cmttimer.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 <dos.h>
#include "cmtlib.h"

static unsigned long far *biosticker=(unsigned long *)0x0040006cl;

/* ----------------------------------------------------------------
** Timer.
** ----------------------------------------------------------------
*/
/*man**************************************************************
NAME
	cmt_tsart - starts a timer

SYNOPSIS
	#include "cmtlib.h"

	void far cdecl cmt_tstart(CMT_TIMER far *t,unsigned long ticks)

DESCRIPTION
	this function starts a timer countdown on the given
	timer for given number of 55 ms clock ticks.
******************************************************************/
void far cdecl cmt_tstart(CMT_TIMER far *t,unsigned long ticks)
{
	if (t) {
		t->length=ticks;		
		disable();
		t->start=*biosticker;
		enable();
		t->end=t->start+ticks;
	}
}

/*man**************************************************************
NAME
	cmt_texpired - check if the timer has expired

SYNOPSIS
	#include "cmtlib.h"

	int far cdecl cmt_texpired(CMT_TIMER far *t)

DESCRIPTION
	this function check if the given timer has expired.

DIAGNOSTICS
	returns 1 if the timer has expired, 0 if it is not.
******************************************************************/
int far cdecl cmt_texpired(CMT_TIMER far *t)
{
unsigned long tick;
	if (t) {
		disable();
		tick=*biosticker;
		enable();
		if (t->end<t->start) {
			tick+=t->start;
			if (tick<t->start && tick>t->end)
				return 1;
		}
		else {
			if (tick>t->end || tick<t->start)
				return 1;
		}
	}
	return 0;
}

/*man**************************************************************
NAME
	cmt_expire - force timer to expire

SYNOPSIS
	#include "cmtlib.h"

	void far cdecl cmt_expire(CMT_TIMER far *t)

DESCRIPTION
	this function immidiately expires the given timer.
******************************************************************/
void far cdecl cmt_expire(CMT_TIMER far *t)
{
	t->end=t->start;
	t->length=0;
}

/*man**************************************************************
NAME
	cmt_sleep - blocks a task for given number of seconds

SYNOPSIS
	#include "cmtlib.h"

	void far cdecl cmt_sleep(unsigned int seconds)

DESCRIPTION
	this is a sleep function it goes into loop giving away
	the calling task's timeslice and waiting for a given
	number of seconds to pass by.

	if number of seconds is 0, cmt_sleep equals to cmt_pause
******************************************************************/
void far cdecl cmt_sleep(unsigned int seconds)
{
CMT_TIMER t;
	if (!seconds)
		cmt_pause();
	else {
		cmt_tstart(&t,(unsigned long)seconds*18L+(seconds/5));
		while (!cmt_texpired(&t))
			cmt_pause();
	}
}