Author: antoine.pitrou Date: Wed Jan 27 22:48:46 2010 New Revision: 77802 Log: Issue #6939: Fix file I/O objects in the `io` module to keep the original file position when calling `truncate()`. It would previously change the file position to the given argument, which goes against the tradition of `ftruncate()` and other truncation APIs. Patch by Pascal Chambon. Modified: python/branches/release26-maint/Lib/io.py python/branches/release26-maint/Lib/test/test_fileio.py python/branches/release26-maint/Lib/test/test_io.py python/branches/release26-maint/Lib/test/test_memoryio.py python/branches/release26-maint/Misc/NEWS python/branches/release26-maint/Modules/_bytesio.c python/branches/release26-maint/Modules/_fileio.c Modified: python/branches/release26-maint/Lib/io.py ============================================================================== --- python/branches/release26-maint/Lib/io.py (original) +++ python/branches/release26-maint/Lib/io.py Wed Jan 27 22:48:46 2010 @@ -880,7 +880,7 @@ elif pos < 0: raise ValueError("negative truncate position %r" % (pos,)) del self._buffer[pos:] - return self.seek(pos) + return pos def readable(self): return True @@ -1215,8 +1215,7 @@ if pos is None: pos = self.tell() # Use seek to flush the read buffer. - self.seek(pos) - return BufferedWriter.truncate(self) + return BufferedWriter.truncate(self, pos) def read(self, n=None): if n is None: @@ -1667,8 +1666,7 @@ self.flush() if pos is None: pos = self.tell() - self.seek(pos) - return self.buffer.truncate() + return self.buffer.truncate(pos) def seek(self, cookie, whence=0): if self.closed: Modified: python/branches/release26-maint/Lib/test/test_fileio.py ============================================================================== --- python/branches/release26-maint/Lib/test/test_fileio.py (original) +++ python/branches/release26-maint/Lib/test/test_fileio.py Wed Jan 27 22:48:46 2010 @@ -197,6 +197,17 @@ f.close() self.fail("no error for invalid mode: %s" % bad_mode) + def testTruncate(self): + f = _fileio._FileIO(TESTFN, 'w') + f.write(bytes(bytearray(range(10)))) + self.assertEqual(f.tell(), 10) + f.truncate(5) + self.assertEqual(f.tell(), 10) + self.assertEqual(f.seek(0, os.SEEK_END), 5) + f.truncate(15) + self.assertEqual(f.tell(), 5) + self.assertEqual(f.seek(0, os.SEEK_END), 15) + def testTruncateOnWindows(self): def bug801631(): # SF bug <http://www.python.org/sf/801631> Modified: python/branches/release26-maint/Lib/test/test_io.py ============================================================================== --- python/branches/release26-maint/Lib/test/test_io.py (original) +++ python/branches/release26-maint/Lib/test/test_io.py Wed Jan 27 22:48:46 2010 @@ -87,6 +87,12 @@ test_support.unlink(test_support.TESTFN) def write_ops(self, f): + + self.assertEqual(f.write(b"blah."), 5) + f.truncate(0) + self.assertEqual(f.tell(), 5) + f.seek(0) + self.assertEqual(f.write(b"blah."), 5) self.assertEqual(f.seek(0), 0) self.assertEqual(f.write(b"Hello."), 6) @@ -98,8 +104,9 @@ self.assertEqual(f.write(b"h"), 1) self.assertEqual(f.seek(-1, 2), 13) self.assertEqual(f.tell(), 13) + self.assertEqual(f.truncate(12), 12) - self.assertEqual(f.tell(), 12) + self.assertEqual(f.tell(), 13) self.assertRaises(TypeError, f.seek, 0.0) def read_ops(self, f, buffered=False): @@ -144,7 +151,7 @@ self.assertEqual(f.tell(), self.LARGE + 2) self.assertEqual(f.seek(0, 2), self.LARGE + 2) self.assertEqual(f.truncate(self.LARGE + 1), self.LARGE + 1) - self.assertEqual(f.tell(), self.LARGE + 1) + self.assertEqual(f.tell(), self.LARGE + 2) self.assertEqual(f.seek(0, 2), self.LARGE + 1) self.assertEqual(f.seek(-1, 2), self.LARGE) self.assertEqual(f.read(2), b"x") Modified: python/branches/release26-maint/Lib/test/test_memoryio.py ============================================================================== --- python/branches/release26-maint/Lib/test/test_memoryio.py (original) +++ python/branches/release26-maint/Lib/test/test_memoryio.py Wed Jan 27 22:48:46 2010 @@ -32,7 +32,7 @@ self.assertEqual(f.seek(0), 0) self.assertEqual(f.write(t("h")), 1) self.assertEqual(f.truncate(12), 12) - self.assertEqual(f.tell(), 