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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 "stringtable.h"
#include "runextensions.h"
#include <QDebug>
#include <QElapsedTimer>
#include <QMutex>
#include <QSet>
#include <QTimer>
// FIXME: Provide tst_StringTable that would run GC, make a sleep inside GC being run in other
// thread and execute destructor of StringTable in main thread. In this case the test should
// ensure that destructor of StringTable waits for its internal thread to finish.
namespace Utils::StringTable {
enum {
GCTimeOut = 10 * 1000 // 10 seconds
};
enum {
DebugStringTable = 0
};
class StringTablePrivate : public QObject
{
public:
StringTablePrivate();
~StringTablePrivate() override { cancelAndWait(); }
void cancelAndWait();
QString insert(const QString &string);
void startGC();
void GC(QFutureInterface<void> &futureInterface);
QFuture<void> m_future;
QMutex m_lock;
QSet<QString> m_strings;
QTimer m_gcCountDown;
};
static StringTablePrivate &stringTable()
{
static StringTablePrivate theStringTable;
return theStringTable;
}
StringTablePrivate::StringTablePrivate()
{
m_strings.reserve(1000);
m_gcCountDown.setObjectName(QLatin1String("StringTable::m_gcCountDown"));
m_gcCountDown.setSingleShot(true);
m_gcCountDown.setInterval(GCTimeOut);
connect(&m_gcCountDown, &QTimer::timeout, this, &StringTablePrivate::startGC);
}
QTCREATOR_UTILS_EXPORT QString insert(const QString &string)
{
return stringTable().insert(string);
}
void StringTablePrivate::cancelAndWait()
{
if (!m_future.isRunning())
return;
m_future.cancel();
m_future.waitForFinished();
}
QString StringTablePrivate::insert(const QString &string)
{
if (string.isEmpty())
return string;
QMutexLocker locker(&m_lock);
// From this point of time any possible new call to startGC() will be held until
// we finish this function. So we are sure that after canceling the running GC() method now,
// no new call to GC() will be executed until we finish this function.
cancelAndWait();
// A possibly running GC() thread already finished, so it's safe to modify m_strings from
// now until we unlock the mutex.
return *m_strings.insert(string);
}
void StringTablePrivate::startGC()
{
QMutexLocker locker(&m_lock);
cancelAndWait();
m_future = Utils::runAsync(&StringTablePrivate::GC, this);
}
QTCREATOR_UTILS_EXPORT void scheduleGC()
{
QMetaObject::invokeMethod(&stringTable().m_gcCountDown, QOverload<>::of(&QTimer::start),
Qt::QueuedConnection);
}
static int bytesSaved = 0;
static inline bool isQStringInUse(const QString &string)
{
QStringPrivate data_ptr = const_cast<QString&>(string).data_ptr();
if (DebugStringTable) {
const int ref = data_ptr->d_ptr()->ref_;
bytesSaved += (ref - 1) * string.size();
if (ref > 10)
qDebug() << ref << string.size() << string.left(50);
}
return data_ptr->isShared() || !data_ptr->isMutable() /* QStringLiteral ? */;
}
void StringTablePrivate::GC(QFutureInterface<void> &futureInterface)
{
int initialSize = 0;
bytesSaved = 0;
QElapsedTimer timer;
if (DebugStringTable) {
initialSize = m_strings.size();
timer.start();
}
// Collect all QStrings which have refcount 1. (One reference in m_strings and nowhere else.)
for (QSet<QString>::iterator i = m_strings.begin(); i != m_strings.end();) {
if (futureInterface.isCanceled())
return;
if (!isQStringInUse(*i))
i = m_strings.erase(i);
else
++i;
}
if (DebugStringTable) {
const int currentSize = m_strings.size();
qDebug() << "StringTable::GC removed" << initialSize - currentSize
<< "strings in" << timer.elapsed() << "ms, size is now" << currentSize
<< "saved: " << bytesSaved << "bytes";
}
}
} // Utils::StringTable
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