django1/django/contrib/gis/geos/io.py

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"""
Module that holds classes for performing I/O operations on GEOS geometry
objects. Specifically, this has Python implementations of WKB/WKT
reader and writer classes.
"""
from ctypes import byref, c_size_t
from django.contrib.gis.geos.base import GEOSBase
from django.contrib.gis.geos.error import GEOSException
from django.contrib.gis.geos.geometry import GEOSGeometry
from django.contrib.gis.geos.libgeos import GEOM_PTR
from django.contrib.gis.geos.prototypes import io as capi
class IOBase(GEOSBase):
"Base class for GEOS I/O objects."
def __init__(self):
# Getting the pointer with the constructor.
self.ptr = self.constructor()
def __del__(self):
# Cleaning up with the appropriate destructor.
if self._ptr: self.destructor(self._ptr)
### WKT Reading and Writing objects ###
# Non-public class for internal use because its `read` method returns
# _pointers_ instead of a GEOSGeometry object.
class _WKTReader(IOBase):
constructor = capi.wkt_reader_create
destructor = capi.wkt_reader_destroy
ptr_type = capi.WKT_READ_PTR
def read(self, wkt):
if not isinstance(wkt, basestring): raise TypeError
return capi.wkt_reader_read(self.ptr, wkt)
class WKTReader(_WKTReader):
def read(self, wkt):
"Returns a GEOSGeometry for the given WKT string."
return GEOSGeometry(super(WKTReader, self).read(wkt))
class WKTWriter(IOBase):
constructor = capi.wkt_writer_create
destructor = capi.wkt_writer_destroy
ptr_type = capi.WKT_WRITE_PTR
def write(self, geom):
"Returns the WKT representation of the given geometry."
return capi.wkt_writer_write(self.ptr, geom.ptr)
### WKB Reading and Writing objects ###
# Non-public class for the same reason as _WKTReader above.
class _WKBReader(IOBase):
constructor = capi.wkb_reader_create
destructor = capi.wkb_reader_destroy
ptr_type = capi.WKB_READ_PTR
def read(self, wkb):
"Returns a _pointer_ to C GEOS Geometry object from the given WKB."
if isinstance(wkb, buffer):
wkb_s = str(wkb)
return capi.wkb_reader_read(self.ptr, wkb_s, len(wkb_s))
elif isinstance(wkb, basestring):
return capi.wkb_reader_read_hex(self.ptr, wkb, len(wkb))
else:
raise TypeError
class WKBReader(_WKBReader):
def read(self, wkb):
"Returns a GEOSGeometry for the given WKB buffer."
return GEOSGeometry(super(WKBReader, self).read(wkb))
class WKBWriter(IOBase):
constructor = capi.wkb_writer_create
destructor = capi.wkb_writer_destroy
ptr_type = capi.WKB_WRITE_PTR
def write(self, geom):
"Returns the WKB representation of the given geometry."
return buffer(capi.wkb_writer_write(self.ptr, geom.ptr, byref(c_size_t())))
def write_hex(self, geom):
"Returns the HEXEWKB representation of the given geometry."
return capi.wkb_writer_write_hex(self.ptr, geom.ptr, byref(c_size_t()))
### WKBWriter Properties ###
# Property for getting/setting the byteorder.
def _get_byteorder(self):
return capi.wkb_writer_get_byteorder(self.ptr)
def _set_byteorder(self, order):
if not order in (0, 1): raise ValueError('Byte order parameter must be 0 (Big Endian) or 1 (Little Endian).')
capi.wkb_writer_set_byteorder(self.ptr, order)
byteorder = property(_get_byteorder, _set_byteorder)
# Property for getting/setting the output dimension.
def _get_outdim(self):
return capi.wkb_writer_get_outdim(self.ptr)
def _set_outdim(self, new_dim):
if not new_dim in (2, 3): raise ValueError('WKB output dimension must be 2 or 3')
capi.wkb_writer_set_outdim(self.ptr, new_dim)
outdim = property(_get_outdim, _set_outdim)
# Property for getting/setting the include srid flag.
def _get_include_srid(self):
return bool(ord(capi.wkb_writer_get_include_srid(self.ptr)))
def _set_include_srid(self, include):
if bool(include): flag = chr(1)
else: flag = chr(0)
capi.wkb_writer_set_include_srid(self.ptr, flag)
srid = property(_get_include_srid, _set_include_srid)
# Instances of the WKT and WKB reader/writer objects.
wkt_r = _WKTReader()
wkt_w = WKTWriter()
wkb_r = _WKBReader()
wkb_w = WKBWriter()