Enums use native enums in C#

Enums should not be (badly) emulated with classes in C# but should
use native C# enums instead. Java implementation made an explicit
choice not to use the (more complex) Java enums, but C# enums are
just light-weight syntactic coating over integral types.

Fixes issue #171.

Change-Id: I9f4d6ba5324400a1e52982e49b58603cb7d7cca7

src/idl_gen_general.cpp

@@ -80,6 +80,8 @@ struct LanguageParameters {
   const char *open_curly;
   const char *const_decl;
   const char *unsubclassable_decl;
+  const char *enum_decl;
+  const char *enum_separator;
   const char *inheritance_marker;
   const char *namespace_ident;
   const char *namespace_begin;
@@ -99,6 +101,8 @@ LanguageParameters language_parameters[] = {
     " {\n",
     " final ",
     "final ",
+    "final class ",
+    ";\n",
     " extends ",
     "package ",
     ";",
@@ -121,6 +125,8 @@ LanguageParameters language_parameters[] = {
     "\n{\n",
     " readonly ",
     "sealed ",
+    "enum ",
+    ",\n",
     " : ",
     "namespace ",
     "\n{",
@@ -144,6 +150,8 @@ LanguageParameters language_parameters[] = {
     "\n{\n",
     "const ",
     " ",
+    "class ",
+    ";\n",
     "",
     "package ",
     "",
@@ -181,6 +189,16 @@ static std::string GenTypeBasic(const LanguageParameters &lang,
   return gtypename[type.base_type * GeneratorOptions::kMAX + lang.language];
 }
 
+// Generate type to be used in user-facing API
+static std::string GenTypeForUser(const LanguageParameters &lang,
+                                  const Type &type) {
+  if (lang.language == GeneratorOptions::kCSharp) {
+    if (type.enum_def != nullptr &&
+          type.base_type != BASE_TYPE_UNION) return type.enum_def->name;
+  }
+  return GenTypeBasic(lang, type);
+}
+
 static std::string GenTypeGet(const LanguageParameters &lang,
                               const Type &type);
 
@@ -240,17 +258,44 @@ static std::string DestinationMask(const LanguageParameters &lang,
   }
 }
 
-// Cast necessary to correctly read serialized unsigned values.
+// Casts necessary to correctly read serialized data
 static std::string DestinationCast(const LanguageParameters &lang,
                                    const Type &type) {
-  if (lang.language == GeneratorOptions::kJava &&
-      (type.base_type == BASE_TYPE_UINT ||
-       (type.base_type == BASE_TYPE_VECTOR &&
-        type.element == BASE_TYPE_UINT))) return "(long)";
+  switch (lang.language) {
+    case GeneratorOptions::kJava:
+      // Cast necessary to correctly read serialized unsigned values.
+      if (type.base_type == BASE_TYPE_UINT ||
+          (type.base_type == BASE_TYPE_VECTOR &&
+           type.element == BASE_TYPE_UINT)) return "(long)";
+      break;
+
+    case GeneratorOptions::kCSharp:
+      // Cast from raw integral types to enum
+      if (type.enum_def != nullptr &&
+        type.base_type != BASE_TYPE_UNION) return "(" + type.enum_def->name + ")";
+        break;
+
+    default:
+      break;
+  }
   return "";
 }
 
-
+// Read value and possibly process it to get proper value
+static std::string DestinationValue(const LanguageParameters &lang,
+  const std::string &name,
+  const Type &type) {
+  std::string type_mask = DestinationMask(lang, type, false);
+  // is a typecast needed? (for C# enums and unsigned values in Java)
+  if (type_mask.length() ||
+    (lang.language == GeneratorOptions::kCSharp &&
+    type.enum_def != nullptr &&
+    type.base_type != BASE_TYPE_UNION)) {
+    return "(" + GenTypeBasic(lang, type) + ")(" + name + type_mask + ")";
+  } else {
+    return name;
+  }
+}
 
