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"""
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
"""
from ctypes import byref
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
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.
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)
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