reverseBytes.c

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

static void reverseBytes (char *bytes, int length) {
    int left = 0;
    int right = length - 1;

    while (left < right) {
        char t = bytes[left];
        bytes[left] = bytes[right];
        bytes[right] = t;
        ++left;
        --right;
    }
}

static void test1 (void)
{
    char bytes1[] = {0xea, 0x45, 0x37, 0x80, 0xb1, 0x0c, 0xb8, 0xe5, 0x65, 0x8f, 0xad, 0xd8, 0xba, 0xa7, 0xf5, 0x1b};
    char reversedBytes1[] = {0x1b, 0xf5, 0xa7, 0xba, 0xd8, 0xad, 0x8f, 0x65, 0xe5, 0xb8, 0x0c, 0xb1, 0x80, 0x37, 0x45, 0xea};
    reverseBytes (bytes1, sizeof(bytes1));
    if (memcmp (bytes1, reversedBytes1, sizeof (bytes1)) != 0) {
        fprintf (stderr, "reversal #1 failed");
        exit (EXIT_FAILURE);
    }
}

static void test2 (void)
{
    char bytes2[] = {0xBE, 0x43, 0xE3, 0x89, 0xD7};
    char reversedBytes2[] = {0xD7, 0x89, 0xE3, 0x43, 0xBE};

    reverseBytes (bytes2, sizeof(bytes2));
    if (memcmp (bytes2, reversedBytes2, sizeof (bytes2)) != 0) {
        fprintf (stderr, "reversal #2 failed");
        exit (EXIT_FAILURE);
    }
}

int main (void) {
    test1 ();
    test2 ();

    return EXIT_SUCCESS;
}