//---------------------------------------------------------
// stallings.cc: prioridad a los lectores
//---------------------------------------------------------

#include <atomic>
#include <chrono>
#include <iostream>
#include <mutex>
#include <random>
#include <thread>

//---------------------------------------------------------

using namespace std;

//---------------------------------------------------------

atomic<bool> run(true);  // finish when false
mutex em_leyendo;        // exclusión mutua leyendo
unsigned leyendo = 0;    // nº lectores
mutex no_escritor;       // exclusion mutua l/e

//---------------------------------------------------------

void seccion_critica(char c)
{
	for (char i = 0; i < 10; ++i)
		cout << c;
	cout << endl;
}

//---------------------------------------------------------

void lector(char c)
{
	while (run)
	{
		em_leyendo.lock();
		if (++leyendo == 1)
			no_escritor.lock();
		em_leyendo.unlock();
		seccion_critica(c);
		em_leyendo.lock();
		if (--leyendo == 0)
			no_escritor.unlock();
		em_leyendo.unlock();
	}
}

//---------------------------------------------------------

void escritor(char c)
{
	while (run)
	{
		no_escritor.lock();
		seccion_critica(c);
		no_escritor.unlock();
	}
}

//---------------------------------------------------------

int main()
{
	const unsigned N = 8;
	thread lectores[N], escritores[N];
	std::default_random_engine engine;
	
	for (unsigned i = 0; i < N; ++i)
		if (engine() & 1)
		{
			  lectores[i] = thread(  lector, '0' + i);
			escritores[i] = thread(escritor, 'a' + i);
		}
		else
		{
			escritores[i] = thread(escritor, 'a' + i);
			  lectores[i] = thread(  lector, '0' + i);
		}
	
	this_thread::sleep_for(100ms);
	run = false;
	
	for(thread& i:   lectores) i.join();
	for(thread& i: escritores) i.join();
}

//---------------------------------------------------------