Defined CodeGenerator Interface and implement C++ (#7771)

include/flatbuffers/code_generator.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2023 Google Inc. All rights reserved.
+ *
+ * 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.
+ */
+
+#ifndef FLATBUFFERS_CODE_GENERATOR_H_
+#define FLATBUFFERS_CODE_GENERATOR_H_
+
+#include <string>
+
+#include "flatbuffers/idl.h"
+
+namespace flatbuffers {
+
+// An code generator interface for producing converting flatbuffer schema into
+// code.
+class CodeGenerator {
+ public:
+  virtual ~CodeGenerator() = default;
+
+  enum Status {
+    OK = 0,
+    ERROR = 1,
+    NOT_IMPLEMENTED = 2,
+  };
+
+  // Generate code from the provided `parser`.
+  //
+  // DEPRECATED: prefer using the other overload of GenerateCode for bfbs.
+  virtual Status GenerateCode(const Parser &parser, const std::string &path,
+                              const std::string &filename) = 0;
+
+  // Generate code from the provided `buffer` of given `length`. The buffer is a
+  // serialized reflection.fbs.
+  virtual Status GenerateCode(const uint8_t *buffer, int64_t length) = 0;
+
+  virtual Status GenerateMakeRule(const Parser &parser, const std::string &path,
+                                  const std::string &filename,
+                                  std::string &output) = 0;
+
+  virtual Status GenerateGrpcCode(const Parser &parser, const std::string &path,
+                                  const std::string &filename) = 0;
+
+  virtual bool IsSchemaOnly() const = 0;
+
+  virtual bool SupportsBfbsGeneration() const = 0;
+
+  virtual IDLOptions::Language Language() const = 0;
+  virtual std::string LanguageName() const = 0;
+
+ protected:
+  CodeGenerator() = default;
+
+ private:
+  // Copying is not supported.
+  CodeGenerator(const CodeGenerator &) = delete;
+  CodeGenerator &operator=(const CodeGenerator &) = delete;
+};
+
+}  // namespace flatbuffers
+
+#endif  // FLATBUFFERS_CODE_GENERATOR_H_

include/flatbuffers/flatc.h

@@ -20,15 +20,21 @@
 #include <functional>
 #include <limits>
 #include <list>
+#include <memory>
 #include <string>
 
 #include "flatbuffers/bfbs_generator.h"
+#include "flatbuffers/code_generator.h"
 #include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/idl.h"
 #include "flatbuffers/util.h"
 
 namespace flatbuffers {
 
+// TODO(derekbailey): It would be better to define these as normal includes and
+// not as extern functions. But this can be done at a later time.
+extern std::unique_ptr<flatbuffers::CodeGenerator> NewCppCodeGenerator();
+
 extern void LogCompilerWarn(const std::string &warn);
 extern void LogCompilerError(const std::string &err);
 
@@ -54,6 +60,8 @@ struct FlatCOptions {
   bool schema_binary = false;
   bool grpc_enabled = false;
   bool requires_bfbs = false;
+
+  std::vector<std::shared_ptr<CodeGenerator>> generators;
 };
 
 struct FlatCOption {
@@ -110,10 +118,13 @@ class FlatCompiler {
 
   explicit FlatCompiler(const InitParams &params) : params_(params) {}
 
+  bool RegisterCodeGenerator(const std::string& flag,
+                             std::shared_ptr<CodeGenerator> code_generator);
+
   int Compile(const FlatCOptions &options);
 
-  std::string GetShortUsageString(const std::string& program_name) const;
-  std::string GetUsageString(const std::string& program_name) const;
+  std::string GetShortUsageString(const std::string &program_name) const;
+  std::string GetUsageString(const std::string &program_name) const;
 
   // Parse the FlatC options from command line arguments.
   FlatCOptions ParseFromCommandLineArguments(int argc, const char **argv);
@@ -141,7 +152,9 @@ class FlatCompiler {
   Parser GetConformParser(const FlatCOptions &options);
 
   std::unique_ptr<Parser> GenerateCode(const FlatCOptions &options,
-                    Parser &conform_parser);
+                                       Parser &conform_parser);
+
+  std::map<std::string, std::shared_ptr<CodeGenerator>> code_generators_;
 
   InitParams params_;
 };