cursor.h

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/* Copyright (c) 2016, 2023, Oracle and/or its affiliates.
 
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the terms of the GNU General Public License, version 2.0, as published by the
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FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
for more details.
 
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this program; if not, write to the Free Software Foundation, Inc.,
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/** @file storage/temptable/include/temptable/cursor.h
TempTable index cursor. */
 
#ifndef TEMPTABLE_CURSOR_H
#define TEMPTABLE_CURSOR_H
 
#include <assert.h>
 
#include "storage/temptable/include/temptable/column.h"
#include "storage/temptable/include/temptable/containers.h"
#include "storage/temptable/include/temptable/indexed_cells.h"
#include "storage/temptable/include/temptable/row.h"
#include "storage/temptable/include/temptable/storage.h"
 
namespace temptable {
 
/** A cursor for iterating over an `Index`. */
class Cursor {
 public:
  /** Constructor. */
  Cursor();
 
  /** Constructor from `Hash_duplicates` iterator. */
  explicit Cursor(
      /** [in] Iterator for cursor initial position. */
      const Hash_duplicates_container::const_iterator &iterator);
 
  /** Constructor from `Tree` iterator. */
  explicit Cursor(
      /** [in] Iterator for cursor initial position. */
      const Tree_container::const_iterator &iterator);
 
  Cursor(const Cursor &) = default;
  Cursor(Cursor &&) noexcept = default;
 
  /** Check if the cursor is positioned.
   * @return true if positioned */
  bool is_positioned() const;
 
  /** Unposition the cursor. */
  void unposition();
 
  /** Get the indexed cells of the current cursor position.
   * @return indexed cells */
  const Indexed_cells &indexed_cells() const;
 
  /** Get a pointer to the row of the current cursor position.
   * @return a pointer to a row */
  Storage::Element *row() const;
 
  /** Export the row that is pointed to by this cursor in mysql write_row()
   * format. */
  void export_row_to_mysql(
      /** [in] Metadata for the columns that constitute the row. */
      const Columns &columns,
      /** [out] Destination buffer to write the row to. */
      unsigned char *mysql_row,
      /** [in] Presumed length of the mysql row in bytes. */
      size_t mysql_row_length) const;
 
  /** Get the underlying hash iterator. The cursor must be on a hash index.
   * @return iterator */
  const Hash_duplicates_container::const_iterator &hash_iterator() const;
 
  /** Get the underlying tree iterator. The cursor must be on a tree index.
   * @return iterator */
  const Tree_container::const_iterator &tree_iterator() const;
 
  /** Copy-assign from another cursor.
   * @return *this */
  Cursor &operator=(
      /** [in] Source cursor to assign from. */
      const Cursor &rhs);
 
  /** Advance the cursor forward.
   * @return *this */
  Cursor &operator++();
 
  /** Recede the cursor backwards.
   * @return *this */
  Cursor &operator--();
 
  /** Check if equal to another cursor.
   * @return true if equal */
  bool operator==(
      /** [in] Cursor to compare with. */
      const Cursor &other) const;
 
  /** Check if not equal to another cursor.
   * @return true if not equal */
  bool operator!=(
      /** [in] Cursor to compare with. */
      const Cursor &other) const;
 
 private:
  /** Type of the index the cursor iterates over. */
  enum class Type : uint8_t {
    /** Hash index. */
    HASH,
    /** Tree index. */
    TREE,
  };
 
  /** Type of the index the cursor iterates over. */
  Type m_type;
 
  /** Indicate whether the cursor is positioned. */
  bool m_is_positioned;
 
  /** Iterator that is used if `m_type == Type::HASH`. */
  Hash_duplicates_container::const_iterator m_hash_iterator;
 
  /** Iterator that is used if `m_type == Type::TREE`. */
  Tree_container::const_iterator m_tree_iterator;
};
 
/* Implementation of inlined methods. */
 
inline Cursor::Cursor() : m_is_positioned(false) {}
 
inline Cursor::Cursor(const Hash_duplicates_container::const_iterator &iterator)
    : m_type(Type::HASH), m_is_positioned(true), m_hash_iterator(iterator) {}
 
inline Cursor::Cursor(const Tree_container::const_iterator &iterator)
    : m_type(Type::TREE), m_is_positioned(true), m_tree_iterator(iterator) {}
 
inline bool Cursor::is_positioned() const { return m_is_positioned; }
 
inline void Cursor::unposition() { m_is_positioned = false; }
 
inline const Indexed_cells &Cursor::indexed_cells() const {
  assert(m_is_positioned);
 
  if (m_type == Type::HASH) {
    return *m_hash_iterator;
  }
 
  assert(m_type == Type::TREE);
  return *m_tree_iterator;
}
 
inline Storage::Element *Cursor::row() const {
  assert(m_is_positioned);
 
  if (m_type == Type::HASH) {
    return m_hash_iterator->row();
  }
 
  assert(m_type == Type::TREE);
  return m_tree_iterator->row();
}
 
inline void Cursor::export_row_to_mysql(const Columns &columns,
                                        unsigned char *mysql_row,
                                        size_t mysql_row_length) const {
  assert(m_is_positioned);
 
  if (m_type == Type::HASH) {
    return m_hash_iterator->export_row_to_mysql(columns, mysql_row,
                                                mysql_row_length);
  }
 
  assert(m_type == Type::TREE);
  return m_tree_iterator->export_row_to_mysql(columns, mysql_row,
                                              mysql_row_length);
}
 
inline const Hash_duplicates_container::const_iterator &Cursor::hash_iterator()
    const {
  assert(m_type == Type::HASH);
  return m_hash_iterator;
}
 
inline const Tree_container::const_iterator &Cursor::tree_iterator() const {
  assert(m_type == Type::TREE);
  return m_tree_iterator;
}
 
inline Cursor &Cursor::operator=(const Cursor &rhs) {
  m_is_positioned = rhs.m_is_positioned;
 
  m_type = rhs.m_type;
 
  if (m_is_positioned) {
    if (m_type == Type::HASH) {
      m_hash_iterator = rhs.m_hash_iterator;
    } else {
      assert(m_type == Type::TREE);
      m_tree_iterator = rhs.m_tree_iterator;
    }
  }
 
  return *this;
}
 
inline Cursor &Cursor::operator++() {
  assert(m_is_positioned);
 
  if (m_type == Type::HASH) {
    ++m_hash_iterator;
  } else {
    assert(m_type == Type::TREE);
    ++m_tree_iterator;
  }
 
  return *this;
}
 
inline Cursor &Cursor::operator--() {
  assert(m_is_positioned);
 
  if (m_type == Type::HASH) {
    /* We don't support decrement on a hash and it shouldn't be called. */
    my_abort();
  } else {
    assert(m_type == Type::TREE);
    --m_tree_iterator;
  }
 
  return *this;
}
 
inline bool Cursor::operator==(const Cursor &other) const {
  assert(m_is_positioned);
 
  if (m_type == Type::HASH) {
    return m_hash_iterator == other.m_hash_iterator;
  }
 
  assert(m_type == Type::TREE);
  return m_tree_iterator == other.m_tree_iterator;
}
 
inline bool Cursor::operator!=(const Cursor &other) const {
  return !(*this == other);
}
 
} /* namespace temptable */
 
#endif /* TEMPTABLE_CURSOR_H */