#include "stdafx.h"

//
// THERE CAN BE NO TRACE STATEMENTS USING XTRACE IN THIS CLASS - IT CAUSES RECIURSION
//
CLock::CLock(void)
{
	try
	{
		cs_valid	 = true;
		cs_thread_id = 0;
		cs_lock	 	 = new CRITICAL_SECTION;
		m_ref = 0;

		 // Initialize the critical section one time only.
		InitializeCriticalSection(cs_lock);
	}
	catch(...)
	{
		cs_valid = false;
	}
}

CLock::~CLock(void)
{
	Unlock();

	DeleteCriticalSection(cs_lock);

	delete cs_lock;
}

void CLock::Lock()
{
	if(GetCurrentThreadId() != cs_thread_id)
	{
       // XTRACE1("Waiting for critical section, GetCurrentThreadId=(%#8.8x)\n", GetCurrentThreadId());
	}
	//
	// NOT IN CRITICAL SECTION
	//
	EnterCriticalSection(cs_lock);
	//
	// IN CRITICAL SECTION
	//
	// copy thread id
	//
	cs_thread_id = GetCurrentThreadId();
	//
	// up ref count
	//
	InterlockedIncrement(&m_ref);

	//XTRACE2("Lock acquired, GetCurrentThreadId=(%#8.8x), refcount=%d\n", GetCurrentThreadId(), int(m_ref));
}

void CLock::Unlock()
{
	if(cs_thread_id == GetCurrentThreadId())
	{
		long last = m_ref;
		//
		// CRITICAL SECTION HELD BY THREAD
		//
		if(InterlockedDecrement(&m_ref) >= 0)
		{
			//
			// must be called once for each call to EnterCriticalSection
			//
			LeaveCriticalSection(cs_lock);
	
			//XTRACE2("Lock released, GetCurrentThreadId=(%#8.8x), refcount=%d\n", GetCurrentThreadId(), int(m_ref));

			//if(last == 1)
			///{
			//	XTRACE("Lock freed\n");
			//}
		}
		else
		{
			InterlockedExchange(&m_ref, 0);
		}
	}
}