Convert "unsigned int" to "unsigned char" vector?

Question

I need to convert a unsigned int in a vector of unsigned char to later translate this address into binary, for a work that needs to simulate a virtual memory. Can someone explain to me how to do this?

Answer 1

The answer you chose as best can be responsible for Undefined behaviour this is may change chunks of memory that do not belong to you causing crashes or bugs. If I were you I would use a [Union][2] to convert, easier, faster and viable.

Take the example here:

#include <stdio.h>
#include <stdlib.h>

int main (void) {

   typedef union _Conversor
   {
       unsigned int inicial; //Valor que vai armazenar
       unsigned char leitor[4];//Para ler todos os bytes unsigned int tem 4 em windows e linux
    }Conversor;

    Conversor conv;
    conv.inicial = 0xCE87;//Valor random
    printf("%02X %02X %02X %02X\n", conv.leitor[0], conv.leitor[1], conv.leitor[2], conv.leitor[3]);


    return 0;   
}

http://ideone.com/58FMdE

Answer 2

If I understand correctly, you want to reinterpret an integer vector for a "byte" vector. So, you can do this here:

#include <stdio.h>
#include <stdlib.h>

#define ASIZE(x) sizeof(x)/sizeof(x[0])

int main (void) {

    const unsigned int teste[5] = {300, 500, 900, 1100, 1300};
    unsigned char *buf = NULL;
    size_t jmp = 0;

    buf = malloc(ASIZE(teste));
    if (!buf) abort();

    for (size_t index = 0; index < ASIZE(teste); index++,jmp+=sizeof(int)) {
            buf[jmp] = teste[index] & 0x000000ff;
            buf[jmp+1] = (teste[index] & 0x0000ff00) >> 8;
            buf[jmp+2] = (teste[index] & 0x00ff0000) >> 16;
            buf[jmp+3] = (teste[index] & 0xff000000) >> 24;
            printf("%u - %u - %u - %u\n", buf[jmp+3], buf[jmp+2], buf[jmp+1], buf[jmp]);
    }

    return 0;
}

The above code makes use of bit manipulation. If you don’t know what this is, just take a look here: http://www.programiz.com/c-programming/bitwise-operators

Answer 3

Basically something like this

unsigned int valor = 1042;
unsigned char vetor[38]; // escolher limite apropriado
int len = snprintf(vetor, sizeof vetor, "%u", valor);
// vetor 'e a string "1042", ou seja
// vetor[0] == '1'; vetor[1] = '0'; vetor[2] = '4'; vetor[3] = '2'; vetor[4] = '\0';

If you want to convert to values instead of characters, decrease '0' every character

for (int k = 0; k < len; k++) vetor[k] -= '0'; // vetor ja nao 'e uma string!
// vetor[0] == 1; vetor[1] = 0; vetor[2] = 4; vetor[3] = 2;