fifo 2k18

#include <stdio.h>
#include <cstdlib>

#define FIFO_OK 0
#define FIFO_NOK -1

char * p = nullptr;

int in = 0, out = 0, count = 0, size = 0;

int NewFifo(int n) {
    if (n > 0 && p == NULL) {
        p = (char*) malloc(n);
        size = n;
        return FIFO_OK;
    }
    else {
        return FIFO_NOK;
    }
}

void DeleteFifo(void) {
    if(p != NULL)
        free(p);
}

int Push(char c) {
    if (size == count || p == NULL)
        return FIFO_NOK;

    *(p + in) = c;
    in++; count++;
    in = in % size;
    return FIFO_OK;
}

int Pop() {
    if(size == 0 ||p == NULL)
        return FIFO_NOK;

    char c = *(p + out);
    count--;
    if (count > 0){
        out++;
        out = out % size;
    }
    return c;
}

int main(void) {

    NewFifo(4);
    Push('A');


    DeleteFifo();

    return 0;
}