import threading
from django.contrib.gis.geos.libgeos import lgeos,notice_h,error_h,CONTEXT_PTR
class GEOSContextHandle(object):
"""
Python object representing a GEOS context handle.
"""
def __init__(self):
# Initializing the context handler for this thread with
# the notice and error handler.
self.ptr = lgeos.initGEOS_r(notice_h, error_h)
def __del__(self):
if self.ptr: lgeos.finishGEOS_r(self.ptr)
# Defining a thread-local object and creating an instance
# to hold a reference to GEOSContextHandle for this thread.
class GEOSContext(threading.local):
handle = None
thread_context = GEOSContext()
def call_geos_threaded(cfunc, args):
"""
This module-level routine calls the specified GEOS C thread-safe
function with the context for this current thread.
"""
# If a context handle does not exist for this thread, initialize one.
if not thread_context.handle:
thread_context.handle = GEOSContextHandle()
# Call the threaded GEOS routine with pointer of the context handle
# as the first argument.
return cfunc(thread_context.handle.ptr, *args)
class GEOSFunc(object):
"""
Class that serves as a wrapper for GEOS C Functions, and will
use thread-safe function variants when available.
"""
def __init__(self, func_name):
try:
# GEOS thread-safe function signatures end with '_r', and
# take an additional context handle parameter.
self.cfunc = getattr(lgeos, func_name + '_r')
self.threaded = True
except AttributeError:
# Otherwise, use usual function.
self.cfunc = getattr(lgeos, func_name)
self.threaded = False
def __call__(self, *args):
if self.threaded:
return call_geos_threaded(self.cfunc, args)
else:
return self.cfunc(*args)
def __str__(self):
return self.cfunc.__name__
# argtypes property
def _get_argtypes(self):
return self.cfunc.argtypes
def _set_argtypes(self, argtypes):
if self.threaded:
new_argtypes = [CONTEXT_PTR]
new_argtypes.extend(argtypes)
self.cfunc.argtypes = new_argtypes
else:
self.cfunc.argtypes = argtypes
argtypes = property(_get_argtypes, _set_argtypes)
# restype property
def _get_restype(self):
return self.cfunc.restype
def _set_restype(self, restype):
self.cfunc.restype = restype
restype = property(_get_restype, _set_restype)
# errcheck property
def _get_errcheck(self):
return self.cfunc.errcheck
def _set_errcheck(self, errcheck):
self.cfunc.errcheck = errcheck
errcheck = property(_get_errcheck, _set_errcheck)
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