Issue #12175: FileIO.readall() now only reads the file position and size once.
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index 141b6de..b3b9e44 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -547,14 +547,14 @@
}
static size_t
-new_buffersize(fileio *self, size_t currentsize)
+new_buffersize(fileio *self, size_t currentsize
+#ifdef HAVE_FSTAT
+ , off_t pos, off_t end
+#endif
+ )
{
#ifdef HAVE_FSTAT
- off_t pos, end;
- struct stat st;
- if (fstat(self->fd, &st) == 0) {
- end = st.st_size;
- pos = lseek(self->fd, 0L, SEEK_CUR);
+ if (end != (off_t)-1) {
/* Files claiming a size smaller than SMALLCHUNK may
actually be streaming pseudo-files. In this case, we
apply the more aggressive algorithm below.
@@ -579,9 +579,14 @@
static PyObject *
fileio_readall(fileio *self)
{
+#ifdef HAVE_FSTAT
+ struct stat st;
+ off_t pos, end;
+#endif
PyObject *result;
Py_ssize_t total = 0;
int n;
+ size_t newsize;
if (self->fd < 0)
return err_closed();
@@ -592,8 +597,23 @@
if (result == NULL)
return NULL;
+#ifdef HAVE_FSTAT
+#if defined(MS_WIN64) || defined(MS_WINDOWS)
+ pos = _lseeki64(self->fd, 0L, SEEK_CUR);
+#else
+ pos = lseek(self->fd, 0L, SEEK_CUR);
+#endif
+ if (fstat(self->fd, &st) == 0)
+ end = st.st_size;
+ else
+ end = (off_t)-1;
+#endif
while (1) {
- size_t newsize = new_buffersize(self, total);
+#ifdef HAVE_FSTAT
+ newsize = new_buffersize(self, total, pos, end);
+#else
+ newsize = new_buffersize(self, total);
+#endif
if (newsize > PY_SSIZE_T_MAX || newsize <= 0) {
PyErr_SetString(PyExc_OverflowError,
"unbounded read returned more bytes "
@@ -632,6 +652,9 @@
return NULL;
}
total += n;
+#ifdef HAVE_FSTAT
+ pos += n;
+#endif
}
if (PyBytes_GET_SIZE(result) > total) {