Merged revisions 68835 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r68835 | antoine.pitrou | 2009-01-21 01:45:36 +0100 (mer., 21 janv. 2009) | 6 lines

  Issue #5008: When a file is opened in append mode with the new IO library,
  do an explicit seek to the end of file (so that e.g. tell() returns the
  file size rather than 0). This is consistent with the behaviour of the
  traditional 2.x file object.
........

3 files changed, 29 insertions, 0 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 967018e..f0b38b6 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -232,6 +232,17 @@ class IOTest(unittest.TestCase):
             else:
                 self.fail("1/0 didn't raise an exception")
 
+    # issue 5008
+    def test_append_mode_tell(self):
+        with io.open(test_support.TESTFN, "wb") as f:
+            f.write(b"xxx")
+        with io.open(test_support.TESTFN, "ab", buffering=0) as f:
+            self.assertEqual(f.tell(), 3)
+        with io.open(test_support.TESTFN, "ab") as f:
+            self.assertEqual(f.tell(), 3)
+        with io.open(test_support.TESTFN, "a") as f:
+            self.assert_(f.tell() > 0)
+
     def test_destructor(self):
         record = []
         class MyFileIO(io.FileIO):
diff --git a/Misc/NEWS b/Misc/NEWS
index 30c3a0f..ca5eef1 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -76,6 +76,11 @@ Core and Builtins
 Library
 -------
 
+- Issue #5008: When a file is opened in append mode with the new IO library,
+  do an explicit seek to the end of file (so that e.g. tell() returns the
+  file size rather than 0). This is consistent with the behaviour of the
+  traditional 2.x file object.
+
 - Issue #3997: zipfiles generated with more than 65536 files could not be
   opened with other applications.
 
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index 0f09ecd..fbe4189 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -41,6 +41,9 @@ PyTypeObject PyFileIO_Type;
 
 #define PyFileIO_Check(op) (PyObject_TypeCheck((op), &PyFileIO_Type))
 
+static PyObject *
+portable_lseek(int fd, PyObject *posobj, int whence);
+
 /* Returns 0 on success, errno (which is < 0) on failure. */
 static int
 internal_close(PyFileIOObject *self)
@@ -296,6 +299,16 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 			goto error;
 	}
 
+	if (append) {
+		/* For consistent behaviour, we explicitly seek to the
+		   end of file (otherwise, it might be done only on the
+		   first write()). */
+		PyObject *pos = portable_lseek(self->fd, NULL, 2);
+		if (pos == NULL)
+			goto error;
+		Py_DECREF(pos);
+	}
+
 	goto done;
 
  error: