zstd_comp.h

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#ifndef LIBBINLOGEVENTS_COMPRESSION_ZSTD_COMP_H_
#define LIBBINLOGEVENTS_COMPRESSION_ZSTD_COMP_H_
 
#include <zstd.h>
 
#include "compressor.h"
#include "libbinlogevents/include/buffer/buffer_sequence_view.h"
#include "libbinlogevents/include/nodiscard.h"
 
struct ZSTD_outBuffer_s;
 
namespace binary_log::transaction::compression {
 
/// Compressor class that uses the ZSTD library.
class Zstd_comp : public Compressor {
 public:
  using typename Compressor::Char_t;
  using typename Compressor::Managed_buffer_sequence_t;
  using typename Compressor::Size_t;
  using Compression_level_t = int;
  static constexpr type type_code = ZSTD;
 
  /// The default compression level for this compressor.
  static constexpr Compression_level_t default_compression_level = 3;
 
  Zstd_comp() = default;
 
  ~Zstd_comp() override;
 
  Zstd_comp(const Zstd_comp &) = delete;
  Zstd_comp(const Zstd_comp &&) = delete;
  Zstd_comp &operator=(const Zstd_comp &rhs) = delete;
  Zstd_comp &operator=(const Zstd_comp &&rhs) = delete;
 
  /// Set the compression level for this compressor.
  ///
  /// This function may be invoked at any time, but will only take
  /// effect the next time a new frame starts, i.e., at the first call
  /// to @c feed after the frame has been reset.
  ///
  /// @param compression_level the new compression level.
  void set_compression_level(Compression_level_t compression_level);
 
 private:
  /// @return ZSTD
  type do_get_type_code() const override;
 
  /// @copydoc Compressor::do_reset
  void do_reset() override;
 
  /// @copydoc Compressor::do_feed
  void do_feed(const Char_t *input_data, Size_t input_size) override;
 
  /// @copydoc Compressor::do_compress
  [[NODISCARD]] Compress_status do_compress(
      Managed_buffer_sequence_t &out) override;
 
  /// @copydoc Compressor::do_finish
  [[NODISCARD]] Compress_status do_finish(
      Managed_buffer_sequence_t &out) override;
 
  /// @copydoc Compressor::do_get_grow_constraint_hint
  [[NODISCARD]] Grow_constraint_t do_get_grow_constraint_hint() const override;
 
  /// Deallocate the ZSTD compression context.
  void destroy();
 
  /// Reset just the ZSTD compressor state, not other state.
  void reset_compressor();
 
  /// Make the ZSTD buffer point to the next available buffer;
  /// allocate one if necessary.
  ///
  /// @param[in,out] managed_buffer_sequence owns the data and
  /// manages the growth.
  ///
  /// @param[out] obuf ZSTD buffer that will be altered to point to
  /// the next available byte in buffer_sequence.
  ///
  /// @retval success managed_buffer_sequence was not full, or its
  /// capacity has been incremented successfully.  obuf has been set
  /// to point to next available byte.
  ///
  /// @retval out_of_memory buffer_sequence was full and an out of
  /// memory error occurred.  buffer_sequence has not been modified.
  ///
  /// @retval exceeds_max_size buffer_sequence was full and at its max
  /// capacity.  buffer_sequence has not been modified.
  [[NODISCARD]] Compress_status get_obuf(
      Managed_buffer_sequence_t &managed_buffer_sequence,
      ZSTD_outBuffer_s &obuf);
 
  /// Account for having written to the output buffer.
  ///
  /// This moves the read/write boundary in the
  /// Managed_buffer_sequence, and also increments
  /// m_total_output_size.
  ///
  /// @param managed_buffer_sequence The buffer sequence that has
  /// been written to.
  ///
  /// @param delta The number of bytes that have been written.
  void move_position(Managed_buffer_sequence_t &managed_buffer_sequence,
                     Size_t delta);
 
  /// The ZSTD compression context.
  ZSTD_CStream *m_ctx{nullptr};
 
  /// The input buffer.
  ZSTD_inBuffer m_ibuf{nullptr, 0, 0};
 
  /// Value used to indicate that no compression level has been specified.
  static constexpr Compression_level_t uninitialized_compression_level{0};
 
  /// True when @c compress has been called and neither @c finish nor
  /// @c reset has yet been called.
  bool m_started{false};
 
  /// Compression level that was set in the @c m_ctx object.
  Compression_level_t m_current_compression_level{
      uninitialized_compression_level};
 
  /// Compression level that was given in @c set_compression_level
  Compression_level_t m_next_compression_level{default_compression_level};
};
 
}  // namespace binary_log::transaction::compression
 
#endif  // ifndef LIBBINLOGEVENTS_COMPRESSION_ZSTD_COMP_H_