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Viewing changes to django/contrib/gis/geos/io.py

  • Committer: Bazaar Package Importer
  • Author(s): Chris Lamb
  • Date: 2010-05-21 07:52:55 UTC
  • mfrom: (1.3.6 upstream)
  • mto: This revision was merged to the branch mainline in revision 28.
  • Revision ID: james.westby@ubuntu.com-20100521075255-ii78v1dyfmyu3uzx
Tags: upstream-1.2
Import upstream version 1.2

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