(322) 0x01. C - Static variables, getline

Specializations > System programming & Algorithm > Linux Programming

Project author

Julien Barbier

Assignment dates

12-07-2020 to 12-15-2020

Description

Introduction to static variables in C and building a clone of the glibc function getline.

Requirements

• Allowed Functions and System Calls
  • read
  • write
  • malloc
  • realloc
  • free
  • strcpy
  • strncpy
  • strcat
  • strdup
  • memset
  • memcpy

Provided file(s)

• man_cat man_gcc the_swing
• zero
• 0-main.c 1-main.c 2-main.c 3-main.c

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Mandatory Tasks

✅ 0. Racing cars

Write a function that keeps track of the number of laps made by several cars in a race.

• Prototype: void race_state(int *id, size_t size)
• id is an array of int representing the “identifier” of each car.
• size is the size of this array
• Each car identifier is unique
• If an identifier is unknown:
  • Create a new car with the number of laps = 0
  • Print Car X joined the race followed by a new line (where X is the identifier)
• Each time the function is called:
  • The number of laps of each cars listed in id must be incremented by 1
  • Print the state of the race:
    • Header: Race state: followed by a new line
    • For each car sorted by the identifier: Car X [Y laps] (where X is the identifier and Y the number of laps already done)
• If your function is called with size = 0, you must free all allocated memory.

File(s): laps.c laps.h
Compiled: gcc -Wall -Wextra -Werror -pedantic 0-main.c laps.c -o laps

✅ 1. _getline

Write a function that reads an entire line from a file descriptor.

• Prototype: char *_getline(const int fd)
• Where fd is the file descriptor to read from
• If there are no more lines to return, or if there is an error, the function should return NULL
• The function returns a null-terminated string that does not include the newline character
• Your header file _getline.h should define a macro called READ_SIZE.
  • This macro defines the number of bytes you will read each time you will call read: read(fd, buffer, READ_SIZE)
  • You are not allowed to read more or less than READ_SIZE bytes at once from fd
  • You are free to pick the value that you want for READ_SIZE
• You can assume that fd will always be the same

File(s): _getline.c _getline.h
Compiled: gcc -Wall -Wextra -Werror -pedantic 1-main.c _getline.c -o getline

✅ 2. _getline: multi-fd

Handle multiple file descriptors.

• When called with -1 you should free everything and reset all your static variables

File(s): _getline.c _getline.h
Compiled: gcc -Wall -Wextra -pedantic -Werror 2-main.c _getline.c -o getline

Advanced Tasks

✅ 3. _getline: ^@

Handle characters \0 in lines.

• Here’s the file used for the example below: zero

$ cat zero
line 1 Holberton.....
line 2 still line 2
line 3 ......School()
$ gcc -g -Wall -Wextra -pedantic 100-main.c _getline.c && ./a.out
6c 69 6e 65 20 31 20 48 6f 6c 62 65 72 74 6f 6e 2e 2e 2e 2e 2e
6c 69 6e 65 20 32 20 00 73 74 69 6c 6c 20 6c 69 6e 65 20 32 00
6c 69 6e 65 20 33 20 2e 2e 2e 2e 2e 2e 53 63 68 6f 6f 6c 28 29
$

File(s): _getline.c _getline.h
Compiled: gcc -Wall -Wextra -pedantic -Werror 100-main.c _getline.c -o getline

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Student

• Samuel Pomeroy - allelomorph