python/lib/Lib/site-packages/django/contrib/gis/geos/collections.py

"""
 This module houses the Geometry Collection objects:
 GeometryCollection, MultiPoint, MultiLineString, and MultiPolygon
"""
from ctypes import c_int, c_uint, byref
from django.contrib.gis.geos.error import GEOSException, GEOSIndexError
from django.contrib.gis.geos.geometry import GEOSGeometry
from django.contrib.gis.geos.libgeos import get_pointer_arr, GEOM_PTR, GEOS_PREPARE
from django.contrib.gis.geos.linestring import LineString, LinearRing
from django.contrib.gis.geos.point import Point
from django.contrib.gis.geos.polygon import Polygon
from django.contrib.gis.geos import prototypes as capi

class GeometryCollection(GEOSGeometry):
    _typeid = 7

    def __init__(self, *args, **kwargs):
        "Initializes a Geometry Collection from a sequence of Geometry objects."

        # Checking the arguments
        if not args:
            raise TypeError('Must provide at least one Geometry to initialize %s.' % self.__class__.__name__)

        if len(args) == 1:
            # If only one geometry provided or a list of geometries is provided
            #  in the first argument.
            if isinstance(args[0], (tuple, list)):
                init_geoms = args[0]
            else:
                init_geoms = args
        else:
            init_geoms = args

        # Ensuring that only the permitted geometries are allowed in this collection
        # this is moved to list mixin super class
        self._check_allowed(init_geoms)

        # Creating the geometry pointer array.
        collection = self._create_collection(len(init_geoms), iter(init_geoms))
        super(GeometryCollection, self).__init__(collection, **kwargs)

    def __iter__(self):
        "Iterates over each Geometry in the Collection."
        for i in xrange(len(self)):
            yield self[i]

    def __len__(self):
        "Returns the number of geometries in this Collection."
        return self.num_geom

    ### Methods for compatibility with ListMixin ###
    def _create_collection(self, length, items):
        # Creating the geometry pointer array.
        geoms = get_pointer_arr(length)
        for i, g in enumerate(items):
            # this is a little sloppy, but makes life easier
            # allow GEOSGeometry types (python wrappers) or pointer types
            geoms[i] = capi.geom_clone(getattr(g, 'ptr', g))

        return capi.create_collection(c_int(self._typeid), byref(geoms), c_uint(length))

    def _get_single_internal(self, index):
        return capi.get_geomn(self.ptr, index)

    def _get_single_external(self, index):
        "Returns the Geometry from this Collection at the given index (0-based)."
        # Checking the index and returning the corresponding GEOS geometry.
        return GEOSGeometry(capi.geom_clone(self._get_single_internal(index)), srid=self.srid)

    def _set_list(self, length, items):
        "Create a new collection, and destroy the contents of the previous pointer."
        prev_ptr = self.ptr
        srid = self.srid
        self.ptr = self._create_collection(length, items)
        if srid: self.srid = srid
        capi.destroy_geom(prev_ptr)

    _set_single = GEOSGeometry._set_single_rebuild
    _assign_extended_slice = GEOSGeometry._assign_extended_slice_rebuild

    @property
    def kml(self):
        "Returns the KML for this Geometry Collection."
        return '<MultiGeometry>%s</MultiGeometry>' % ''.join([g.kml for g in self])

    @property
    def tuple(self):
        "Returns a tuple of all the coordinates in this Geometry Collection"
        return tuple([g.tuple for g in self])
    coords = tuple

# MultiPoint, MultiLineString, and MultiPolygon class definitions.
class MultiPoint(GeometryCollection):
    _allowed = Point
    _typeid = 4

class MultiLineString(GeometryCollection):
    _allowed = (LineString, LinearRing)
    _typeid = 5

    @property
    def merged(self):
        """ 
        Returns a LineString representing the line merge of this 
        MultiLineString.
        """ 
        return self._topology(capi.geos_linemerge(self.ptr))         

class MultiPolygon(GeometryCollection):
    _allowed = Polygon
    _typeid = 6

    @property
    def cascaded_union(self):
        "Returns a cascaded union of this MultiPolygon."
        if GEOS_PREPARE:
            return GEOSGeometry(capi.geos_cascaded_union(self.ptr), self.srid)
        else:
            raise GEOSException('The cascaded union operation requires GEOS 3.1+.')

# Setting the allowed types here since GeometryCollection is defined before
# its subclasses.
GeometryCollection._allowed = (Point, LineString, LinearRing, Polygon, MultiPoint, MultiLineString, MultiPolygon)