ComponentInformationCache.h

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#pragma once
 
#include <QtCore/QString>
#include <QtCore/QDir>
#include <QtCore/QMap>
 
class ComponentInformationCache : public QObject
{
    Q_OBJECT
public:
    ComponentInformationCache(const QDir& path, int maxNumFiles);
 
    static ComponentInformationCache& defaultInstance();
 
    QString access(const QString& fileTag);
 
    QString insert(const QString &fileTag, const QString& fileName);
 
private:
 
    static constexpr const char* _metaExtension = ".meta";
    static constexpr const char* _cacheExtension = ".cache";
 
    using AccessCounterType = uint64_t;
 
    struct Meta {
        uint32_t magic{0x9a9cad0e};
        uint32_t version{0};
        AccessCounterType accessCounter{0};
    };
 
    void initializeDirectory();
    void removeOldEntries();
 
    QString metaFileName(const QString& fileTag);
    QString dataFileName(const QString& fileTag);
 
    const QDir _path;
    const int _maxNumFiles;
 
    AccessCounterType _nextAccessCounter{0};
    int _numFiles{0};
    QMap<AccessCounterType, QString> _cachedFiles;
};