qpixmapcache.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qpixmapcache.h"
#include "qobject.h"
#include "qdebug.h"
#include "qpixmapcache_p.h"
#include "qthread.h"
#include "qcoreapplication.h"
 
using namespace std::chrono_literals;
 
QT_BEGIN_NAMESPACE
 
static const int cache_limit_default = 10240; // 10 MB cache limit
 
static inline qsizetype cost(const QPixmap &pixmap)
{
    // make sure to do a 64bit calculation; qsizetype might be smaller
    const qint64 costKb = static_cast<qint64>(pixmap.width())
                        * pixmap.height() * pixmap.depth() / (8 * 1024);
    const qint64 costMax = std::numeric_limits<qsizetype>::max();
    // a small pixmap should have at least a cost of 1(kb)
    return static_cast<qsizetype>(qBound(1LL, costKb, costMax));
}
 
static inline bool qt_pixmapcache_thread_test()
{
    if (Q_LIKELY(QCoreApplication::instance() && QThread::currentThread() == QCoreApplication::instance()->thread()))
        return true;
 
    return false;
}
 
QPixmapCache::Key::Key() : d(nullptr)
{
}
 
QPixmapCache::Key::Key(const Key &other)
{
    if (other.d)
        ++(other.d->ref);
    d = other.d;
}
 
QPixmapCache::Key::~Key()
{
    if (d && --(d->ref) == 0)
        delete d;
}
 
bool QPixmapCache::Key::operator ==(const Key &key) const
{
    return (d == key.d);
}
 
bool QPixmapCache::Key::isValid() const noexcept
{
    return d && d->isValid;
}
 
QPixmapCache::Key &QPixmapCache::Key::operator =(const Key &other)
{
    if (d != other.d) {
        if (other.d)
            ++(other.d->ref);
        if (d && --(d->ref) == 0)
            delete d;
        d = other.d;
    }
    return *this;
}
 
class QPMCache : public QObject, public QCache<QPixmapCache::Key, QPixmapCacheEntry>
{
    Q_OBJECT
public:
    QPMCache();
    ~QPMCache();
 
    void timerEvent(QTimerEvent *) override;
    bool insert(const QString& key, const QPixmap &pixmap, int cost);
    QPixmapCache::Key insert(const QPixmap &pixmap, int cost);
    bool remove(const QString &key);
    bool remove(const QPixmapCache::Key &key);
 
    void resizeKeyArray(int size);
    QPixmapCache::Key createKey();
    void releaseKey(const QPixmapCache::Key &key);
    void clear();
 
    QPixmap *object(const QString &key) const;
    QPixmap *object(const QPixmapCache::Key &key) const;
 
    static inline QPixmapCache::KeyData *get(const QPixmapCache::Key &key)
    {return key.d;}
 
    static QPixmapCache::KeyData* getKeyData(QPixmapCache::Key *key);
 
    bool flushDetachedPixmaps(bool nt);
 
private:
    static constexpr auto soon_time = 10s;
    static constexpr auto flush_time = 30s;
    int *keyArray;
    int theid;
    int ps;
    int keyArraySize;
    int freeKey;
    QHash<QString, QPixmapCache::Key> cacheKeys;
    bool t;
};
 
QT_BEGIN_INCLUDE_NAMESPACE
#include "qpixmapcache.moc"
QT_END_INCLUDE_NAMESPACE
 
size_t QPixmapCache::Key::hash(size_t seed) const noexcept
{
    return qHash(this->d ? this->d->key : 0, seed);
}
 
QPMCache::QPMCache()
    : QObject(nullptr),
      QCache<QPixmapCache::Key, QPixmapCacheEntry>(cache_limit_default),
      keyArray(nullptr), theid(0), ps(0), keyArraySize(0), freeKey(0), t(false)
{
}
QPMCache::~QPMCache()
{
    clear();
    free(keyArray);
}
 
/*
  This is supposed to cut the cache size down by about 25% in a
  minute once the application becomes idle, to let any inserted pixmap
  remain in the cache for some time before it becomes a candidate for
  cleaning-up, and to not cut down the size of the cache while the
  cache is in active use.
 
