/*
 * Copyright (C) 2001-2008 Jacek Sieka, arnetheduck on gmail point com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#if !defined(CRITICAL_SECTION_H)
#define CRITICAL_SECTION_H

#include "Thread.h"

namespace dcpp {

class CriticalSection
{
#ifdef _WIN32
public:
	void enter() throw() {
		EnterCriticalSection(&cs);
		dcdrun(counter++);
	}
	void leave() throw() {
		dcassert(--counter >= 0);
		LeaveCriticalSection(&cs);
	}
	CriticalSection() throw() {
		dcdrun(counter = 0;);
		InitializeCriticalSection(&cs);
	}
	~CriticalSection() throw() {
		dcassert(counter==0);
		DeleteCriticalSection(&cs);
	}
private:
	dcdrun(long counter);
	CRITICAL_SECTION cs;
#else
public:
	CriticalSection() throw() {
		pthread_mutexattr_init(&ma);
		pthread_mutexattr_settype(&ma, PTHREAD_MUTEX_RECURSIVE);
		pthread_mutex_init(&mtx, &ma);
	}
	~CriticalSection() throw() {
		pthread_mutex_destroy(&mtx);
		pthread_mutexattr_destroy(&ma);
	}
	void enter() throw() { pthread_mutex_lock(&mtx); }
	void leave() throw() { pthread_mutex_unlock(&mtx); }
	pthread_mutex_t& getMutex() { return mtx; }
private:
	pthread_mutex_t mtx;
	pthread_mutexattr_t ma;
#endif
	CriticalSection(const CriticalSection&);
	CriticalSection& operator=(const CriticalSection&);
};

/**
 * A fast, non-recursive and unfair implementation of the Critical Section.
 * It is meant to be used in situations where the risk for lock conflict is very low,
 * i e locks that are held for a very short time. The lock is _not_ recursive, i e if
 * the same thread will try to grab the lock it'll hang in a never-ending loop. The lock
 * is not fair, i e the first to try to enter a locked lock is not guaranteed to be the
 * first to get it when it's freed...
 */
class FastCriticalSection {
public:
#ifdef _WIN32
	FastCriticalSection() : state(0) { }

	void enter() {
		while(Thread::safeExchange(state, 1) == 1) {
			Thread::yield();
		}
	}
	void leave() {
		Thread::safeDec(state);
	}
private:
	volatile long state;

#else
	// We have to use a pthread (nonrecursive) mutex, didn't find any test_and_set on linux...
	FastCriticalSection() {
		static pthread_mutex_t fastmtx = PTHREAD_MUTEX_INITIALIZER;
		mtx = fastmtx;
	}
	~FastCriticalSection() { pthread_mutex_destroy(&mtx); }
	void enter() { pthread_mutex_lock(&mtx); }
	void leave() { pthread_mutex_unlock(&mtx); }
private:
	pthread_mutex_t mtx;
#endif
};

template<class T>
class LockBase {
public:
	LockBase(T& aCs) throw() : cs(aCs) { cs.enter(); }
	~LockBase() throw() { cs.leave(); }
private:
	LockBase& operator=(const LockBase&);
	T& cs;
};
typedef LockBase<CriticalSection> Lock;
typedef LockBase<FastCriticalSection> FastLock;

} // namespace dcpp

#endif // !defined(CRITICAL_SECTION_H)
