Source code for django.contrib.gis.gdal.datasource

"""
 DataSource is a wrapper for the OGR Data Source object, which provides
 an interface for reading vector geometry data from many different file
 formats (including ESRI shapefiles).

 When instantiating a DataSource object, use the filename of a
 GDAL-supported data source.  For example, a SHP file or a
 TIGER/Line file from the government.

 The ds_driver keyword is used internally when a ctypes pointer
 is passed in directly.

 Example:
  ds = DataSource('/home/foo/bar.shp')
  for layer in ds:
      for feature in layer:
          # Getting the geometry for the feature.
          g = feature.geom

          # Getting the 'description' field for the feature.
          desc = feature['description']

          # We can also increment through all of the fields
          #  attached to this feature.
          for field in feature:
              # Get the name of the field (e.g. 'description')
              nm = field.name

              # Get the type (integer) of the field, e.g. 0 => OFTInteger
              t = field.type

              # Returns the value the field; OFTIntegers return ints,
              #  OFTReal returns floats, all else returns string.
              val = field.value
"""
# ctypes prerequisites.
from ctypes import byref

# The GDAL C library, OGR exceptions, and the Layer object.
from django.contrib.gis.gdal.base import GDALBase
from django.contrib.gis.gdal.driver import Driver
from django.contrib.gis.gdal.error import GDALException, OGRIndexError
from django.contrib.gis.gdal.layer import Layer
# Getting the ctypes prototypes for the DataSource.
from django.contrib.gis.gdal.prototypes import ds as capi
from django.utils import six
from django.utils.encoding import force_bytes, force_text
from django.utils.six.moves import range


# For more information, see the OGR C API source code:
#  http://www.gdal.org/ogr/ogr__api_8h.html
#
# The OGR_DS_* routines are relevant here.
[docs]class DataSource(GDALBase): "Wraps an OGR Data Source object." def __init__(self, ds_input, ds_driver=False, write=False, encoding='utf-8'): # The write flag. if write: self._write = 1 else: self._write = 0 # See also http://trac.osgeo.org/gdal/wiki/rfc23_ogr_unicode self.encoding = encoding Driver.ensure_registered() if isinstance(ds_input, six.string_types): # The data source driver is a void pointer. ds_driver = Driver.ptr_type() try: # OGROpen will auto-detect the data source type. ds = capi.open_ds(force_bytes(ds_input), self._write, byref(ds_driver)) except GDALException: # Making the error message more clear rather than something # like "Invalid pointer returned from OGROpen". raise GDALException('Could not open the datasource at "%s"' % ds_input) elif isinstance(ds_input, self.ptr_type) and isinstance(ds_driver, Driver.ptr_type): ds = ds_input else: raise GDALException('Invalid data source input type: %s' % type(ds_input)) if ds: self.ptr = ds self.driver = Driver(ds_driver) else: # Raise an exception if the returned pointer is NULL raise GDALException('Invalid data source file "%s"' % ds_input) def __del__(self): "Destroys this DataStructure object." if self._ptr and capi: capi.destroy_ds(self._ptr) def __iter__(self): "Allows for iteration over the layers in a data source." for i in range(self.layer_count): yield self[i] def __getitem__(self, index): "Allows use of the index [] operator to get a layer at the index." if isinstance(index, six.string_types): l = capi.get_layer_by_name(self.ptr, force_bytes(index)) if not l: raise OGRIndexError('invalid OGR Layer name given: "%s"' % index) elif isinstance(index, int): if index < 0 or index >= self.layer_count: raise OGRIndexError('index out of range') l = capi.get_layer(self._ptr, index) else: raise TypeError('Invalid index type: %s' % type(index)) return Layer(l, self) def __len__(self): "Returns the number of layers within the data source." return self.layer_count def __str__(self): "Returns OGR GetName and Driver for the Data Source." return '%s (%s)' % (self.name, str(self.driver)) @property def layer_count(self): "Returns the number of layers in the data source." return capi.get_layer_count(self._ptr) @property def name(self): "Returns the name of the data source." name = capi.get_ds_name(self._ptr) return force_text(name, self.encoding, strings_only=True)