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gh-90102: Optimize io.FileIO.isatty() #112495

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gh-90102: Optimize io.FileIO.isatty() #112495

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b1ef1fa
gh-90102: Optimize io.FileIO.isatty()
serhiy-storchaka Nov 28, 2023
fae5fc5
Fix a race condition.
serhiy-storchaka Nov 28, 2023
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2023-11-28-17-22-03.gh-issue-90102.JrgowE.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Optimize :meth:`io.FileIO.isatty`. Only invoke the ``isatty()`` system call
for character devices and cache the result. It also makes :func:`open` a bit faster.
25 changes: 17 additions & 8 deletions Modules/_io/fileio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,7 @@ typedef struct {
unsigned int writable : 1;
unsigned int appending : 1;
signed int seekable : 2; /* -1 means unknown */
int isatty : 2; /* -1 means unknown */
unsigned int closefd : 1;
char finalizing;
unsigned int blksize;
Expand Down Expand Up @@ -195,6 +196,7 @@ fileio_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
self->writable = 0;
self->appending = 0;
self->seekable = -1;
self->isatty = -1;
self->blksize = 0;
self->closefd = 1;
self->weakreflist = NULL;
Expand Down Expand Up @@ -475,6 +477,11 @@ _io_FileIO___init___impl(fileio *self, PyObject *nameobj, const char *mode,
if (fdfstat.st_blksize > 1)
self->blksize = fdfstat.st_blksize;
#endif /* HAVE_STRUCT_STAT_ST_BLKSIZE */
#ifdef S_ISCHR
if (!S_ISCHR(fdfstat.st_mode)) {
self->isatty = 0;
}
#endif /* S_ISCHR */
}

#if defined(MS_WINDOWS) || defined(__CYGWIN__)
Expand Down Expand Up @@ -1141,16 +1148,18 @@ static PyObject *
_io_FileIO_isatty_impl(fileio *self)
/*[clinic end generated code: output=932c39924e9a8070 input=cd94ca1f5e95e843]*/
{
long res;

if (self->fd < 0)
return err_closed();
Py_BEGIN_ALLOW_THREADS
_Py_BEGIN_SUPPRESS_IPH
res = isatty(self->fd);
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS
return PyBool_FromLong(res);
if (self->isatty < 0) {
int res;
Py_BEGIN_ALLOW_THREADS
_Py_BEGIN_SUPPRESS_IPH
res = isatty(self->fd);
_Py_END_SUPPRESS_IPH
Py_END_ALLOW_THREADS
self->isatty = res;
}
return PyBool_FromLong(self->isatty);
}

#include "clinic/fileio.c.h"
Expand Down