From b03a44c4ac506f02a164fb5d5e9ce1fdacd546de Mon Sep 17 00:00:00 2001
From: watson1978 <watson1978@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 27 Oct 2017 14:55:03 +0000
Subject: [PATCH] string.c: Improve String#prepend performance if only one
 argument is given
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* string.c (rb_str_prepend_multi): Prepend the string without generating
    temporary String object if only one argument is given.
	This is very similar with https://github.com/ruby/ruby/pull/1634

	String#prepend -> 47.5 % up

    [Fix GH-1670] [ruby-core:82195] [Bug #13773]

* Before
      String#prepend      1.517M (± 1.8%) i/s -      7.614M in   5.019819s

* After
      String#prepend      2.236M (± 3.4%) i/s -     11.234M in   5.029716s

* Test code
require 'benchmark/ips'

Benchmark.ips do |x|
  x.report "String#prepend" do |loop|
    loop.times { "!".prepend("hello") }
  end
end

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60480 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 string.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/string.c b/string.c
index 050ef27d9b..e9204fc233 100644
--- a/string.c
+++ b/string.c
@@ -3077,7 +3077,10 @@ rb_str_prepend_multi(int argc, VALUE *argv, VALUE str)
 {
     str_modifiable(str);
 
-    if (argc > 0) {
+    if (argc == 1) {
+	rb_str_update(str, 0L, 0L, argv[0]);
+    }
+    else if (argc > 1) {
 	int i;
 	VALUE arg_str = rb_str_tmp_new(0);
 	rb_enc_copy(arg_str, str);