42 São Paulo - ft_get_next_line

A function that reads a file line-by-line.

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📜 Table of Contents

• About
• Getting Started
• Github Actions
• 42 São Paulo

🧐 About

What can I say that @harm-smits hasn't said already?

get_next_line is a function that reads an entire line from a file indexed by a file descriptor fd. It then alocates a string with the contents of that line without the linebreak '\n' and points line to it.

We don't have to pass anything allocated to get_next_line, we just pass the address of a pointer that will point to the allocated string. line should be freeable with free() after the function call unless an error occured.

We will incrementally read the file with read(), which advances its position in the file dexample escriptor automatically.

We need to use a static pointer as a read buffer to access what was read in previous calls.

We need to handle the following situations:

1. If the read buffer doesn't have a '\n', we concatenate with the previous buffer and call read again.
2. If the read buffer has a '\n', we concatenate with the previous buffer up to '\n'.
3. If we reach the end of the file (read() == 0), we concatenate with the previous buffer.
4. We finally point line to an allocated string that contains the entire line without the '\n'. Then we release the memory allocated in the intermediate strings and return 1 or 0 for '\n' and end_of_file respectively.
5. If the parameters have any problems (BUFFER_SIZE <= 0), or if in any operation we were unable to allocate memory, we free whatever memory was allocated and return -1.

pt-br

Tem essa documentacao bem legal do @harm-smits.

O get_next_line lê uma linha inteira do arquivo indexado por fd, e faz o ponterio line apontar para uma string allocada com os conteudos dessa linha sem a quebra de linha '\n'.

Nao temos que passar nada allocado para o get_next_line, apenas passar o endereco de um ponteiro que vai apontar para a string allocada. Precisamos poder dar free() nessa string allocada depois da chamada.

A gente vai ler o arquivo com a funcao read(), que avanca a sua posicao no file descriptor automaticamente.

A gente precisa usar um ponteiro estatico como buffer do read para poder acessar o que foi lido pelo read nas chamadas anteriores.

Precisamos tratar as seguintes situacoes:

1. Se o buffer lido nao tem '\n', concatenamos com o buffer anterior e chamamos read novamente.
2. Se o buffer lido tem '\n', concatenamos com o buffer anterior ate o '\n'.
3. Se chegamos no final do arquivo (read() = 0), concatenamos com o buffer anterior.
4. Finalmente temos que apontar o ponteiro line passado para uma string allocada que contenha a linha inteira sem o '\n'. Depois liberamos a memoria allocada nas strings intermediarias e retornamos 1 ou 0 para '\n' ou final do arquivo respectivamente.
5. Se os parametros tem algum problema (BUFFER_SIZE <= 0), ou em alguma dessas operacaoes nao conseguimos allocar memoria, liberamos toda a memoria allocada e retornamos -1.

🏁 Getting Started

⚙️ Prerequisites

All you need is a shell and a C compiler like gcc or clang.

🖥️ Installing

To compile the entire thing just clone the repo and run make with a positive BUFFER_SIZE:

$ git clone https://github.com/librity/ft_get_next_line.git
$ cd ft_get_next_line
$ make d="'BUFFER_SIZE=42'"

This will generate a get_next_line.a archive, which you can compile with the example file:

$ gcc -g -D BUFFER_SIZE=42 -I ./includes ./examples/example.c get_next_line.a
$ ./a.out

🐙 Github Actions

Norminette Github Action by @AdrianWR

🛸 42 São Paulo

Part of the larger 42 Network, 42 São Paulo is a software engineering school that offers a healthy alternative to traditional education:

• It doesn't have any teachers and classes.
• Students learn by cooperating and correcting each other's work (peer-to-peer learning).
• Its focus is as much on social skills as it is on technical skills.
• It's completely free to anyone that passes its selection process - The Piscine

It's an amazing school, and I'm grateful for the opportunity.