[1.3.X] Fixed integer overflows that occurred when `OFTReal` fields were treated as `OFTInteger`.

Backport of 15946 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@15960 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/gdal/field.py

@@ -33,6 +33,7 @@ class Field(GDALBase):
         # OFTReal with no precision should be an OFTInteger.
         if isinstance(self, OFTReal) and self.precision == 0:
             self.__class__ = OFTInteger
+            self._double = True
 
     def __str__(self):
         "Returns the string representation of the Field."
@@ -95,9 +96,16 @@ class Field(GDALBase):
 
 ### The Field sub-classes for each OGR Field type. ###
 class OFTInteger(Field):
+    _double = False
+
     @property
     def value(self):
         "Returns an integer contained in this field."
+        if self._double:
+            # If this is really from an OFTReal field with no precision,
+            # read as a double and cast as Python int (to prevent overflow).
+            return int(self.as_double())
+        else:
             return self.as_int()
 
     @property

django/contrib/gis/gdal/tests/test_ds.py

@@ -1,7 +1,8 @@
-import os, os.path, unittest
+import os
+import unittest
 from django.contrib.gis.gdal import DataSource, Envelope, OGRGeometry, OGRException, OGRIndexError, GDAL_VERSION
 from django.contrib.gis.gdal.field import OFTReal, OFTInteger, OFTString
-from django.contrib.gis.geometry.test_data import get_ds_file, TestDS
+from django.contrib.gis.geometry.test_data import get_ds_file, TestDS, TEST_DATA
 
 # List of acceptable data sources.
 ds_list = (TestDS('test_point', nfeat=5, nfld=3, geom='POINT', gtype=1, driver='ESRI Shapefile',
@@ -72,7 +73,7 @@ class DataSourceTest(unittest.TestCase):
                 self.assertEqual(source.nfld, len(layer.fields))
 
                 # Testing the layer's extent (an Envelope), and it's properties
-                if source.driver == 'VRT' and (GDAL_VERSION > (1, 7, 0) and GDAL_VERSION < (1, 7, 3)):
+                if source.driver == 'VRT' and (GDAL_VERSION >= (1, 7, 0) and GDAL_VERSION < (1, 7, 3)):
                     # There's a known GDAL regression with retrieving the extent
                     # of a VRT layer in versions 1.7.0-1.7.2:
                     #  http://trac.osgeo.org/gdal/ticket/3783
@@ -217,6 +218,16 @@ class DataSourceTest(unittest.TestCase):
         lyr.spatial_filter = None
         self.assertEqual(3, len(lyr))
 
+    def test07_integer_overflow(self):
+        "Testing that OFTReal fields, treated as OFTInteger, do not overflow."
+        # Using *.dbf from Census 2010 TIGER Shapefile for Texas,
+        # which has land area ('ALAND10') stored in a Real field
+        # with no precision.
+        ds = DataSource(os.path.join(TEST_DATA, 'texas.dbf'))
+        feat = ds[0][0]
+        # Reference value obtained using `ogrinfo`.
+        self.assertEqual(676586997978, feat.get('ALAND10'))
+
 def suite():
     s = unittest.TestSuite()
     s.addTest(unittest.makeSuite(DataSourceTest))