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       1                 :            : /***************************************************************************
       2                 :            :     qgsfeatureiterator.h
       3                 :            :     ---------------------
       4                 :            :     begin                : Juli 2012
       5                 :            :     copyright            : (C) 2012 by Martin Dobias
       6                 :            :     email                : wonder dot sk at gmail dot com
       7                 :            :  ***************************************************************************
       8                 :            :  *                                                                         *
       9                 :            :  *   This program is free software; you can redistribute it and/or modify  *
      10                 :            :  *   it under the terms of the GNU General Public License as published by  *
      11                 :            :  *   the Free Software Foundation; either version 2 of the License, or     *
      12                 :            :  *   (at your option) any later version.                                   *
      13                 :            :  *                                                                         *
      14                 :            :  ***************************************************************************/
      15                 :            : #ifndef QGSFEATUREITERATOR_H
      16                 :            : #define QGSFEATUREITERATOR_H
      17                 :            : 
      18                 :            : #include "qgis_core.h"
      19                 :            : #include "qgsfeaturerequest.h"
      20                 :            : #include "qgsindexedfeature.h"
      21                 :            : 
      22                 :            : class QgsFeedback;
      23                 :            : 
      24                 :            : /**
      25                 :            :  * \ingroup core
      26                 :            :  * \brief Internal feature iterator to be implemented within data providers
      27                 :            :  */
      28                 :            : class CORE_EXPORT QgsAbstractFeatureIterator
      29                 :            : {
      30                 :            :   public:
      31                 :            : 
      32                 :            :     //! Status of expression compilation for filter expression requests
      33                 :            :     enum CompileStatus
      34                 :            :     {
      35                 :            :       NoCompilation, //!< Expression could not be compiled or not attempt was made to compile expression
      36                 :            :       PartiallyCompiled, //!< Expression was partially compiled, but extra checks need to be applied to features
      37                 :            :       Compiled, //!< Expression was fully compiled and delegated to data provider source
      38                 :            :     };
      39                 :            : 
      40                 :            :     //! base class constructor - stores the iteration parameters
      41                 :            :     QgsAbstractFeatureIterator( const QgsFeatureRequest &request );
      42                 :            : 
      43                 :            :     //! destructor makes sure that the iterator is closed properly
      44                 :        318 :     virtual ~QgsAbstractFeatureIterator() = default;
      45                 :            : 
      46                 :            :     //! fetch next feature, return TRUE on success
      47                 :            :     virtual bool nextFeature( QgsFeature &f );
      48                 :            : 
      49                 :            :     //! reset the iterator to the starting position
      50                 :            :     virtual bool rewind() = 0;
      51                 :            :     //! end of iterating: free the resources / lock
      52                 :            :     virtual bool close() = 0;
      53                 :            : 
      54                 :            :     /**
      55                 :            :      * Attach an object that can be queried regularly by the iterator to check
      56                 :            :      * if it must stopped. This is mostly useful for iterators where a single
      57                 :            :      * nextFeature()/fetchFeature() iteration might be very long. A typical use case is the
      58                 :            :      * WFS provider. When nextFeature()/fetchFeature() is reasonably fast, it is not necessary
      59                 :            :      * to implement this method. The default implementation does nothing.
      60                 :            :      * \note not available in Python bindings
      61                 :            :      * \since QGIS 2.16
      62                 :            :      */
      63                 :            :     virtual void setInterruptionChecker( QgsFeedback *interruptionChecker ) SIP_SKIP;
      64                 :            : 
      65                 :            :     /**
      66                 :            :      * Returns the status of expression compilation for filter expression requests.
      67                 :            :      * \since QGIS 2.16
      68                 :            :      */
      69                 :            :     CompileStatus compileStatus() const { return mCompileStatus; }
      70                 :            : 
      71                 :            :     /**
      72                 :            :      * Returns if this iterator is valid.
      73                 :            :      * An invalid feature iterator is not able to provide a reliable source for data.
      74                 :            :      * If an iterator is invalid, either give up or try to send the request again (preferably
      75                 :            :      * after a timeout to give the system some time to stay responsive).
      76                 :            :      *
      77                 :            :      * If you want to check if the iterator successfully completed, better use QgsFeatureIterator::isClosed().
