contiki_protothread源码

pt下载地址：http://dunkels.com/adam/pt/download.html

/*
 * Copyright (c) 2004-2005, Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This file is part of the uIP TCP/IP stack
 *
 * Author: Adam Dunkels <adam@sics.se>
 *
 * $Id: pt.h,v 1.2 2006/06/12 08:00:30 adam Exp $
 */

/**
 * \addtogroup pt
 * @{
 */

/**
 * \file
 * Protothreads implementation.
 * \author
 * Adam Dunkels <adam@sics.se>
 *
 */

#ifndef __PT_H__
#define __PT_H__
#if 0
#include "lc.h"
#else 
typedef unsigned short lc_t;

#define LC_INIT(s) s = 0;

#define LC_RESUME(s) switch(s) { case 0:

#define LC_SET(s) s = __LINE__; case __LINE__:

#define LC_END(s) }	
#endif

struct pt {
  lc_t lc;
};

#define PT_WAITING 0
#define PT_EXITED  1
#define PT_ENDED   2
#define PT_YIELDED 3

/**
 * \name Initialization
 * @{
 */

/**
 * Initialize a protothread.
 *
 * Initializes a protothread. Initialization must be done prior to
 * starting to execute the protothread.
 *
 * \param pt A pointer to the protothread control structure.
 *
 * \sa PT_SPAWN()
 *
 * \hideinitializer
 */
#define PT_INIT(pt)   LC_INIT((pt)->lc)

/** @} */

/**
 * \name Declaration and definition
 * @{
 */

/**
 * Declaration of a protothread.
 *
 * This macro is used to declare a protothread. All protothreads must
 * be declared with this macro.
 *
 * \param name_args The name and arguments of the C function
 * implementing the protothread.
 *
 * \hideinitializer
 *声明一个线程,如PT_THREAD(task(struct pt *pt)) {...}
 */
#define PT_THREAD(name_args) char name_args

/**
 * Declare the start of a protothread inside the C function
 * implementing the protothread.
 *
 * This macro is used to declare the starting point of a
 * protothread. It should be placed at the start of the function in
 * which the protothread runs. All C statements above the PT_BEGIN()
 * invokation will be executed each time the protothread is scheduled.
 *
 * \param pt A pointer to the protothread control structure.
 *
 * \hideinitializer
 */
#define PT_BEGIN(pt) { char PT_YIELD_FLAG = 1; LC_RESUME((pt)->lc)

/**
 * Declare the end of a protothread.
 *
 * This macro is used for declaring that a protothread ends. It must
 * always be used together with a matching PT_BEGIN() macro.
 *
 * \param pt A pointer to the protothread control structure.
 *
 * \hideinitializer
 */
#define PT_END(pt) LC_END((pt)->lc); PT_YIELD_FLAG = 0; \
                   PT_INIT(pt); return PT_ENDED; }

/** @} */

/**
 * \name Blocked wait
 * @{
 */

/**
 * Block and wait until condition is true.
 *
 * This macro blocks the protothread until the specified condition is
 * true.
 *
 * \param pt A pointer to the protothread control structure.
 * \param condition The condition.
 *
 * \hideinitializer
 *阻塞等待，直到条件满足
 */
#define PT_WAIT_UNTIL(pt, condition)	        \
  do {						\
    LC_SET((pt)->lc);				\
    if(!(condition)) {				\
      return PT_WAITING;			\
    }						\
  } while(0)

/**
 * Block and wait while condition is true.
 *
 * This function blocks and waits while condition is true. See
 * PT_WAIT_UNTIL().
 *
 * \param pt A pointer to the protothread control structure.
 * \param cond The condition.
 *
 * \hideinitializer
 *阻塞等待，直到条件不满足
 */
#define PT_WAIT_WHILE(pt, cond)  PT_WAIT_UNTIL((pt), !(cond))

/** @} */

/**
 * \name Hierarchical protothreads
 * @{
 */

/**
 * Block and wait until a child protothread completes.
 *
 * This macro schedules a child protothread. The current protothread
 * will block until the child protothread completes.
 *
 * \note The child protothread must be manually initialized with the
 * PT_INIT() function before this function is used.
 *
 * \param pt A pointer to the protothread control structure.
 * \param thread The child protothread with arguments
 *
 * \sa PT_SPAWN()
 *
 * \hideinitializer
 *等待线程thread执行完毕
 */
#define PT_WAIT_THREAD(pt, thread) PT_WAIT_WHILE((pt), PT_SCHEDULE(thread))

/**
 * Spawn a child protothread and wait until it exits.
 *
 * This macro spawns a child protothread and waits until it exits. The
 * macro can only be used within a protothread.
 *
 * \param pt A pointer to the protothread control structure.
 * \param child A pointer to the child protothread's control structure.
 * \param thread The child protothread with arguments
 *
 * \hideinitializer
 *创建pt的子线程child
 */
#define PT_SPAWN(pt, child, thread)		\
  do {						\
    PT_INIT((child));				\
    PT_WAIT_THREAD((pt), (thread));		\
  } while(0)

/** @} */

/**
 * \name Exiting and restarting
 * @{
 */

/**
 * Restart the protothread.
 *
 * This macro will block and cause the running protothread to restart
 * its execution at the place of the PT_BEGIN() call.
 *
 * \param pt A pointer to the protothread control structure.
 *
 * \hideinitializer
 *线程重启
 */
#define PT_RESTART(pt)				\
  do {						\
    PT_INIT(pt);				\
    return PT_WAITING;			\
  } while(0)

