commit 357bad7101df196d7f4ea3dc6ed9a6436afb022c
author Louie Lu <louie.lu@hopebaytech.com> Fri Feb 24 11:59:49 2017 +0800
committer Raymond Hettinger <rhettinger@users.noreply.github.com> Thu Feb 23 22:59:49 2017 -0500
tree a733b279089ee8202980a144ea40ba447d711ff1
parent abb3b8ad94d699c8560d94ee9bac9c917b382abe

bpo-29634: Reduce deque repeat execution when maxlen exist and size is not 1 (#255) (#255)

Modules/_collectionsmodule.c

diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 8615bf1..44e9e11 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -731,6 +731,10 @@
     if (seq == NULL)
         return seq;
 
+    /* Reduce the number of repetitions when maxlen would be exceeded */
+    if (deque->maxlen >= 0 && n * size > deque->maxlen)
+        n = (deque->maxlen + size - 1) / size;
+
     for (i = 0 ; i < n-1 ; i++) {
         rv = deque_extend(deque, seq);
         if (rv == NULL) {