      78                 :            :      *
      79                 :            :      * \since QGIS 3.0
      80                 :            :      */
      81                 :          0 :     virtual bool isValid() const
      82                 :            :     {
      83                 :          0 :       return mValid;
      84                 :            :     }
      85                 :            : 
      86                 :            :     /**
      87                 :            :      * Indicator if there was an error when sending the compiled query to the server.
      88                 :            :      * This indicates that there is something wrong with the expression compiler.
      89                 :            :      *
      90                 :            :      * \since QGIS 3.2
      91                 :            :      */
      92                 :            :     bool compileFailed() const;
      93                 :            : 
      94                 :            :   protected:
      95                 :            : 
      96                 :            :     /**
      97                 :            :      * If you write a feature iterator for your provider, this is the method you
      98                 :            :      * need to implement!!
      99                 :            :      *
     100                 :            :      * \param f The feature to write to
     101                 :            :      * \returns  TRUE if a feature was written to f
     102                 :            :      */
     103                 :            :     virtual bool fetchFeature( QgsFeature &f ) = 0;
     104                 :            : 
     105                 :            :     /**
     106                 :            :      * By default, the iterator will fetch all features and check if the feature
     107                 :            :      * matches the expression.
     108                 :            :      * If you have a more sophisticated metodology (SQL request for the features...)
     109                 :            :      * and you check for the expression in your fetchFeature method, you can just
     110                 :            :      * redirect this call to fetchFeature so the default check will be omitted.
     111                 :            :      *
     112                 :            :      * \param f The feature to write to
     113                 :            :      * \returns  TRUE if a feature was written to f
     114                 :            :      */
     115                 :            :     virtual bool nextFeatureFilterExpression( QgsFeature &f );
     116                 :            : 
     117                 :            :     /**
     118                 :            :      * By default, the iterator will fetch all features and check if the id
     119                 :            :      * is in the request.
     120                 :            :      * If you have a more sophisticated metodology (SQL request for the features...)
     121                 :            :      * and you are sure, that any feature you return from fetchFeature will match
     122                 :            :      * if the request was FilterFids you can just redirect this call to fetchFeature
     123                 :            :      * so the default check will be omitted.
     124                 :            :      *
     125                 :            :      * \param f The feature to write to
     126                 :            :      * \returns  TRUE if a feature was written to f
     127                 :            :      */
     128                 :            :     virtual bool nextFeatureFilterFids( QgsFeature &f );
     129                 :            : 
     130                 :            :     /**
     131                 :            :      * Transforms \a feature's geometry according to the specified coordinate \a transform.
     132                 :            :      * If \a feature has no geometry or \a transform is invalid then calling this method
     133                 :            :      * has no effect and will be shortcut.
     134                 :            :      * Iterators should call this method before returning features to ensure that any
     135                 :            :      * QgsFeatureRequest::destinationCrs() set on the request is respected.
     136                 :            :      * \since QGIS 3.0
     137                 :            :      */
     138                 :            :     void geometryToDestinationCrs( QgsFeature &feature, const QgsCoordinateTransform &transform ) const;
     139                 :            : 
     140                 :            : 
     141                 :            :     /**
     142                 :            :      * Returns a rectangle representing the original request's QgsFeatureRequest::filterRect().
     143                 :            :      * If \a transform is a valid coordinate transform, the return rectangle will represent
     144                 :            :      * the requested filterRect() transformed to the source's coordinate reference system.
     145                 :            :      * Iterators should call this method and use the returned rectangle for filtering
     146                 :            :      * features to ensure that any QgsFeatureRequest::destinationCrs() set on the request is respected.
     147                 :            :      * Will throw a QgsCsException if the rect cannot be transformed from the destination CRS.
     148                 :            :      * \since QGIS 3.0
     149                 :            :      */
     150                 :            :     QgsRectangle filterRectToSourceCrs( const QgsCoordinateTransform &transform ) const SIP_THROW( QgsCsException );
     151                 :            : 
     152                 :            :     //! A copy of the feature request.
     153                 :            :     QgsFeatureRequest mRequest;
     154                 :            : 
     155                 :            :     //! Sets to TRUE, as soon as the iterator is closed.
     156                 :            :     bool mClosed = false;
     157                 :            : 
     158                 :            :     /**
     159                 :            :      * A feature iterator may be closed already but still be serving features from the cache.
