add IO#rewind

2 files changed, 15 insertions, 0 deletions

diff --git a/mrblib/io.rb b/mrblib/io.rb
index 30eb47404..4d2fda5f3 100644
--- a/mrblib/io.rb
+++ b/mrblib/io.rb
@@ -141,6 +141,10 @@ class IO
     seek(i, SEEK_SET)
   end
 
+  def rewind
+    seek(0, SEEK_SET)
+  end
+
   def seek(i, whence = SEEK_SET)
     raise IOError if closed?
     @pos = sysseek(i, whence)
diff --git a/test/io.rb b/test/io.rb
index a5ce7e049..a9bdc3e4f 100644
--- a/test/io.rb
+++ b/test/io.rb
@@ -256,6 +256,17 @@ assert('IO#pos=, IO#seek') do
   io.closed?
 end
 
+assert('IO#rewind') do
+  fd = IO.sysopen $mrbtest_io_rfname
+  io = IO.new fd
+  assert_equal 'm', io.getc
+  assert_equal 1, io.pos
+  assert_equal 0, io.rewind
+  assert_equal 0, io.pos
+  io.close
+  io.closed?
+end
+
 assert('IO#gets') do
   fd = IO.sysopen $mrbtest_io_rfname
   io = IO.new fd