src/DirLocker.h

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // MuldeR's Utilities for Qt
   3 // Copyright (C) 2004-2019 LoRd_MuldeR <MuldeR2@GMX.de>
   4 //
   5 // This library is free software; you can redistribute it and/or
   6 // modify it under the terms of the GNU Lesser General Public
   7 // License as published by the Free Software Foundation; either
   8 // version 2.1 of the License, or (at your option) any later version.
   9 //
  10 // This library is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 // Lesser General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU Lesser General Public
  16 // License along with this library; if not, write to the Free Software
  17 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  18 //
  19 // http://www.gnu.org/licenses/lgpl-2.1.txt
  20 //////////////////////////////////////////////////////////////////////////////////
  21
  22 #pragma once
  23
  24 //MUtils
  25 #include <MUtils/Global.h>
  26
  27 //StdLib
  28 #include <stdexcept>
  29
  30 //Qt
  31 #include <QString>
  32 #include <QFile>
  33
  34 ///////////////////////////////////////////////////////////////////////////////
  35 // Directory Locker
  36 ///////////////////////////////////////////////////////////////////////////////
  37
  38 namespace MUtils
  39 {
  40         namespace Internal
  41         {
  42                 class DirLockException : public std::runtime_error
  43                 {
  44                 public:
  45                         DirLockException(const char *const message)
  46                         :
  47                                 std::runtime_error(message)
  48                         {
  49                         }
  50                 };
  51
  52                 class DirLock
  53                 {
  54                 public:
  55                         DirLock(const QString dirPath)
  56                         :
  57                                 m_dirPath(dirPath)
  58                         {
  59                                 bool okay = false;
  60                                 const QByteArray testData = QByteArray(TEST_DATA);
  61                                 if(m_dirPath.isEmpty())
  62                                 {
  63                                         throw DirLockException("Path must not be empty!");
  64                                 }
  65                                 for(int i = 0; i < 32; i++)
  66                                 {
  67                                         m_lockFile.reset(new QFile(QString("%1/~%2.lck").arg(m_dirPath, MUtils::next_rand_str())));
  68                                         if(m_lockFile->open(QIODevice::WriteOnly | QIODevice::Truncate | QIODevice::Unbuffered))
  69                                         {
  70                                                 if(m_lockFile->write(testData) >= testData.size())
  71                                                 {
  72                                                         if(m_lockFile->error() == QFile::NoError)
  73                                                         {
  74                                                                 okay = true;
  75                                                                 break;
  76                                                         }
  77                                                 }
  78                                                 m_lockFile->remove();
  79                                         }
  80                                 }
  81                                 if(!okay)
  82                                 {
  83                                         throw DirLockException("Locking has failed!");
  84                                 }
  85                         }
  86
  87                         ~DirLock(void)
  88                         {
  89                                 bool okay = false;
  90                                 if(!m_lockFile.isNull())
  91                                 {
  92                                         for(int i = 0; i < 16; i++)
  93                                         {
  94                                                 if(m_lockFile->remove() || (!m_lockFile->exists()))
  95                                                 {
  96                                                         okay = true;
  97                                                         break;
  98                                                 }
  99                                                 OS::sleep_ms(125);
 100                                         }
 101                                 }
 102                                 if(!okay)
 103                                 {
 104                                         qWarning("DirLock: The lock file could not be removed!");
 105                                 }
 106                         }
 107
 108                         inline const QString &getPath(void) const
 109                         {
 110                                 return m_dirPath;
 111                         }
 112
 113                 private:
 114                         static const char *const TEST_DATA;
 115                         const QString m_dirPath;
 116                         QScopedPointer<QFile> m_lockFile;
 117                 };
 118
 119                 const char *const DirLock::TEST_DATA = "7QtDxPWotHGQYv1xHyQHFKjTB5u5VYKHE20NMDAgLRYoy16CZN7mEYijbjCJpORnoBbtHCzqyy1a6BLCMMiTUZpLzgjg4qnN505egUBqk3wMhPsYjFpkng9i37mWd1iF";
 120         }
 121 }