src/idl_gen_grpc.cpp

/*
 * Copyright 2014 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.
 */

// independent from idl_parser, since this code is not needed for most clients

#include "flatbuffers/flatbuffers.h"
#include "flatbuffers/idl.h"
#include "flatbuffers/util.h"

#include "src/compiler/cpp_generator.h"

namespace flatbuffers {

class FlatBufMethod : public grpc_generator::Method {
 public:
  enum Streaming { kNone, kClient, kServer, kBiDi };

  FlatBufMethod(const RPCCall *method)
    : method_(method) {
    streaming_ = kNone;
    auto val = method_->attributes.Lookup("streaming");
    if (val) {
      if (val->constant == "client") streaming_ = kClient;
      if (val->constant == "server") streaming_ = kServer;
      if (val->constant == "bidi") streaming_ = kBiDi;
    }
  }

  std::string name() const { return method_->name; }

  std::string GRPCType(const StructDef &sd) const {
    return "flatbuffers::BufferRef<" + sd.name + ">";
  }

  std::string input_type_name() const {
    return GRPCType(*method_->request);
  }
  std::string output_type_name() const {
    return GRPCType(*method_->response);
  }

  bool NoStreaming() const { return streaming_ == kNone; }
  bool ClientOnlyStreaming() const { return streaming_ == kClient; }
  bool ServerOnlyStreaming() const { return streaming_ == kServer; }
  bool BidiStreaming() const { return streaming_ == kBiDi; }

 private:
  const RPCCall *method_;
  Streaming streaming_;
};

class FlatBufService : public grpc_generator::Service {
 public:
  FlatBufService(const ServiceDef *service) : service_(service) {}

  std::string name() const { return service_->name; }

  int method_count() const {
    return static_cast<int>(service_->calls.vec.size());
  };

  std::unique_ptr<const grpc_generator::Method> method(int i) const {
    return std::unique_ptr<const grpc_generator::Method>(
          new FlatBufMethod(service_->calls.vec[i]));
  };

 private:
  const ServiceDef *service_;
};

class FlatBufPrinter : public grpc_generator::Printer {
 public:
  FlatBufPrinter(std::string *str)
    : str_(str), escape_char_('$'), indent_(0) {}

  void Print(const std::map<std::string, std::string> &vars,
             const char *string_template) {
    std::string s = string_template;
    // Replace any occurrences of strings in "vars" that are surrounded
    // by the escape character by what they're mapped to.
    size_t pos;
    while ((pos = s.find(escape_char_)) != std::string::npos) {
      // Found an escape char, must also find the closing one.
      size_t pos2 = s.find(escape_char_, pos + 1);
      // If placeholder not closed, ignore.
      if (pos2 == std::string::npos) break;
      auto it = vars.find(s.substr(pos + 1, pos2 - pos - 1));
      // If unknown placeholder, ignore.
      if (it == vars.end()) break;
      // Subtitute placeholder.
      s.replace(pos, pos2 - pos + 1, it->second);
    }
    Print(s.c_str());
  }

  void Print(const char *s) {
    // Add this string, but for each part separated by \n, add indentation.
    for (;;) {
      // Current indentation.
      str_->insert(str_->end(), indent_ * 2, ' ');
      // See if this contains more than one line.
      const char * lf = strchr(s, '\n');
      if (lf) {
        (*str_) += std::string(s, lf + 1);
        s = lf + 1;
        if (!*s) break;  // Only continue if there's more lines.
      } else {
        (*str_) += s;
        break;
      }
    }
  }

  void Indent() { indent_++; }
  void Outdent() { indent_--; assert(indent_ >= 0); }

 private:
  std::string *str_;
  char escape_char_;
  int indent_;
};

class FlatBufFile : public grpc_generator::File {
 public:
  FlatBufFile(const Parser &parser, const std::string &file_name)
    : parser_(parser), file_name_(file_name) {}
  FlatBufFile &operator=(const FlatBufFile &);

  std::string filename() const { return file_name_; }
  std::string filename_without_ext() const {
    return StripExtension(file_name_);
  }

  std::string message_header_ext() const { return "_generated.h"; }
  std::string service_header_ext() const { return ".grpc.fb.h"; }

  std::string package() const {
    return parser_.namespaces_.back()->GetFullyQualifiedName("");
  }

  std::vector<std::string> package_parts() const {
    return parser_.namespaces_.back()->components;
  }

  std::string additional_headers() const {
    return "#include \"flatbuffers/grpc.h\"\n";
  }

  int service_count() const {
    return static_cast<int>(parser_.services_.vec.size());
  };

  std::unique_ptr<const grpc_generator::Service> service(int i) const {
    return std::unique_ptr<const grpc_generator::Service> (
          new FlatBufService(parser_.services_.vec[i]));
  }

  std::unique_ptr<grpc_generator::Printer> CreatePrinter(std::string *str) const {
    return std::unique_ptr<grpc_generator::Printer>(
          new FlatBufPrinter(str));
  }

 private:
  const Parser &parser_;
  const std::string &file_name_;
};

bool GenerateGRPC(const Parser &parser,
                  const std::string &/*path*/,
                  const std::string &file_name) {

  int nservices = 0;
  for (auto it = parser.services_.vec.begin();
       it != parser.services_.vec.end(); ++it) {
    if (!(*it)->generated) nservices++;
  }
  if (!nservices) return true;

  grpc_cpp_generator::Parameters generator_parameters;
  // TODO(wvo): make the other parameters in this struct configurable.
  generator_parameters.use_system_headers = true;

  FlatBufFile fbfile(parser, file_name);

  std::string header_code =
      grpc_cpp_generator::GetHeaderPrologue(&fbfile, generator_parameters) +
      grpc_cpp_generator::GetHeaderIncludes(&fbfile, generator_parameters) +
      grpc_cpp_generator::GetHeaderServices(&fbfile, generator_parameters) +
      grpc_cpp_generator::GetHeaderEpilogue(&fbfile, generator_parameters);

  std::string source_code =
      grpc_cpp_generator::GetSourcePrologue(&fbfile, generator_parameters) +
      grpc_cpp_generator::GetSourceIncludes(&fbfile, generator_parameters) +
      grpc_cpp_generator::GetSourceServices(&fbfile, generator_parameters) +
      grpc_cpp_generator::GetSourceEpilogue(&fbfile, generator_parameters);

  return flatbuffers::SaveFile((file_name + ".grpc.fb.h").c_str(),
                               header_code, false) &&
         flatbuffers::SaveFile((file_name + ".grpc.fb.cc").c_str(),
                               source_code, false);
}

}  // namespace flatbuffers