Ensure that binary buffer is used at all times.

lib/openssl/buffering.rb

@@ -22,6 +22,29 @@
 module OpenSSL::Buffering
   include Enumerable
 
+  # A buffer which will retain binary encoding.
+  class Buffer < String
+    BINARY = Encoding::BINARY
+
+    def initialize
+      super
+
+      force_encoding(BINARY)
+    end
+
+    def << string
+      if string.encoding == BINARY
+        super(string)
+      else
+        super(string.b)
+      end
+
+      return self
+    end
+
+    alias concat <<
+  end
+
   ##
   # The "sync mode" of the SSLSocket.
   #
@@ -40,7 +63,7 @@ module OpenSSL::Buffering
   def initialize(*)
     super
     @eof = false
-    @rbuffer = String.new
+    @rbuffer = Buffer.new
     @sync = @io.sync
   end
 
@@ -312,7 +335,7 @@ def eof?
   # buffer is flushed to the underlying socket.
 
   def do_write(s)
-    @wbuffer = String.new unless defined? @wbuffer
+    @wbuffer = Buffer.new unless defined? @wbuffer
     @wbuffer << s
     @wbuffer.force_encoding(Encoding::BINARY)
     @sync ||= false
@@ -398,7 +421,7 @@ def <<(s)
   # See IO#puts for full details.
 
   def puts(*args)
-    s = String.new
+    s = Buffer.new
     if args.empty?
       s << "\n"
     end
@@ -416,7 +439,7 @@ def puts(*args)
   # See IO#print for full details.
 
   def print(*args)
-    s = String.new
+    s = Buffer.new
     args.each{ |arg| s << arg.to_s }
     do_write(s)
     nil

test/test_buffering.rb

@@ -10,7 +10,7 @@ class IO
     attr_accessor :sync
 
     def initialize
-      @io = String.new
+      @io = Buffer.new
       def @io.sync
         true
       end
@@ -41,6 +41,13 @@ def setup
     @io = IO.new
   end
 
+  def test_encoding
+    @io.write '😊'
+    @io.flush
+
+    assert_equal @io.string.encoding, Encoding::BINARY
+  end
+
   def test_flush
     @io.write 'a'