  When the last detached pixmap has been deleted from the cache, kill the
  timer so Qt won't keep the CPU from going into sleep mode. Currently
  the timer is not restarted when the pixmap becomes unused, but it does
  restart once something else is added (i.e. the cache space is actually needed).
 
  Returns \c true if any were removed.
*/
bool QPMCache::flushDetachedPixmaps(bool nt)
{
    auto mc = maxCost();
    const qsizetype currentTotal = totalCost();
    const qsizetype oldSize = size();
    if (currentTotal)
        setMaxCost(nt ? currentTotal * 3 / 4 : currentTotal - 1);
    setMaxCost(mc);
    ps = totalCost();
    return size() != oldSize;
}
 
void QPMCache::timerEvent(QTimerEvent *)
{
    bool nt = totalCost() == ps;
    if (!flushDetachedPixmaps(nt)) {
        killTimer(theid);
        theid = 0;
    } else if (nt != t) {
        killTimer(theid);
        theid = startTimer(nt ? soon_time : flush_time);
        t = nt;
    }
}
 
 
QPixmap *QPMCache::object(const QString &key) const
{
    if (const auto it = cacheKeys.find(key); it != cacheKeys.cend())
        return object(it.value());
    return nullptr;
}
 
QPixmap *QPMCache::object(const QPixmapCache::Key &key) const
{
    Q_ASSERT(key.isValid());
    QPixmap *ptr = QCache<QPixmapCache::Key, QPixmapCacheEntry>::object(key);
    //We didn't find the pixmap in the cache, the key is not valid anymore
    if (!ptr)
        const_cast<QPMCache *>(this)->releaseKey(key);
    return ptr;
}
 
bool QPMCache::insert(const QString& key, const QPixmap &pixmap, int cost)
{
    //If for the same key we add already a pixmap we should delete it
    remove(key);
 
    // this will create a new key; the old one has been removed
    auto k = insert(pixmap, cost);
    if (k.isValid()) {
        k.d->stringKey = key;
        cacheKeys[key] = std::move(k);
        return true;
    }
    return false;
}
 
QPixmapCache::Key QPMCache::insert(const QPixmap &pixmap, int cost)
{
    QPixmapCache::Key cacheKey = createKey(); // invalidated by ~QPixmapCacheEntry on failed insert
    bool success = QCache<QPixmapCache::Key, QPixmapCacheEntry>::insert(cacheKey, new QPixmapCacheEntry(cacheKey, pixmap), cost);
    Q_ASSERT(success || !cacheKey.isValid());
    if (success) {
        if (!theid) {
            theid = startTimer(flush_time);
            t = false;
        }
    }
    return cacheKey;
}
 
bool QPMCache::remove(const QString &key)
{
    const auto cacheKey = cacheKeys.take(key);
    return cacheKey.isValid() && remove(cacheKey);
}
 
bool QPMCache::remove(const QPixmapCache::Key &key)
{
    return QCache<QPixmapCache::Key, QPixmapCacheEntry>::remove(key);
}
 
void QPMCache::resizeKeyArray(int size)
{
    if (size <= keyArraySize || size == 0)
        return;
    keyArray = q_check_ptr(static_cast<int *>(realloc(keyArray,
                    size * sizeof(int))));
    for (int i = keyArraySize; i != size; ++i)
        keyArray[i] = i + 1;
    keyArraySize = size;
}
 
QPixmapCache::Key QPMCache::createKey()
{
    if (freeKey == keyArraySize)
        resizeKeyArray(keyArraySize ? keyArraySize << 1 : 2);
    int id = freeKey;
    freeKey = keyArray[id];
    QPixmapCache::Key key;
    QPixmapCache::KeyData *d = QPMCache::getKeyData(&key);
    d->key = ++id;
    return key;
}
 
void QPMCache::releaseKey(const QPixmapCache::Key &key)
{
    QPixmapCache::KeyData *keyData = key.d;
    if (!keyData)
        return;
    if (!keyData->stringKey.isNull())
        cacheKeys.remove(keyData->stringKey);
    if (keyData->key > keyArraySize || keyData->key <= 0)
        return;
    keyData->key--;
    keyArray[keyData->key] = freeKey;
    freeKey = keyData->key;
    keyData->isValid = false;
    keyData->key = 0;
}
 
void QPMCache::clear()
{
    free(keyArray);
    keyArray = nullptr;
    freeKey = 0;
    keyArraySize = 0;
    //Mark all keys as invalid
    const QList<QPixmapCache::Key> keys = QCache<QPixmapCache::Key, QPixmapCacheEntry>::keys();
    for (const auto &key : keys) {
        if (key.d)
            key.d->isValid = false;
    }
    QCache<QPixmapCache::Key, QPixmapCacheEntry>::clear();
    // Nothing left to flush; stop the timer
    if (theid) {
        killTimer(theid);
        theid = 0;
    }
}
 
