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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#include "qtlockedfile.h"
#include <qt_windows.h>
#include <QFileInfo>
namespace SharedTools {
#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;
}
}
} // namespace SharedTools
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