0x07-pointers_arrays_strings

Requirements

General

• Allowed editors: vi, vim, emacs
• All your files will be compiled on Ubuntu 14.04 LTS
• Your programs and functions will be compiled with gcc 4.8.4 using the flags -Wall -Werror -Wextra and -pedantic
• All your files should end with a new line
• A README.md file, at the root of the folder of the project is mandatory
• Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl
• You are not allowed to use global variables
• No more than 5 functions per file
• You are not allowed to use the standard library. Any use of functions like printf, puts, etc… is forbidden
• You are allowed to use _putchar
• You don’t have to push _putchar.c, we will use our file. If you do it won’t be taken into account
• In the following examples, the main.c files are shown as examples. You can use them to test your functions, but you don’t have to push them to your repo (if you do we won’t take them into account). We will use our own main.c files at compilation. Our main.c files might be different from the one shown in the examples
• The prototypes of all your functions and the prototype of the function _putchar should be included in your header file called holberton.h
• Don’t forget to push your header file

Tasks

0. memset

File: 0-memset.c

Write a function that fills memory with a constant byte.

• Prototype: char *_memset(char *s, char b, unsigned int n);
• The _memset() function fills the first n bytes of the memory area pointed to by s with the constant byte b
• Returns a pointer to the memory area s FYI: The standard library provides a similar function: memset. Run man memset to learn more.

julien@ubuntu:~/0x07$ cat 0-main.c
#include "holberton.h"
#include <stdio.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 Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char buffer[98] = {0x00};

    simple_print_buffer(buffer, 98);
    _memset(buffer, 0x01, 95);
    printf("-------------------------------------------------\n");
    simple_print_buffer(buffer, 98);    
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 0-main.c 0-memset.c -o 0-memset
julien@ubuntu:~/0x07$ ./0-memset 
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
-------------------------------------------------
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x00 0x00 0x00
julien@ubuntu:~/0x07$ 

1. memcpy

File: 1-memcpy.c

Write a function that copies memory area.

• Prototype: char *_memcpy(char *dest, char *src, unsigned int n); The _memcpy() function copies n bytes from memory area src to memory area dest
• Returns a pointer to dest FYI: The standard library provides a similar function: memcpy. Run man memcpy to learn more.

julien@ubuntu:~/0x07$ cat 1-main.c
#include "holberton.h"
#include <stdio.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 Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char buffer[98] = {0};
    char buffer2[98] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14};

    simple_print_buffer(buffer, 98);
    _memcpy(buffer + 50, buffer2, 10);
    printf("-------------------------------------------------\n");
    simple_print_buffer(buffer, 98);    
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 1-main.c 1-memcpy.c -o 1-memcpy
julien@ubuntu:~/0x07$ ./1-memcpy 
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
-------------------------------------------------
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x01 0x02 0x03 0x04 0x05 0x07 0x07 0x08 0x09 0x0a
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
julien@ubuntu:~/0x07$ 

2. strchr

File: 2-strchr.c

Write a function that locates a character in a string.

• Prototype: char *_strchr(char *s, char c);
• Returns a pointer to the first occurrence of the character c in the string s, or - NULL if the character is not found FYI: The standard library provides a similar function: strchr. Run man strchr to learn more.

julien@ubuntu:~/0x07$ cat 2-main.c
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s = "hello";
    char *f;

    f = _strchr(s, 'l');

    if (f != NULL)
    {
        printf("%s\n", f);
    }
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 2-main.c 2-strchr.c -o 2-strchr
julien@ubuntu:~/0x07$ ./2-strchr 
llo
julien@ubuntu:~/0x07$ 

3. strspn

File: 3-strspn.c

Write a function that gets the length of a prefix substring.

• Prototype: unsigned int _strspn(char *s, char *accept);
• Returns the number of bytes in the initial segment of s which consist only of bytes from accept FYI: The standard library provides a similar function: strspn. Run man strspn to learn more.

julien@ubuntu:~/0x07$ cat 3-main.c
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s = "hello, world";
    char *f = "oleh";
    unsigned int n;

    n = _strspn(s, f);
    printf("%u\n", n);
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 3-main.c 3-strspn.c -o 3-strspn
julien@ubuntu:~/0x07$ ./3-strspn 
5
julien@ubuntu:~/0x07$ 

4. strpbrk

File: 4-strpbrk.c

Write a function that searches a string for any of a set of bytes.