QPixmapCache::KeyData* QPMCache::getKeyData(QPixmapCache::Key *key)
{
    if (!key->d)
        key->d = new QPixmapCache::KeyData;
    return key->d;
}
 
Q_GLOBAL_STATIC(QPMCache, pm_cache)
 
int Q_AUTOTEST_EXPORT q_QPixmapCache_keyHashSize()
{
    return pm_cache()->size();
}
 
QPixmapCacheEntry::~QPixmapCacheEntry()
{
    pm_cache()->releaseKey(key);
}
 
bool QPixmapCache::find(const QString &key, QPixmap *pixmap)
{
    if (key.isEmpty() || !qt_pixmapcache_thread_test())
        return false;
    QPixmap *ptr = pm_cache()->object(key);
    if (ptr && pixmap)
        *pixmap = *ptr;
    return ptr != nullptr;
}
 
bool QPixmapCache::find(const Key &key, QPixmap *pixmap)
{
    if (!qt_pixmapcache_thread_test())
        return false;
    //The key is not valid anymore, a flush happened before probably
    if (!key.d || !key.d->isValid)
        return false;
    QPixmap *ptr = pm_cache()->object(key);
    if (ptr && pixmap)
        *pixmap = *ptr;
    return ptr != nullptr;
}
 
bool QPixmapCache::insert(const QString &key, const QPixmap &pixmap)
{
    if (key.isEmpty() || !qt_pixmapcache_thread_test())
        return false;
    return pm_cache()->insert(key, pixmap, cost(pixmap));
}
 
QPixmapCache::Key QPixmapCache::insert(const QPixmap &pixmap)
{
    if (!qt_pixmapcache_thread_test())
        return QPixmapCache::Key();
    return pm_cache()->insert(pixmap, cost(pixmap));
}
 
#if QT_DEPRECATED_SINCE(6, 6)
#endif // QT_DEPRECATED_SINCE(6, 6)
 
int QPixmapCache::cacheLimit()
{
    if (!qt_pixmapcache_thread_test())
        return 0;
    return pm_cache()->maxCost();
}
 
void QPixmapCache::setCacheLimit(int n)
{
    if (!qt_pixmapcache_thread_test())
        return;
    pm_cache()->setMaxCost(n);
}
 
void QPixmapCache::remove(const QString &key)
{
    if (key.isEmpty() || !qt_pixmapcache_thread_test())
        return;
    pm_cache()->remove(key);
}
 
void QPixmapCache::remove(const Key &key)
{
    if (!qt_pixmapcache_thread_test())
        return;
    //The key is not valid anymore, a flush happened before probably
    if (!key.d || !key.d->isValid)
        return;
    pm_cache()->remove(key);
}
 
void QPixmapCache::clear()
{
    if (!QCoreApplication::closingDown() && !qt_pixmapcache_thread_test())
        return;
    QT_TRY {
        if (pm_cache.exists())
            pm_cache->clear();
    } QT_CATCH(const std::bad_alloc &) {
        // if we ran out of memory during pm_cache(), it's no leak,
        // so just ignore it.
    }
}
 
Q_AUTOTEST_EXPORT void qt_qpixmapcache_flush_detached_pixmaps() // for tst_qpixmapcache
{
    if (!qt_pixmapcache_thread_test())
        return;
    pm_cache()->flushDetachedPixmaps(true);
}
 
Q_AUTOTEST_EXPORT int qt_qpixmapcache_qpixmapcache_total_used() // for tst_qpixmapcache
{
    if (!qt_pixmapcache_thread_test())
        return 0;
    return (pm_cache()->totalCost()+1023) / 1024;
}
 
QT_END_NAMESPACE