New class QgsOgrUtils w/helper functions for working with OGR features

Also includes handy function for converting a string to a QgsFeatureList or QgsFields by using OGR to parse the string. This allows eg conversion of GeoJSON to QgsFeatures.
qgis · Mar 1, 2016 · 3f62cd4 · 3f62cd4
1 parent 3f80649
commit 3f62cd4
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diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
@@ -154,6 +154,7 @@ SET(QGIS_CORE_SRCS
   qgsobjectcustomproperties.cpp
   qgsofflineediting.cpp
   qgsogcutils.cpp
+  qgsogrutils.cpp
   qgsowsconnection.cpp
   qgspaintenginehack.cpp
   qgspallabeling.cpp

diff --git a/src/core/qgsogrutils.cpp b/src/core/qgsogrutils.cpp
@@ -0,0 +1,315 @@
+/***************************************************************************
+                             qgsogrutils.cpp
+                             ---------------
+    begin                : February 2016
+    copyright            : (C) 2016 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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsogrutils.h"
+#include "qgsapplication.h"
+#include "qgslogger.h"
+#include "qgsgeometry.h"
+#include <QTextCodec>
+#include <QUuid>
+
+#if defined(GDAL_VERSION_NUM) && GDAL_VERSION_NUM >= 1800
+#define TO8(x)   (x).toUtf8().constData()
+#define TO8F(x)  (x).toUtf8().constData()
+#define FROM8(x) QString::fromUtf8(x)
+#else
+#define TO8(x)   (x).toLocal8Bit().constData()
+#define TO8F(x)  QFile::encodeName( x ).constData()
+#define FROM8(x) QString::fromLocal8Bit(x)
+#endif
+
+QgsFeature QgsOgrUtils::readOgrFeature( OGRFeatureH ogrFet, const QgsFields& fields, QTextCodec* encoding )
+{
+  QgsFeature feature;
+  if ( !ogrFet )
+  {
+    feature.setValid( false );
+    return feature;
+  }
+
+  feature.setFeatureId( OGR_F_GetFID( ogrFet ) );
+  feature.setValid( true );
+
+  if ( !readOgrFeatureGeometry( ogrFet, feature ) )
+  {
+    feature.setValid( false );
+  }
+
+  if ( !readOgrFeatureAttributes( ogrFet, fields, feature, encoding ) )
+  {
+    feature.setValid( false );
+  }
+
+  return feature;
+}
+
+QgsFields QgsOgrUtils::readOgrFields( OGRFeatureH ogrFet, QTextCodec* encoding )
+{
+  QgsFields fields;
+
+  if ( !ogrFet )
+    return fields;
+
+  int fieldCount = OGR_F_GetFieldCount( ogrFet );
+  for ( int i = 0; i < fieldCount; ++i )
+  {
+    OGRFieldDefnH fldDef = OGR_F_GetFieldDefnRef( ogrFet, i );
+    if ( !fldDef )
+    {
+      fields.append( QgsField() );
+      continue;
+    }
+
+    QString name = encoding->toUnicode( OGR_Fld_GetNameRef( fldDef ) );
+    QVariant::Type varType;
+    switch ( OGR_Fld_GetType( fldDef ) )
+    {
+      case OFTInteger:
+        varType = QVariant::Int;
+        break;
+#if defined(GDAL_VERSION_NUM) && GDAL_VERSION_NUM >= 2000000
+      case OFTInteger64:
+        varType = QVariant::LongLong;
+        break;
+#endif
+      case OFTReal:
+        varType = QVariant::Double;
+        break;
+#if defined(GDAL_VERSION_NUM) && GDAL_VERSION_NUM >= 1400
+      case OFTDate:
+        varType = QVariant::Date;
+        break;
