Option to disable key and value normalization.

rasterio/_env.pyx

@@ -59,12 +59,17 @@ def driver_count():
     return GDALGetDriverCount() + OGRGetDriverCount()
 
 
-cpdef get_gdal_config(key):
+cpdef get_gdal_config(key, normalize=True):
     """Get the value of a GDAL configuration option"""
-    key = key.upper().encode('utf-8')
+    if normalize:
+        key = key.upper()
+
+    key = key.encode('utf-8')
     val = CPLGetConfigOption(<const char *>key, NULL)
     if not val:
         return None
+    elif not normalize:
+        return val
     else:
         if val == u'ON':
             return True
@@ -74,19 +79,23 @@ cpdef get_gdal_config(key):
             return val
 
 
-cpdef set_gdal_config(key, val):
+cpdef set_gdal_config(key, val, normalize=True):
     """Set a GDAL configuration option's value"""
-    key = key.upper().encode('utf-8')
+    if normalize:
+        key = key.upper()
+    key = key.encode('utf-8')
     if isinstance(val, string_types):
         val = val.encode('utf-8')
-    else:
+    elif normalize:
         val = ('ON' if val else 'OFF').encode('utf-8')
     CPLSetConfigOption(<const char *>key, <const char *>val)
 
 
-cpdef del_gdal_config(key):
+cpdef del_gdal_config(key, normalize=True):
     """Delete a GDAL configuration option"""
-    key = key.upper().encode('utf-8')
+    if normalize:
+        key = key.upper()
+    key = key.encode('utf-8')
     CPLSetConfigOption(<const char *>key, NULL)
 
 

tests/test_env.py

@@ -41,6 +41,17 @@ def test_gdal_config_accessers():
     assert get_gdal_config('foo') is None
 
 
+def test_gdal_config_accessors_no_normalize():
+    """Disables casting keys to upper case and normalizing values to boolean
+    Python values.
+    """
+    assert get_gdal_config('foo') is None
+    set_gdal_config('foo', 'ON', normalize=False)
+    assert get_gdal_config('foo', normalize=False) == 'ON'
+    del_gdal_config('foo', normalize=False)
+    assert get_gdal_config('foo', normalize=False) is None
+
+
 # The 'gdalenv' fixture ensures that gdal configuration is deleted
 # at the end of the test, making tests as isolates as GDAL allows.