 static std::string GenDefaultValue(const Value &value) {
   return value.type.base_type == BASE_TYPE_BOOL
@@ -269,50 +314,61 @@ static void GenEnum(const LanguageParameters &lang, EnumDef &enum_def,
   // to map directly to how they're used in C/C++ and file formats.
   // That, and Java Enums are expensive, and not universally liked.
   GenComment(enum_def.doc_comment, code_ptr, &lang.comment_config);
-  code += std::string("public ") + lang.unsubclassable_decl;
-  code += "class " + enum_def.name + lang.open_curly;
-  code += "  private " + enum_def.name + "() { }\n";
+  code += std::string("public ") + lang.enum_decl + enum_def.name;
+  if (lang.language == GeneratorOptions::kCSharp) {
+    code += lang.inheritance_marker + GenTypeBasic(lang, enum_def.underlying_type);
+  }
+  code += lang.open_curly;
+  if (lang.language == GeneratorOptions::kJava) {
+    code += "  private " + enum_def.name + "() { }\n";
+  }
   for (auto it = enum_def.vals.vec.begin();
        it != enum_def.vals.vec.end();
        ++it) {
     auto &ev = **it;
     GenComment(ev.doc_comment, code_ptr, &lang.comment_config, "  ");
-    code += "  public static";
-    code += lang.const_decl;
-    code += GenTypeBasic(lang, enum_def.underlying_type);
+    if (lang.language != GeneratorOptions::kCSharp) {
+      code += "  public static";
+      code += lang.const_decl;
+      code += GenTypeBasic(lang, enum_def.underlying_type);
+    }
     code += " " + ev.name + " = ";
-    code += NumToString(ev.value) + ";\n";
+    code += NumToString(ev.value);
+    code += lang.enum_separator;
   }
 
   // Generate a generate string table for enum values.
-  // Problem is, if values are very sparse that could generate really big
-  // tables. Ideally in that case we generate a map lookup instead, but for
-  // the moment we simply don't output a table at all.
-  auto range = enum_def.vals.vec.back()->value -
-               enum_def.vals.vec.front()->value + 1;
-  // Average distance between values above which we consider a table
-  // "too sparse". Change at will.
-  static const int kMaxSparseness = 5;
-  if (range / static_cast<int64_t>(enum_def.vals.vec.size()) < kMaxSparseness) {
-    code += "\n  private static";
-    code += lang.const_decl;
-    code += lang.string_type;
-    code += "[] names = { ";
-    auto val = enum_def.vals.vec.front()->value;
-    for (auto it = enum_def.vals.vec.begin();
-         it != enum_def.vals.vec.end();
-         ++it) {
-      while (val++ != (*it)->value) code += "\"\", ";
-      code += "\"" + (*it)->name + "\", ";
+  // We do not do that for C# where this functionality is native.
+  if (lang.language != GeneratorOptions::kCSharp) {
+    // Problem is, if values are very sparse that could generate really big
+    // tables. Ideally in that case we generate a map lookup instead, but for
+    // the moment we simply don't output a table at all.
+    auto range = enum_def.vals.vec.back()->value -
+      enum_def.vals.vec.front()->value + 1;
+    // Average distance between values above which we consider a table
+    // "too sparse". Change at will.
+    static const int kMaxSparseness = 5;
+    if (range / static_cast<int64_t>(enum_def.vals.vec.size()) < kMaxSparseness) {
+      code += "\n  private static";
+      code += lang.const_decl;
+      code += lang.string_type;
+      code += "[] names = { ";
+      auto val = enum_def.vals.vec.front()->value;
+      for (auto it = enum_def.vals.vec.begin();
+        it != enum_def.vals.vec.end();
+        ++it) {
+        while (val++ != (*it)->value) code += "\"\", ";
+        code += "\"" + (*it)->name + "\", ";
+      }
+      code += "};\n\n";
+      code += "  public static ";
+      code += lang.string_type;
+      code += " " + MakeCamel("name", lang.first_camel_upper);
+      code += "(int e) { return names[e";
+      if (enum_def.vals.vec.front()->value)
+        code += " - " + enum_def.vals.vec.front()->name;
+      code += "]; }\n";
     }
-    code += "};\n\n";
-    code += "  public static ";
-    code += lang.string_type;
-    code += " " + MakeCamel("name", lang.first_camel_upper);
-    code += "(int e) { return names[e";
-    if (enum_def.vals.vec.front()->value)
-      code += " - " + enum_def.vals.vec.front()->name;
-    code += "]; }\n";
   }
 