+      case OFTTime:
+        varType = QVariant::Time;
+        break;
+      case OFTDateTime:
+        varType = QVariant::DateTime;
+        break;
+      case OFTString:
+#endif
+      default:
+        varType = QVariant::String; // other unsupported, leave it as a string
+    }
+    fields.append( QgsField( name, varType ) );
+  }
+  return fields;
+}
+
+QVariant QgsOgrUtils::getOgrFeatureAttribute( OGRFeatureH ogrFet, const QgsFields& fields, int attIndex, QTextCodec* encoding , bool* ok )
+{
+  if ( !ogrFet || attIndex < 0 || attIndex >= fields.count() )
+  {
+    if ( ok )
+      *ok = false;
+    return QVariant();
+  }
+
+  OGRFieldDefnH fldDef = OGR_F_GetFieldDefnRef( ogrFet, attIndex );
+
+  if ( ! fldDef )
+  {
+    if ( ok )
+      *ok = false;
+
+    QgsDebugMsg( "ogrFet->GetFieldDefnRef(attindex) returns NULL" );
+    return QVariant();
+  }
+
+  QVariant value;
+
+  if ( ok )
+    *ok = true;
+
+  if ( OGR_F_IsFieldSet( ogrFet, attIndex ) )
+  {
+    switch ( fields.at( attIndex ).type() )
+    {
+      case QVariant::String:
+        value = QVariant( encoding->toUnicode( OGR_F_GetFieldAsString( ogrFet, attIndex ) ) );
+        break;
+      case QVariant::Int:
+        value = QVariant( OGR_F_GetFieldAsInteger( ogrFet, attIndex ) );
+        break;
+#if defined(GDAL_VERSION_NUM) && GDAL_VERSION_NUM >= 2000000
+      case QVariant::LongLong:
+        value = QVariant( OGR_F_GetFieldAsInteger64( ogrFet, attIndex ) );
+        break;
+#endif
+      case QVariant::Double:
+        value = QVariant( OGR_F_GetFieldAsDouble( ogrFet, attIndex ) );
+        break;
+      case QVariant::Date:
+      case QVariant::DateTime:
+      case QVariant::Time:
+      {
+        int year, month, day, hour, minute, second, tzf;
+
+        OGR_F_GetFieldAsDateTime( ogrFet, attIndex, &year, &month, &day, &hour, &minute, &second, &tzf );
+        if ( fields.at( attIndex ).type() == QVariant::Date )
+          value = QDate( year, month, day );
+        else if ( fields.at( attIndex ).type() == QVariant::Time )
+          value = QTime( hour, minute, second );
+        else
+          value = QDateTime( QDate( year, month, day ), QTime( hour, minute, second ) );
+      }
+      break;
+      default:
+        Q_ASSERT_X( false, "QgsOgrUtils::getOgrFeatureAttribute", "unsupported field type" );
+        if ( ok )
+          *ok = false;
+    }
+  }
+  else
+  {
+    value = QVariant( QString::null );
+  }
+
+  return value;
+}
+
+bool QgsOgrUtils::readOgrFeatureAttributes( OGRFeatureH ogrFet, const QgsFields& fields, QgsFeature& feature, QTextCodec* encoding )
+{
+  // read all attributes
+  feature.initAttributes( fields.count() );
+  feature.setFields( fields );
+
+  if ( !ogrFet )
+    return false;
+
+  bool ok = false;
+  for ( int idx = 0; idx < fields.count(); ++idx )
+  {
+    QVariant value = getOgrFeatureAttribute( ogrFet, fields, idx, encoding, &ok );
+    if ( ok )
+    {
+      feature.setAttribute( idx, value );
+    }
+  }
+  return true;
+}
+
+bool QgsOgrUtils::readOgrFeatureGeometry( OGRFeatureH ogrFet, QgsFeature& feature )
