qgsabstractcontentcache.h

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/***************************************************************************
                         qgsabstractcontentcache.h
                         ---------------
    begin                : December 2018
    copyright            : (C) 2018 by Nyall Dawson
    email                : nyall dot dawson at gmail dot com
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#ifndef QGSABSTRACTCONTENTCACHE_H
#define QGSABSTRACTCONTENTCACHE_H
 
#include "qgis_core.h"
#include "qgis_sip.h"
#include "qgsapplication.h"
#include "qgslogger.h"
#include "qgsmessagelog.h"
#include "qgsnetworkaccessmanager.h"
#include "qgsnetworkcontentfetchertask.h"
#include "qgsvariantutils.h"
 
#include <QCache>
#include <QDateTime>
#include <QFile>
#include <QFileInfo>
#include <QList>
#include <QNetworkReply>
#include <QObject>
#include <QRecursiveMutex>
#include <QSet>
#include <QUrl>

class CORE_EXPORT QgsAbstractContentCacheEntry
{
  public:

    QgsAbstractContentCacheEntry( const QString &path ) ;
 
    virtual ~QgsAbstractContentCacheEntry() = default;
 
    QgsAbstractContentCacheEntry( const QgsAbstractContentCacheEntry &rh ) = delete;
    QgsAbstractContentCacheEntry &operator=( const QgsAbstractContentCacheEntry &rh ) = delete;

    QString path;

    QDateTime fileModified;

    QElapsedTimer fileModifiedLastCheckTimer;

    int mFileModifiedCheckTimeout = 30000;

    QgsAbstractContentCacheEntry *nextEntry = nullptr;

    QgsAbstractContentCacheEntry *previousEntry = nullptr;
 
    bool operator==( const QgsAbstractContentCacheEntry &other ) const
    {
      return other.path == path;
    }

    virtual int dataSize() const = 0;

    virtual void dump() const = 0;
 
  protected:

    virtual bool isEqual( const QgsAbstractContentCacheEntry *other ) const = 0;
 
  private:
#ifdef SIP_RUN
    QgsAbstractContentCacheEntry( const QgsAbstractContentCacheEntry &rh );
#endif
 
};

class CORE_EXPORT QgsAbstractContentCacheBase: public QObject
{
    Q_OBJECT
 
  public:

    QgsAbstractContentCacheBase( QObject *parent );

    static bool parseBase64DataUrl( const QString &path, QString *mimeType SIP_OUT = nullptr, QString *data SIP_OUT = nullptr );
 

    static bool parseEmbeddedStringData( const QString &path, QString *mimeType SIP_OUT = nullptr, QString *data SIP_OUT = nullptr );

    static bool isBase64Data( const QString &path );

    virtual bool invalidateCacheEntry( const QString &path );
 
  signals:

    void remoteContentFetched( const QString &url );
 
  protected:

    virtual bool checkReply( QNetworkReply *reply, const QString &path ) const
    {
      Q_UNUSED( reply )
      Q_UNUSED( path )
      return true;
    }
 
  protected slots:

    virtual void onRemoteContentFetched( const QString &url, bool success );
 
};
 
#ifndef SIP_RUN

template<class T>
class CORE_EXPORT QgsAbstractContentCache : public QgsAbstractContentCacheBase
{
 
  public:

    QgsAbstractContentCache( QObject *parent SIP_TRANSFERTHIS = nullptr,
                             const QString &typeString = QString(),
                             long maxCacheSize = 20000000,
                             int fileModifiedCheckTimeout = 30000 )
      : QgsAbstractContentCacheBase( parent )
      , mMaxCacheSize( maxCacheSize )
      , mFileModifiedCheckTimeout( fileModifiedCheckTimeout )
      , mTypeString( typeString.isEmpty() ? QObject::tr( "Content" ) : typeString )
    {
    }
 
    ~QgsAbstractContentCache() override
    {
      qDeleteAll( mEntryLookup );
    }
 
    bool invalidateCacheEntry( const QString &path ) override
    {
      const QMutexLocker locker( &mMutex );
 
      const QList<T *> entries = mEntryLookup.values( path );
      if ( entries.isEmpty() )
        return false;
 
      for ( T *entry : entries )
      {
        takeEntryFromList( entry );
        mEntryLookup.remove( path, entry );
        mTotalSize -= entry->dataSize();
        delete entry;
      }
 
      return true;
    }
 
  protected:

    void trimToMaximumSize()
    {
      //only one entry in cache
      if ( mLeastRecentEntry == mMostRecentEntry )
      {
        return;
      }
      T *entry = mLeastRecentEntry;
      while ( entry && ( mTotalSize > mMaxCacheSize ) )
      {
        T *bkEntry = entry;
        entry = static_cast< T * >( entry->nextEntry );
 
        takeEntryFromList( bkEntry );
        mEntryLookup.remove( bkEntry->path, bkEntry );
        mTotalSize -= bkEntry->dataSize();
        delete bkEntry;
      }
    }

    QByteArray getContent( const QString &path, const QByteArray &missingContent, const QByteArray &fetchingContent, bool blocking = false ) const;
 
    void onRemoteContentFetched( const QString &url, bool success ) override
    {
      const QMutexLocker locker( &mMutex );
      mPendingRemoteUrls.remove( url );
 
