79 lines
2.2 KiB
Python
79 lines
2.2 KiB
Python
"""
|
|
Intermediaries supporting GEOS topological operations
|
|
|
|
These methods all take Shapely geometries and other Python objects and delegate
|
|
to GEOS functions via ctypes.
|
|
|
|
These methods return ctypes objects that should be recast by the caller.
|
|
"""
|
|
|
|
from ctypes import byref, c_double
|
|
from shapely.geos import TopologicalError, lgeos
|
|
|
|
|
|
class Validating(object):
|
|
|
|
def _validate(self, ob, stop_prepared=False):
|
|
if ob is None or ob._geom is None:
|
|
raise ValueError("Null geometry supports no operations")
|
|
if stop_prepared and hasattr(ob, 'prepared'):
|
|
raise ValueError("Prepared geometries cannot be operated on")
|
|
|
|
|
|
class Delegating(Validating):
|
|
|
|
def __init__(self, name):
|
|
self.fn = lgeos.methods[name]
|
|
|
|
def _check_topology(self, err, *geoms):
|
|
"""Raise TopologicalError if geoms are invalid.
|
|
|
|
Else, raise original error.
|
|
"""
|
|
for geom in geoms:
|
|
if not geom.is_valid:
|
|
raise TopologicalError(
|
|
"The operation '%s' could not be performed. "
|
|
"Likely cause is invalidity of the geometry %s" % (
|
|
self.fn.__name__, repr(geom)))
|
|
raise err
|
|
|
|
|
|
class BinaryRealProperty(Delegating):
|
|
|
|
def __call__(self, this, other):
|
|
self._validate(this)
|
|
self._validate(other, stop_prepared=True)
|
|
d = c_double()
|
|
retval = self.fn(this._geom, other._geom, byref(d))
|
|
return d.value
|
|
|
|
|
|
class UnaryRealProperty(Delegating):
|
|
|
|
def __call__(self, this):
|
|
self._validate(this)
|
|
d = c_double()
|
|
retval = self.fn(this._geom, byref(d))
|
|
return d.value
|
|
|
|
|
|
class BinaryTopologicalOp(Delegating):
|
|
|
|
def __call__(self, this, other, *args):
|
|
self._validate(this)
|
|
self._validate(other, stop_prepared=True)
|
|
product = self.fn(this._geom, other._geom, *args)
|
|
if product is None:
|
|
err = TopologicalError(
|
|
"This operation could not be performed. Reason: unknown")
|
|
self._check_topology(err, this, other)
|
|
return product
|
|
|
|
|
|
class UnaryTopologicalOp(Delegating):
|
|
|
|
def __call__(self, this, *args):
|
|
self._validate(this)
|
|
return self.fn(this._geom, *args)
|