cmtmsg.c

简单实现多任务的C语言库 可以实现各个任务间的简单的消息通讯

#include "cmtlib.h"

/* ----------------------------------------------------------------
** Messages.
** ----------------------------------------------------------------
*/
/*man**************************************************************
NAME
	cmt_send - send a message to another task

SYNOPSIS
	#include "cmtlib.h"

	int far cdecl cmt_send(void far *msg,CMT_TASK far *task)

DESCRIPTION
	this function send one message to given task. as each task
	has room only for one active message, this function fails
	if the task already has a pending message. use cmt_psend()
	to send multiple messages.

DIAGNOSTICS
	if the message was delivered successfully, this function
	returns 1, otherwise it returns 0.
******************************************************************/
int far cdecl cmt_send(void far *msg,CMT_TASK far *task)
{
	if (!task->message) {
		task->message=msg;
		return 1;
	}
	return 0;
}
/*man**************************************************************
NAME
	cmt_receive - receives a message

SYNOPSIS
	#include "cmtlib.h"

	void far * far cdecl cmt_receive(void)

DESCRIPTION
	this function receives a message send with cmt_send()
	to current task. if there is no penging message, the caller
	blocks until message arrives.

DIGANOSTICS
	returns a received message
******************************************************************/
void far * far cdecl cmt_receive(void)
{
void far *m;
	while (!_cmtactivetask->message)
		cmt_pause();
	m=_cmtactivetask->message;
	_cmtactivetask->message=NULL;
	return m;
}

/*man**************************************************************
NAME
	cmt_recvclr - return a message if there is any

SYNOPSIS
	#include "cmtlib.h"

	void far * far cmt_recvclr(void)

DESCRIPTION
	this function can be used for two different tasks -
	it returns a message if there is one waiting, but
	as a side effect, it also discards any waiting
	messages

DIAGNOSTICS
	returns a message or NULL
******************************************************************/
void far * far cdecl cmt_recvclr(void)
{
void far *m;
	m=_cmtactivetask->message;
	_cmtactivetask->message=NULL;
	return m;
}

/*man**************************************************************
NAME
	cmt_recvtim - waits for a message

SYNOPSIS
	#include "cmtlib.h"

	void far * far cdecl cmt_recvtim(unsiged int clocks)

DESCRIPTION
	this message waits for a given number of 10-msec
	intervals for a message to arrive, blocking
	while doing so. note that the actual time delay is
	only precise to 55ms, which is timer tick period on
	PC. the code uses clocks*100/55 to get a number of
	timer ticks it should wait.

DIAGNOSTICS
	returns a message or NULL
******************************************************************/
void far * far cdecl cmt_recvtim(unsigned int clocks)
{
CMT_TIMER t;
void far *m;
	cmt_tstart(&t,((unsigned long)clocks*100L/55L));
	while (!_cmtactivetask->message && !cmt_texpired(&t))
		cmt_pause();
	m=_cmtactivetask->message;
	_cmtactivetask->message=NULL;
	return m;
}