   // Close the class
@@ -364,8 +420,8 @@ static void GenStructArgs(const LanguageParameters &lang,
                     (field.value.type.struct_def->name + "_").c_str());
     } else {
       code += ", ";
-      code += GenTypeBasic(lang,
-                           DestinationType(lang, field.value.type, false));
+      code += GenTypeForUser(lang,
+                             DestinationType(lang, field.value.type, false));
       code += " ";
       code += nameprefix;
       code += MakeCamel(field.name, lang.first_camel_upper);
@@ -397,13 +453,7 @@ static void GenStructBody(const LanguageParameters &lang,
       code += "    builder." + FunctionStart(lang, 'P') + "ut";
       code += GenMethod(lang, field.value.type) + "(";
       auto argname = nameprefix + MakeCamel(field.name, lang.first_camel_upper);
-      std::string type_mask = DestinationMask(lang, field.value.type, false);
-      if (type_mask.length()) {
-        code += "(" + GenTypeBasic(lang, field.value.type) + ")";
-        code += "(" + argname + type_mask + ")";
-      } else {
-        code += argname;
-      }
+      code += DestinationValue(lang, argname, field.value.type);
       code += ");\n";
     }
   }
@@ -464,7 +514,11 @@ static void GenStruct(const LanguageParameters &lang, const Parser &parser,
     GenComment(field.doc_comment, code_ptr, &lang.comment_config, "  ");
     std::string type_name = GenTypeGet(lang, field.value.type);
     std::string type_name_dest =
-      GenTypeGet(lang, DestinationType(lang, field.value.type, true));
+      lang.language == GeneratorOptions::kCSharp &&
+        field.value.type.enum_def != nullptr &&
+        field.value.type.base_type != BASE_TYPE_UNION
+          ? field.value.type.enum_def->name
+          : GenTypeGet(lang, DestinationType(lang, field.value.type, true));
     std::string dest_mask = DestinationMask(lang, field.value.type, true);
     std::string dest_cast = DestinationCast(lang, field.value.type);
     std::string method_start = "  public " + type_name_dest + " " +
@@ -612,8 +666,8 @@ static void GenStruct(const LanguageParameters &lang, const Parser &parser,
         auto &field = **it;
         if (field.deprecated) continue;
         code += ",\n      ";
-        code += GenTypeBasic(lang,
-                             DestinationType(lang, field.value.type, false));
+        code += GenTypeForUser(lang,
+                               DestinationType(lang, field.value.type, false));
         code += " ";
         code += field.name;
         // Java doesn't have defaults, which means this method must always
@@ -661,20 +715,14 @@ static void GenStruct(const LanguageParameters &lang, const Parser &parser,
       code += "  public static void " + FunctionStart(lang, 'A') + "dd";
       code += MakeCamel(field.name);
       code += "(FlatBufferBuilder builder, ";
-      code += GenTypeBasic(lang,
-                           DestinationType(lang, field.value.type, false));
+      code += GenTypeForUser(lang,
+                             DestinationType(lang, field.value.type, false));
       auto argname = MakeCamel(field.name, false);
       if (!IsScalar(field.value.type.base_type)) argname += "Offset";
       code += " " + argname + ") { builder." + FunctionStart(lang, 'A') + "dd";
       code += GenMethod(lang, field.value.type) + "(";
       code += NumToString(it - struct_def.fields.vec.begin()) + ", ";
-      std::string type_mask = DestinationMask(lang, field.value.type, false);
-      if (type_mask.length()) {
-        code += "(" + GenTypeBasic(lang, field.value.type) + ")";
-        code += "(" + argname + type_mask + ")";
-      } else {
-        code += argname;
-      }
+      code += DestinationValue(lang, argname, field.value.type);
       code += ", " + GenDefaultValue(field.value);
       code += "); }\n";
       if (field.value.type.base_type == BASE_TYPE_VECTOR) {

