Add support for serialization of basic features

reflection.fbs is only supported for now. monster_test.fbs isn't
supported yet.

Author: kou

lib/flatbuffers.rb

@@ -12,9 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+require_relative "flatbuffers/serializer"
 require_relative "flatbuffers/enum"
 require_relative "flatbuffers/flags"
 require_relative "flatbuffers/struct"
-require_relative "flatbuffers/table"
+require_relative "flatbuffers/root_table"
 require_relative "flatbuffers/union"
 require_relative "flatbuffers/version"

lib/flatbuffers/data_definable.rb

@@ -0,0 +1,26 @@
+# Copyright 2025 Sutou Kouhei <[email protected]>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module FlatBuffers
+  module DataDefinable
+    def define_data
+      ::Struct.new(*self::FIELDS.collect(&:name)) do
+        members.each do |member|
+          next unless member.end_with?("?")
+          alias_method :"#{member.to_s.delete_suffix("?")}=", :"#{member}="
+        end
+      end
+    end
+  end
+end

lib/flatbuffers/field.rb

@@ -0,0 +1,30 @@
+# Copyright 2025 Sutou Kouhei <[email protected]>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require_relative "view"
+
+module FlatBuffers
+  class Field
+    attr_reader :name
+    attr_reader :offset
+    attr_reader :base_type
+    attr_reader :index
+    def initialize(name, offset, base_type)
+      @name = name
+      @offset = offset
+      @base_type = base_type
+      @index = View::VTable.compute_field_index(@offset)
+    end
+  end
+end

lib/flatbuffers/generator.rb

@@ -338,14 +338,99 @@ def generate_object(writer, object)
       start_modules(writer, namespaces)
 
       if object.struct?
+        is_root_table = false
         parent = "::FlatBuffers::Struct"
       else
-        parent = "::FlatBuffers::Table"
+        is_root_table = (object.name == @schema.root_table&.name)
+        if is_root_table
+          parent = "::FlatBuffers::RootTable"
+        else
+          parent = "::FlatBuffers::Table"
+        end
       end
       generate_documentation(writer, object.documentation)
       writer << "class #{to_class_name(name)} < #{parent}"
       writer.indent
 
+      if is_root_table
+        writer << "class << self"
+        writer.indent
+
+        writer << "def file_identifier"
+        writer.indent
+        writer << to_ruby_code(@schema.file_ident)
+        writer.end
+        writer << ""
+        writer << "def file_extension"
+        writer.indent
+        writer << to_ruby_code(@schema.file_ext)
+        writer.end
+
+        writer.end
+        writer << ""
+      end
+
+      generate_object_fields(writer, object)
+
+      writer << "Data = define_data"
+      writer << ""
+
+      generate_object_methods(writer, object, namespaces)
+
+      writer.end # class
+
+      end_modules(writer, namespaces)
+    end
+
+    def generate_object_fields(writer, object)
+      writer << "FIELDS = ["
+      writer.indent
+
+      offset_sorted_fields = object.fields&.sort_by(&:offset)
+      offset_sorted_fields&.each do |field|
+        # Skip writing deprecated fields altogether.
+        next if field.deprecated?
+
+        method_name = to_method_name(field.name)
+        type = field.type
+        base_type = type.base_type
+        if base_type == Reflection::BaseType::BOOL
+          method_name = "#{method_name}?".delete_prefix("is_")
+        end
+        ruby_offset = to_ruby_code(field.offset)
+        case base_type
+        when Reflection::BaseType::OBJ
+          object = @schema.objects[type.index]
+          *object_namespaces, object_name = denamespace(object.name)
+          klass = to_absolute_class_name(@outer_namespaces,
+                                         object_namespaces,
+                                         object_name)
+          ruby_base_type = to_ruby_code(klass)
+        when Reflection::BaseType::VECTOR
+          element_base_type = type.element
+          if element_base_type == Reflection::BaseType::OBJ
+            object = @schema.objects[type.index]
+            *object_namespaces, object_name = denamespace(object.name)
+            klass = to_absolute_class_name(@outer_namespaces,
+                                           object_namespaces,
+                                           object_name)
+            ruby_base_type = "[#{to_ruby_code(klass)}]"
+          else
+            ruby_base_type = "[:#{to_lower_snake_case(element_base_type.name)}]"
+          end
+        else
+          ruby_base_type = ":#{to_lower_snake_case(base_type.name)}"
+        end
+        writer << ("::FlatBuffers::Field.new(" +
+                   ":#{method_name}, #{ruby_offset}, #{ruby_base_type}),")
+      end
+
+      writer.unindent
+      writer << "]"
+      writer << ""
+    end
+
+    def generate_object_methods(writer, object, namespaces)
       n_processed_fields = 0
       object.fields&.each do |field|
         # Skip writing deprecated fields altogether.
@@ -474,10 +559,6 @@ def generate_object(writer, object)
 
         n_processed_fields += 1
       end
-
-      writer.end # class
-
-      end_modules(writer, namespaces)
     end
 
     def generate_documentation(writer, documentation)

lib/flatbuffers/reflection/schema.rb

@@ -13,7 +13,7 @@
 
 module FlatBuffers
   module Reflection
-    class Schema < ::FlatBuffers::Table
+    class Schema < ::FlatBuffers::RootTable
       def advanced_features
         field_offset = @view.unpack_virtual_offset(16)
         if field_offset.zero?

lib/flatbuffers/root_table.rb

@@ -0,0 +1,57 @@
+# Copyright 2025 Sutou Kouhei <[email protected]>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require_relative "serializer"
+require_relative "table"
+require_relative "view"
+
+module FlatBuffers
+  class RootTable < Table
+    class << self
+      def save(base_name, data)
+        name = "#{base_name}.#{file_extension}"
+        File.open(name, "wb") do |output|
+          output.print(serialize(data))
+        end
+      end
+
+      def serialize(data, table_serializer=nil)
+        if table_serializer
+          # Referenced table
+          super(data, table_serializer)
+        else
+          # Root table
+          serializer = Serializer.new(file_identifier)
+          serializer.start_table do |table_serializer|
+            super(data, table_serializer)
+          end
+        end
+      end
+    end
+
+    def initialize(input)
+      if input.is_a?(View)
+        # Referenced table
+        super
+      else
+        # Root table
+        if input.is_a?(String)
+          input = IO::Buffer.for(input)
+        end
+        offset = input.get_value(:u32, 0)
+        super(View.new(input, offset, have_vtable: true))
+      end
+    end
+  end
+end