From dd89a618b3d8ffce3f31f45d4e628cad34fd46b6 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Tue, 13 Apr 2021 07:24:56 +0900
Subject: mruby-io: fix `IO#ungetbyte`; ref #5389

- remove `Integer#chr` (thus `mruby-sting-ext`) dependency
- fix the behavior when `c.is_a? String`
- fix the behavior when `c > 255`
---
 mrbgems/mruby-io/mrblib/io.rb | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/mrbgems/mruby-io/mrblib/io.rb b/mrbgems/mruby-io/mrblib/io.rb
index a60562846..9ce49e51a 100644
--- a/mrbgems/mruby-io/mrblib/io.rb
+++ b/mrbgems/mruby-io/mrblib/io.rb
@@ -184,9 +184,15 @@ class IO
     nil
   end
 
-  def ungetbyte(substr)
-    substr = substr.chr if substr.is_a? Integer
-    ungetc substr
+  def ungetbyte(c)
+    if c.is_a? String
+      c = c.getbyte(0)
+    else
+      c &= 0xff
+    end
+    s = " "
+    s.setbyte(0,c)
+    ungetc s
   end
 
   def read(length = nil, outbuf = "")
-- 
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