Back

GitHub

---

Get_next_line

Summary

Is an individual project about creating a function that returns the next line from a file descriptor, without knowing its size beforehand. One of the goal of this project is to learn a highly interesting concept in C programming: static variables, and to gain a deeper understanding of allocations, whether they happen on the stack memory or in the heap memory, the manipulation and the life cycle of a buffer, the unexpected complexity implied in the use of one or many static variables.

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

	if (fd < 0 || BUFFER_SIZE <= 0 || read(fd, 0, 0) < 0)
		return (NULL);
	staticbuf = ftread(fd, staticbuf);
	if (!staticbuf)
		return (NULL);
	line = findline(staticbuf);
	staticbuf = nextline(staticbuf);
	return (line);
}

Introduction

This project will not only allow you to add a very convenient function to your collection, but it will also make you learn a highly interesting new concept in C programming: static variables.

Mandatory part

Write a function that returns a line read from a file descriptor

• Repeated calls (e.g., using a loop) to your get_next_line() function should let you read the text file pointed to by the file descriptor, one line at a time.
• Your function should return the line that was read. If there is nothing else to read or if an error occurred, it should return NULL.
• Make sure that your function works as expected both when reading a file and when reading from the standard input.
• Please note that the returned line should include the terminating \n character, except if the end of file was reached and does not end with a \n character.
• Your header file get_next_line.h must at least contain the prototype of the get_next_line() function.
• Add all the helper functions you need in the get_next_line_utils.c file.
• Because you will have to read files in get_next_line(), add this option to your compiler call: -D BUFFER_SIZE=n It will define the buffer size for read(). The buffer size value will be modified by your peer-evaluators and the Moulinette in order to test your code.
• You will compile your code as follows (a buffer size of 42 is used as an example):
  cc -Wall -Wextra -Werror -D BUFFER_SIZE=42 *.c
• We consider that get_next_line() has an undefined behavior if the file pointed to by the file descriptor changed since the last call whereas read() didn’t reach the end of file.
• We also consider that get_next_line() has an undefined behavior when reading a binary file. However, you can implement a logical way to handle this behavior if you want to.

Frobbiden

• You are not allowed to use your libft in this project.
• lseek() is forbidden.
• Global variables are forbidden.

Bonus part

This project is straightforward and doesn’t allow complex bonuses. However, we trust your creativity. If you completed the mandatory part, give a try to this bonus part.

Here are the bonus part requirements:

• Develop get_next_line() using only one static variable.
• Your get_next_line() can manage multiple file descriptors at the same time. For example, if you can read from the file descriptors 3, 4 and 5, you should be able to read from a different fd per call without losing the reading thread of each file descriptor or returning a line from another fd. It means that you should be able to call get_next_line() to read from fd 3, then fd 4, then 5, then once again 3, once again 4, and so forth.