/**
 * Exit the protothread.
 *
 * This macro causes the protothread to exit. If the protothread was
 * spawned by another protothread, the parent protothread will become
 * unblocked and can continue to run.
 *
 * \param pt A pointer to the protothread control structure.
 *
 * \hideinitializer
 *线程退出
 */
#define PT_EXIT(pt)				\
  do {						\
    PT_INIT(pt);				\
    return PT_EXITED;			\
  } while(0)

/** @} */

/**
 * \name Calling a protothread
 * @{
 */

/**
 * Schedule a protothread.
 *
 * This function shedules a protothread. The return value of the
 * function is non-zero if the protothread is running or zero if the
 * protothread has exited.
 *
 * \param f The call to the C function implementing the protothread to
 * be scheduled
 *
 * \hideinitializer
 *调度线程， 如PT_SCHEDULE(task(&pt_a));
 */
#define PT_SCHEDULE(f) ((f) == PT_WAITING)

/** @} */

/**
 * \name Yielding from a protothread
 * @{
 */

/**
 * Yield from the current protothread.
 *
 * This function will yield the protothread, thereby allowing other
 * processing to take place in the system.
 *
 * \param pt A pointer to the protothread control structure.
 *
 * \hideinitializer
 *挂起pt线程，以此释放CPU给其它线程去执行，当PT_YIELD_FLAG满足时退出锁死
 *
 */
#define PT_YIELD(pt)				\
  do {						\
    PT_YIELD_FLAG = 0;				\
    LC_SET((pt)->lc);				\
    if(PT_YIELD_FLAG == 0) {			\
      return PT_YIELDED;			\
    }						\
  } while(0)

/**
 * \brief      Yield from the protothread until a condition occurs.
 * \param pt   A pointer to the protothread control structure.
 * \param cond The condition.
 *
 *             This function will yield the protothread, until the
 *             specified condition evaluates to true.
 *
 *
 * \hideinitializer
 *挂起pt线程，以此释放CPU给其它线程去执行,当PT_YIELD_FLAG和cond都同时满足时才退出锁死
 */
#define PT_YIELD_UNTIL(pt, cond)		\
  do {						\
    PT_YIELD_FLAG = 0;				\
    LC_SET((pt)->lc);				\
    if((PT_YIELD_FLAG == 0) || !(cond)) {	\
      return PT_YIELDED;			\
    }						\
  } while(0)

/** @} */

#endif /* __PT_H__ */

/** @} */

示例：

char run_a = 0;
char run_b = 0;

char task_a(struct pt *pt)
{
 { char PT_YIELD_FLAG = 1; switch((pt)->lc) { case 0:;
 while(1) {
  do { (pt)->lc = 10; case 10:; if(!(run_a)) { return 0; } } while(0);
  run_a = 0;
  run_b = 1;
  printf("%s\n", __FUNCTION__);
 }
 }; PT_YIELD_FLAG = 0; (pt)->lc = 0;; return 2; };
}

char task_b(struct pt *pt)
{
 { char PT_YIELD_FLAG = 1; switch((pt)->lc) { case 0:;
 while(1){
  run_a = 1;
  do { (pt)->lc = 23; case 23:; if(!(run_b)) { return 0; } } while(0);
  run_b = 0;
  printf("%s\n", __FUNCTION__);
 }
 }; PT_YIELD_FLAG = 0; (pt)->lc = 0;; return 2; };
}

int main()
{
 struct pt pt_a;
 struct pt pt_b;

 (&pt_a)->lc = 0;;
 (&pt_b)->lc = 0;;
 while(1) {
  ((task_a(&pt_a)) == 0);
  ((task_b(&pt_b)) == 0);
  sleep(1);
 }
 return 0;
}
///////////////////////////////////////////////////////////////////////////////
好处：
1.子线程如果在程序某处条件不满足会阻塞退出线程，在下次得到调度的时候能直接跳转到上次阻塞的地方继续执行。
如果是普通的函数调用，则会从函数开始依次重新执行，这显然不是我们想要的。
///////////////////////////////////////////////////////////////////////////////
#include <stdio.h>
#include "pt.h"
char run_a = 0;
char run_b = 0;

PT_THREAD(task_a(struct pt *pt))
{
	PT_BEGIN(pt);
	while(1)
		PT_WAIT_UNTIL(pt, run_a);
		run_a = 0;
		run_b = 1;
		printf("%s\n", __FUNCTION__);
	}
	PT_END(pt);	
}

PT_THREAD(task_b(struct pt *pt))
{
	PT_BEGIN(pt);
	while(1){
		run_a = 1;
		PT_WAIT_UNTIL(pt, run_b);
		run_b = 0;
		printf("%s\n", __FUNCTION__);
	}	
	PT_END(pt);	
}

int main()
{
	struct pt pt_a;
	struct pt pt_b;
	
	PT_INIT(&pt_a);
	PT_INIT(&pt_b);
	while(1) {
		PT_SCHEDULE(task_a(&pt_a));
		PT_SCHEDULE(task_b(&pt_b));
		sleep(1);
	}
	return 0;
}