SO lab7 ex1

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <pthread.h>

#define MAX_RESOURCES 5
int available_resources = MAX_RESOURCES;
pthread_mutex_t mtx;

int decrease_count(int count)
{
    pthread_mutex_lock(&mtx);
    if(available_resources < count)
    {
        pthread_mutex_unlock(&mtx);
        return -1;
    }
    else
    {
        available_resources -= count;
        printf("Got %d resources %d remaining\n", count, available_resources);
    }
    pthread_mutex_unlock(&mtx);
    return 0;
}

int increase_count(int count)
{
    pthread_mutex_lock(&mtx);
    available_resources += count;
    printf("Released %d resources %d remaining\n", count, available_resources);
    pthread_mutex_unlock(&mtx);

    return 0;
}

void* solve(void *arg)
{
    int count = (int) arg;

    while (decrease_count(count) == -1);
    increase_count(count);

    return NULL;
}


int main(int argc, char* argv[])
{

    pthread_t thr[MAX_RESOURCES + 2];
    printf("MAX_RESOURCES = %d\n", available_resources);
    for (int i = 0; i < MAX_RESOURCES; i++)
    {
        int count;
        count = rand() % (MAX_RESOURCES + 1);
        if (pthread_create(&thr[i], NULL, solve, count))
        {
            perror(NULL);
            return errno;
        }
    }

    for (int i = 0; i < MAX_RESOURCES; i++) pthread_join(thr[i], NULL);
    pthread_mutex_destroy(&mtx);

    return 0;
}