wownero-lws/src/wire/json/write.h

// Copyright (c) 2020, The Monero Project
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//
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//    of conditions and the following disclaimer in the documentation and/or other
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#pragma once

#include <array>
#include <boost/utility/string_ref.hpp>
#include <cstdint>
#include <limits>
#include <rapidjson/writer.h>

#include "byte_stream.h" // monero/contrib/epee/include
#include "span.h"        // monero/contrib/epee/include
#include "wire/field.h"
#include "wire/filters.h"
#include "wire/json/base.h"
#include "wire/traits.h"
#include "wire/write.h"

namespace wire
{
  constexpr const std::size_t uint_to_string_size =
    std::numeric_limits<std::uintmax_t>::digits10 + 2;

  //! Writes JSON tokens one-at-a-time for DOMless output.
  class json_writer : public writer
  {
    epee::byte_stream bytes_;
    rapidjson::Writer<epee::byte_stream> formatter_;
    bool needs_flush_;

    //! \return True if buffer needs to be cleared
    virtual void do_flush(epee::span<const uint8_t>);

    //! Flush written bytes to `do_flush(...)` if configured
    void check_flush();

  protected:
    json_writer(epee::byte_stream&& out, bool needs_flush)
      : writer(), bytes_(std::move(out)), formatter_(bytes_), needs_flush_(needs_flush)
    {}

    //! \throw std::logic_error if incomplete JSON tree
    void check_complete();

    //! \throw std::logic_error if incomplete JSON tree. \return JSON bytes
    epee::byte_stream take_json();

    //! Flush bytes in local buffer to `do_flush(...)`
    void flush()
    {
      do_flush({bytes_.data(), bytes_.size()});
      bytes_ = epee::byte_stream{}; // TODO create .clear() method in monero project
    }

  public:
    //! JSON does not need array sizes.
    static constexpr std::false_type need_array_size() noexcept { return{}; }

    json_writer(const json_writer&) = delete;
    virtual ~json_writer() noexcept;
    json_writer& operator=(const json_writer&) = delete;

    //! \return Null-terminated buffer containing uint as decimal ascii
    static std::array<char, uint_to_string_size> to_string(std::uintmax_t) noexcept;

    void boolean(bool) override final;

    void integer(int) override final;
    void integer(std::intmax_t) override final;

    void unsigned_integer(unsigned) override final;
    void unsigned_integer(std::uintmax_t) override final;

    void real(double) override final;

    void string(boost::string_ref) override final;
    void binary(epee::span<const std::uint8_t> source) override final;

    void enumeration(std::size_t index, epee::span<char const* const> enums) override final;

    void start_array(std::size_t) override final;
    void end_array() override final;

    void start_object(std::size_t) override final;
    void key(std::uintmax_t) override final;
    void key(boost::string_ref) override final;
    void key(unsigned, boost::string_ref) override final;
    void end_object() override final;
  };

  //! Buffers entire JSON message in memory
  struct json_slice_writer final : json_writer
  {
    using sink = epee::byte_stream;

    explicit json_slice_writer(sink&& out)
      : json_writer(std::move(out), false)
    {}

    explicit json_slice_writer()
      : json_writer(epee::byte_stream{}, false)
    {}

    //! \throw std::logic_error if incomplete JSON tree \return JSON bytes
    epee::byte_stream take_sink()
    {
      return json_writer::take_json();
    }
  };

  //! Periodically flushes JSON data to `std::ostream`
  class json_stream_writer final : public json_writer
  {
    std::ostream& dest;

    virtual void do_flush(epee::span<const std::uint8_t>) override final;
  public:
    explicit json_stream_writer(std::ostream& dest)
      : json_writer(epee::byte_stream{}, true), dest(dest)
    {}

    //! Flush remaining bytes to stream \throw std::logic_error if incomplete JSON tree
    void finish()
    {
      check_complete();
      flush();
    }
  };
}