#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h> // strcpy
#include <unistd.h> // usleep

#define MICROS (1)
#define THREADS (5)
#define ACCESSES (5)

char * names[] = {"alpha",   "bravo",    "charlie", "delta",
                  "echo",    "foxtrot",  "golf",    "hotel",
                  "india",   "juliet",   "kilo",    "lima",
                  "mike",    "november", "oscar",   "papa",
                  "quebec",  "romeo",    "sierra",  "tango",
                  "uniform", "victor",   "whiskey", "x-ray",
                  "yankee",  "zulu"};

// could be a good idea to use XCHG asm operation as atomic

void mutex_lock();
void mutex_unlock();

int mx = 0;
int counter = 0;
char pool[128] = {0};
pthread_t threads[THREADS];

void fill_pool()
{
    counter++;
    strcpy(pool, names[random() % 26]);
}

void show_pool(int number)
{
    printf("%04d - %04d - %s\n", counter, number, pool);
}

void * thread_fnc(void * index)
{
    int number = (int)index;
    int i;
    for (i = 0; i < ACCESSES; i++)
    {
        usleep(random() % 10000);
        mutex_lock();
        {
            fill_pool();
            show_pool(number);
        }
        mutex_unlock();
    }
}

void mutex_lock()
{
    while (mx) /* needs atomic */
    {
        usleep(MICROS);
    }

    mx = 1;
}

void mutex_unlock()
{
    mx = 0;
}

int main()
{
    int i;

    printf(" ##  - THRD - name\n");

    for (i = 0; i < THREADS; i++)
        pthread_create(&threads[i], NULL, thread_fnc, (void *)i);

    for (i = 0; i < THREADS; i++)
        pthread_join(threads[i], NULL);

    return 0;
}