      T *nextEntry = mLeastRecentEntry;
      while ( T *entry = nextEntry )
      {
        nextEntry = static_cast< T * >( entry->nextEntry );
        if ( entry->path == url )
        {
          takeEntryFromList( entry );
          mEntryLookup.remove( entry->path, entry );
          mTotalSize -= entry->dataSize();
          delete entry;
        }
      }
 
      if ( success )
        emit remoteContentFetched( url );
    }

    bool waitForTaskFinished( QgsNetworkContentFetcherTask *task ) const
    {
      // Wait up to timeout seconds for task finished
      if ( task->waitForFinished( QgsNetworkAccessManager::timeout() ) )
      {
        // The wait did not time out
        // Third step, check status as complete
        if ( task->status() == QgsTask::Complete )
        {
          // Fourth step, force the signal fetched to be sure reply has been checked
 
          // ARGH this is BAD BAD BAD. The connection will get called twice as a result!!!
          task->fetched();
          return true;
        }
      }
      return false;
    }

    T *findExistingEntry( T *entryTemplate )
    {
      //search entries in mEntryLookup
      const QString path = entryTemplate->path;
      T *currentEntry = nullptr;
      const QList<T *> entries = mEntryLookup.values( path );
      QDateTime modified;
      for ( T *cacheEntry : entries )
      {
        if ( cacheEntry->isEqual( entryTemplate ) )
        {
          if ( mFileModifiedCheckTimeout <= 0 || cacheEntry->fileModifiedLastCheckTimer.hasExpired( mFileModifiedCheckTimeout ) )
          {
            if ( !modified.isValid() )
              modified = QFileInfo( path ).lastModified();
 
            if ( cacheEntry->fileModified != modified )
              continue;
            else
              cacheEntry->fileModifiedLastCheckTimer.restart();
          }
          currentEntry = cacheEntry;
          break;
        }
      }
 
      //if not found: insert entryTemplate as a new entry
      if ( !currentEntry )
      {
        currentEntry = insertCacheEntry( entryTemplate );
      }
      else
      {
        delete entryTemplate;
        entryTemplate = nullptr;
        ( void )entryTemplate;
        takeEntryFromList( currentEntry );
        if ( !mMostRecentEntry ) //list is empty
        {
          mMostRecentEntry = currentEntry;
          mLeastRecentEntry = currentEntry;
        }
        else
        {
          mMostRecentEntry->nextEntry = currentEntry;
          currentEntry->previousEntry = mMostRecentEntry;
          currentEntry->nextEntry = nullptr;
          mMostRecentEntry = currentEntry;
        }
      }
 
      //debugging
      //printEntryList();
 
      return currentEntry;
    }
    mutable QRecursiveMutex mMutex;

    long mTotalSize = 0;

    long mMaxCacheSize = 20000000;
 
  private:

    T *insertCacheEntry( T *entry )
    {
      entry->mFileModifiedCheckTimeout = mFileModifiedCheckTimeout;
 
      if ( !entry->path.startsWith( QLatin1String( "base64:" ) ) )
      {
        entry->fileModified = QFileInfo( entry->path ).lastModified();
        entry->fileModifiedLastCheckTimer.start();
      }
 
      mEntryLookup.insert( entry->path, entry );
 
      //insert to most recent place in entry list
      if ( !mMostRecentEntry ) //inserting first entry
      {
        mLeastRecentEntry = entry;
        mMostRecentEntry = entry;
        entry->previousEntry = nullptr;
        entry->nextEntry = nullptr;
      }
      else
      {
        entry->previousEntry = mMostRecentEntry;
        entry->nextEntry = nullptr;
        mMostRecentEntry->nextEntry = entry;
        mMostRecentEntry = entry;
      }
 
      trimToMaximumSize();
      return entry;
    }
 

    void takeEntryFromList( T *entry )
    {
      if ( !entry )
      {
        return;
      }
 
      if ( entry->previousEntry )
      {
        entry->previousEntry->nextEntry = entry->nextEntry;
      }
      else
      {
        mLeastRecentEntry = static_cast< T * >( entry->nextEntry );
      }
      if ( entry->nextEntry )
      {
        entry->nextEntry->previousEntry = entry->previousEntry;
      }
      else
      {
        mMostRecentEntry = static_cast< T * >( entry->previousEntry );
      }
    }

    void printEntryList()
    {
      QgsDebugMsgLevel( QStringLiteral( "****************cache entry list*************************" ), 1 );
      QgsDebugMsgLevel( "Cache size: " + QString::number( mTotalSize ), 1 );
      T *entry = mLeastRecentEntry;
      while ( entry )
      {
        QgsDebugMsgLevel( QStringLiteral( "***Entry:" ), 1 );
        entry->dump();
        entry = static_cast< T * >( entry->nextEntry );
      }
    }

    QMultiHash< QString, T * > mEntryLookup;

    int mFileModifiedCheckTimeout = 30000;
 
    //The content cache keeps the entries on a double connected list, moving the current entry to the front.
    //That way, removing entries for more space can start with the least used objects.
    T *mLeastRecentEntry = nullptr;
    T *mMostRecentEntry = nullptr;
 
    mutable QCache< QString, QByteArray > mRemoteContentCache;
    mutable QSet< QString > mPendingRemoteUrls;
 
    QString mTypeString;
 
    friend class TestQgsSvgCache;
    friend class TestQgsImageCache;
};
 
#endif
 
#endif // QGSABSTRACTCONTENTCACHE_H