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Issue #6939: Fix file I/O objects in the io module to keep the original

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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.
This commit is contained in:
Antoine Pitrou 2010-01-27 21:48:46 +00:00
parent f333014467
commit ca5a06aaa9
7 changed files with 81 additions and 28 deletions
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1
Modules/_bytesio.c
View file

@ -445,7 +445,6 @@ bytesio_truncate(BytesIOObject *self, PyObject *args)
if (resize_buffer(self, size) < 0)
return NULL;
}
self->pos = size;
return PyInt_FromSsize_t(size);
}

68
Modules/_fileio.c
View file

@ -646,8 +646,10 @@ fileio_tell(PyFileIOObject *self, PyObject *args)
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 @@ fileio_truncate(PyFileIOObject *self, PyObject *args)
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)