     160                 :            :      * This is done when we serve features which have been pre-fetched and the order by has
     161                 :            :      * been locally sorted.
     162                 :            :      * In such a scenario, all resources have been released (mClosed is TRUE) but the deads
     163                 :            :      * are still alive.
     164                 :            :      */
     165                 :            :     bool mZombie = false;
     166                 :            : 
     167                 :            :     // TODO QGIS 4: make this private
     168                 :            : 
     169                 :            :     /**
     170                 :            :      * reference counting (to allow seamless copying of QgsFeatureIterator instances)
     171                 :            :      */
     172                 :            :     int refs = 0;
     173                 :            :     //! Add reference
     174                 :            :     void ref();
     175                 :            :     //! Remove reference, delete if refs == 0
     176                 :            :     void deref();
     177                 :            :     friend class QgsFeatureIterator;
     178                 :            : 
     179                 :            :     //! Number of features already fetched by iterator
     180                 :            :     long mFetchedCount = 0;
     181                 :            : 
     182                 :            :     //! Status of compilation of filter expression
     183                 :            :     CompileStatus mCompileStatus = NoCompilation;
     184                 :            : 
     185                 :            :     bool mCompileFailed = false;
     186                 :            : 
     187                 :            :     //! Setup the simplification of geometries to fetch using the specified simplify method
     188                 :            :     virtual bool prepareSimplification( const QgsSimplifyMethod &simplifyMethod );
     189                 :            : 
     190                 :            :     /**
     191                 :            :      * An invalid state of a feature iterator indicates that there was a problem with
     192                 :            :      * even getting it up and running.
     193                 :            :      * This should be set to FALSE by subclasses if they have problems connecting to
     194                 :            :      * the provider.
     195                 :            :      * Do NOT set this to FALSE when the feature iterator closes or has no features but
     196                 :            :      * we are sure, that it's just an empty dataset.
     197                 :            :      */
     198                 :            :     bool mValid = true;
     199                 :            : 
     200                 :            :   private:
     201                 :            :     bool mUseCachedFeatures = false;
     202                 :            :     QList<QgsIndexedFeature> mCachedFeatures;
     203                 :            :     QList<QgsIndexedFeature>::ConstIterator mFeatureIterator;
     204                 :            : 
     205                 :            :     //! returns whether the iterator supports simplify geometries on provider side
     206                 :            :     virtual bool providerCanSimplify( QgsSimplifyMethod::MethodType methodType ) const;
     207                 :            : 
     208                 :            :     /**
     209                 :            :      * Should be overwritten by providers which implement an own order by strategy
     210                 :            :      * If the own order by strategy is successful, return TRUE, if not, return FALSE
     211                 :            :      * and a local order by will be triggered instead.
     212                 :            :      * By default returns FALSE
     213                 :            :      *
     214                 :            :      * \since QGIS 2.14
     215                 :            :      */
     216                 :            :     virtual bool prepareOrderBy( const QList<QgsFeatureRequest::OrderByClause> &orderBys );
     217                 :            : 
     218                 :            :     /**
     219                 :            :      * Setup the orderby. Internally calls prepareOrderBy and if FALSE is returned will
     220                 :            :      * cache all features and order them with local expression evaluation.
     221                 :            :      *
     222                 :            :      * \since QGIS 2.14
     223                 :            :      */
     224                 :            :     void setupOrderBy( const QList<QgsFeatureRequest::OrderByClause> &orderBys );
     225                 :            : };
     226                 :            : 
     227                 :            : 
     228                 :            : /**
     229                 :            :  * \ingroup core
     230                 :            :  * \brief Helper template that cares of two things: 1. automatic deletion of source if owned by iterator, 2. notification of open/closed iterator.
