The error "DPY-2030: LOB offset must be greater than zero" is now raised

when the offset parameter to LOB.read() is zero or negative (#13).

Author: anthony-tuininga

doc/src/release_notes.rst

@@ -15,6 +15,9 @@ Thin Mode Changes
 
 #)  Added support for getthing the LOB chunk size
     (`issue 14 <https://github.com/oracle/python-oracledb/issues/14>`__).
+#)  The error `DPY-2030: LOB offset must be greater than zero` is now raised
+    when the offset parameter to :func:`LOB.read()` is zero or negative
+    (`issue 13 <https://github.com/oracle/python-oracledb/issues/13>`__).
 #)  Internally make use of the `TCP_NODELAY` socket option to remove delays
     in socket reads.
 

src/oracledb/errors.py

@@ -153,6 +153,7 @@ def _raise_from_string(exc_type: Exception, message: str) -> None:
 ERR_INVALID_POOL_PARAMS = 2027
 ERR_EXPECTING_LIST_FOR_ARRAY_VAR = 2028
 ERR_HTTPS_PROXY_REQUIRES_TCPS = 2029
+ERR_INVALID_LOB_OFFSET = 2030
 
 # error numbers that result in NotSupportedError
 ERR_TIME_NOT_SUPPORTED = 3000
@@ -306,6 +307,8 @@ def _raise_from_string(exc_type: Exception, message: str) -> None:
             'invalid connect descriptor "{data}"',
     ERR_INVALID_CONNECT_PARAMS:
             'invalid connection params',
+    ERR_INVALID_LOB_OFFSET:
+            'LOB offset must be greater than zero',
     ERR_INVALID_MAKEDSN_ARG:
             '"{name}" argument contains invalid values',
     ERR_INVALID_NUMBER:

src/oracledb/lob.py

@@ -113,6 +113,8 @@ def read(self, offset: int=1, amount: int=None) -> Union[str, bytes]:
                 amount = amount - offset + 1
             else:
                 amount = 1
+        if offset <= 0:
+            errors._raise_err(errors.ERR_INVALID_LOB_OFFSET)
         return self._impl.read(offset, amount)
 
     def setfilename(self, dir_alias: str, name: str) -> None:

tests/test_1900_lob_var.py

@@ -164,6 +164,10 @@ def __test_lob_operations(self, lob_type):
         self.assertEqual(lob.size(), 75000)
         lob.write(write_value, 75001)
         self.assertEqual(lob.size(), 75000 + len(write_value))
+        self.assertRaisesRegex(oracledb.DatabaseError, "^DPY-2030:",
+                               lob.read, 0)
+        self.assertRaisesRegex(oracledb.DatabaseError, "^DPY-2030:",
+                               lob.read, -25)
         self.assertEqual(lob.read(), long_string + write_value)
         lob.write(write_value, 1)
         self.assertEqual(lob.read(),