• Prototype: char *_strpbrk(char *s, char *accept);
• The _strpbrk() function locates the first occurrence in the string s of any of the bytes in the string accept
• Returns a pointer to the byte in s that matches one of the bytes in accept, or - NULL if no such byte is found FYI: The standard library provides a similar function: strpbrk. Run man strpbrk to learn more.

julien@ubuntu:~/0x07$ cat 4-main.c
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s = "hello, world";
    char *f = "world";
    char *t;

    t = _strpbrk(s, f);
    printf("%s\n", t);
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 4-main.c 4-strpbrk.c -o 4-strpbrk
julien@ubuntu:~/0x07$ ./4-strpbrk 
llo, world
julien@ubuntu:~/0x07$ 

5. strstr

File: 5-strstr.c

Write a function that locates a substring.

• Prototype: char *_strstr(char *haystack, char *needle);
• The _strstr() function finds the first occurrence of the substring needle in the string haystack. The terminating null bytes (\0) are not compared
• Returns a pointer to the beginning of the located substring, or NULL if the substring is not found. FYI: The standard library provides a similar function: strstr. Run man strstr to learn more.

julien@ubuntu:~/0x07$ cat 5-main.c
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s = "hello, world";
    char *f = "world";
    char *t;

    t = _strstr(s, f);
    printf("%s\n", t);
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 5-main.c 5-strstr.c -o 5-strstr
julien@ubuntu:~/0x07$ ./5-strstr 
world
julien@ubuntu:~/0x07$ 

6. Chess is mental torture

File: 7-print_chessboard.c

Write a function that prints the chessboard.

• Prototype: void print_chessboard(char (*a)[8]);

julien@ubuntu:~/0x07$ cat 7-main.c 
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char board[8][8] = {
        {'r', 'k', 'b', 'q', 'k', 'b', 'k', 'r'},
        {'p', 'p', 'p', 'p', 'p', 'p', 'p', 'p'},
        {' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '},
        {' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '},
        {' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '},
        {' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '},
        {'P', 'P', 'P', 'P', 'P', 'P', 'P', 'P'},
        {'R', 'K', 'B', 'Q', 'K', 'B', 'K', 'R'},
    };
    print_chessboard(board);
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra _putchar.c 7-main.c 7-print_chessboard.c -o 7-print_chessboard
julien@ubuntu:~/0x07$ ./7-print_chessboard 
rkbqkbkr
pppppppp




PPPPPPPP
RKBQKBKR
julien@ubuntu:~/c/curriculum_by_julien/holbertonschool-low_level_programming/0x07$ 

7. The line of life is a ragged diagonal between duty and desire

File: 8-print_diagsums.c

Write a function that prints the sum of the two diagonals of a square matrix of integers.

• Prototype: void print_diagsums(int *a, int size);
• Format: see example
• You are allowed to use the standard library Note that in the following example we are casting an int[][] into an int*. This is not something you should do. The goal here is to make sure you understand how an array of array is stored in memory.

julien@ubuntu:~/0x07$ cat 8-main.c
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    int c3[3][3] = {
        {0, 1, 5},
        {10, 11, 12},
        {1000, 101, 102},
    };
    int c5[5][5] = {
        {0, 1, 5, 12124, 1234},
        {10, 11, 12, 123521, 12512},
        {1000, 101, 102, 12545, 214543435},
        {100, 1012451, 11102, 12545, 214543435},
        {10, 12401, 10452, 11542545, 1214543435},
    };
    print_diagsums((int *)c3, 3);
    print_diagsums((int *)c5, 5);
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 8-main.c 8-print_diagsums.c -o 8-print_diagsums
julien@ubuntu:~/0x07$ ./8-print_diagsums 
113, 1016
1214556093, 1137318
julien@ubuntu:~/0x07$ 

8. Double pointer, double fun

File: 9-set_string.c

Write a function that sets the value of a pointer to a char.

• Prototype: void set_string(char **s, char *to);

julien@ubuntu:~/0x07$ cat 9-main.c
#include "holberton.h"
#include <stdio.h>

/**
 * main - check the code for Holberton School students.
 *
 * Return: Always 0.
 */
int main(void)
{
    char *s0 = "Anne Cognet";
    char *s1 = "Asaia Palacios";

    printf("%s, %s\n", s0, s1);
    set_string(&s1, s0);
    printf("%s, %s\n", s0, s1);
    return (0);
}
julien@ubuntu:~/0x07$ gcc -Wall -pedantic -Werror -Wextra 9-main.c 9-set_string.c -o 9-set_string
julien@ubuntu:~/0x07$ ./9-set_string 
Anne Cognet, Asaia Palacios
Anne Cognet, Anne Cognet
julien@ubuntu:~/0x07$ 

9. My primary goal of hacking was the intellectual curiosity, the seduction of adventure

File: 101-crackme_password

Create a file that contains the password for the crackme2 executable.

• Your file should contain the exact password, no new line, no extra space ltrace, ldd, gdb and objdump can help
• You may need to install the openssl library to run the crakme2 program: sudo apt-get install libssl-dev