tests/FlatBuffers.Test/FlatBuffersExampleTests.cs

@@ -72,7 +72,7 @@ namespace FlatBuffers.Test
             Monster.AddHp(fbb, (short)80);
             Monster.AddName(fbb, str);
             Monster.AddInventory(fbb, inv);
-            Monster.AddTestType(fbb, (byte)1);
+            Monster.AddTestType(fbb, Any.Monster);
             Monster.AddTest(fbb, mon2);
             Monster.AddTest4(fbb, test4);
             Monster.AddTestarrayofstring(fbb, testArrayOfString);
@@ -111,7 +111,7 @@ namespace FlatBuffers.Test
             Assert.AreEqual((short)5, t.A());
             Assert.AreEqual((sbyte)6, t.B());
 
-            Assert.AreEqual((byte)Any.Monster, monster.TestType());
+            Assert.AreEqual(Any.Monster, monster.TestType());
 
             var monster2 = new Monster();
             Assert.IsTrue(monster.Test(monster2) != null);
@@ -148,10 +148,10 @@ namespace FlatBuffers.Test
 
         public void TestEnums()
         {
-            Assert.AreEqual(Color.Name(Color.Red), "Red");
-            Assert.AreEqual(Color.Name(Color.Blue), "Blue");
-            Assert.AreEqual(Any.Name(Any.NONE), "NONE");
-            Assert.AreEqual(Any.Name(Any.Monster), "Monster");
+            Assert.AreEqual("Red", Color.Red.ToString());
+            Assert.AreEqual("Blue", Color.Blue.ToString());
+            Assert.AreEqual("NONE", Any.NONE.ToString());
+            Assert.AreEqual("Monster", Any.Monster.ToString());
         }
     }
 }

tests/MyGame/Example/Any.cs

@@ -3,15 +3,10 @@
 namespace MyGame.Example
 {
 
-public sealed class Any
+public enum Any : byte
 {
-  private Any() { }
-  public static readonly byte NONE = 0;
-  public static readonly byte Monster = 1;
-
-  private static readonly string[] names = { "NONE", "Monster", };
-
-  public static string Name(int e) { return names[e]; }
+ NONE = 0,
+ Monster = 1,
 };
 
 

tests/MyGame/Example/Color.cs

@@ -3,16 +3,11 @@
 namespace MyGame.Example
 {
 
-public sealed class Color
+public enum Color : sbyte
 {
-  private Color() { }
-  public static readonly sbyte Red = 1;
-  public static readonly sbyte Green = 2;
-  public static readonly sbyte Blue = 8;
-
-  private static readonly string[] names = { "Red", "Green", "", "", "", "", "", "Blue", };
-
-  public static string Name(int e) { return names[e - Red]; }
+ Red = 1,
+ Green = 2,
+ Blue = 8,
 };
 
