mutex_lock.h

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/* Copyright (c) 2014, 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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   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 MUTEX_LOCK_INCLUDED
#define MUTEX_LOCK_INCLUDED
 
/**
  @file include/mutex_lock.h
*/
#include <mysql/psi/mysql_mutex.h>
#include <utility>
 
/**
  A simple wrapper around a mutex:
  Grabs the mutex in the CTOR, releases it in the DTOR.
  The mutex may be NULL, in which case this is a no-op.
  Templated to allow unit testing with mocked mutex. Not copyable since
  ownership of a mutex cannot be shared, but movable so that ownership can be
  transferred to a different Mutex_lock.
*/
template <class MUTEX>
class Generic_mutex_lock {
 public:
  Generic_mutex_lock() noexcept = default;
  Generic_mutex_lock(MUTEX *mutex, const char *src_file, int src_line) noexcept
      : m_mutex(mutex), m_src_file(src_file), m_src_line(src_line) {
    if (m_mutex) {
      mysql_mutex_lock_with_src(m_mutex, m_src_file, m_src_line);
    }
  }
  ~Generic_mutex_lock() noexcept {
    if (m_mutex) {
      mysql_mutex_unlock_with_src(m_mutex, m_src_file, m_src_line);
    }
  }
  Generic_mutex_lock(const Generic_mutex_lock &) = delete;
  Generic_mutex_lock(Generic_mutex_lock &&src) noexcept
      : m_mutex{src.m_mutex},
        m_src_file{src.m_src_file},
        m_src_line{src.m_src_line} {
    src.m_mutex = nullptr;
    src.m_src_file = nullptr;
    src.m_src_line = 0;
  }
 
  Generic_mutex_lock &operator=(const Generic_mutex_lock &) = delete;
  Generic_mutex_lock &operator=(Generic_mutex_lock &&src) noexcept {
    Generic_mutex_lock tmp{std::move(src)};
    std::swap(m_mutex, tmp.m_mutex);
    m_src_file = tmp.m_src_file;
    m_src_line = tmp.m_src_line;
    return *this;
  }
 
 private:
  MUTEX *m_mutex = nullptr;
  const char *m_src_file = nullptr;
  int m_src_line = 0;
};
 
using Mutex_lock = Generic_mutex_lock<mysql_mutex_t>;
 
#define MUTEX_LOCK(NAME, X) const Mutex_lock NAME(X, __FILE__, __LINE__)
 
#endif  // MUTEX_LOCK_INCLUDED