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 /****************************************************************************
 **
 ** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of Qt Creator.
 **
 ** Commercial License Usage
 ** Licensees holding valid commercial Qt licenses may use this file in
 ** accordance with the commercial license agreement provided with the
 ** Software or, alternatively, in accordance with the terms contained in
 ** a written agreement between you and Digia.  For licensing terms and
 ** conditions see http://www.qt.io/licensing.  For further information
 ** use the contact form at http://www.qt.io/contact-us.
 **
 ** GNU Lesser General Public License Usage
 ** Alternatively, this file may be used under the terms of the GNU Lesser
 ** General Public License version 2.1 or version 3 as published by the Free
 ** Software Foundation and appearing in the file LICENSE.LGPLv21 and
 ** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
 ** following information to ensure the GNU Lesser General Public License
 ** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
 ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
 **
 ** In addition, as a special exception, Digia gives you certain additional
 ** rights.  These rights are described in the Digia Qt LGPL Exception
 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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 ****************************************************************************/
 
 #include "qtlockedfile.h"
 
 #include <qt_windows.h>
 #include <QFileInfo>
 
 
 
 #define SEMAPHORE_PREFIX "QtLockedFile semaphore "
 #define MUTEX_PREFIX "QtLockedFile mutex "
 #define SEMAPHORE_MAX 100
 
 static QString errorCodeToString(DWORD errorCode)
 {
     QString result;
     char *data = 0;
     FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
                     0, errorCode, 0,
                     (char*)&data, 0, 0);
     result = QString::fromLocal8Bit(data);
     if (data != 0)
         LocalFree(data);
 
     if (result.endsWith(QLatin1Char('\n')))
         result.truncate(result.length() - 1);
 
     return result;
 }
 
 bool QtLockedFile::lock(LockMode mode, bool block)
 {
     if (!isOpen()) {
         qWarning("QtLockedFile::lock(): file is not opened");
         return false;
     }
 
     if (mode == m_lock_mode)
         return true;
 
     if (m_lock_mode != 0)
         unlock();
 
     if (m_semaphore_hnd == 0) {
         QFileInfo fi(*this);
         QString sem_name = QString::fromLatin1(SEMAPHORE_PREFIX)
                            + fi.absoluteFilePath().toLower();
 
         m_semaphore_hnd = CreateSemaphoreW(0, SEMAPHORE_MAX, SEMAPHORE_MAX,
                                            (TCHAR*)sem_name.utf16());
 
         if (m_semaphore_hnd == 0) {
             qWarning("QtLockedFile::lock(): CreateSemaphore: %s",
                      errorCodeToString(GetLastError()).toLatin1().constData());
             return false;
         }
     }
 
     bool gotMutex = false;
     int decrement;
     if (mode == ReadLock) {
         decrement = 1;
     } else {
         decrement = SEMAPHORE_MAX;
         if (m_mutex_hnd == 0) {
             QFileInfo fi(*this);
             QString mut_name = QString::fromLatin1(MUTEX_PREFIX)
                                + fi.absoluteFilePath().toLower();
 
             m_mutex_hnd = CreateMutexW(NULL, FALSE, (TCHAR*)mut_name.utf16());
 
             if (m_mutex_hnd == 0) {
                 qWarning("QtLockedFile::lock(): CreateMutex: %s",
                          errorCodeToString(GetLastError()).toLatin1().constData());
                 return false;
             }
         }
         DWORD res = WaitForSingleObject(m_mutex_hnd, block ? INFINITE : 0);
         if (res == WAIT_TIMEOUT)
             return false;
         if (res == WAIT_FAILED) {
             qWarning("QtLockedFile::lock(): WaitForSingleObject (mutex): %s",
                      errorCodeToString(GetLastError()).toLatin1().constData());
             return false;
         }
         gotMutex = true;
     }
 
     for (int i = 0; i < decrement; ++i) {
         DWORD res = WaitForSingleObject(m_semaphore_hnd, block ? INFINITE : 0);
         if (res == WAIT_TIMEOUT) {
             if (i) {
                 // A failed nonblocking rw locking. Undo changes to semaphore.
                 if (ReleaseSemaphore(m_semaphore_hnd, i, NULL) == 0) {
                     qWarning("QtLockedFile::unlock(): ReleaseSemaphore: %s",
                              errorCodeToString(GetLastError()).toLatin1().constData());
                     // Fall through
                 }
             }
             if (gotMutex)
                 ReleaseMutex(m_mutex_hnd);
             return false;
     }
         if (res != WAIT_OBJECT_0) {
             if (gotMutex)
                 ReleaseMutex(m_mutex_hnd);
             qWarning("QtLockedFile::lock(): WaitForSingleObject (semaphore): %s",
                         errorCodeToString(GetLastError()).toLatin1().constData());
             return false;
         }
     }
 
     m_lock_mode = mode;
     if (gotMutex)
         ReleaseMutex(m_mutex_hnd);
     return true;
 }
 
 bool QtLockedFile::unlock()
 {
     if (!isOpen()) {
         qWarning("QtLockedFile::unlock(): file is not opened");
         return false;
     }
 
     if (!isLocked())
         return true;
 
     int increment;
     if (m_lock_mode == ReadLock)
         increment = 1;
     else
         increment = SEMAPHORE_MAX;
 
     DWORD ret = ReleaseSemaphore(m_semaphore_hnd, increment, 0);
     if (ret == 0) {
         qWarning("QtLockedFile::unlock(): ReleaseSemaphore: %s",
                     errorCodeToString(GetLastError()).toLatin1().constData());
         return false;
     }
 
     m_lock_mode = QtLockedFile::NoLock;
     remove();
     return true;
 }
 
 QtLockedFile::~QtLockedFile()
 {
     if (isOpen())
         unlock();
     if (m_mutex_hnd != 0) {
         DWORD ret = CloseHandle(m_mutex_hnd);
         if (ret == 0) {
             qWarning("QtLockedFile::~QtLockedFile(): CloseHandle (mutex): %s",
                         errorCodeToString(GetLastError()).toLatin1().constData());
         }
         m_mutex_hnd = 0;
     }
     if (m_semaphore_hnd != 0) {
         DWORD ret = CloseHandle(m_semaphore_hnd);
         if (ret == 0) {
             qWarning("QtLockedFile::~QtLockedFile(): CloseHandle (semaphore): %s",
                         errorCodeToString(GetLastError()).toLatin1().constData());
         }
         m_semaphore_hnd = 0;
     }
 }