Start encoding string fields

lib/protoboeuf/codegen.rb

@@ -128,6 +128,26 @@ def encode_bool(field)
         eocode
       end
 
+      def encode_string(field)
+        tag = (field.number << 3) | field.wire_type
+        # Empty string is default value, so encodes nothing
+        <<-eocode
+        val = @#{field.name}.encode(Encoding::UTF_8).force_encoding(Encoding::ASCII_8BIT)
+        if val.bytesize > 0
+          ## encode the tag
+          buff << #{sprintf("%#04x", tag)}
+          len = val.bytesize
+          while len > 0
+            byte = len & 0x7F
+            len >>= 7
+            byte |= 0x80 if len > 0
+            buff << byte
+          end
+          buff.concat(val)
+        end
+        eocode
+      end
+
       def encode_uint64(field)
         tag = (field.number << 3) | field.wire_type
         # Zero is the default value, so it encodes zero bytes

test/message_test.rb

@@ -595,6 +595,24 @@ def test_encode_bool
     assert_equal expected, actual
   end
 
+  def test_encode_string
+    code = ProtoBoeuf.parse_string <<-eoboeuf
+syntax = "proto3";
+
+message StringValue {
+  string value = 1;
+}
+    eoboeuf
+
+    m = Module.new { class_eval code.to_ruby }
+
+    ["", "hello world", "foobar", "nöel", "some emoji 🎉👍❤️ and some math ∮𝛅x"].each do |s|
+      actual = m::StringValue.encode m::StringValue.new(value: s)
+      expected = ::Google::Protobuf::StringValue.encode(::Google::Protobuf::StringValue.new(value: s))
+      assert_equal expected, actual, "Failed during encoding of #{s.inspect}"
+    end
+  end
+
   def test_encode_uint32
     code = ProtoBoeuf.parse_string <<-eoboeuf
 syntax = "proto3";