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