gcs_message_stage_lz4.h

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/* Copyright (c) 2016, 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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   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
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, 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 GCS_MESSAGE_STAGE_LZ4_H
#define GCS_MESSAGE_STAGE_LZ4_H
 
#include <lz4.h>
#include <utility>
#include <vector>
 
#include "plugin/group_replication/libmysqlgcs/include/mysql/gcs/gcs_types.h"
#include "plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_message_stages.h"
 
/**
  This class implements LZ4 compression. It is a stateless
  service class, thence it is thread safe.
 */
class Gcs_message_stage_lz4 : public Gcs_message_stage {
 public:
  /*
   Methods inherited from the Gcs_message_stage class.
   */
  Gcs_message_stage::stage_status skip_apply(
      uint64_t const &original_payload_size) const override;
 
  std::unique_ptr<Gcs_stage_metadata> get_stage_header() override;
 
 protected:
  std::pair<bool, std::vector<Gcs_packet>> apply_transformation(
      Gcs_packet &&packet) override;
 
  std::pair<Gcs_pipeline_incoming_result, Gcs_packet> revert_transformation(
      Gcs_packet &&packet) override;
 
  Gcs_message_stage::stage_status skip_revert(
      const Gcs_packet &packet) const override;
 
 public:
  /**
   The default threshold value in bytes.
   */
  static constexpr unsigned long long DEFAULT_THRESHOLD = 1024;
 
  /**
   Creates an instance of the stage with the default threshold in bytes set.
   */
  explicit Gcs_message_stage_lz4() : m_threshold(DEFAULT_THRESHOLD) {}
 
  /**
   Creates an instance of the stage with the given threshold in bytes.
 
   @param enabled enables this message stage
   @param compress_threshold messages with the payload larger
                             than compress_threshold in bytes are compressed.
   */
  explicit Gcs_message_stage_lz4(bool enabled,
                                 unsigned long long compress_threshold)
      : Gcs_message_stage(enabled), m_threshold(compress_threshold) {}
 
  ~Gcs_message_stage_lz4() override = default;
 
  /*
   Return the stage code.
   */
  Stage_code get_stage_code() const override { return Stage_code::ST_LZ4_V1; }
 
  /**
    Sets the threshold in bytes after which compression kicks in.
 
    @param threshold if the payload exceeds these many bytes, then
                     the message is compressed.
   */
  void set_threshold(unsigned long long threshold) { m_threshold = threshold; }
 
  /**
   Return the maximum payload size in bytes that can be compressed.
   */
  static constexpr unsigned long long max_input_compression() noexcept {
    /*
    The code expects that the following assumption will always hold.
    */
    static_assert(
        LZ4_MAX_INPUT_SIZE <= std::numeric_limits<int>::max(),
        "Maximum input size for lz compression exceeds the expected value");
    return LZ4_MAX_INPUT_SIZE;
  }
 
 private:
  /**
   This marks the threshold in bytes above which a message gets compressed.
   Messages that are smaller than this threshold are not compressed.
   */
  unsigned long long m_threshold;
};
 
class Gcs_message_stage_lz4_v2 : public Gcs_message_stage_lz4 {
 public:
  /**
   Creates an instance of the stage with the default threshold in bytes.
   */
  explicit Gcs_message_stage_lz4_v2() : Gcs_message_stage_lz4() {}
 
  /**
   Creates an instance of the stage with the given threshold in bytes.
 
   @param enabled enables this message stage
   @param compress_threshold messages with the payload larger
   than compress_threshold in bytes are compressed.
   */
  explicit Gcs_message_stage_lz4_v2(bool enabled,
                                    unsigned long long compress_threshold)
      : Gcs_message_stage_lz4(enabled, compress_threshold) {}
 
  ~Gcs_message_stage_lz4_v2() override = default;
 
  /*
   Return the stage code.
   */
  Stage_code get_stage_code() const override { return Stage_code::ST_LZ4_V2; }
};
 
class Gcs_message_stage_lz4_v3 : public Gcs_message_stage_lz4 {
 public:
  /**
   Creates an instance of the stage with the default threshold in bytes.
   */
  explicit Gcs_message_stage_lz4_v3() : Gcs_message_stage_lz4() {}
 
  /**
   Creates an instance of the stage with the given threshold in bytes.
 
   @param enabled enables this message stage
   @param compress_threshold messages with the payload larger
   than compress_threshold in bytes are compressed.
   */
  explicit Gcs_message_stage_lz4_v3(bool enabled,
                                    unsigned long long compress_threshold)
      : Gcs_message_stage_lz4(enabled, compress_threshold) {}
 
  ~Gcs_message_stage_lz4_v3() override {}
 
  /*
   Return the stage code.
   */
  Stage_code get_stage_code() const override { return Stage_code::ST_LZ4_V3; }
};
 
#endif /* GCS_MESSAGE_STAGE_LZ4_H */