library file.

Available Makefile rules

• make : Compiles the library.
• make clean : Removes object files.
• make fclean : Removes object files and libft.a.
• make re : Runs fclean then make.

Resources

• IME USP - Language C - Professor Paulo Feofiloff's Algorithms Project, with many basic concepts explained in a didactic way.
• Linux Man Pages - To read the documentation of the original C functions.
• Linked Lists in C — Conceptual overview of single linked list data structures.

AI Usage Disclosure

Artificial Intelligence was used during the development of this project for the following purposes:

• Resource gathering — finding useful reference links to research and study new programming concepts.
• Debugging assistance — identifying and handling edge cases for various functions.
• Mock evaluation — reviewing the code and asking conceptual questions to deepen my understanding of memory management and pointers.

No code was automatically generated or copy-pasted; all implementation logic was written entirely by me.