+{
+  if ( !ogrFet )
+    return false;
+
+  OGRGeometryH geom = OGR_F_GetGeometryRef( ogrFet );
+  if ( !geom )
+    feature.setGeometry( nullptr );
+  else
+    feature.setGeometry( ogrGeometryToQgsGeometry( geom ) );
+
+  return true;
+}
+
+QgsGeometry* QgsOgrUtils::ogrGeometryToQgsGeometry( OGRGeometryH geom )
+{
+  if ( !geom )
+    return nullptr;
+
+  // get the wkb representation
+  int memorySize = OGR_G_WkbSize( geom );
+  unsigned char *wkb = new unsigned char[memorySize];
+  OGR_G_ExportToWkb( geom, ( OGRwkbByteOrder ) QgsApplication::endian(), wkb );
+
+  QgsGeometry *g = new QgsGeometry();
+  g->fromWkb( wkb, memorySize );
+  return g;
+}
+
+QgsFeatureList QgsOgrUtils::stringToFeatureList( const QString& string, const QgsFields& fields, QTextCodec* encoding )
+{
+  QgsFeatureList features;
+  if ( string.isEmpty() )
+    return features;
+
+  QString randomFileName = QString( "/vsimem/%1" ).arg( QUuid::createUuid() );
+
+  // create memory file system object from string buffer
+  QByteArray ba = string.toUtf8();
+  VSIFCloseL( VSIFileFromMemBuffer( TO8( randomFileName ), reinterpret_cast< GByte* >( ba.data() ),
+                                    static_cast< vsi_l_offset >( ba.size() ), FALSE ) );
+
+  OGRDataSourceH hDS = OGROpen( TO8( randomFileName ), false, nullptr );
+  if ( !hDS )
+  {
+    VSIUnlink( TO8( randomFileName ) );
+    return features;
+  }
+
+  OGRLayerH ogrLayer = OGR_DS_GetLayer( hDS, 0 );
+  if ( !ogrLayer )
+  {
+    OGR_DS_Destroy( hDS );
+    VSIUnlink( TO8( randomFileName ) );
+    return features;
+  }
+
+  OGRFeatureH oFeat;
+  while (( oFeat = OGR_L_GetNextFeature( ogrLayer ) ) )
+  {
+    QgsFeature feat = readOgrFeature( oFeat, fields, encoding );
+    if ( feat.isValid() )
+      features << feat;
+
+    OGR_F_Destroy( oFeat );
+  }
+
+  OGR_DS_Destroy( hDS );
+  VSIUnlink( "/vsimem/clipboard.dat" );
+
+  return features;
+}
+
+QgsFields QgsOgrUtils::stringToFields( const QString& string, QTextCodec* encoding )
+{
+  QgsFields fields;
+  if ( string.isEmpty() )
+    return fields;
+
+  QString randomFileName = QString( "/vsimem/%1" ).arg( QUuid::createUuid() );
+
+  // create memory file system object from buffer
+  QByteArray ba = string.toUtf8();
+  VSIFCloseL( VSIFileFromMemBuffer( TO8( randomFileName ), reinterpret_cast< GByte* >( ba.data() ),
+                                    static_cast< vsi_l_offset >( ba.size() ), FALSE ) );
+
+  OGRDataSourceH hDS = OGROpen( TO8( randomFileName ), false, nullptr );
+  if ( !hDS )
+  {
+    VSIUnlink( TO8( randomFileName ) );
+    return fields;
+  }
+
+  OGRLayerH ogrLayer = OGR_DS_GetLayer( hDS, 0 );
+  if ( !ogrLayer )
+  {
+    OGR_DS_Destroy( hDS );
+    VSIUnlink( TO8( randomFileName ) );
+    return fields;
+  }
+
+  OGRFeatureH oFeat;
+  //read in the first feature only
+  if (( oFeat = OGR_L_GetNextFeature( ogrLayer ) ) )
+  {
+    fields = readOgrFields( oFeat, encoding );
+    OGR_F_Destroy( oFeat );
+  }
+
+  OGR_DS_Destroy( hDS );
+  VSIUnlink( TO8( randomFileName ) );
+  return fields;
+}