     231                 :            :  * \note not available in Python bindings (although present in SIP file)
     232                 :            : */
     233                 :            : template<typename T>
     234                 :            : class QgsAbstractFeatureIteratorFromSource : public QgsAbstractFeatureIterator
     235                 :            : {
     236                 :            :   public:
     237                 :        318 :     QgsAbstractFeatureIteratorFromSource( T *source, bool ownSource, const QgsFeatureRequest &request )
     238                 :        318 :       : QgsAbstractFeatureIterator( request )
     239                 :        318 :       , mSource( source )
     240                 :        318 :       , mOwnSource( ownSource )
     241                 :        636 :     {
     242                 :        318 :       mSource->iteratorOpened( this );
     243                 :        318 :     }
     244                 :            : 
     245                 :        318 :     ~QgsAbstractFeatureIteratorFromSource() override
     246                 :        318 :     {
     247                 :        318 :       if ( mOwnSource )
     248                 :        133 :         delete mSource;
     249                 :        318 :     }
     250                 :            : 
     251                 :            :   protected:
     252                 :            :     //! to be called by from subclass in close()
     253                 :        318 :     void iteratorClosed() { mSource->iteratorClosed( this ); }
     254                 :            : 
     255                 :            :     T *mSource = nullptr;
     256                 :            :     bool mOwnSource;
     257                 :            : };
     258                 :            : 
     259                 :            : 
     260                 :            : /**
     261                 :            :  * \ingroup core
     262                 :            :  * \brief Wrapper for iterator of features from vector data provider or vector layer
     263                 :            :  */
     264                 :            : class CORE_EXPORT QgsFeatureIterator
     265                 :            : {
     266                 :            :   public:
     267                 :            : 
     268                 :            : #ifdef SIP_RUN
     269                 :            :     QgsFeatureIterator *__iter__();
     270                 :            :     % MethodCode
     271                 :            :     sipRes = sipCpp;
     272                 :            :     % End
     273                 :            : 
     274                 :            :     SIP_PYOBJECT __next__() SIP_TYPEHINT( QgsFeature );
     275                 :            :     % MethodCode
     276                 :            :     std::unique_ptr< QgsFeature > f = std::make_unique< QgsFeature >();
     277                 :            :     bool result = false;
     278                 :            :     Py_BEGIN_ALLOW_THREADS
     279                 :            :     result = ( sipCpp->nextFeature( *f ) );
     280                 :            :     Py_END_ALLOW_THREADS
     281                 :            :     if ( result )
     282                 :            :       sipRes = sipConvertFromType( f.release(), sipType_QgsFeature, Py_None );
     283                 :            :     else
     284                 :            :     {
     285                 :            :       PyErr_SetString( PyExc_StopIteration, "" );
     286                 :            :     }
     287                 :            :     % End
     288                 :            : #endif
     289                 :            : 
     290                 :            :     //! Construct invalid iterator
     291                 :        316 :     QgsFeatureIterator() = default;
     292                 :            :     //! Construct a valid iterator
     293                 :            :     QgsFeatureIterator( QgsAbstractFeatureIterator *iter SIP_TRANSFER );
     294                 :            :     //! Copy constructor copies the iterator, increases ref.count
     295                 :            :     QgsFeatureIterator( const QgsFeatureIterator &fi );
     296                 :            :     //! Destructor deletes the iterator if it has no more references
     297                 :            :     ~QgsFeatureIterator();
     298                 :            : 
     299                 :            :     QgsFeatureIterator &operator=( const QgsFeatureIterator &other );
     300                 :            : 
     301                 :            :     bool nextFeature( QgsFeature &f );
     302                 :            :     bool rewind();
     303                 :            :     bool close();
     304                 :            : 
     305                 :            :     /**
     306                 :            :      * Will return if this iterator is valid.
     307                 :            :      * An invalid iterator was probably introduced by a failed attempt to acquire a connection
     308                 :            :      * or is a default constructed iterator.
     309                 :            :      *
     310                 :            :      * \see isClosed to check if the iterator successfully completed and returned all the features.
     311                 :            :      *
     312                 :            :      * \since QGIS 3.0
     313                 :            :      */
     314                 :            :     bool isValid() const;
     315                 :            : 
     316                 :            :     //! find out whether the iterator is still valid or closed already
     317                 :            :     bool isClosed() const;
     318                 :            : 
     319                 :            :     /**
     320                 :            :      * Attach an object that can be queried regularly by the iterator to check
     321                 :            :      * if it must stopped. This is mostly useful for iterators where a single
     322                 :            :      * nextFeature()/fetchFeature() iteration might be very long. A typical use case is the
     323                 :            :      * WFS provider.
