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 489e560..6265258 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -233,6 +233,17 @@ 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(support.TESTFN, "wb") as f:
+            f.write(b"xxx")
+        with io.open(support.TESTFN, "ab", buffering=0) as f:
+            self.assertEqual(f.tell(), 3)
+        with io.open(support.TESTFN, "ab") as f:
+            self.assertEqual(f.tell(), 3)
+        with io.open(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 35506cb..b92048c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -137,6 +137,11 @@ 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 #5013: Fixed a bug in FileHandler which occurred when the delay
   parameter was set.
 
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index 5b840c0..7a71837 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -55,6 +55,9 @@ 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, -1 with exception set on failure. */
 static int
 internal_close(PyFileIOObject *self)
@@ -315,6 +318,16 @@ 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: