python/plugins/processing/tools/vector.py

@@ -25,6 +25,8 @@
 
 __revision__ = '$Format:%H$'
 
+import uuid
+
 from PyQt4.QtCore import *
 from qgis.core import *
 from processing.core.ProcessingConfig import ProcessingConfig
@@ -274,3 +276,51 @@ def combineVectorFields(layerA, layerB):
         fields.append(field)
 
     return fields
+
+
+def duplicateInMemory(layer, newName='', addToRegistry=False):
+    """Return a memory copy of a layer
+
+    layer: QgsVectorLayer that shall be copied to memory.
+    new_name: The name of the copied layer.
+    add_to_registry: if True, the new layer will be added to the QgsMapRegistry
+
+    Returns an in-memory copy of a layer.
+    """
+    if newName is '':
+        newName = layer.name() + ' (Memory)'
+
+    if layer.type() == QgsMapLayer.VectorLayer:
+        geomType = layer.geometryType()
+        if geomType == QGis.Point:
+            strType = 'Point'
+        elif geomType == QGis.Line:
+            strType = 'Line'
+        elif geomType == QGis.Polygon:
+            strType = 'Polygon'
+        else:
+            raise RuntimeError('Layer is whether Point nor Line nor Polygon')
+    else:
+        raise RuntimeError('Layer is not a VectorLayer')
+
+    crs = layer.crs().authid().lower()
+    myUuid = str(uuid.uuid4())
+    uri = '%s?crs=%s&index=yes&uuid=%s' % (strType, crs, myUuid)
+    memLayer = QgsVectorLayer(uri, newName, 'memory')
+    memProvider = memLayer.dataProvider()
+
+    provider = layer.dataProvider()
+    fields = provider.fields().toList()
+    memProvider.addAttributes(fields)
+    memLayer.updateFields()
+
+    for ft in provider.getFeatures():
+        memProvider.addFeatures([ft])
+
+    if addToRegistry:
+        if memLayer.isValid():
+            QgsMapLayerRegistry.instance().addMapLayer(memLayer)
+        else:
+            raise RuntimeError('Layer invalid')
+
+    return memLayer