 

tests/MyGame/Example/Monster.cs

@@ -18,8 +18,8 @@ public sealed class Monster : Table {
   public string Name() { int o = __offset(10); return o != 0 ? __string(o + bb_pos) : null; }
   public byte Inventory(int j) { int o = __offset(14); return o != 0 ? bb.Get(__vector(o) + j * 1) : (byte)0; }
   public int InventoryLength() { int o = __offset(14); return o != 0 ? __vector_len(o) : 0; }
-  public sbyte Color() { int o = __offset(16); return o != 0 ? bb.GetSbyte(o + bb_pos) : (sbyte)8; }
-  public byte TestType() { int o = __offset(18); return o != 0 ? bb.Get(o + bb_pos) : (byte)0; }
+  public Color Color() { int o = __offset(16); return o != 0 ? (Color)bb.GetSbyte(o + bb_pos) : (Color)8; }
+  public Any TestType() { int o = __offset(18); return o != 0 ? (Any)bb.Get(o + bb_pos) : (Any)0; }
   public Table Test(Table obj) { int o = __offset(20); return o != 0 ? __union(obj, o) : null; }
   public Test Test4(int j) { return Test4(new Test(), j); }
   public Test Test4(Test obj, int j) { int o = __offset(22); return o != 0 ? obj.__init(__vector(o) + j * 4, bb) : null; }
@@ -55,8 +55,8 @@ public sealed class Monster : Table {
   public static void AddInventory(FlatBufferBuilder builder, int inventoryOffset) { builder.AddOffset(5, inventoryOffset, 0); }
   public static int CreateInventoryVector(FlatBufferBuilder builder, byte[] data) { builder.StartVector(1, data.Length, 1); for (int i = data.Length - 1; i >= 0; i--) builder.AddByte(data[i]); return builder.EndVector(); }
   public static void StartInventoryVector(FlatBufferBuilder builder, int numElems) { builder.StartVector(1, numElems, 1); }
-  public static void AddColor(FlatBufferBuilder builder, sbyte color) { builder.AddSbyte(6, color, 8); }
-  public static void AddTestType(FlatBufferBuilder builder, byte testType) { builder.AddByte(7, testType, 0); }
+  public static void AddColor(FlatBufferBuilder builder, Color color) { builder.AddSbyte(6, (sbyte)(color), 8); }
+  public static void AddTestType(FlatBufferBuilder builder, Any testType) { builder.AddByte(7, (byte)(testType), 0); }
   public static void AddTest(FlatBufferBuilder builder, int testOffset) { builder.AddOffset(8, testOffset, 0); }
   public static void AddTest4(FlatBufferBuilder builder, int test4Offset) { builder.AddOffset(9, test4Offset, 0); }
   public static void StartTest4Vector(FlatBufferBuilder builder, int numElems) { builder.StartVector(4, numElems, 2); }

tests/MyGame/Example/Vec3.cs

@@ -12,11 +12,11 @@ public sealed class Vec3 : Struct {
   public float Y() { return bb.GetFloat(bb_pos + 4); }
   public float Z() { return bb.GetFloat(bb_pos + 8); }
   public double Test1() { return bb.GetDouble(bb_pos + 16); }
-  public sbyte Test2() { return bb.GetSbyte(bb_pos + 24); }
+  public Color Test2() { return (Color)bb.GetSbyte(bb_pos + 24); }
   public Test Test3() { return Test3(new Test()); }
   public Test Test3(Test obj) { return obj.__init(bb_pos + 26, bb); }
 
-  public static int CreateVec3(FlatBufferBuilder builder, float X, float Y, float Z, double Test1, sbyte Test2, short Test_A, sbyte Test_B) {
+  public static int CreateVec3(FlatBufferBuilder builder, float X, float Y, float Z, double Test1, Color Test2, short Test_A, sbyte Test_B) {
     builder.Prep(16, 32);
     builder.Pad(2);
     builder.Prep(2, 4);
@@ -24,7 +24,7 @@ public sealed class Vec3 : Struct {
     builder.PutSbyte(Test_B);
     builder.PutShort(Test_A);
     builder.Pad(1);
-    builder.PutSbyte(Test2);
+    builder.PutSbyte((sbyte)(Test2));
     builder.PutDouble(Test1);
     builder.Pad(4);
     builder.PutFloat(Z);