THUAI6/CAPI/cpp/grpc/include/upb/mini_table.hpp

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 * Copyright (c) 2009-2021, Google LLC
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
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 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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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_ */