127 lines
4.5 KiB
Python
127 lines
4.5 KiB
Python
"""
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This module houses the ctypes initialization procedures, as well
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as the notice and error handler function callbacks (get called
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when an error occurs in GEOS).
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This module also houses GEOS Pointer utilities, including
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get_pointer_arr(), and GEOM_PTR.
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"""
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import atexit, os, re, sys
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from ctypes import c_char_p, Structure, CDLL, CFUNCTYPE, POINTER
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from ctypes.util import find_library
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from django.contrib.gis.geos.error import GEOSException
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# NumPy supported?
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try:
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from numpy import array, ndarray
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HAS_NUMPY = True
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except ImportError:
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HAS_NUMPY = False
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# Custom library path set?
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try:
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from django.conf import settings
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lib_path = settings.GEOS_LIBRARY_PATH
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except (AttributeError, EnvironmentError, ImportError):
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lib_path = None
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# Setting the appropriate names for the GEOS-C library.
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if lib_path:
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lib_names = None
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elif os.name == 'nt':
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# Windows NT libraries
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lib_names = ['libgeos_c-1']
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elif os.name == 'posix':
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# *NIX libraries
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lib_names = ['geos_c']
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else:
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raise RuntimeError('Unsupported OS "%s"' % os.name)
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# Using the ctypes `find_library` utility to find the the path to the GEOS
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# shared library. This is better than manually specifiying each library name
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# and extension (e.g., libgeos_c.[so|so.1|dylib].).
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if lib_names:
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for lib_name in lib_names:
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lib_path = find_library(lib_name)
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if not lib_path is None: break
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# No GEOS library could be found.
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if lib_path is None:
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raise RuntimeError('Could not find the GEOS library (tried "%s"). '
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'Try setting GEOS_LIBRARY_PATH in your settings.' %
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'", "'.join(lib_names))
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# Getting the GEOS C library. The C interface (CDLL) is used for
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# both *NIX and Windows.
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# See the GEOS C API source code for more details on the library function calls:
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# http://geos.refractions.net/ro/doxygen_docs/html/geos__c_8h-source.html
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lgeos = CDLL(lib_path)
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# The notice and error handler C function callback definitions.
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# Supposed to mimic the GEOS message handler (C below):
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# "typedef void (*GEOSMessageHandler)(const char *fmt, ...);"
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NOTICEFUNC = CFUNCTYPE(None, c_char_p, c_char_p)
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def notice_h(fmt, lst, output_h=sys.stdout):
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try:
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warn_msg = fmt % lst
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except:
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warn_msg = fmt
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output_h.write('GEOS_NOTICE: %s\n' % warn_msg)
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notice_h = NOTICEFUNC(notice_h)
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ERRORFUNC = CFUNCTYPE(None, c_char_p, c_char_p)
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def error_h(fmt, lst, output_h=sys.stderr):
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try:
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err_msg = fmt % lst
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except:
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err_msg = fmt
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output_h.write('GEOS_ERROR: %s\n' % err_msg)
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error_h = ERRORFUNC(error_h)
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# The initGEOS routine should be called first, however, that routine takes
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# the notice and error functions as parameters. Here is the C code that
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# is wrapped:
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# "extern void GEOS_DLL initGEOS(GEOSMessageHandler notice_function, GEOSMessageHandler error_function);"
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lgeos.initGEOS(notice_h, error_h)
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#### GEOS Geometry C data structures, and utility functions. ####
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# Opaque GEOS geometry structures, used for GEOM_PTR and CS_PTR
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class GEOSGeom_t(Structure): pass
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class GEOSCoordSeq_t(Structure): pass
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# Pointers to opaque GEOS geometry structures.
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GEOM_PTR = POINTER(GEOSGeom_t)
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CS_PTR = POINTER(GEOSCoordSeq_t)
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# Used specifically by the GEOSGeom_createPolygon and GEOSGeom_createCollection
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# GEOS routines
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def get_pointer_arr(n):
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"Gets a ctypes pointer array (of length `n`) for GEOSGeom_t opaque pointer."
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GeomArr = GEOM_PTR * n
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return GeomArr()
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# Returns the string version of the GEOS library. Have to set the restype
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# explicitly to c_char_p to ensure compatibility accross 32 and 64-bit platforms.
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geos_version = lgeos.GEOSversion
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geos_version.argtypes = None
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geos_version.restype = c_char_p
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# Regular expression should be able to parse version strings such as
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# '3.0.0rc4-CAPI-1.3.3', or '3.0.0-CAPI-1.4.1'
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version_regex = re.compile(r'^(?P<version>\d+\.\d+\.\d+)(rc(?P<release_candidate>\d+))?-CAPI-(?P<capi_version>\d+\.\d+\.\d+)$')
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def geos_version_info():
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"""
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Returns a dictionary containing the various version metadata parsed from
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the GEOS version string, including the version number, whether the version
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is a release candidate (and what number release candidate), and the C API
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version.
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"""
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ver = geos_version()
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m = version_regex.match(ver)
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if not m: raise GEOSException('Could not parse version info string "%s"' % ver)
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return dict((key, m.group(key)) for key in ('version', 'release_candidate', 'capi_version'))
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# Calling the finishGEOS() upon exit of the interpreter.
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atexit.register(lgeos.finishGEOS)
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