bpo-30228: FileIO seek() and tell() set seekable (#1384)
FileIO.seek() and FileIO.tell() method now set the internal seekable
attribute to avoid one syscall on open() (in buffered or text mode).
The seekable property is now also more reliable since its value is
set correctly on memory allocation failure.
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index 922db3e..a09c39f7 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -73,6 +73,9 @@
#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)
{
@@ -98,11 +101,6 @@
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)
@@ -478,7 +476,7 @@
/* 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);
@@ -600,13 +598,14 @@
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);
@@ -865,9 +864,10 @@
/* 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} */
@@ -884,8 +884,9 @@
}
#endif /* SEEK_SET */
- if (posobj == NULL)
+ if (posobj == NULL) {
pos = 0;
+ }
else {
if(PyFloat_Check(posobj)) {
PyErr_SetString(PyExc_TypeError, "an integer is required");
@@ -909,6 +910,11 @@
#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);
@@ -943,7 +949,7 @@
if (self->fd < 0)
return err_closed();
- return portable_lseek(self->fd, pos, whence);
+ return portable_lseek(self, pos, whence);
}
/*[clinic input]
@@ -961,7 +967,7 @@
if (self->fd < 0)
return err_closed();
- return portable_lseek(self->fd, NULL, 1);
+ return portable_lseek(self, NULL, 1);
}
#ifdef HAVE_FTRUNCATE
@@ -992,7 +998,7 @@
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;
}