How do I make a circular queue thread-safe? - c++

Question

So my Enqueue and Dequeue functions are below. How do I take what I have and make it thread safe? I thought about using a mutex from Windows.h, but I'd like to not limit my program to Windows-only, if possible.
void Queue::Enqueue(int num){
//increase recorded size
size++;
//stick in num
numbers[nextSpace] = num;
//find the next available space
nextSpace = (++nextSpace) % maxSize;
}
int Queue::Dequeue(){
int temp;
temp = items[curSpace];
curSpace = (++curSpace) % maxSize;
size--;
return temp;
}

Answer 1

You can refer this code (with pthreads):
#include<pthread.h>
#define DEFAULT_SIZE 100
class circularQueue{
private:
int *m_queue;
int p_head;
int p_tail;
int m_cap;
pthread_mutex_t mp = PTHREAD_MUTEX_INITIALIZER;
public:
circularQueue(int size)
{
/*in case invalid input*/
if(size<0)
size = DEFAULT_SIZE ;
m_queue = new int[size];
p_head = 0;
p_tail = -1;
m_cap = 0;
pthread_mutex_init(&mp,NULL);
}
bool enqueue(int x)
{
bool res= false;
p_thread_mutex_lock(&mp);
/*queue is full*/
if(m_cap == size)
{
res = false;
}
else
{
m_queue[(++p_tail)%size)] = x;
++m_cap;
res = true;
}
p_thread_mutex_unlock(&mp);
return res;
}
int dequeue()
{
int res=0;
pthread_mutex_lock(&mp);
/*empty queue*/
if(m_cap == 0)
{
throw("empty queue!");
pthread_mutex_unlock(&mp);
}
else{
res = m_queue[p_head];
p_head = (p_head+1)%size;
}
pthread_mutex_unlock(&mp);
return res;
}
~virtual circularQueue()
{
delete[] m_queue;
m_queue = NULL;
pthread_mutex_destroy(&mp);
}
}