/*****************************************************************************

Copyright (c) 1995, 2021, 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.

This program is also distributed with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
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
separately licensed software that they have included with MySQL.

This program is distributed in the hope that it will be useful,
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 along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file include/os0thread.h
The interface to the operating system
process and thread control primitives

Created 9/8/1995 Heikki Tuuri
*******************************************************/

#ifndef os0thread_h
#define os0thread_h

#include "univ.i"

/* Maximum number of threads which can be created in the program;
this is also the size of the wait slot array for MySQL threads which
can wait inside InnoDB */

#define	OS_THREAD_MAX_N		srv_max_n_threads

/* Possible fixed priorities for threads */
#define OS_THREAD_PRIORITY_NONE		100
#define OS_THREAD_PRIORITY_BACKGROUND	1
#define OS_THREAD_PRIORITY_NORMAL	2
#define OS_THREAD_PRIORITY_ABOVE_NORMAL	3

#ifdef _WIN32
typedef DWORD			os_thread_id_t;	/*!< In Windows the thread id
						is an unsigned long int */
extern "C"  {
typedef LPTHREAD_START_ROUTINE	os_thread_func_t;
}

/** Macro for specifying a Windows thread start function. */
#define DECLARE_THREAD(func)	WINAPI func

/** Required to get around a build error on Windows. Even though our functions
are defined/declared as WINAPI f(LPVOID a); the compiler complains that they
are defined as: os_thread_ret_t (__cdecl*)(void*). Because our functions
don't access the arguments and don't return any value, we should be safe. */
#define os_thread_create(f,a,i)	\
	os_thread_create_func(reinterpret_cast<os_thread_func_t>(f), a, i)

#else

typedef pthread_t		os_thread_id_t;	/*!< In Unix we use the thread
						handle itself as the id of
						the thread */
extern "C"  { typedef void*	(*os_thread_func_t)(void*); }

/** Macro for specifying a POSIX thread start function. */
#define DECLARE_THREAD(func)	func
#define os_thread_create(f,a,i)	os_thread_create_func(f, a, i)

#endif /* _WIN32 */

/* Define a function pointer type to use in a typecast */
typedef void* (*os_posix_f_t) (void*);

#ifdef HAVE_PSI_INTERFACE
/* Define for performance schema registration key */
struct mysql_pfs_key_t {
public:

        /** Default Constructor */
        mysql_pfs_key_t() {
                s_count++;
        }

        /** Constructor */
        mysql_pfs_key_t(unsigned int    val) : m_value(val) {}

        /** Retreive the count.
        @return number of keys defined */
        static int get_count() {
                return s_count;
        }

        /* Key value. */
        unsigned int            m_value;

private:

        /** To keep count of number of PS keys defined. */
        static unsigned int     s_count;
};
#endif /* HAVE_PSI_INTERFACE */

/** Number of threads active. */
extern	ulint	os_thread_count;

/***************************************************************//**
Compares two thread ids for equality.
@return TRUE if equal */
ibool
os_thread_eq(
/*=========*/
	os_thread_id_t	a,	/*!< in: OS thread or thread id */
	os_thread_id_t	b);	/*!< in: OS thread or thread id */
/****************************************************************//**
Converts an OS thread id to a ulint. It is NOT guaranteed that the ulint is
unique for the thread though!
@return thread identifier as a number */
ulint
os_thread_pf(
/*=========*/
	os_thread_id_t	a);	/*!< in: OS thread identifier */
/****************************************************************//**
Creates a new thread of execution. The execution starts from
the function given.
NOTE: We count the number of threads in os_thread_exit(). A created
thread should always use that to exit so thatthe thread count will be
decremented.
We do not return an error code because if there is one, we crash here. */
void
os_thread_create_func(
/*==================*/
	os_thread_func_t	func,		/*!< in: pointer to function
						from which to start */
	void*			arg,		/*!< in: argument to start
						function */
	os_thread_id_t*		thread_id);	/*!< out: id of the created
						thread, or NULL */

/** Waits until the specified thread completes and joins it.
Its return value is ignored.
@param[in,out]	thread	thread to join */
void
os_thread_join(
	os_thread_id_t	thread);

/** Exits the current thread.
@param[in]	detach	if true, the thread will be detached right before
exiting. If false, another thread is responsible for joining this thread */
void
os_thread_exit(
	bool	detach = true)
	UNIV_COLD MY_ATTRIBUTE((noreturn));

/*****************************************************************//**
Returns the thread identifier of current thread.
@return current thread identifier */
os_thread_id_t
os_thread_get_curr_id(void);
/*========================*/
/*****************************************************************//**
Advises the os to give up remainder of the thread's time slice. */
void
os_thread_yield(void);
/*=================*/
/*****************************************************************//**
The thread sleeps at least the time given in microseconds. */
void
os_thread_sleep(
/*============*/
	ulint	tm);	/*!< in: time in microseconds */

/**
Initializes OS thread management data structures. */
void
os_thread_init();
/*============*/

/**
Frees OS thread management data structures. */
void
os_thread_free();
/*============*/

/*****************************************************************//**
Check if there are threads active.
@return true if the thread count > 0. */
bool
os_thread_active();
/*==============*/

#ifndef UNIV_NONINL
#include "os0thread.ic"
#endif

#endif
