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** This file is part of the Qt Solutions component.
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#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);
  }
}
