LIBFT

A custom C library implementing standard library functions

📋 Table of Contents

• About
• Project Objectives
• Functions Implemented
  • Part 1: Standard Library Functions
  • Part 2: Additional Functions
  • Bonus: Linked List Functions
• Compilation
• Usage
• Testing
• Project Structure
• 42 School Standards

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📖 About

Libft is the first project at 42 School where students recreate essential C standard library functions from scratch. This project serves as the foundation for all future C projects at 42, teaching low-level programming concepts, memory management, and the implementation details of commonly used functions.

The library provides a comprehensive set of utility functions for string manipulation, memory management, character validation, linked list operations, and more.

🎯 Project Objectives

• Understand standard library functions by implementing them from scratch
• Learn memory management and proper allocation/deallocation practices
• Master pointer manipulation and understanding of C data structures
• Develop debugging skills and attention to detail
• Follow strict coding standards (42 Norm)
• Create reusable code that can be used in future 42 projects

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🔧 Functions Implemented

Part 1: Standard Library Functions

Recreation of existing C standard library functions

Character Classification & Conversion

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

String Functions

Function	Description
ft_strlen	Calculate string length
ft_strchr	Locate character in string
ft_strrchr	Locate character in string (reverse)
ft_strncmp	Compare strings up to n characters
ft_strlcpy	Size-bounded string copying
ft_strlcat	Size-bounded string concatenation
ft_strnstr	Locate substring in string
ft_atoi	Convert string to integer

Memory Functions

Function	Description
ft_memset	Fill memory with constant byte
ft_bzero	Zero a byte string
ft_memcpy	Copy memory area
ft_memmove	Copy memory area (handles overlap)
ft_memchr	Scan memory for character
ft_memcmp	Compare memory areas
ft_calloc	Allocate and zero memory
ft_strdup	Duplicate string

Part 2: Additional Functions

New functions not in the standard library

Function	Description
ft_substr	Extract substring
ft_strjoin	Concatenate two strings
ft_strtrim	Trim characters from string
ft_split	Split string by delimiter
ft_itoa	Convert integer to string
ft_strmapi	Apply function to each character
ft_striteri	Apply function to each character (with index)
ft_putchar_fd	Output character to file descriptor
ft_putstr_fd	Output string to file descriptor
ft_putendl_fd	Output string + newline to file descriptor
ft_putnbr_fd	Output number to file descriptor

Bonus: Linked List Functions

Functions for manipulating linked lists

Function	Description
ft_lstnew	Create new list element
ft_lstadd_front	Add element at beginning of list
ft_lstsize	Count elements in list
ft_lstlast	Return last element of list
ft_lstadd_back	Add element at end of list
ft_lstdelone	Delete single element
ft_lstclear	Delete and free list
ft_lstiter	Iterate through list
ft_lstmap	Apply function to each element

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🛠 Compilation

Requirements

• GCC compiler
• Make

Build Library

# Compile the main library
make

# Compile with bonus functions
make bonus

# Clean object files
make clean

# Clean everything (objects + library)
make fclean

# Recompile everything
make re

Compiler Flags

The library is compiled with strict flags to ensure code quality:

-Wall -Werror -Wextra

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🚀 Usage

Basic Usage

1. Include the header in your C file:

#include "libft.h"

2. Compile your program with the library:

gcc -Wall -Wextra -Werror your_program.c -L. -lft -o your_program

Example Program

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

int main(void)
{
    char *str = "Hello, 42!";
    char *substr;
    char **split_result;
    int i;

    // String length
    printf("Length of '%s': %zu\n", str, ft_strlen(str));
    
    // Substring extraction
    substr = ft_substr(str, 7, 2);
    printf("Substring: %s\n", substr);
    free(substr);
    
    // String splitting
    split_result = ft_split(str, ' ');
    i = 0;
    while (split_result[i])
    {
        printf("Word %d: %s\n", i, split_result[i]);
        free(split_result[i]);
        i++;
    }
    free(split_result);
    
    return (0);
}

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✅ Testing

Manual Testing

Create test files to verify function behavior:

# Create a simple test file
cat > test_libft.c << 'EOF'
#include "libft.h"
#include <stdio.h>
#include <string.h>

int main(void)
{
    // Test ft_strlen vs strlen
    char *test = "Test string";
    printf("ft_strlen: %zu, strlen: %zu\n", ft_strlen(test), strlen(test));
    
    // Test ft_strchr vs strchr
    printf("ft_strchr: %s, strchr: %s\n", ft_strchr(test, 's'), strchr(test, 's'));
    
    return (0);
}
EOF

# Compile and run
gcc -Wall -Wextra -Werror test_libft.c -L. -lft -o test_libft
./test_libft

Third-Party Testers

Popular testing frameworks for libft:

• libft-unit-test
• libftTester
• francinette

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📁 Project Structure

libft/
├── Makefile              # Build configuration
├── libft.h               # Header file with function prototypes
├── README.md             # Project documentation
├── ft_*.c                # Source files for each function
└── libft.a               # Compiled static library (after make)

Function Categories

• ft_is*.c - Character classification functions
• ft_to*.c - Character conversion functions
• ft_str*.c - String manipulation functions
• ft_mem*.c - Memory operation functions
• ft_put*.c - Output functions
• ft_lst*.c - Linked list functions (bonus)

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📏 42 School Standards

This project follows the strict 42 Norm coding standard:

• ✅ Maximum 25 lines per function
• ✅ Maximum 80 characters per line
• ✅ No global variables
• ✅ No for loops (only while)
• ✅ Proper variable declarations
• ✅ Consistent indentation and formatting
• ✅ Comprehensive error handling
• ✅ No memory leaks

Memory Management

All functions that allocate memory:

• Return NULL on allocation failure
• Properly handle edge cases
• Are tested for memory leaks with valgrind

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🎓 Skills Developed

Through this project, I gained experience in:

• Low-level C programming and system calls
• Memory management and debugging memory issues
• Algorithm implementation and optimization
• Code organization and modular programming
• Testing methodologies and edge case handling
• Documentation and code maintenance

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📝 License

This project is part of the 42 School curriculum. Code is provided for educational purposes.

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Author: cadenegr
School: 42 Berlin
Project: libft
Date: June 2023