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qgsvectordataprovider.h
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qgsvectordataprovider.h
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/***************************************************************************
qgsvectordataprovider.h - DataProvider Interface for vector layers
--------------------------------------
Date : 23-Sep-2004
Copyright : (C) 2004 by Marco Hugentobler
email : marco.hugentobler@autoform.ch
***************************************************************************
* *
* 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. *
* *
***************************************************************************/
/* $Id$ */
#ifndef QGSVECTORDATAPROVIDER_H
#define QGSVECTORDATAPROVIDER_H
class QTextCodec;
#include <QList>
#include <QSet>
#include <QMap>
//QGIS Includes
#include "qgis.h"
#include "qgsdataprovider.h"
#include "qgsvectorlayer.h"
#include "qgsfield.h"
typedef QMap<QString, QString> QgsNewAttributesMap;
typedef QMap<QString, QVariant::Type> QgsNativeTypeMap;
/** \ingroup core
* This is the base class for vector data providers.
*
* Data providers abstract the retrieval and writing (where supported)
* of feature and attrubute information from a spatial datasource.
*
*
*/
class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider
{
public:
// If you add to this, please also add to capabilitiesString()
/**
* enumeration with capabilities that providers might implement
*/
enum Capability
{
NoCapabilities = 0,
AddFeatures = 1,
DeleteFeatures = 1 << 1,
ChangeAttributeValues = 1 << 2,
AddAttributes = 1 << 3,
DeleteAttributes = 1 << 4,
SaveAsShapefile = 1 << 5,
CreateSpatialIndex = 1 << 6,
SelectAtId = 1 << 7,
ChangeGeometries = 1 << 8,
SelectGeometryAtId = 1 << 9,
RandomSelectGeometryAtId = 1 << 10,
SequentialSelectGeometryAtId = 1 << 11
};
/** bitmask of all provider's editing capabilities */
const static int EditingCapabilities = AddFeatures | DeleteFeatures |
ChangeAttributeValues | ChangeGeometries | AddAttributes | DeleteAttributes;
/**
* Constructor of the vector provider
* @param uri uniform resource locator (URI) for a dataset
*/
QgsVectorDataProvider( QString uri = QString() );
/**
* Destructor
*/
virtual ~QgsVectorDataProvider();
/**
* Returns the permanent storage type for this layer as a friendly name.
*/
virtual QString storageType() const;
/** Select features based on a bounding rectangle. Features can be retrieved with calls to nextFeature.
* @param fetchAttributes list of attributes which should be fetched
* @param rect spatial filter
* @param fetchGeometry true if the feature geometry should be fetched
* @param useIntersect true if an accurate intersection test should be used,
* false if a test based on bounding box is sufficient
*/
virtual void select( QgsAttributeList fetchAttributes = QgsAttributeList(),
QgsRectangle rect = QgsRectangle(),
bool fetchGeometry = true,
bool useIntersect = false ) = 0;
/**
* Update the feature count based on current spatial filter. If not
* overridden in the data provider this function returns -1
*/
virtual long updateFeatureCount();
/**
* Gets the feature at the given feature ID.
* @param featureId of the feature to be returned
* @param feature which will receive the data
* @param fetchGeometry flag which if true, will cause the geometry to be fetched from the provider
* @param fetchAttributes a list containing the indexes of the attribute fields to copy
* @return True when feature was found, otherwise false
*
* Default implementation traverses all features until it finds the one with correct ID.
* In case the provider supports reading the feature directly, override this function.
*/
virtual bool featureAtId( int featureId,
QgsFeature& feature,
bool fetchGeometry = true,
QgsAttributeList fetchAttributes = QgsAttributeList() );
/**
* Get the next feature resulting from a select operation.
* @param feature feature which will receive data from the provider
* @return true when there was a feature to fetch, false when end was hit
*/
virtual bool nextFeature( QgsFeature& feature ) = 0;
/**
* Get feature type.
* @return int representing the feature type
*/
virtual QGis::WkbType geometryType() const = 0;
/**
* Number of features in the layer
* @return long containing number of features
*/
virtual long featureCount() const = 0;
/**
* Number of attribute fields for a feature in the layer
*/
virtual uint fieldCount() const = 0;
/**
* Return a map of indexes with field names for this layer
* @return map of fields
* @see QgsFieldMap
*/
virtual const QgsFieldMap &fields() const = 0;
/**
* Return a short comment for the data that this provider is
* providing access to (e.g. the comment for postgres table).
