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0x0B-malloc_free

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0x0B. C - malloc, free

Tasks

0. Float like a butterfly, sting like a bee

mandatory

Write a function that creates an array of chars, and initializes it with a specific char.

  • Prototype: char *create_array(unsigned int size, char c);
  • Returns NULL if size = 0
  • Returns a pointer to the array, or NULL if it fails
julien@ubuntu:~/0x0a. malloc, free$ cat 0-main.c
#include "holberton.h"
#include <stdio.h>
#include <stdlib.h>

/**
 * simple_print_buffer - prints buffer in hexa
 * @buffer: the address of memory to print
 * @size: the size of the memory to print
 *
 * Return: Nothing.
 */
void simple_print_buffer(char *buffer, unsigned int size)
{
    unsigned int i;

    i = 0;
    while (i < size)
    {
        if (i % 10)
        {
            printf(" ");
        }
        if (!(i % 10) && i)
        {
            printf("\n");
        }
        printf("0x%02x", buffer[i]);
        i++;
    }
    printf("\n");
}

/**
 * main - check the code for ALX School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *buffer;

    buffer = create_array(98, 'H');
    if  (buffer == NULL)
    {
        printf("failed to allocate memory\n");
        return (1);
    }
    simple_print_buffer(buffer, 98);
    free(buffer);
    return (0);
}
julien@ubuntu:~/0x0a. malloc, free$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 0-main.c 0-create_array.c -o a
julien@ubuntu:~/0x0a. malloc, free$ ./a
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
0x48 0x48 0x48 0x48 0x48 0x48 0x48 0x48
julien@ubuntu:~/0x0a. malloc, free$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0B-malloc_free
  • File: 0-create_array.c

1. The woman who has no imagination has no wings

mandatory

Write a function that returns a pointer to a newly allocated space in memory, which contains a copy of the string given as a parameter.

  • Prototype: char *_strdup(char *str);
  • The _strdup() function returns a pointer to a new string which is a duplicate of the string str. Memory for the new string is obtained with malloc, and can be freed with free.
  • Returns NULL if str = NULL
  • On success, the _strdup function returns a pointer to the duplicated string. It returns NULL if insufficient memory was available

FYI: The standard library provides a similar function: strdup. Run man strdup to learn more.

julien@ubuntu:~/0x0a. malloc, free$ cat 1-main.c
#include "holberton.h"
#include <stdio.h>
#include <stdlib.h>

/**
 * main - check the code for ALX School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s;

    s = _strdup("Holberton");
    if (s == NULL)
    {
        printf("failed to allocate memory\n");
        return (1);
    }
    printf("%s\n", s);
    free(s);
    return (0);
}
julien@ubuntu:~/0x0a. malloc, free$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 1-main.c 1-strdup.c -o s
julien@ubuntu:~/0x0a. malloc, free$ ./s
Holberton
julien@ubuntu:~/0x0a. malloc, free$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0B-malloc_free
  • File: 1-strdup.c

2. He who is not courageous enough to take risks will accomplish nothing in life

mandatory

Write a function that concatenates two strings.

  • Prototype: char *str_concat(char *s1, char *s2);
  • The returned pointer should point to a newly allocated space in memory which contains the contents of s1, followed by the contents of s2, and null terminated
  • if NULL is passed, treat it as an empty string
  • The function should return NULL on failure
julien@ubuntu:~/0x0a. malloc, free$ cat 2-main.c
#include "holberton.h"
#include <stdio.h>
#include <stdlib.h>

/**
 * main - check the code for ALX School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s;

    s = str_concat("Betty ", "Holberton");
    if (s == NULL)
    {
        printf("failed\n");
        return (1);
    }
    printf("%s\n", s);
    free(s);
    return (0);
}
julien@ubuntu:~/0x0a. malloc, free$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 2-main.c 2-str_concat.c -o c
julien@ubuntu:~/c/curriculum_by_julien/holbertonschool-low_level_programming/0x0a. malloc, free$ ./c | cat -e
Betty Holberton$
julien@ubuntu:~/c/curriculum_by_julien/holbertonschool-low_level_programming/0x0a. malloc, free$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0B-malloc_free
  • File: 2-str_concat.c

3. If you even dream of beating me you'd better wake up and apologize

mandatory

Write a function that returns a pointer to a 2 dimensional array of integers.

