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bpo-30228: FileIO seek() and tell() set seekable #1384

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Merged
vstinner merged 1 commit into from
May 2, 2017
Merged

bpo-30228: FileIO seek() and tell() set seekable #1384

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3 changes: 3 additions & 0 deletions Misc/NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -317,6 +317,9 @@ Extension Modules
Library
-------

- bpo-30228: The seek() and tell() methods of io.FileIO now set the internal
seekable attribute to avoid one syscall on open() (in buffered or text mode).

- bpo-30190: unittest's assertAlmostEqual and assertNotAlmostEqual provide a
better message in case of failure which includes the difference between
left and right arguments. (patch by Giampaolo Rodola')
Expand Down
36 changes: 21 additions & 15 deletions Modules/_io/fileio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,9 @@ _Py_IDENTIFIER(name);

#define PyFileIO_Check(op) (PyObject_TypeCheck((op), &PyFileIO_Type))

/* Forward declarations */
static PyObject* portable_lseek(fileio *self, PyObject *posobj, int whence);

int
_PyFileIO_closed(PyObject *self)
{
Expand All @@ -98,11 +101,6 @@ fileio_dealloc_warn(fileio *self, PyObject *source)
Py_RETURN_NONE;
}

static PyObject *
portable_lseek(int fd, PyObject *posobj, int whence);

static PyObject *portable_lseek(int fd, PyObject *posobj, int whence);

/* Returns 0 on success, -1 with exception set on failure. */
static int
internal_close(fileio *self)
Expand Down Expand Up @@ -478,7 +476,7 @@ _io_FileIO___init___impl(fileio *self, PyObject *nameobj, const char *mode,
/* 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);
PyObject *pos = portable_lseek(self, NULL, 2);
if (pos == NULL)
goto error;
Py_DECREF(pos);
Expand Down Expand Up @@ -600,13 +598,14 @@ _io_FileIO_seekable_impl(fileio *self)
if (self->fd < 0)
return err_closed();
if (self->seekable < 0) {
PyObject *pos = portable_lseek(self->fd, NULL, SEEK_CUR);
/* portable_lseek() sets the seekable attribute */
PyObject *pos = portable_lseek(self, NULL, SEEK_CUR);
assert(self->seekable >= 0);
if (pos == NULL) {
PyErr_Clear();
self->seekable = 0;
} else {
}
else {
Py_DECREF(pos);
self->seekable = 1;
}
}
return PyBool_FromLong((long) self->seekable);
Expand Down Expand Up @@ -865,9 +864,10 @@ _io_FileIO_write_impl(fileio *self, Py_buffer *b)

/* Cribbed from posix_lseek() */
static PyObject *
portable_lseek(int fd, PyObject *posobj, int whence)
portable_lseek(fileio *self, PyObject *posobj, int whence)
{
Py_off_t pos, res;
int fd = self->fd;

#ifdef SEEK_SET
/* Turn 0, 1, 2 into SEEK_{SET,CUR,END} */
Expand All @@ -884,8 +884,9 @@ portable_lseek(int fd, PyObject *posobj, int whence)
}
#endif /* SEEK_SET */

if (posobj == NULL)
if (posobj == NULL) {
pos = 0;
}
else {
if(PyFloat_Check(posobj)) {
PyErr_SetString(PyExc_TypeError, "an integer is required");
Expand All @@ -909,6 +910,11 @@ portable_lseek(int fd, PyObject *posobj, int whence)
#endif
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS

if (self->seekable < 0) {
self->seekable = (res >= 0);
}

if (res < 0)
return PyErr_SetFromErrno(PyExc_OSError);

Expand Down Expand Up @@ -943,7 +949,7 @@ _io_FileIO_seek_impl(fileio *self, PyObject *pos, int whence)
if (self->fd < 0)
return err_closed();

return portable_lseek(self->fd, pos, whence);
return portable_lseek(self, pos, whence);
}

/*[clinic input]
Expand All @@ -961,7 +967,7 @@ _io_FileIO_tell_impl(fileio *self)
if (self->fd < 0)
return err_closed();

return portable_lseek(self->fd, NULL, 1);
return portable_lseek(self, NULL, 1);
}

#ifdef HAVE_FTRUNCATE
Expand Down Expand Up @@ -992,7 +998,7 @@ _io_FileIO_truncate_impl(fileio *self, PyObject *posobj)

if (posobj == Py_None || posobj == NULL) {
/* Get the current position. */
posobj = portable_lseek(fd, NULL, 1);
posobj = portable_lseek(self, NULL, 1);
if (posobj == NULL)
return NULL;
}
Expand Down