* io.c (rb_io_s_binwrite): use mode "r+b" instead of "ab" to handle

  offset correctly.  [ruby-core:28517]

* test/ruby/test_io.rb: use assert_equal instead of assert.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@26826 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/io.c b/io.c
index 3c64944c76..dcf411c433 100644
--- a/io.c
+++ b/io.c
@@ -8025,7 +8025,7 @@ rb_io_s_binwrite(int argc, VALUE *argv, VALUE io)
     rb_scan_args(argc, argv, "21", NULL, &warg.str, &offset);
     if (!NIL_P(offset)) {
 	NUM2OFFT(offset);
-	mode = "ab:ASCII-8BIT";
+	mode = "r+b:ASCII-8BIT";
     }
     else {
 	mode = "wb:ASCII-8BIT";