From 65524a622e0e4d10b8498c7b8e1478239f5f478c Mon Sep 17 00:00:00 2001
From: StealthCentral <35307184+StealthCentral@users.noreply.github.com>
Date: Wed, 10 Jan 2018 11:56:45 -0600
Subject: [PATCH] Update shutil.py

improved copyfileobj to use less memory
---
 Lib/shutil.py | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/Lib/shutil.py b/Lib/shutil.py
index bd4760f1a7409d5..39cf3c6d6123e85 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -75,11 +75,18 @@ class RegistryError(Exception):
 
 def copyfileobj(fsrc, fdst, length=16*1024):
     """copy data from file-like object fsrc to file-like object fdst"""
+    buf = memoryview(bytearray(length))
+    # localize
+    readinto = fsrc.readinto
+    write = fdst.write
+    # run loop
     while 1:
-        buf = fsrc.read(length)
-        if not buf:
+        recv_len = readinto(buf)
+        if recv_len < length:
+            # write remaining content if any.
+            write(buf[:recv_len])
             break
-        fdst.write(buf)
+        write(buf)
 
 def _samefile(src, dst):
     # Macintosh, Unix.