125 lines
4.2 KiB
Python
125 lines
4.2 KiB
Python
# The GDAL C library, OGR exception, and the Field object
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from django.contrib.gis.gdal.base import GDALBase
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from django.contrib.gis.gdal.error import OGRException, OGRIndexError
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from django.contrib.gis.gdal.field import Field
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from django.contrib.gis.gdal.geometries import OGRGeometry, OGRGeomType
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# ctypes function prototypes
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from django.contrib.gis.gdal.prototypes import ds as capi, geom as geom_api
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from django.utils.encoding import force_bytes, force_text
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from django.utils import six
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from django.utils.six.moves import xrange
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# For more information, see the OGR C API source code:
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# http://www.gdal.org/ogr/ogr__api_8h.html
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#
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# The OGR_F_* routines are relevant here.
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class Feature(GDALBase):
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"""
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This class that wraps an OGR Feature, needs to be instantiated
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from a Layer object.
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"""
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#### Python 'magic' routines ####
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def __init__(self, feat, layer):
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"""
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Initializes Feature from a pointer and its Layer object.
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"""
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if not feat:
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raise OGRException('Cannot create OGR Feature, invalid pointer given.')
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self.ptr = feat
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self._layer = layer
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def __del__(self):
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"Releases a reference to this object."
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if self._ptr: capi.destroy_feature(self._ptr)
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def __getitem__(self, index):
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"""
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Gets the Field object at the specified index, which may be either
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an integer or the Field's string label. Note that the Field object
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is not the field's _value_ -- use the `get` method instead to
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retrieve the value (e.g. an integer) instead of a Field instance.
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"""
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if isinstance(index, six.string_types):
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i = self.index(index)
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else:
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if index < 0 or index > self.num_fields:
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raise OGRIndexError('index out of range')
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i = index
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return Field(self, i)
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def __iter__(self):
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"Iterates over each field in the Feature."
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for i in xrange(self.num_fields):
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yield self[i]
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def __len__(self):
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"Returns the count of fields in this feature."
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return self.num_fields
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def __str__(self):
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"The string name of the feature."
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return 'Feature FID %d in Layer<%s>' % (self.fid, self.layer_name)
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def __eq__(self, other):
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"Does equivalence testing on the features."
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return bool(capi.feature_equal(self.ptr, other._ptr))
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#### Feature Properties ####
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@property
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def encoding(self):
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return self._layer._ds.encoding
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@property
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def fid(self):
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"Returns the feature identifier."
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return capi.get_fid(self.ptr)
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@property
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def layer_name(self):
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"Returns the name of the layer for the feature."
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name = capi.get_feat_name(self._layer._ldefn)
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return force_text(name, self.encoding, strings_only=True)
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@property
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def num_fields(self):
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"Returns the number of fields in the Feature."
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return capi.get_feat_field_count(self.ptr)
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@property
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def fields(self):
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"Returns a list of fields in the Feature."
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return [capi.get_field_name(capi.get_field_defn(self._layer._ldefn, i))
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for i in xrange(self.num_fields)]
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@property
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def geom(self):
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"Returns the OGR Geometry for this Feature."
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# Retrieving the geometry pointer for the feature.
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geom_ptr = capi.get_feat_geom_ref(self.ptr)
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return OGRGeometry(geom_api.clone_geom(geom_ptr))
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@property
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def geom_type(self):
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"Returns the OGR Geometry Type for this Feture."
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return OGRGeomType(capi.get_fd_geom_type(self._layer._ldefn))
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#### Feature Methods ####
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def get(self, field):
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"""
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Returns the value of the field, instead of an instance of the Field
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object. May take a string of the field name or a Field object as
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parameters.
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"""
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field_name = getattr(field, 'name', field)
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return self[field_name].value
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def index(self, field_name):
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"Returns the index of the given field name."
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i = capi.get_field_index(self.ptr, force_bytes(field_name))
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if i < 0:
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raise OGRIndexError('invalid OFT field name given: "%s"' % field_name)
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return i
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