/django/contrib/gis/geos/prototypes/geom.py

  1from ctypes import c_char_p, c_int, c_size_t, c_ubyte, c_uint, POINTER
  2from django.contrib.gis.geos.libgeos import CS_PTR, GEOM_PTR, PREPGEOM_PTR, GEOS_PREPARE
  3from django.contrib.gis.geos.prototypes.errcheck import \
  4    check_geom, check_minus_one, check_sized_string, check_string, check_zero
  5from django.contrib.gis.geos.prototypes.threadsafe import GEOSFunc
  6
  7# This is the return type used by binary output (WKB, HEX) routines.
  8c_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.
 17class geos_char_p(c_char_p):
 18    pass
 19
 20### ctypes generation functions ###
 21def 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
 29def 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
 36def 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
 43def geom_index(func):
 44    "For GEOS routines that return geometries from an index."
 45    return geom_output(func, [GEOM_PTR, c_int])
 46
 47def 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
 57def 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
 67from_hex = bin_constructor(GEOSFunc('GEOSGeomFromHEX_buf'))
 68from_wkb = bin_constructor(GEOSFunc('GEOSGeomFromWKB_buf'))
 69from_wkt = geom_output(GEOSFunc('GEOSGeomFromWKT'), [c_char_p])
 70
 71# Deprecated output routines
 72to_hex = bin_output(GEOSFunc('GEOSGeomToHEX_buf'))
 73to_wkb = bin_output(GEOSFunc('GEOSGeomToWKB_buf'))
 74to_wkt = string_from_geom(GEOSFunc('GEOSGeomToWKT'))
 75
 76# The GEOS geometry type, typeid, num_coordites and number of geometries
 77geos_normalize = int_from_geom(GEOSFunc('GEOSNormalize'))
 78geos_type = string_from_geom(GEOSFunc('GEOSGeomType'))
 79geos_typeid = int_from_geom(GEOSFunc('GEOSGeomTypeId'))
 80get_dims = int_from_geom(GEOSFunc('GEOSGeom_getDimensions'), zero=True)
 81get_num_coords = int_from_geom(GEOSFunc('GEOSGetNumCoordinates'))
 82get_num_geoms = int_from_geom(GEOSFunc('GEOSGetNumGeometries'))
 83
 84# Geometry creation factories
 85create_point = geom_output(GEOSFunc('GEOSGeom_createPoint'), [CS_PTR])
 86create_linestring = geom_output(GEOSFunc('GEOSGeom_createLineString'), [CS_PTR])
 87create_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.
 91create_polygon = geom_output(GEOSFunc('GEOSGeom_createPolygon'), None)
 92create_collection = geom_output(GEOSFunc('GEOSGeom_createCollection'), None)
 93
 94# Ring routines
 95get_extring = geom_output(GEOSFunc('GEOSGetExteriorRing'), [GEOM_PTR])
 96get_intring = geom_index(GEOSFunc('GEOSGetInteriorRingN'))
 97get_nrings = int_from_geom(GEOSFunc('GEOSGetNumInteriorRings'))
 98
 99# Collection Routines
100get_geomn = geom_index(GEOSFunc('GEOSGetGeometryN'))
101
102# Cloning
103geom_clone = GEOSFunc('GEOSGeom_clone')
104geom_clone.argtypes = [GEOM_PTR]
105geom_clone.restype = GEOM_PTR
106
107# Destruction routine.
108destroy_geom = GEOSFunc('GEOSGeom_destroy')
109destroy_geom.argtypes = [GEOM_PTR]
110destroy_geom.restype = None
111
112# SRID routines
113geos_get_srid = GEOSFunc('GEOSGetSRID')
114geos_get_srid.argtypes = [GEOM_PTR]
115geos_get_srid.restype = c_int
116
117geos_set_srid = GEOSFunc('GEOSSetSRID')
118geos_set_srid.argtypes = [GEOM_PTR, c_int]
119geos_set_srid.restype = None