*/
virtual QString dataComment() const;
/** Restart reading features from previous select operation */
virtual void rewind() = 0;
/**
* Returns the minimum value of an attribute
* @param index the index of the attribute
*
* Default implementation walks all numeric attributes and caches minimal
* and maximal values. If provider has facilities to retrieve minimal
* value directly, override this function.
*/
virtual QVariant minimumValue( int index );
/**
* Returns the maximum value of an attribute
* @param index the index of the attribute
*
* Default implementation walks all numeric attributes and caches minimal
* and maximal values. If provider has facilities to retrieve maximal
* value directly, override this function.
*/
virtual QVariant maximumValue( int index );
/**
* Return unique values of an attribute
* @param index the index of the attribute
* @param values reference to the list to fill
*
* Default implementation simply iterates the features
*/
virtual void uniqueValues( int index, QList<QVariant> &uniqueValues );
/**
* Adds a list of features
* @return true in case of success and false in case of failure
*/
virtual bool addFeatures( QgsFeatureList &flist );
/**
* Deletes one or more features
* @param id list containing feature ids to delete
* @return true in case of success and false in case of failure
*/
virtual bool deleteFeatures( const QgsFeatureIds &id );
/**
* Adds new attributes
* @param attributes map with attribute name as key and type as value
* @return true in case of success and false in case of failure
*/
virtual bool addAttributes( const QgsNewAttributesMap & attributes );
/**
* Deletes existing attributes
* @param attributes a set containing names of attributes
* @return true in case of success and false in case of failure
*/
virtual bool deleteAttributes( const QgsAttributeIds& attributes );
/**
* Changes attribute values of existing features.
* @param attr_map a map containing changed attributes
* @return true in case of success and false in case of failure
*/
virtual bool changeAttributeValues( const QgsChangedAttributesMap & attr_map );
/**
* Returns the default value for field specified by @c fieldId
*/
virtual QVariant defaultValue( int fieldId );
/**
* Changes geometries of existing features
* @param geometry_map A QgsGeometryMap whose index contains the feature IDs
* that will have their geometries changed.
* The second map parameter being the new geometries themselves
* @return True in case of success and false in case of failure
*/
virtual bool changeGeometryValues( QgsGeometryMap & geometry_map );
/**
* Creates a spatial index on the datasource (if supported by the provider type).
* @return true in case of success
*/
virtual bool createSpatialIndex();
/** Returns a bitmask containing the supported capabilities
Note, some capabilities may change depending on whether
a spatial filter is active on this provider, so it may
be prudent to check this value per intended operation.
*/
virtual int capabilities() const;
/**
* Returns the above in friendly format.
*/
QString capabilitiesString() const;
/**
* Set encoding used for accessing data from layer
*/
virtual void setEncoding( const QString& e );
/**
* Get encoding which is used for accessing data
*/
QString encoding() const;
/**
* Returns the index of a field name or -1 if the field does not exist
*/
int fieldNameIndex( const QString& fieldName ) const;
/**Return a map where the key is the name of the field and the value is its index*/
QMap<QString, int> fieldNameMap() const;
/**
* Return list of indexes to fetch all attributes in nextFeature()
*/
virtual QgsAttributeList attributeIndexes();
/**Returns the names of the numerical types*/
const QgsNativeTypeMap &supportedNativeTypes() const;
/**
* Set whether provider should also return features that don't have
* associated geometry. FALSE by default
*/
void enableGeometrylessFeatures( bool fetch );
protected:
QVariant convertValue( QVariant::Type type, QString value );
void fillMinMaxCache();
bool mCacheMinMaxDirty;
QMap<int, QVariant> mCacheMinValues, mCacheMaxValues;
/** Encoding */
QTextCodec* mEncoding;
/** should provider fetch also features that don't have geometry? */
bool mFetchFeaturesWithoutGeom;
/**True if geometry should be added to the features in nextFeature calls*/
bool mFetchGeom;
/**List of attribute indices to fetch with nextFeature calls*/
QgsAttributeList mAttributesToFetch;
/**The names of the providers native types*/
QgsNativeTypeMap mSupportedNativeTypes;
};
#endif