#include "stdafx.h"

#include "QtLockedFile.h"

#include <qt_windows.h>
#include <QFileInfo>



#define MUTEX_PREFIX "QtLockedFile mutex "

// Maximum number of concurrent read locks. Must not be greater than MAXIMUM_WAIT_OBJECTS
#define MAX_READERS MAXIMUM_WAIT_OBJECTS

#if QT_VERSION >= 0x050000
#define QT_WA(unicode, ansi) unicode
#endif



QtLockedFile::QtLockedFile()
	: QFile()
{
	wmutex = 0;
	rmutex = 0;
	m_lock_mode = NoLock;
}

QtLockedFile::QtLockedFile(const QString &name)
	: QFile(name)
{
	wmutex = 0;
	rmutex = 0;
	m_lock_mode = NoLock;
}

bool QtLockedFile::open(OpenMode mode)
{
	if (mode & QIODevice::Truncate)
	{
		qWarning("QtLockedFile::open(): Truncate mode not allowed.");
		return false;
	}

	return QFile::open(mode);
}

bool QtLockedFile::isLocked() const
{
	return m_lock_mode != NoLock;
}

QtLockedFile::LockMode QtLockedFile::lockMode() const
{
	return m_lock_mode;
}

Qt::HANDLE QtLockedFile::getMutexHandle(int idx, bool doCreate)
{
	if (mutexname.isEmpty())
	{
		QFileInfo fi(*this);
		mutexname = QString::fromLatin1(MUTEX_PREFIX) + fi.absoluteFilePath().toLower();
	}

	QString mname(mutexname);
	if (idx >= 0)
		mname += QString::number(idx);

	Qt::HANDLE mutex;
	if (doCreate)
	{
		QT_WA( { mutex = CreateMutexW(NULL, FALSE, (TCHAR*)mname.utf16()); },
				{ mutex = CreateMutexA(NULL, FALSE, mname.toLocal8Bit().constData()); } );
	}
	else
	{
		QT_WA( { mutex = OpenMutexW(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, (TCHAR*)mname.utf16()); },
				{ mutex = OpenMutexA(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, mname.toLocal8Bit().constData()); } );
	}

	if (!mutex)
	{
		if (doCreate)
			qErrnoWarning("QtLockedFile::lock(): CreateMutex failed");
		else if (GetLastError() != ERROR_FILE_NOT_FOUND)
			qErrnoWarning("QtLockedFile::lock(): OpenMutex failed");

		return 0;
	}

	return mutex;
}

bool QtLockedFile::waitMutex(Qt::HANDLE mutex, bool doBlock)
{
	Q_ASSERT(mutex);
	DWORD res = WaitForSingleObject(mutex, doBlock ? INFINITE : 0);
	switch (res)
	{
	case WAIT_OBJECT_0:
	case WAIT_ABANDONED:
		return true;
		break;

	case WAIT_TIMEOUT:
		break;

	default:
		qErrnoWarning("QtLockedFile::lock(): WaitForSingleObject failed");
	}

	return false;
}



bool QtLockedFile::lock(LockMode mode, bool block)
{
	if (!isOpen())
	{
		qWarning("QtLockedFile::lock(): file is not opened");
		return false;
	}

	if (mode == NoLock)
		return unlock();

	if (mode == m_lock_mode)
		return true;

	if (m_lock_mode != NoLock)
		unlock();

	if (!wmutex && !(wmutex = getMutexHandle(-1, true)))
		return false;

	if (!waitMutex(wmutex, block))
		return false;

	if (mode == ReadLock)
	{
		int idx = 0;
		for (; idx < MAX_READERS; idx++)
		{
			rmutex = getMutexHandle(idx, false);
			if (!rmutex || waitMutex(rmutex, false))
				break;
			CloseHandle(rmutex);
		}
		bool ok = true;
		if (idx >= MAX_READERS)
		{
			qWarning("QtLockedFile::lock(): too many readers");
			rmutex = 0;
			ok = false;
		}
		else if (!rmutex)
		{
			rmutex = getMutexHandle(idx, true);
			if (!rmutex || !waitMutex(rmutex, false))
				ok = false;
		}

		if (!ok && rmutex)
		{
			CloseHandle(rmutex);
			rmutex = 0;
		}

		ReleaseMutex(wmutex);
		if (!ok)
			return false;
	}
	else
	{
		Q_ASSERT(rmutexes.isEmpty());
		for (int i = 0; i < MAX_READERS; i++)
		{
			Qt::HANDLE mutex = getMutexHandle(i, false);
			if (mutex)
				rmutexes.append(mutex);
		}

		if (rmutexes.size())
		{
			DWORD res = WaitForMultipleObjects(rmutexes.size(), rmutexes.constData(), TRUE, block ? INFINITE : 0);
			if (res != WAIT_OBJECT_0 && res != WAIT_ABANDONED)
			{
				if (res != WAIT_TIMEOUT)
					qErrnoWarning("QtLockedFile::lock(): WaitForMultipleObjects failed");
				m_lock_mode = WriteLock;  // trick unlock() to clean up - semiyucky
				unlock();
				return false;
			}
		}
	}

	m_lock_mode = mode;
	return true;
}

bool QtLockedFile::unlock()
{
	if (!isOpen())
	{
		qWarning("QtLockedFile::unlock(): file is not opened");
		return false;
	}

	if (!isLocked())
		return true;

	if (m_lock_mode == ReadLock)
	{
		ReleaseMutex(rmutex);
		CloseHandle(rmutex);
		rmutex = 0;
	}
	else
	{
		foreach(Qt::HANDLE mutex, rmutexes)
		{
			ReleaseMutex(mutex);
			CloseHandle(mutex);
		}
		rmutexes.clear();
		ReleaseMutex(wmutex);
	}

	m_lock_mode = QtLockedFile::NoLock;
	return true;
}

QtLockedFile::~QtLockedFile()
{
	if (isOpen())
		unlock();

	if (wmutex)
		CloseHandle(wmutex);
}
