From c37b1222fb733f6de0bba6d85014e27b76963d65 Mon Sep 17 00:00:00 2001
From: Cody Maloney <cmaloney@theoreticalchaos.com>
Date: Thu, 30 Jan 2025 21:40:19 -0800
Subject: [PATCH] Revert "gh-129005: _pyio.BufferedIO remove copy on readall
 (#129454)"

This reverts commit e1c4ba928852eac0b0e0bded1c314e3e36975286.
---
 Lib/_pyio.py                                                   | 3 ---
 .../Library/2025-01-29-00-00-01.gh-issue-129005.aV_3O8.rst     | 2 --
 2 files changed, 5 deletions(-)
 delete mode 100644 Misc/NEWS.d/next/Library/2025-01-29-00-00-01.gh-issue-129005.aV_3O8.rst

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 755e0258770891..76a27910da4d5f 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -1062,9 +1062,6 @@ def _read_unlocked(self, n=None):
                 if chunk is None:
                     return buf[pos:] or None
                 else:
-                    # Avoid slice + copy if there is no data in buf
-                    if not buf:
-                        return chunk
                     return buf[pos:] + chunk
             chunks = [buf[pos:]]  # Strip the consumed bytes.
             current_size = 0
diff --git a/Misc/NEWS.d/next/Library/2025-01-29-00-00-01.gh-issue-129005.aV_3O8.rst b/Misc/NEWS.d/next/Library/2025-01-29-00-00-01.gh-issue-129005.aV_3O8.rst
deleted file mode 100644
index 48ee57109be2ff..00000000000000
--- a/Misc/NEWS.d/next/Library/2025-01-29-00-00-01.gh-issue-129005.aV_3O8.rst
+++ /dev/null
@@ -1,2 +0,0 @@
-:mod:`!_pyio`: Remove an unnecessary copy when ``_pyio.BufferedReader.read()``
-is called to read all data from a file and has no data already in buffer.