#include <stdio.h>

void fn(char *p, unsigned char *b, const char len)
{
    if (*p == len - 1)
    {
        for (char i = 1; i < len; i++)
        {
            b[i - 1] = b[i];
        }
        b[len - 1] = '\0';
        (*p)--;
    }
}

int main(int argc, char **argv)
{
    char pos = 4;
    unsigned char buffer[] = "abcde";

    for (char i = 0; i < 5; i++)
    {
        printf("%d ", buffer[i]);
    }
    printf("%d\n", pos);

    fn(&pos, buffer, 5);

    for (char i = 0; i < 5; i++)
    {
        printf("%d ", buffer[i]);
    }
    printf("%d\n", pos);

    fn(&pos, buffer, 5);

    for (char i = 0; i < 5; i++)
    {
        printf("%d ", buffer[i]);
    }
    printf("%d\n", pos);

    return 0;
}