  • Prototype: int **alloc_grid(int width, int height);
  • Each element of the grid should be initialized to 0
  • The function should return NULL on failure
  • If width or height is 0 or negative, return NULL
julien@ubuntu:~/0x0a. malloc, free$ cat 3-main.c
#include "holberton.h"
#include <stdio.h>
#include <stdlib.h>

/**
 * print_grid - prints a grid of integers
 * @grid: the address of the two dimensional grid
 * @width: width of the grid
 * @height: height of the grid
 *
 * Return: Nothing.
 */
void print_grid(int **grid, int width, int height)
{
    int w;
    int h;

    h = 0;
    while (h < height)
    {
        w = 0;
        while (w < width)
        {
            printf("%d ", grid[h][w]);
            w++;
        }
        printf("\n");
        h++;
    }
}

/**
 * main - check the code for ALX School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    int **grid;

    grid = alloc_grid(6, 4);
    if (grid == NULL)
    {
        return (1);
    }
    print_grid(grid, 6, 4);
    printf("\n");
    grid[0][3] = 98;
    grid[3][4] = 402;
    print_grid(grid, 6, 4);
    return (0);
}
julien@ubuntu:~/0x0a. malloc, free$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 3-main.c 3-alloc_grid.c -o g
julien@ubuntu:~/0x0a. malloc, free$ ./g
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0

0 0 0 98 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 402 0
julien@ubuntu:~/0x0a. malloc, free$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0B-malloc_free
  • File: 3-alloc_grid.c

4. It's not bragging if you can back it up

mandatory

Write a function that frees a 2 dimensional grid previously created by your alloc_grid function.

  • Prototype: void free_grid(int **grid, int height);
  • Note that we will compile with your alloc_grid.c file. Make sure it compiles.
julien@ubuntu:~/0x0a. malloc, free$ cat 4-main.c
#include "holberton.h"
#include <stdio.h>
#include <stdlib.h>

/**
 * print_grid - prints a grid of integers
 * @grid: the address of the two dimensional grid
 * @width: width of the grid
 * @height: height of the grid
 *
 * Return: Nothing.
 */
void print_grid(int **grid, int width, int height)
{
    int w;
    int h;

    h = 0;
    while (h < height)
    {
        w = 0;
        while (w < width)
        {
            printf("%d ", grid[h][w]);
            w++;
        }
        printf("\n");
        h++;
    }
}

/**
 * main - check the code for ALX School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    int **grid;

    grid = alloc_grid(6, 4);
    if (grid == NULL)
    {
        return (1);
    }
    print_grid(grid, 6, 4);
    printf("\n");
    grid[0][3] = 98;
    grid[3][4] = 402;
    print_grid(grid, 6, 4);
    free_grid(grid, 4);
    return (0);
}
julien@ubuntu:~/0x0a. malloc, free$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 4-main.c 3-alloc_grid.c 4-free_grid.c -o f
julien@ubuntu:~/0x0a. malloc, free$ valgrind ./f
==5013== Memcheck, a memory error detector
==5013== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==5013== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==5013== Command: ./f
==5013==
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0

0 0 0 98 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 402 0
==5013==
==5013== HEAP SUMMARY:
==5013==     in use at exit: 0 bytes in 0 blocks
==5013==   total heap usage: 6 allocs, 6 frees, 1,248 bytes allocated
==5013==
==5013== All heap blocks were freed -- no leaks are possible
==5013==
==5013== For counts of detected and suppressed errors, rerun with: -v
==5013== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
julien@ubuntu:~/0x0a. malloc, free$

Repo:

  • GitHub repository: alx-low_level_programming
  • Directory: 0x0B-malloc_free
  • File: 4-free_grid.c