RUBY-947 force binary encoding for message fields

lib/mongo/protocol/serializers.rb

@@ -74,7 +74,7 @@ module CString
         # @param value [String] The string to be serialized.
         # @return [String] Buffer with serialized value.
         def self.serialize(buffer, value)
-          buffer << value
+          buffer << value.force_encoding(BSON::BINARY)
           buffer << NULL
         end
       end

lib/mongo/server/connection.rb

@@ -188,7 +188,7 @@ def setup_authentication!
         end
       end
 
-      def write(messages, buffer = '')
+      def write(messages, buffer = ''.force_encoding(BSON::BINARY))
         start_size = 0
         messages.each do |message|
           message.serialize(buffer, max_bson_object_size)

spec/mongo/protocol/query_spec.rb

@@ -220,6 +220,19 @@
       it 'serializes the namespace' do
         expect(field).to be_cstring(ns)
       end
+
+      context 'when the namespace contains unicode characters' do
+        let(:field) { bytes[20..40] }
+
+        let(:coll) do
+          'områder'
+        end
+
+        it 'serializes the namespace' do
+          expect(field).to be_cstring(ns)
+        end
+
+      end
     end
 
     describe 'skip' do

spec/support/matchers.rb

@@ -20,7 +20,7 @@
 
 RSpec::Matchers.define :be_cstring do |string|
   match do |actual|
-    actual == "#{string}\0"
+    actual == "#{string.force_encoding(BSON::BINARY)}\0"
   end
 end