Add basic code generation

This just walks the AST returned by the parser and generates code

Author: tenderlove

lib/protobuff/codegen.rb

@@ -0,0 +1,157 @@
+require "erb"
+
+module ProtoBuff
+  class CodeGen
+    CLASS_TEMPLATE = ERB.new(<<-ruby, trim_mode: '-')
+class <%= message.name %>
+  <%- if message.fields.length > 0 -%>
+  attr_accessor <%= message.fields.map { |f| ":" + f.name }.join(", ") %>
+
+  def self.decode(buff)
+    decode_from(ProtoBuff::Decoder.new(buff), buff.bytesize)
+  end
+
+  def self.decode_from(decoder, len)
+    obj = <%= message.name %>.new
+
+    while true
+      break if decoder.index >= len
+
+      tag = decoder.pull_tag
+      <%- message.fields.each_with_index do |field, idx| -%>
+      <%= idx == 0 ? "if" : "elsif" %> tag == <%= tag_for_field(field, field.number) %>
+        <%= decode_code(field) %>
+      <%- end -%>
+      else
+        raise
+      end
+    end
+
+    obj
+  end
+
+  def initialize(<%= initialize_signature(message) %>)
+  <%- for field in message.fields -%>
+    @<%= field.name %> = <%= field.name %>
+  <%- end -%>
+  <%- end -%>
+  end
+end
+    ruby
+
+    PACKED_REPEATED = ERB.new(<<ruby)
+        idx = 0
+        goal = decoder.index + decoder.pull_uint64
+        list = obj.<%= field.name %>
+        while true
+          break if decoder.index >= goal
+          list[idx] = <%= decode_subtype(field) %>
+          idx += 1
+        end
+ruby
+
+    def initialize(ast)
+      @ast = ast
+    end
+
+    def to_ruby
+      @ast.messages.map { |message|
+        CLASS_TEMPLATE.result(binding)
+      }.join
+    end
+
+    private
+
+    def default_for(field)
+      case field.qualifier
+      when :optional
+        case field.type
+        when "string"
+          '""'
+        when "uint64", "int32", "sint32", "uint32"
+          0
+        when "bool"
+          false
+        when /[A-Z]+\w+/ # FIXME: this doesn't seem right...
+          'nil'
+        else
+          raise "Unknown field type #{field.type}"
+        end
+      when :repeated
+        "[]"
+      else
+        raise "Unknown qualifier #{field.type}"
+      end
+    end
+
+    def initialize_signature(msg)
+      msg.fields.map { |f| "#{f.name}: #{default_for(f)}" }.join(", ")
+    end
+
+    def tag_for_field(field, idx)
+      sprintf("%#02x", (idx << 3 | wire_type(field)))
+    end
+
+    VARINT = 0
+    I64 = 1
+    LEN = 2
+    I32 = 5
+
+    def wire_type(field)
+      case field.qualifier
+      when :optional
+        case field.type
+        when "string"
+          LEN
+        when "int32", "uint64", "bool", "sint32", "uint32"
+          VARINT
+        when /[A-Z]+\w+/ # FIXME: this doesn't seem right...
+          LEN
+        else
+          raise "Unknown wire type for field #{field.type}"
+        end
+      when :repeated
+        LEN
+      else
+        raise "Unknown qualifier #{field.qualifier}"
+      end
+    end
+
+    def decode_subtype(field)
+      case field.type
+      when "string"
+        "decoder.pull_string"
+      when "uint64"
+        "decoder.pull_uint64"
+      when "int32"
+        "decoder.pull_int32"
+      when "uint32"
+        "decoder.pull_uint32"
+      when "sint32"
+        "decoder.pull_sint32"
+      when "bool"
+        "decoder.pull_boolean"
+      when /[A-Z]+\w+/ # FIXME: this doesn't seem right...
+        "#{field.type}.decode_from(decoder, decoder.index + decoder.pull_uint64)"
+      else
+        raise "Unknown field type #{field.type}"
+      end
+    end
+
+    def decode_code(field)
+      case field.qualifier
+      when :optional
+        "obj.#{field.name} = #{decode_subtype(field)}"
+      when :repeated
+        case field.type
+        when "uint32"
+          PACKED_REPEATED.result(binding)
+        else
+          raise "Unknown field type #{field.type}"
+        end
+      else
+        raise "Unknown qualifier #{field.qualifier}"
+      end
+    end
+  end
+end

test/codegen_test.rb

@@ -0,0 +1,35 @@
+require "helper"
+
+module ProtoBuff
+  class CodeGenTest < Test
+    def test_make_ruby
+      unit = ProtoBuff.parse_string('message TestMessage { string id = 1; uint64 shop_id = 2; bool boolean = 3; }')
+      gen = CodeGen.new unit
+      klass = Class.new { self.class_eval gen.to_ruby }
+      obj = klass::TestMessage.new
+      assert_equal "", obj.id
+      assert_equal 0, obj.shop_id
+      assert_equal false, obj.boolean
+    end
+
+    def test_int32
+      unit = ProtoBuff.parse_string('message Test1 { optional int32 a = 1; }')
+      gen = CodeGen.new unit
+      klass = Class.new { self.class_eval gen.to_ruby }
+      obj = klass::Test1.new
+      assert_equal 0, obj.a
+    end
+
+    def test_fixture_file
+      unit = ProtoBuff.parse_file('./test/fixtures/test.proto')
+
+      gen = CodeGen.new unit
+
+      klass = Class.new { self.class_eval gen.to_ruby }
+      obj = klass::Test1.new
+      assert_equal 0, obj.a
+
+      assert_equal [], klass::TestRepeatedField.new.e
+    end
+  end
+end

test/helper.rb

@@ -3,6 +3,7 @@
 require "proto/test/fixtures/test_pb"
 require "protobuff/decoder"
 require "protobuff/parser"
+require "protobuff/codegen"
 
 module ProtoBuff
   class Test < Minitest::Test