classic_protocol_codec_frame.h

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/*
  Copyright (c) 2019, 2024, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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  permission to link the program and your derivative works with the
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  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef MYSQL_ROUTER_CLASSIC_PROTOCOL_CODEC_FRAME_H_
#define MYSQL_ROUTER_CLASSIC_PROTOCOL_CODEC_FRAME_H_
 
#include <cstddef>  // size_t
#include <cstdint>  // uint8_t
#include <memory>
#include <system_error>  // error_code
#include <utility>       // move
 
#include "mysql/harness/stdx/expected.h"
#include "mysqlrouter/classic_protocol_codec_base.h"
#include "mysqlrouter/classic_protocol_codec_error.h"
#include "mysqlrouter/classic_protocol_codec_wire.h"
#include "mysqlrouter/classic_protocol_frame.h"
#include "mysqlrouter/classic_protocol_wire.h"
 
namespace classic_protocol {
 
/**
 * Codec of a Frame Header.
 */
template <>
class Codec<frame::Header> : public impl::EncodeBase<Codec<frame::Header>> {
  template <class Accumulator>
  constexpr auto accumulate_fields(Accumulator &&accu) const {
    return accu.step(wire::FixedInt<3>(v_.payload_size()))
        .step(wire::FixedInt<1>(v_.seq_id()))
        .result();
  }
 
 public:
  using value_type = frame::Header;
  using __base = impl::EncodeBase<Codec<value_type>>;
 
  friend __base;
 
  constexpr Codec(value_type v, capabilities::value_type caps)
      : __base(caps), v_{std::move(v)} {}
 
  static constexpr size_t max_size() noexcept { return 4; }
 
  static stdx::expected<std::pair<size_t, value_type>, std::error_code> decode(
      const net::const_buffer &buffer, capabilities::value_type caps) {
    impl::DecodeBufferAccumulator accu(buffer, caps);
 
    auto payload_size_res = accu.template step<wire::FixedInt<3>>();
    auto seq_id_res = accu.template step<wire::FixedInt<1>>();
 
    if (!accu.result()) return stdx::unexpected(accu.result().error());
 
    return std::make_pair(
        accu.result().value(),
        value_type(payload_size_res->value(), seq_id_res->value()));
  }
 
 private:
  const value_type v_;
};
 
/**
 * Codec of Compressed Header.
 */
template <>
class Codec<frame::CompressedHeader>
    : public impl::EncodeBase<Codec<frame::CompressedHeader>> {
  template <class Accumulator>
  auto accumulate_fields(Accumulator &&accu) const {
    return accu.step(wire::FixedInt<3>(v_.payload_size()))
        .step(wire::FixedInt<1>(v_.seq_id()))
        .step(wire::FixedInt<3>(v_.uncompressed_size()))
        .result();
  }
 
 public:
  using value_type = frame::CompressedHeader;
  using __base = impl::EncodeBase<Codec<value_type>>;
 
  friend __base;
 
  constexpr Codec(value_type v, capabilities::value_type caps)
      : __base(caps), v_{std::move(v)} {}
 
  static size_t max_size() noexcept { return 7; }
 
  static stdx::expected<std::pair<size_t, value_type>, std::error_code> decode(
      const net::const_buffer &buffer, capabilities::value_type caps) {
    impl::DecodeBufferAccumulator accu(buffer, caps);
 
    auto payload_size_res = accu.template step<wire::FixedInt<3>>();
    auto seq_id_res = accu.template step<wire::FixedInt<1>>();
    auto uncompressed_size_res = accu.template step<wire::FixedInt<3>>();
 
    if (!accu.result()) return stdx::unexpected(accu.result().error());
 
    return std::make_pair(
        accu.result().value(),
        value_type(payload_size_res->value(), seq_id_res->value(),
                   uncompressed_size_res->value()));
  }
 
 private:
  const value_type v_;
};
 
/**
 * Codec for a Frame.
 *
 * Frame is
 *
 * - header
 * - payload
 */
template <class PayloadType>
class Codec<frame::Frame<PayloadType>>
    : public impl::EncodeBase<Codec<frame::Frame<PayloadType>>> {
  template <class Accumulator>
  constexpr auto accumulate_fields(Accumulator &&accu) const {
    return accu
        .step(frame::Header(
            Codec<PayloadType>(v_.payload(), this->caps()).size(), v_.seq_id()))
        .step(PayloadType(v_.payload()))
        .result();
  }
 
 public:
  using value_type = frame::Frame<PayloadType>;
  using __base = impl::EncodeBase<Codec<value_type>>;
 
  friend __base;
 
  constexpr Codec(value_type v, capabilities::value_type caps)
      : __base(caps), v_{std::move(v)} {}
 
  static stdx::expected<std::pair<size_t, value_type>, std::error_code> decode(
      net::const_buffer buffer, capabilities::value_type caps) {
    impl::DecodeBufferAccumulator accu(buffer, caps);
 
    auto header_res = accu.template step<frame::Header>();
    if (!accu.result()) return stdx::unexpected(accu.result().error());
 
    constexpr const size_t header_size{Codec<frame::Header>::max_size()};
 
    // check the payload is at least what we expect.
    if (buffer.size() < header_size + header_res->payload_size()) {
      return stdx::unexpected(
          make_error_code(classic_protocol::codec_errc::not_enough_input));
    }
 
    auto payload_res =
        accu.template step<PayloadType>(header_res->payload_size());
 
    if (!accu.result()) return stdx::unexpected(accu.result().error());
 
    return std::make_pair(
        accu.result().value(),
        value_type(header_res->seq_id(), payload_res.value()));
  }
 
 private:
  const value_type v_;
};
}  // namespace classic_protocol
 
#endif