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

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This program is free software; you can redistribute it and/or modify it under
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*****************************************************************************/

/*******************************************************************//**
@file include/ut0wqueue.h
A work queue

Created 4/26/2006 Osku Salerma
************************************************************************/

/*******************************************************************//**
A Work queue. Threads can add work items to the queue and other threads can
wait for work items to be available and take them off the queue for
processing.
************************************************************************/

#ifndef IB_WORK_QUEUE_H
#define IB_WORK_QUEUE_H

#include "ut0list.h"
#include "mem0mem.h"

// Forward declaration
struct ib_list_t;

/** Work queue */
struct ib_wqueue_t
{
	/** Mutex protecting everything */
	ib_mutex_t	mutex;
	/** Work item list */
	ib_list_t*	items;
	/** event we use to signal additions to list;
	os_event_set() and os_event_reset() are protected by the mutex */
	os_event_t	event;
};

/****************************************************************//**
Create a new work queue.
@return work queue */
ib_wqueue_t*
ib_wqueue_create();
/*===============*/

/****************************************************************//**
Free a work queue. */
void
ib_wqueue_free(
/*===========*/
	ib_wqueue_t*	wq);		/*!< in: work queue */

/** Add a work item to the queue.
@param[in,out]	wq		work queue
@param[in]	item		work item
@param[in,out]	heap		memory heap to use for allocating list node
@param[in]	wq_locked	work queue mutex locked */
void
ib_wqueue_add(ib_wqueue_t* wq, void* item, mem_heap_t* heap,
	      bool wq_locked = false);

/** Check if queue is empty.
@param wq wait queue
@return whether the queue is empty */
bool ib_wqueue_is_empty(ib_wqueue_t* wq);

/****************************************************************//**
Wait for a work item to appear in the queue.
@return work item */
void*
ib_wqueue_wait(
/*===========*/
	ib_wqueue_t*	wq);		/*!< in: work queue */

/********************************************************************
Wait for a work item to appear in the queue for specified time. */
void*
ib_wqueue_timedwait(
/*================*/
					/* out: work item or NULL on timeout*/
	ib_wqueue_t*	wq,		/* in: work queue */
	ulint		wait_in_usecs); /* in: wait time in micro seconds */

/********************************************************************
Return first item on work queue or NULL if queue is empty
@return work item or NULL */
void*
ib_wqueue_nowait(
/*=============*/
	ib_wqueue_t*	wq);		/*<! in: work queue */
/********************************************************************
Get number of items on queue.
@return number of items on queue */
ulint
ib_wqueue_len(
/*==========*/
	ib_wqueue_t*	wq);		/*<! in: work queue */

#endif /* IB_WORK_QUEUE_H */
