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/** @file include/lob0undo.h
 Undo logging small changes to BLOBs. */

#ifndef lob0undo_h
#define lob0undo_h

#include <list>
#include "dict0mem.h"
#include "mem0mem.h"
#include "univ.i"

namespace lob {

/** Undo information about LOB data alone without including LOB index. */
struct undo_data_t {
  /** Apply the undo information to the given LOB.
  @param[in]	index		clustered index containing the LOB.
  @param[in]	lob_mem		LOB on which the given undo will be
                                  applied.
  @param[in]    len             length of LOB.
  @param[in]    lob_version     lob version number
  @param[in]    first_page_no   the first page number of lob */
  void apply(dict_index_t *index, byte *lob_mem, size_t len, size_t lob_version,
             page_no_t first_page_no);

  /** The LOB first page number. */
  page_no_t m_page_no = FIL_NULL;

  /** The LOB version number on which this undo should be applied. */
  ulint m_version = 0;

  /** The offset within LOB where partial update happened. */
  ulint m_offset = 0;

  /** The length of the modification. */
  ulint m_length = 0;

  /** Changes to the LOB data. */
  byte *m_old_data = nullptr;

  /** Copy the old data from the undo page into this object.
  @param[in]  undo_ptr  the pointer into the undo log record.
  @param[in]  len       length of the old data.
  @return pointer past the old data. */
  const byte *copy_old_data(const byte *undo_ptr, ulint len);

  /** Free allocated memory for old data. */
  void destroy();

  std::ostream &print(std::ostream &out) const;
};

inline std::ostream &operator<<(std::ostream &out, const undo_data_t &obj) {
  return (obj.print(out));
}

/** Container to hold a sequence of undo log records containing modification
of BLOBs. */
struct undo_seq_t {
  /** Constructor.
  @param[in]	field_no	the field number of LOB.*/
  undo_seq_t(ulint field_no) : m_field_no(field_no), m_undo_list(nullptr) {}

  /** Apply the undo log records on the given LOB in memory.
  @param[in]	index	the clustered index to which LOB belongs.
  @param[in]	lob	the BLOB in memory.
  @param[in]	len	the length of BLOB in memory.
  @param[in]	lob_version	the LOB version number.
  @param[in]	first_page_no	the first page number of BLOB.*/
  void apply(dict_index_t *index, byte *lob, size_t len, size_t lob_version,
             page_no_t first_page_no) {
    if (m_undo_list != nullptr) {
      for (auto iter = m_undo_list->begin(); iter != m_undo_list->end();
           ++iter) {
        iter->apply(index, lob, len, lob_version, first_page_no);
      }
    }
  }

  /** Get the field number of BLOB.
  @return the field number of BLOB. */
  ulint get_field_no() const { return (m_field_no); }

  /** Append the given undo log record to the end of container.
  @param[in]	u1	the undo log record information. */
  void push_back(undo_data_t &u1) {
    if (m_undo_list == nullptr) {
      m_undo_list = UT_NEW_NOKEY(std::list<undo_data_t>());
    }
    m_undo_list->push_back(u1);
  }

  /** Destroy the contents of this undo sequence list. */
  void destroy() {
    if (m_undo_list != nullptr) {
      std::for_each(m_undo_list->begin(), m_undo_list->end(),
                    [](undo_data_t &obj) { obj.destroy(); });
      m_undo_list->clear();
      UT_DELETE(m_undo_list);
      m_undo_list = nullptr;
    }
  }

  /** Check if any undo log exists to apply. */
  bool exists() const {
    return (m_undo_list == nullptr ? false : !m_undo_list->empty());
  }

  ulint m_field_no;

 private:
  std::list<undo_data_t> *m_undo_list = nullptr;
};

/** The list of modifications to be applied on LOBs to get older versions.
Given a field number, it should be able to obtain the list of undo
information. */
struct undo_vers_t {
 public:
  /** Get the undo log sequence object for the given field number, which
  represents one blob.
  @param[in]    field_no   the field number of the blob.
  @return the undo sequence object or nullptr. */
  undo_seq_t *get_undo_sequence_if_exists(ulint field_no) {
    if (m_versions == nullptr) {
      return (nullptr);
    } else {
      for (auto iter = m_versions->begin(); iter != m_versions->end(); ++iter) {
        if ((*iter)->get_field_no() == field_no) {
          return (*iter);
        }
      }
    }
    return (nullptr);
  }

  /** Get the undo log sequence object for the given field number, which
  represents one blob.  The undo sequence object is allocated if it does
  not exist.
  @param[in]    field_no   the field number of the blob.
  @return the undo sequence object. */
  undo_seq_t *get_undo_sequence(ulint field_no) {
    if (m_versions == nullptr) {
      m_versions = UT_NEW_NOKEY(std::list<undo_seq_t *>());
    } else {
      for (auto iter = m_versions->begin(); iter != m_versions->end(); ++iter) {
        if ((*iter)->get_field_no() == field_no) {
          return (*iter);
        }
      }
    }

    undo_seq_t *seq = UT_NEW_NOKEY(undo_seq_t(field_no));
    m_versions->push_back(seq);

    return (seq);
  }

  /** Empty the collected LOB undo information from cache. */
  void reset() {
    if (m_versions != nullptr) {
      for (auto iter = m_versions->begin(); iter != m_versions->end(); ++iter) {
        (*iter)->destroy();
        UT_DELETE(*iter);
      }
      m_versions->clear();
    }
  }

  /** Apply the undo log record on the given LOB in memory.
  @param[in]	clust_index	the clust index to which LOB belongs.
  @param[in]	field_no	the field number of the LOB.
  @param[in]	lob		the LOB data.
  @param[in]	len		the length of LOB.
  @param[in]	lob_version	LOB version number.
  @param[in]	first_page	the first page number of LOB.*/
  void apply(dict_index_t *clust_index, ulint field_no, byte *lob, size_t len,
             size_t lob_version, page_no_t first_page) {
    undo_seq_t *seq = get_undo_sequence_if_exists(field_no);

    if (seq != nullptr) {
      seq->apply(clust_index, lob, len, lob_version, first_page);
    }
  }

  /** Destroy the accumulated undo_seq_t objects. */
  void destroy() {
    if (m_versions != nullptr) {
      reset();
      UT_DELETE(m_versions);
      m_versions = nullptr;
    }
  }

  /** Check if the undo contained older versions.
  @return true if there are no older versions, false otherwise. */
  bool is_empty() const { return (m_versions->empty()); }

  /** Destructor to free the resources. */
  ~undo_vers_t() { destroy(); }

 private:
  /** Maintain a list of undo_seq_t objects. */
  std::list<undo_seq_t *> *m_versions = nullptr;
};

} /* namespace lob */

#endif /* lob0undo_h */