A rapidly hacked solution ‐ you never know, could work! - kevshouse/GNL_42 GitHub Wiki

Welcome to the GNL_42 wiki!

To solve this problem, we need to create a function get_next_line that reads a line from a file descriptor each time it is called. The function should handle different buffer sizes and efficiently manage memory while adhering to specific constraints.

Approach

  • Static Variable:

     Use a static variable to retain data between successive 
 calls to get_next_line. This allows the function to remember leftover data
 from previous reads.

  • Reading in Chunks:

     Read data from the file descriptor in chunks defined by 
 BUFFER_SIZE. This avoids reading the entire file at once and handles large 
 files efficiently.

  • Line Extraction:

     After each read, check the static buffer for a newline 
 character. If found, extract the line up to the newline and keep the remaining
 data in the static buffer for subsequent calls.

  • Memory Management:

      Properly manage memory allocation and deallocation to 
  prevent leaks. Use helper functions for string operations to keep the code
  modular and clean.

  • Edge Cases:

      Handle cases where the file ends without a newline, very large 
  buffer sizes, and correct error checking for file operations.

Solution Code

// get_next_line.h

#ifndef GET_NEXT_LINE_H
# define GET_NEXT_LINE_H

# include <stdlib.h>
# include <unistd.h>

char	*get_next_line(int fd);
size_t	ft_strlen(const char *s);
char	*ft_strchr(const char *s, int c);
char	*ft_strjoin_free(char *s1, char *s2);
char	*ft_strdup(const char *s1);
size_t	ft_strlcpy(char *dst, const char *src, size_t dstsize);

#endif
// get_next_line.c
#include "get_next_line.h"

static char	*extract_line(char **static_buffer)
{
	char	*newline_ptr;
	char	*line;
	char	*remaining;

	newline_ptr = ft_strchr(*static_buffer, '\n');
	if (!newline_ptr)
		return (NULL);
	line = malloc(newline_ptr - *static_buffer + 2);
	if (!line)
		return (NULL);
	ft_strlcpy(line, *static_buffer, newline_ptr - *static_buffer + 2);
	remaining = NULL;
	if (*(newline_ptr + 1) != '\0')
		remaining = ft_strdup(newline_ptr + 1);
	free(*static_buffer);
	*static_buffer = remaining;
	return (line);
}

static char	*read_buffer(int fd, char *static_buffer)
{
	char	*temp_buffer;
	ssize_t	bytes_read;

	temp_buffer = malloc(BUFFER_SIZE + 1);
	if (!temp_buffer)
		return (NULL);
	bytes_read = read(fd, temp_buffer, BUFFER_SIZE);
	if (bytes_read <= 0)
	{
		free(temp_buffer);
		if (bytes_read == 0)
			return (static_buffer);
		return (NULL);
	}
	temp_buffer[bytes_read] = '\0';
	return (ft_strjoin_free(static_buffer, temp_buffer));
}

char	*get_next_line(int fd)
{
	static char	*static_buffer;
	char		*line;

	if (fd < 0 || BUFFER_SIZE <= 0)
		return (NULL);
	line = extract_line(&static_buffer);
	if (line)
		return (line);
	static_buffer = read_buffer(fd, static_buffer);
	if (!static_buffer)
		return (NULL);
	while (!ft_strchr(static_buffer, '\n'))
	{
		static_buffer = read_buffer(fd, static_buffer);
		if (!static_buffer)
			break ;
	}
	line = extract_line(&static_buffer);
	if (!line && static_buffer)
	{
		line = static_buffer;
		static_buffer = NULL;
	}
	return (line);
}
// get_next_line_utils.c
#include "get_next_line.h"

size_t	ft_strlen(const char *s)
{
	size_t	len;

	len = 0;
	while (s[len])
		len++;
	return (len);
}

char	*ft_strchr(const char *s, int c)
{
	while (*s)
	{
		if (*s == (char)c)
			return ((char *)s);
		s++;
	}
	if ((char)c == '\0')
		return ((char *)s);
	return (NULL);
}

char	*ft_strdup(const char *s1)
{
	char	*dup;
	size_t	len;

	len = ft_strlen(s1) + 1;
	dup = malloc(len);
	if (!dup)
		return (NULL);
	ft_strlcpy(dup, s1, len);
	return (dup);
}

size_t	ft_strlcpy(char *dst, const char *src, size_t dstsize)
{
	size_t	i;

	if (dstsize == 0)
		return (ft_strlen(src));
	i = 0;
	while (src[i] && i < dstsize - 1)
	{
		dst[i] = src[i];
		i++;
	}
	dst[i] = '\0';
	return (ft_strlen(src));
}

char	*ft_strjoin_free(char *s1, char *s2)
{
	char	*result;
	size_t	s1_len;
	size_t	s2_len;

	if (!s1 && !s2)
		return (NULL);
	s1_len = 0;
	if (s1)
		s1_len = ft_strlen(s1);
	s2_len = ft_strlen(s2);
	result = malloc(s1_len + s2_len + 1);
	if (!result)
	{
		free(s1);
		free(s2);
		return (NULL);
	}
	if (s1)
		ft_strlcpy(result, s1, s1_len + 1);
	else
		result[0] = '\0';
	ft_strlcpy(result + s1_len, s2, s2_len + 1);
	free(s1);
	free(s2);
	return (result);
}

Explanation

  • Static Variable:

The static buffer retains data between function calls, allowing partial reads to be accumulated until a newline is found.

  • *Reading in Chunks:

     The read_buffer function reads data into a temporary buffer,
 which is then appended to the static buffer using ft_strjoin_free.

  • Line Extraction:

     The extract_line function checks for a newline in the static 
 buffer. If found, it splits the line and updates the static buffer with the 
 remaining data.

  • Memory Management:

     Helper functions handle string operations and memory 
 management, ensuring no leaks. 

 The ft_strjoin_free function safely joins 
 strings and frees old buffers.

  • Edge Cases:

     Handles EOF, lines without terminating newlines, and varying buffer
 sizes by efficiently managing reads and memory.

This approach ensures efficient reading and memory usage, adhering to the problem constraints and School 42's norm requirements.

⚠️ **GitHub.com Fallback** ⚠️