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qtlockedfile_win.cpp
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qtlockedfile_win.cpp
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/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the Qt Solutions component.
**
** $QT_BEGIN_LICENSE:BSD$
** You may use this file under the terms of the BSD license as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
** * Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** * Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
** * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
** of its contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
#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
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()); } );
if (!mutex) {
qErrnoWarning("QtLockedFile::lock(): CreateMutex failed");
return 0;
}
}
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 (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);
}

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