1 """

     2  This module houses the ctypes initialization procedures, as well

     3  as the notice and error handler function callbacks (get called

     4  when an error occurs in GEOS).

     5 

     6  This module also houses GEOS Pointer utilities, including

     7  get_pointer_arr(), and GEOM_PTR.

     8 """

     9 import atexit, os, re, sys

    10 from ctypes import c_char_p, Structure, CDLL, CFUNCTYPE, POINTER

    11 from ctypes.util import find_library

    12 from django.contrib.gis.geos.error import GEOSException

    13 

    14 # NumPy supported?

    15 try:

    16     from numpy import array, ndarray

    17     HAS_NUMPY = True

    18 except ImportError:

    19     HAS_NUMPY = False

    20 

    21 # Custom library path set?

    22 try:

    23     from django.conf import settings

    24     lib_path = settings.GEOS_LIBRARY_PATH

    25 except (AttributeError, EnvironmentError, ImportError):

    26     lib_path = None

    27 

    28 # Setting the appropriate names for the GEOS-C library.

    29 if lib_path:

    30     lib_names = None

    31 elif os.name == 'nt':

    32     # Windows NT libraries

    33     lib_names = ['libgeos_c-1']

    34 elif os.name == 'posix':

    35     # *NIX libraries

    36     lib_names = ['geos_c']

    37 else:

    38     raise ImportError('Unsupported OS "%s"' % os.name)

    39 

    40 # Using the ctypes `find_library` utility to find the the path to the GEOS 

    41 # shared library.  This is better than manually specifiying each library name 

    42 # and extension (e.g., libgeos_c.[so|so.1|dylib].).

    43 if lib_names: 

    44     for lib_name in lib_names:

    45         lib_path = find_library(lib_name)

    46         if not lib_path is None: break

    47 

    48 # No GEOS library could be found.

    49 if lib_path is None: 

    50     raise ImportError('Could not find the GEOS library (tried "%s"). '

    51                         'Try setting GEOS_LIBRARY_PATH in your settings.' % 

    52                         '", "'.join(lib_names))

    53 

    54 # Getting the GEOS C library.  The C interface (CDLL) is used for

    55 #  both *NIX and Windows.

    56 # See the GEOS C API source code for more details on the library function calls:

    57 #  http://geos.refractions.net/ro/doxygen_docs/html/geos__c_8h-source.html

    58 lgeos = CDLL(lib_path)

    59 

    60 # The notice and error handler C function callback definitions.

    61 #  Supposed to mimic the GEOS message handler (C below):

    62 #  "typedef void (*GEOSMessageHandler)(const char *fmt, ...);"

    63 NOTICEFUNC = CFUNCTYPE(None, c_char_p, c_char_p)

    64 def notice_h(fmt, lst, output_h=sys.stdout):

    65     try:

    66         warn_msg = fmt % lst

    67     except:

    68         warn_msg = fmt 

    69     output_h.write('GEOS_NOTICE: %s\n' % warn_msg)

    70 notice_h = NOTICEFUNC(notice_h)

    71 

    72 ERRORFUNC = CFUNCTYPE(None, c_char_p, c_char_p)

    73 def error_h(fmt, lst, output_h=sys.stderr):

    74     try:

    75         err_msg = fmt % lst

    76     except:

    77         err_msg = fmt

    78     output_h.write('GEOS_ERROR: %s\n' % err_msg)

    79 error_h = ERRORFUNC(error_h)

    80 

    81 # The initGEOS routine should be called first, however, that routine takes

    82 #  the notice and error functions as parameters.  Here is the C code that

    83 #  is wrapped:

    84 #  "extern void GEOS_DLL initGEOS(GEOSMessageHandler notice_function, GEOSMessageHandler error_function);"

    85 lgeos.initGEOS(notice_h, error_h)

    86 

    87 #### GEOS Geometry C data structures, and utility functions. ####

    88 

    89 # Opaque GEOS geometry structures, used for GEOM_PTR and CS_PTR

    90 class GEOSGeom_t(Structure): pass

    91 class GEOSCoordSeq_t(Structure): pass

    92 

    93 # Pointers to opaque GEOS geometry structures.

    94 GEOM_PTR = POINTER(GEOSGeom_t)

    95 CS_PTR = POINTER(GEOSCoordSeq_t)

    96 

    97 # Used specifically by the GEOSGeom_createPolygon and GEOSGeom_createCollection 

    98 #  GEOS routines

    99 def get_pointer_arr(n):

   100     "Gets a ctypes pointer array (of length `n`) for GEOSGeom_t opaque pointer."

   101     GeomArr = GEOM_PTR * n

   102     return GeomArr()

   103 

   104 # Returns the string version of the GEOS library. Have to set the restype 

   105 # explicitly to c_char_p to ensure compatibility accross 32 and 64-bit platforms.

   106 geos_version = lgeos.GEOSversion

   107 geos_version.argtypes = None   

   108 geos_version.restype = c_char_p

   109 

   110 # Regular expression should be able to parse version strings such as

   111 # '3.0.0rc4-CAPI-1.3.3', or '3.0.0-CAPI-1.4.1'

   112 version_regex = re.compile(r'^(?P<version>\d+\.\d+\.\d+)(rc(?P<release_candidate>\d+))?-CAPI-(?P<capi_version>\d+\.\d+\.\d+)$')

   113 def geos_version_info():

   114     """

   115     Returns a dictionary containing the various version metadata parsed from

   116     the GEOS version string, including the version number, whether the version

   117     is a release candidate (and what number release candidate), and the C API

   118     version.

   119     """

   120     ver = geos_version()

   121     m = version_regex.match(ver)

   122     if not m: raise GEOSException('Could not parse version info string "%s"' % ver)

   123     return dict((key, m.group(key)) for key in ('version', 'release_candidate', 'capi_version'))

   124 

   125 # Calling the finishGEOS() upon exit of the interpreter.

   126 atexit.register(lgeos.finishGEOS)