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from cx_Oracle import CLOB
from django.contrib.gis.db.backends.base.adapter import WKTAdapter
from django.contrib.gis.geos import GeometryCollection, Polygon
from django.utils.six.moves import range
class OracleSpatialAdapter(WKTAdapter):
input_size = CLOB
def __init__(self, geom):
"""
Oracle requires that polygon rings are in proper orientation. This
affects spatial operations and an invalid orientation may cause
failures. Correct orientations are:
* Outer ring - counter clockwise
* Inner ring(s) - clockwise
"""
if isinstance(geom, Polygon):
self._fix_polygon(geom)
elif isinstance(geom, GeometryCollection):
self._fix_geometry_collection(geom)
self.wkt = geom.wkt
self.srid = geom.srid
def _fix_polygon(self, poly):
# Fix single polygon orientation as described in __init__()
if self._isClockwise(poly.exterior_ring):
poly.exterior_ring = list(reversed(poly.exterior_ring))
for i in range(1, len(poly)):
if not self._isClockwise(poly[i]):
poly[i] = list(reversed(poly[i]))
return poly
def _fix_geometry_collection(self, coll):
# Fix polygon orientations in geometry collections as described in
# __init__()
for i, geom in enumerate(coll):
if isinstance(geom, Polygon):
coll[i] = self._fix_polygon(geom)
def _isClockwise(self, coords):
# A modified shoelace algorithm to determine polygon orientation.
# See https://en.wikipedia.org/wiki/Shoelace_formula
n = len(coords)
area = 0.0
for i in range(n):
j = (i + 1) % n
area += coords[i][0] * coords[j][1]
area -= coords[j][0] * coords[i][1]
return area < 0.0
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