classic_frame.h

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/*
  Copyright (c) 2022, 2025, 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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  but not limited to OpenSSL) that is licensed under separate terms,
  as designated in a particular file or component or in included license
  documentation.  The authors of MySQL hereby grant you an additional
  permission to link the program and your derivative works with the
  separately licensed software that they have either included with
  the program or referenced in the documentation.
 
  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
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  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef ROUTING_CLASSIC_FRAME_INCLUDED
#define ROUTING_CLASSIC_FRAME_INCLUDED
 
#include <system_error>
 
#include "channel.h"
#include "classic_connection_base.h"
#include "mysql/harness/stdx/expected.h"
 
class ClassicFrame {
 public:
  static stdx::expected<void, std::error_code> ensure_has_msg_prefix(
      Channel *src_channel, ClassicProtocolState *src_protocol);
 
  [[nodiscard]] static stdx::expected<void, std::error_code>
  ensure_has_full_frame(Channel *src_channel,
                        ClassicProtocolState *src_protocol);
 
  /**
   * recv a full message sequence into the channel's recv_plain_buffer()
   */
  [[nodiscard]] static stdx::expected<size_t, std::error_code>
  recv_frame_sequence(Channel *src_channel, ClassicProtocolState *src_protocol);
 
  static stdx::expected<void, std::error_code> ensure_server_greeting(
      Channel *src_channel, ClassicProtocolState *src_protocol);
 
  static stdx::expected<void, std::error_code> ensure_frame_header(
      Channel *src_channel, ClassicProtocolState *src_protocol);
 
  template <class T>
  static constexpr uint8_t cmd_byte() {
    return classic_protocol::Codec<T>::cmd_byte();
  }
 
  /**
   * receive a classic protocol message frame from a channel.
   */
  template <class Msg>
  static inline stdx::expected<Msg, std::error_code> recv_msg(
      Channel *src_channel, ClassicProtocolState *src_protocol,
      classic_protocol::capabilities::value_type caps) {
    auto read_res =
        ClassicFrame::recv_frame_sequence(src_channel, src_protocol);
    if (!read_res) return stdx::make_unexpected(read_res.error());
 
    auto num_of_frames = *read_res;
    if (num_of_frames > 1) {
      // more than one frame.
      auto frame_sequence_buf = src_channel->recv_plain_view();
 
      // assemble the payload from multiple frames.
 
      auto &payload_buf = src_channel->payload_buffer();
      payload_buf.clear();
 
      while (!frame_sequence_buf.empty()) {
        auto hdr_res =
            classic_protocol::decode<classic_protocol::frame::Header>(
                net::buffer(frame_sequence_buf), caps);
        if (!hdr_res) return stdx::make_unexpected(hdr_res.error());
 
        // skip the hdr.
        frame_sequence_buf =
            frame_sequence_buf.last(frame_sequence_buf.size() - hdr_res->first);
 
        auto frame_payload =
            frame_sequence_buf.first(hdr_res->second.payload_size());
 
        payload_buf.insert(payload_buf.end(), frame_payload.begin(),
                           frame_payload.end());
 
        frame_sequence_buf = frame_sequence_buf.last(
            frame_sequence_buf.size() - hdr_res->second.payload_size());
      }
 
      auto decode_res =
          classic_protocol::decode<Msg>(net::buffer(payload_buf), caps);
      if (!decode_res) return stdx::make_unexpected(decode_res.error());
 
      return decode_res->second;
    } else {
      auto &recv_buf = src_channel->recv_plain_view();
 
      auto decode_res =
          classic_protocol::decode<classic_protocol::frame::Frame<Msg>>(
              net::buffer(recv_buf), caps);
      if (!decode_res) return stdx::make_unexpected(decode_res.error());
 
      return decode_res->second.payload();
    }
  }
 
  template <class Msg>
  static inline stdx::expected<Msg, std::error_code> recv_msg(
      Channel *src_channel, ClassicProtocolState *src_protocol) {
    return recv_msg<Msg>(src_channel, src_protocol,
                         src_protocol->shared_capabilities());
  }
 
  template <class Msg>
  static inline stdx::expected<size_t, std::error_code> send_msg(
      Channel *dst_channel, ClassicProtocolState *dst_protocol, Msg msg,
      classic_protocol::capabilities::value_type caps) {
    auto encode_res = classic_protocol::encode(
        classic_protocol::frame::Frame<Msg>(++dst_protocol->seq_id(),
                                            std::forward<Msg>(msg)),
        caps, net::dynamic_buffer(dst_channel->send_plain_buffer()));
    if (!encode_res) return encode_res;
 
    return dst_channel->flush_to_send_buf();
  }
 
  template <class Msg>
  static inline stdx::expected<size_t, std::error_code> send_msg(
      Channel *dst_channel, ClassicProtocolState *dst_protocol, Msg msg) {
    return send_msg<Msg>(dst_channel, dst_protocol, std::forward<Msg>(msg),
                         dst_protocol->shared_capabilities());
  }
};
 
/**
 * receive a StmtExecute message from a channel.
 *
 * specialization of recv_msg<> as StmtExecute needs a the data from the
 * StmtPrepareOk.
 */
template <>
inline stdx::expected<classic_protocol::borrowed::message::client::StmtExecute,
                      std::error_code>
ClassicFrame::recv_msg<
    classic_protocol::borrowed::message::client::StmtExecute>(
    Channel *src_channel, ClassicProtocolState *src_protocol,
    classic_protocol::capabilities::value_type caps) {
  using msg_type = classic_protocol::borrowed::message::client::StmtExecute;
 
  auto read_res = ClassicFrame::recv_frame_sequence(src_channel, src_protocol);
  if (!read_res) return stdx::make_unexpected(read_res.error());
 
  const auto &recv_buf = src_channel->recv_plain_view();
 
  auto frame_decode_res = classic_protocol::decode<
      classic_protocol::frame::Frame<classic_protocol::borrowed::wire::String>>(
      net::buffer(recv_buf), caps);
  if (!frame_decode_res) {
    return stdx::make_unexpected(frame_decode_res.error());
  }
 
  src_protocol->seq_id(frame_decode_res->second.seq_id());
 
  auto decode_res = classic_protocol::decode<msg_type>(
      net::buffer(frame_decode_res->second.payload().value()), caps,
      [src_protocol](auto stmt_id)
          -> stdx::expected<std::vector<msg_type::ParamDef>, std::error_code> {
        const auto it = src_protocol->prepared_statements().find(stmt_id);
        if (it == src_protocol->prepared_statements().end()) {
          return stdx::make_unexpected(make_error_code(
              classic_protocol::codec_errc::statement_id_not_found));
        }
 
        std::vector<msg_type::ParamDef> params;
        params.reserve(it->second.parameters.size());
 
        for (const auto &param : it->second.parameters) {
          params.emplace_back(param.type_and_flags);
        }
 
        return params;
      });
  if (!decode_res) return stdx::make_unexpected(decode_res.error());
 
  return decode_res->second;
}
 
#endif