Get Next Line

Get Next Line is a project at 42 School that implements a function to read and return the next line from a file descriptor. This allows line-by-line reading of text files, standard input, or other data streams. The project emphasizes memory management, dynamic buffer handling, and multi-line retrieval using a static variable.

Function Overview

get_next_line(int fd):
- The core function of this project, get_next_line reads from the specified file descriptor fd and returns the next line, including the newline character (\n) if present.
- Uses a static variable to store any remaining characters from the previous read, enabling seamless line-by-line reading across multiple calls.
- Returns NULL if an error occurs, fd is invalid, BUFFER_SIZE is invalid, or the end of the file is reached.

Bonus Functionality: Multiple File Descriptors

In the bonus version, get_next_line supports reading from multiple file descriptors concurrently, allowing separate reading states for each file.

To enable this:

Static rest Array: The static rest variable was replaced with an array, rest[FD_LEN], where FD_LEN specifies the maximum number of file descriptors that can be read simultaneously.
Each fd has its own entry in the rest array, enabling get_next_line to track line reading progress for each file individually.

Helper Functions

read_line(int fd, char *buffer, char *rest):
- Reads chunks of data from the file descriptor into buffer and appends them to rest, which stores leftover data from previous reads.
- Stops reading if a newline character (\n) is found or when there’s no more data to read.
- Returns rest with all the data read.
get_rest(char *line):
- Extracts any remaining data after the newline character in line, saving it in rest for the next call to get_next_line.
- Modifies line to only include the current line.
- Returns the remainder to be stored in rest.
free_buffer(char **buffer):
- Frees the allocated memory for buffer and sets it to NULL.
- Used to prevent memory leaks by freeing memory after each read.

Utility Functions

ft_strlen(const char *s): Returns the length of a string.
ft_calloc(size_t nmemb, size_t size): Allocates memory and initializes it to zero.
ft_substr(char const *s, unsigned int start, size_t len): Creates a substring from a string.
ft_strjoin(char const *s1, char const *s2): Concatenates two strings into a new string.
ft_strchr(const char *s, int c): Finds the first occurrence of a character in a string.

Compilation and Usage

Define `BUFFER_SIZE`

To control the number of bytes read at a time, use the -D flag during compilation. BUFFER_SIZE is also defined in the header file with a default value, so the program will work even if it’s not defined during compilation.

In the header file:

#ifndef BUFFER_SIZE
# define BUFFER_SIZE 42
#endif

Or when compiling:

cc -Wall -Werror -Wextra -D BUFFER_SIZE=5 get_next_line.c get_next_line_utils.c main.c -o get_next_line

Define `FD_LEN`

In the bonus version, FD_LEN defines the maximum number of file descriptors supported. It is defined in the header file with a default value, but you can also control this number using the -D flag during compilation.

In the header file:

#ifndef FD_LEN
# define FD_LEN 42
#endif

To compile the bonus version:

cc -Wall -Werror -Wextra -D BUFFER_SIZE=5 -D FD_LEN=5 get_next_line_bonus.c get_next_line_utils_bonus.c main_bonus.c -o get_next_line_bonus

Key Points

Efficient Memory Handling: Uses ft_calloc and free_buffer for dynamic memory management.
Static Array for Multiple Descriptors: The static rest array (rest[FD_LEN]) allows tracking leftover data for multiple file descriptors.
Customizable Buffer and FD Limit: Adjust BUFFER_SIZE and FD_LEN to optimize performance based on expected file sizes and system memory.

carolcal/42_gnl