protobuf/upb/mini_table.hpp

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 *     * Redistributions of source code must retain the above copyright
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#ifndef UPB_MINI_TABLE_HPP_
#define UPB_MINI_TABLE_HPP_

#include <assert.h>

#include <string>

#include "upb/mini_table.h"

namespace upb {

class MtDataEncoder {
 public:
  MtDataEncoder() : appender_(&encoder_) {}

  bool StartMessage(uint64_t msg_mod) {
    return appender_([=](char* buf) {
      return upb_MtDataEncoder_StartMessage(&encoder_, buf, msg_mod);
    });
  }

  bool PutField(upb_FieldType type, uint32_t field_num, uint64_t field_mod) {
    return appender_([=](char* buf) {
      return upb_MtDataEncoder_PutField(&encoder_, buf, type, field_num,
                                        field_mod);
    });
  }

  bool StartOneof() {
    return appender_([=](char* buf) {
      return upb_MtDataEncoder_StartOneof(&encoder_, buf);
    });
  }

  bool PutOneofField(uint32_t field_num) {
    return appender_([=](char* buf) {
      return upb_MtDataEncoder_PutOneofField(&encoder_, buf, field_num);
    });
  }

  void StartEnum() { upb_MtDataEncoder_StartEnum(&encoder_); }

  bool PutEnumValue(uint32_t enum_value) {
    return appender_([=](char* buf) {
      return upb_MtDataEncoder_PutEnumValue(&encoder_, buf, enum_value);
    });
  }

  bool EndEnum() {
    return appender_(
        [=](char* buf) { return upb_MtDataEncoder_EndEnum(&encoder_, buf); });
  }

  const std::string& data() const { return appender_.data(); }

 private:
  class StringAppender {
   public:
    StringAppender(upb_MtDataEncoder* e) { e->end = buf_ + sizeof(buf_); }

    template <class T>
    bool operator()(T&& func) {
      char* end = func(buf_);
      if (!end) return false;
      // C++ does not guarantee that string has doubling growth behavior, but
      // we need it to avoid O(n^2).
      str_.reserve(_upb_Log2CeilingSize(str_.size() + (end - buf_)));
      str_.append(buf_, end - buf_);
      return true;
    }

    const std::string& data() const { return str_; }

   private:
    char buf_[kUpb_MtDataEncoder_MinSize];
    std::string str_;
  };

  upb_MtDataEncoder encoder_;
  StringAppender appender_;
};

}  // namespace upb

#endif /* UPB_MINI_TABLE_HPP_ */