12) + self.assertEqual(f.tell(), 1) def test_write(self): buf = self.buftype("hello world\n") @@ -83,7 +83,8 @@ # truncate() accepts long objects self.assertEqual(memio.truncate(4L), 4) self.assertEqual(memio.getvalue(), buf[:4]) - self.assertEqual(memio.tell(), 4) + self.assertEqual(memio.tell(), 6) + memio.seek(0, 2) memio.write(buf) self.assertEqual(memio.getvalue(), buf[:4] + buf) pos = memio.tell() Modified: python/branches/release26-maint/Misc/NEWS ============================================================================== --- python/branches/release26-maint/Misc/NEWS (original) +++ python/branches/release26-maint/Misc/NEWS Wed Jan 27 22:48:46 2010 @@ -53,6 +53,11 @@ Library ------- +- Issue #6939: Fix file I/O objects in the `io` module to keep the original + file position when calling `truncate()`. It would previously change the + file position to the given argument, which goes against the tradition of + ftruncate() and other truncation APIs. Patch by Pascal Chambon. + - Issue #7792: Registering non-classes to ABCs raised an obscure error. - Issue #7773: Fix an UnboundLocalError in platform.linux_distribution() when Modified: python/branches/release26-maint/Modules/_bytesio.c ============================================================================== --- python/branches/release26-maint/Modules/_bytesio.c (original) +++ python/branches/release26-maint/Modules/_bytesio.c Wed Jan 27 22:48:46 2010 @@ -445,7 +445,6 @@ if (resize_buffer(self, size) < 0) return NULL; } - self->pos = size; return PyInt_FromSsize_t(size); } Modified: python/branches/release26-maint/Modules/_fileio.c ============================================================================== --- python/branches/release26-maint/Modules/_fileio.c (original) +++ python/branches/release26-maint/Modules/_fileio.c Wed Jan 27 22:48:46 2010 @@ -646,8 +646,10 @@ static PyObject * fileio_truncate(PyFileIOObject *self, PyObject *args) { - PyObject *posobj = NULL; + PyObject *posobj = NULL; /* the new size wanted by the user */ +#ifndef MS_WINDOWS Py_off_t pos; +#endif int ret; int fd; @@ -662,56 +664,86 @@ if (posobj == Py_None || posobj == NULL) { /* Get the current position. */ - posobj = portable_lseek(fd, NULL, 1); - if (posobj == NULL) + posobj = portable_lseek(fd, NULL, 1); + if (posobj == NULL) return NULL; - } - else { - /* Move to the position to be truncated. */ - posobj = portable_lseek(fd, posobj, 0); - } - -#if defined(HAVE_LARGEFILE_SUPPORT) - pos = PyLong_AsLongLong(posobj); -#else - pos = PyLong_AsLong(posobj); -#endif - if (PyErr_Occurred()) - return NULL; + } + else { + Py_INCREF(posobj); + } #ifdef MS_WINDOWS /* MS _chsize doesn't work if newsize doesn't fit in 32 bits, so don't even try using it. */ { + PyObject *oldposobj, *tempposobj; HANDLE hFile; + + /* we save the file pointer position */ + oldposobj = portable_lseek(fd, NULL, 1); + if (oldposobj == NULL) { + Py_DECREF(posobj); + return NULL; + } + + /* we then move to the truncation position */ + tempposobj = portable_lseek(fd, posobj, 0); + if (tempposobj == NULL) { + Py_DECREF(oldposobj); + Py_DECREF(posobj); + return NULL; + } + Py_DECREF(tempposobj); /* Truncate. Note that this may grow the file! */ Py_BEGIN_ALLOW_THREADS errno = 0; hFile = (HANDLE)_get_osfhandle(fd); - ret = hFile == (HANDLE)-1; + ret = hFile == (HANDLE)-1; /* testing for INVALID_HANDLE value */ if (ret == 0) { ret = SetEndOfFile(hFile) == 0; if (ret) errno = EACCES; } Py_END_ALLOW_THREADS + + /* we restore the file pointer position in any case */ + tempposobj = portable_lseek(fd, oldposobj, 0); + Py_DECREF(oldposobj); + if (tempposobj == NULL) { + Py_DECREF(posobj); + return NULL; + } + Py_DECREF(tempposobj); } #else + +#if defined(HAVE_LARGEFILE_SUPPORT) + pos = PyLong_AsLongLong(posobj); +#else + pos = PyLong_AsLong(posobj); +#endif + if (PyErr_Occurred()){ + Py_DECREF(posobj); + return NULL; + } + Py_BEGIN_ALLOW_THREADS errno = 0; ret = ftruncate(fd, pos); Py_END_ALLOW_THREADS + #endif /* !MS_WINDOWS */ if (ret != 0) { + Py_DECREF(posobj); PyErr_SetFromErrno(PyExc_IOError); return NULL; } return posobj; } -#endif +#endif /* HAVE_FTRUNCATE */ static char * mode_string(PyFileIOObject *self)