From 2229a2aa0fcd76bd5498417aca934d6ec7a211ef Mon Sep 17 00:00:00 2001
From: Tomoyuki Sahara <tsahara@iij.ad.jp>
Date: Fri, 30 Sep 2016 16:27:11 +0900
Subject: reimplement #eof.  fixes #66.

---
 mrblib/io.rb | 27 ++++++---------------------
 test/io.rb   | 25 ++++++++++++++++++++-----
 2 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/mrblib/io.rb b/mrblib/io.rb
index 4bcf4f800..8408aea87 100644
--- a/mrblib/io.rb
+++ b/mrblib/io.rb
@@ -133,20 +133,12 @@ class IO
   end
 
   def eof?
-    return true if @buf && @buf.size > 0
-
-    ret = false
-    char = ''
-
     begin
-      char = sysread(1)
-    rescue EOFError => e
-      ret = true
-    ensure
-      _ungets(char)
+      buf = _read_buf
+      return buf.size == 0
+    rescue EOFError
+      return true
     end
-
-    ret
   end
   alias_method :eof, :eof?
 
@@ -176,24 +168,17 @@ class IO
     @buf = sysread(BUF_SIZE)
   end
 
-  def _ungets(substr)
+  def ungetc(substr)
     raise TypeError.new "expect String, got #{substr.class}" unless substr.is_a?(String)
-    raise IOError if @pos == 0 || @pos.nil?
     @pos -= substr.size
     if @buf.empty?
-      @buf = substr
+      @buf = substr.dup
     else
       @buf = substr + @buf
     end
     nil
   end
 
-  def ungetc(char)
-    raise IOError if @pos == 0 || @pos.nil?
-    _ungets(char)
-    nil
-  end
-
   def read(length = nil)
     unless length.nil?
       unless length.is_a? Fixnum
diff --git a/test/io.rb b/test/io.rb
index 1b0a2d52e..c3f78da7e 100644
--- a/test/io.rb
+++ b/test/io.rb
@@ -70,14 +70,29 @@ end
 #assert('IO#each_line', '15.2.20.5.5') do
 
 assert('IO#eof?', '15.2.20.5.6') do
+  if false  # XXX: not implemented yet
+    io = IO.new(IO.sysopen($mrbtest_io_wfname, 'w'), 'w')
+    assert_raise(IOError) do
+      io.eof?
+    end
+  end
+
+  # empty file
+  io = IO.open(IO.sysopen($mrbtest_io_wfname, 'w'), 'w')
+  io.close
+  io = IO.open(IO.sysopen($mrbtest_io_wfname, 'r'), 'r')
+  assert_true io.eof?
+  io.close
+
+  # nonempty file
   io = IO.new(IO.sysopen($mrbtest_io_rfname))
-  $mrbtest_io_msg.each_char { |ch|
-    # XXX
-    #assert_false io.eof?
-    io.getc
-  }
+  assert_false io.eof?
+  io.readchar
+  assert_false io.eof?
+  io.read
   assert_true io.eof?
   io.close
+
   true
 end
 
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