libgeos.py 文件源码

def load_geos():
    # Custom library path set?
    try:
        from django.conf import settings
        lib_path = settings.GEOS_LIBRARY_PATH
    except (AttributeError, EnvironmentError,
            ImportError, ImproperlyConfigured):
        lib_path = None

    # Setting the appropriate names for the GEOS-C library.
    if lib_path:
        lib_names = None
    elif os.name == 'nt':
        # Windows NT libraries
        lib_names = ['geos_c', 'libgeos_c-1']
    elif os.name == 'posix':
        # *NIX libraries
        lib_names = ['geos_c', 'GEOS']
    else:
        raise ImportError('Unsupported OS "%s"' % os.name)

    # Using the ctypes `find_library` utility to find the path to the GEOS
    # shared library.  This is better than manually specifying each library name
    # and extension (e.g., libgeos_c.[so|so.1|dylib].).
    if lib_names:
        for lib_name in lib_names:
            lib_path = find_library(lib_name)
            if lib_path is not None:
                break

    # No GEOS library could be found.
    if lib_path is None:
        raise ImportError(
            'Could not find the GEOS library (tried "%s"). '
            'Try setting GEOS_LIBRARY_PATH in your settings.' %
            '", "'.join(lib_names)
        )
    # Getting the GEOS C library.  The C interface (CDLL) is used for
    # both *NIX and Windows.
    # See the GEOS C API source code for more details on the library function calls:
    #  http://geos.refractions.net/ro/doxygen_docs/html/geos__c_8h-source.html
    _lgeos = CDLL(lib_path)
    # Here we set up the prototypes for the initGEOS_r and finishGEOS_r
    # routines.  These functions aren't actually called until they are
    # attached to a GEOS context handle -- this actually occurs in
    # geos/prototypes/threadsafe.py.
    _lgeos.initGEOS_r.restype = CONTEXT_PTR
    _lgeos.finishGEOS_r.argtypes = [CONTEXT_PTR]
    return _lgeos


# The notice and error handler C function callback definitions.
# Supposed to mimic the GEOS message handler (C below):
#  typedef void (*GEOSMessageHandler)(const char *fmt, ...);