     324                 :            :      * \note not available in Python bindings
     325                 :            :      * \since QGIS 2.16
     326                 :            :      */
     327                 :            :     void setInterruptionChecker( QgsFeedback *interruptionChecker ) SIP_SKIP;
     328                 :            : 
     329                 :            :     /**
     330                 :            :      * Returns the status of expression compilation for filter expression requests.
     331                 :            :      * \since QGIS 2.16
     332                 :            :      */
     333                 :            :     QgsAbstractFeatureIterator::CompileStatus compileStatus() const { return mIter->compileStatus(); }
     334                 :            : 
     335                 :            :     /**
     336                 :            :      * Indicator if there was an error when sending the compiled query to the server.
     337                 :            :      * This indicates that there is something wrong with the expression compiler.
     338                 :            :      *
     339                 :            :      * \since QGIS 3.2
     340                 :            :      */
     341                 :            :     bool compileFailed() const { return mIter->compileFailed(); }
     342                 :            : 
     343                 :            :     friend bool operator== ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 ) SIP_SKIP;
     344                 :            :     friend bool operator!= ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 ) SIP_SKIP;
     345                 :            : 
     346                 :            :   protected:
     347                 :        316 :     QgsAbstractFeatureIterator *mIter = nullptr;
     348                 :            : 
     349                 :            : 
     350                 :            : };
     351                 :            : 
     352                 :            : #ifndef SIP_RUN
     353                 :            : 
     354                 :        318 : inline QgsFeatureIterator::QgsFeatureIterator( QgsAbstractFeatureIterator *iter )
     355                 :        318 :   : mIter( iter )
     356                 :            : {
     357                 :        318 :   if ( iter )
     358                 :        318 :     iter->ref();
     359                 :        318 : }
     360                 :            : 
     361                 :         14 : inline QgsFeatureIterator::QgsFeatureIterator( const QgsFeatureIterator &fi )
     362                 :         14 :   : mIter( fi.mIter )
     363                 :            : {
     364                 :         14 :   if ( mIter )
     365                 :         14 :     mIter->ref();
     366                 :         14 : }
     367                 :            : 
     368                 :        648 : inline QgsFeatureIterator::~QgsFeatureIterator()
     369                 :            : {
     370                 :        648 :   if ( mIter )
     371                 :        468 :     mIter->deref();
     372                 :        648 : }
     373                 :            : 
     374                 :       2501 : inline bool QgsFeatureIterator::nextFeature( QgsFeature &f )
     375                 :            : {
     376                 :       2501 :   return mIter ? mIter->nextFeature( f ) : false;
     377                 :            : }
     378                 :            : 
     379                 :          0 : inline bool QgsFeatureIterator::rewind()
     380                 :            : {
     381                 :          0 :   if ( mIter )
     382                 :          0 :     mIter->mFetchedCount = 0;
     383                 :            : 
     384                 :          0 :   return mIter ? mIter->rewind() : false;
     385                 :            : }
     386                 :            : 
     387                 :        160 : inline bool QgsFeatureIterator::close()
     388                 :            : {
     389                 :        160 :   if ( mIter )
     390                 :        135 :     mIter->mFetchedCount = 0;
     391                 :            : 
     392                 :        160 :   return mIter ? mIter->close() : false;
     393                 :            : }
     394                 :            : 
     395                 :       1159 : inline bool QgsFeatureIterator::isClosed() const
     396                 :            : {
     397                 :       1159 :   return mIter ? mIter->mClosed && !mIter->mZombie : true;
     398                 :            : }
     399                 :            : 
     400                 :            : inline bool operator== ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 )
     401                 :            : {
     402                 :            :   return fi1.mIter == fi2.mIter;
     403                 :            : }
     404                 :            : 
     405                 :            : inline bool operator!= ( const QgsFeatureIterator &fi1, const QgsFeatureIterator &fi2 )
     406                 :            : {
     407                 :            :   return !( fi1 == fi2 );
     408                 :            : }
     409                 :            : 
     410                 :          2 : inline void QgsFeatureIterator::setInterruptionChecker( QgsFeedback *interruptionChecker )
     411                 :            : {
     412                 :          2 :   if ( mIter )
     413                 :          2 :     mIter->setInterruptionChecker( interruptionChecker );
     414                 :          2 : }
     415                 :            : 
     416                 :            : #endif
     417                 :            : 
     418                 :            : #endif // QGSFEATUREITERATOR_H