python/lib/django_1_4/django/contrib/gis/geos/prototypes/geom.py

   1 from ctypes import c_char_p, c_int, c_size_t, c_ubyte, POINTER
   2 from django.contrib.gis.geos.libgeos import CS_PTR, GEOM_PTR
   3 from django.contrib.gis.geos.prototypes.errcheck import (
   4     check_geom, check_minus_one, check_sized_string, check_string, check_zero)
   5 from django.contrib.gis.geos.prototypes.threadsafe import GEOSFunc
   6
   7 # This is the return type used by binary output (WKB, HEX) routines.
   8 c_uchar_p = POINTER(c_ubyte)
   9
  10 # We create a simple subclass of c_char_p here because when the response
  11 # type is set to c_char_p, you get a _Python_ string and there's no way
  12 # to access the string's address inside the error checking function.
  13 # In other words, you can't free the memory allocated inside GEOS.  Previously,
  14 # the return type would just be omitted and the integer address would be
  15 # used -- but this allows us to be specific in the function definition and
  16 # keeps the reference so it may be free'd.
  17 class geos_char_p(c_char_p):
  18     pass
  19
  20 ### ctypes generation functions ###
  21 def bin_constructor(func):
  22     "Generates a prototype for binary construction (HEX, WKB) GEOS routines."
  23     func.argtypes = [c_char_p, c_size_t]
  24     func.restype = GEOM_PTR
  25     func.errcheck = check_geom
  26     return func
  27
  28 # HEX & WKB output
  29 def bin_output(func):
  30     "Generates a prototype for the routines that return a a sized string."
  31     func.argtypes = [GEOM_PTR, POINTER(c_size_t)]
  32     func.errcheck = check_sized_string
  33     func.restype = c_uchar_p
  34     return func
  35
  36 def geom_output(func, argtypes):
  37     "For GEOS routines that return a geometry."
  38     if argtypes: func.argtypes = argtypes
  39     func.restype = GEOM_PTR
  40     func.errcheck = check_geom
  41     return func
  42
  43 def geom_index(func):
  44     "For GEOS routines that return geometries from an index."
  45     return geom_output(func, [GEOM_PTR, c_int])
  46
  47 def int_from_geom(func, zero=False):
  48     "Argument is a geometry, return type is an integer."
  49     func.argtypes = [GEOM_PTR]
  50     func.restype = c_int
  51     if zero:
  52         func.errcheck = check_zero
  53     else:
  54         func.errcheck = check_minus_one
  55     return func
  56
  57 def string_from_geom(func):
  58     "Argument is a Geometry, return type is a string."
  59     func.argtypes = [GEOM_PTR]
  60     func.restype = geos_char_p
  61     func.errcheck = check_string
  62     return func
  63
  64 ### ctypes prototypes ###
  65
  66 # Deprecated creation routines from WKB, HEX, WKT
  67 from_hex = bin_constructor(GEOSFunc('GEOSGeomFromHEX_buf'))
  68 from_wkb = bin_constructor(GEOSFunc('GEOSGeomFromWKB_buf'))
  69 from_wkt = geom_output(GEOSFunc('GEOSGeomFromWKT'), [c_char_p])
  70
  71 # Deprecated output routines
  72 to_hex = bin_output(GEOSFunc('GEOSGeomToHEX_buf'))
  73 to_wkb = bin_output(GEOSFunc('GEOSGeomToWKB_buf'))
  74 to_wkt = string_from_geom(GEOSFunc('GEOSGeomToWKT'))
  75
  76 # The GEOS geometry type, typeid, num_coordites and number of geometries
  77 geos_normalize = int_from_geom(GEOSFunc('GEOSNormalize'))
  78 geos_type = string_from_geom(GEOSFunc('GEOSGeomType'))
  79 geos_typeid = int_from_geom(GEOSFunc('GEOSGeomTypeId'))
  80 get_dims = int_from_geom(GEOSFunc('GEOSGeom_getDimensions'), zero=True)
  81 get_num_coords = int_from_geom(GEOSFunc('GEOSGetNumCoordinates'))
  82 get_num_geoms = int_from_geom(GEOSFunc('GEOSGetNumGeometries'))
  83
  84 # Geometry creation factories
  85 create_point = geom_output(GEOSFunc('GEOSGeom_createPoint'), [CS_PTR])
  86 create_linestring = geom_output(GEOSFunc('GEOSGeom_createLineString'), [CS_PTR])
  87 create_linearring = geom_output(GEOSFunc('GEOSGeom_createLinearRing'), [CS_PTR])
  88
  89 # Polygon and collection creation routines are special and will not
  90 # have their argument types defined.
  91 create_polygon = geom_output(GEOSFunc('GEOSGeom_createPolygon'), None)
  92 create_collection = geom_output(GEOSFunc('GEOSGeom_createCollection'), None)
  93
  94 # Ring routines
  95 get_extring = geom_output(GEOSFunc('GEOSGetExteriorRing'), [GEOM_PTR])
  96 get_intring = geom_index(GEOSFunc('GEOSGetInteriorRingN'))
  97 get_nrings = int_from_geom(GEOSFunc('GEOSGetNumInteriorRings'))
  98
  99 # Collection Routines
 100 get_geomn = geom_index(GEOSFunc('GEOSGetGeometryN'))
 101
 102 # Cloning
 103 geom_clone = GEOSFunc('GEOSGeom_clone')
 104 geom_clone.argtypes = [GEOM_PTR]
 105 geom_clone.restype = GEOM_PTR
 106
 107 # Destruction routine.
 108 destroy_geom = GEOSFunc('GEOSGeom_destroy')
 109 destroy_geom.argtypes = [GEOM_PTR]
 110 destroy_geom.restype = None
 111
 112 # SRID routines
 113 geos_get_srid = GEOSFunc('GEOSGetSRID')
 114 geos_get_srid.argtypes = [GEOM_PTR]
 115 geos_get_srid.restype = c_int
 116
 117 geos_set_srid = GEOSFunc('GEOSSetSRID')
 118 geos_set_srid.argtypes = [GEOM_PTR, c_int]
 119 geos_set_srid.restype = None