用c实现“基于线程的多任务系统的实现”

#include <stdlib.h>
#include <dos.h>
#include <string.h>
#include <math.h>
#include <stdio.h>
#define GET_INDOS 0X34
#define GET_GRIT_ERR 0X5D06
#define FINISHED 0
#define RUNNING 1
#define READY 2
#define BLOCKED 3
#define NTCB 6
#define TIMEOUT 2
#define LOW 1
#define NORMAL 20
#define HIGH 40
unsigned CurrentTcb;
char far *indos_ptr =0;
char far *crit_err_ptr =0;
int timecount ;
typedef int (far *codeptr )(void);
void interrupt (*old_int8)(void);
void interrupt (*old_int23)(void);
struct TCB
{
unsigned int *stack;
unsigned ss,sp;
char state,pri,name[10];
}Tcb[NTCB];
int DosBusy();
void InitinDos(void);
int seektcb(void);
int creat(char*name,codeptr code,int stacklen,char ptr);
void over(void);
int all_finished(void);
void interrupt new_int8(void);
void interrupt new_int23(void);
void interrupt swith(void);
void SeekNext(void);
void mian();
void InitInDos()
{
union REGS regs;
struct SREGS segregs;
regs.h.ah=GET_INDOS;
intdosx(®s,®s,&segregs);
indos_ptr=MK_FP(segregs.es,regs.x.bx);
if(_osmajor<3)
crit_err_ptr=indos_ptr+1;
else if(_osmajor==3&&_osmajor==0)
crit_err_ptr=indos_ptr-1;
else
{
regs.x.ax=GET_GRIT_ERR;
intdosx(®s,®s,&segregs);
crit_err_ptr=MK_FP(segregs.ds,regs.x.si);
}
}
int DosBusy(void)
{
if (indos_ptr&&crit_err_ptr)
return (*indos_ptr||*crit_err_ptr);
else
return(-1);
}
void InitTcb(void)
{
int i;
for(i=0;i<NTCB;i++)
{
Tcb[i].name[0]='/0';
Tcb[i].state=FINISHED;
Tcb[i].pri=LOW;
}
}
int seektcb(void)
{
int i,newtcb=-1;
for(i=NTCB-1;i>=0;i--)
{
if (Tcb[i].state==FINISHED)
newtcb=i;
}
return newtcb;
}
int creat(char*name,codeptr code,int stacklen,char pri)
{
unsigned int *stack;
int newtcb;
if ((newtcb=seektcb())==-1)
{
printf("tcb is full!");
return 0;
}
strcpy(Tcb[newtcb].name,name);
Tcb[newtcb].state=READY;
Tcb[newtcb].pri=pri;
if ((stack=malloc(stacklen*sizeof(int)))==NULL)
{
printf("malloc error");
exit(0);
}
Tcb[newtcb].stack=stack;
Tcb[newtcb].ss=FP_SEG(stack);
stack=stack+(stacklen-2);
*stack=FP_SEG(over);
stack--;
printf("%d",stack);
*stack=FP_OFF(over);
stack--;
*stack=0x200;
stack--;
*stack=FP_SEG(code);
stack--;
*stack=FP_OFF(code);
stack-=5;
*stack=_ES;
stack--;
*stack=_DS;
stack-=3;
Tcb[newtcb].sp=FP_OFF(stack);
return newtcb;
}
void over(void)
{
disable();
free(Tcb[CurrentTcb].stack);
Tcb[CurrentTcb].name[0]='/0';
Tcb[CurrentTcb].state=FINISHED;
swith();
enable();
}
int all_finished(void)
{
int i ;
for(i=1;i<NTCB;i++)
{
if (Tcb[i].state!=FINISHED)
return 0;
}
return 1;
}
void interrupt new_int8(void)
{
disable();
(*old_int8)();
timecount++;
if(timecount>=TIMEOUT)
{
if (DosBusy())
return;
Tcb[CurrentTcb].ss=_SS;
Tcb[CurrentTcb].sp=_SP;
Tcb[CurrentTcb].state=READY;
SeekNext();
_SS=Tcb[CurrentTcb].ss;
_SP=Tcb[CurrentTcb].sp;
Tcb[CurrentTcb].state=RUNNING;
timecount=0;
}
enable();
}
void interrupt new_int23(void)
{
setvect(8,old_int8);
setvect(0x23,old_int23);
(*old_int23)();
}
void SeekNext(void)
{
int i,j=0,iTcb=0,pri=-1;
disable();
for(i=1;i<NTCB;i++)
{
if (Tcb[i].pri>pri&&Tcb[i].state==READY)
{
j++;
if(iTcb!=0)
Tcb[iTcb].pri++;
pri=Tcb[i].pri;
iTcb=i;
}
else if(Tcb[i].state==READY)
Tcb[i].pri++;
}
if (j>1)
Tcb[iTcb].pri--;
CurrentTcb=iTcb;
enable();
return;
}
void interrupt swith(void)
{
disable();
if(Tcb[CurrentTcb].state!=FINISHED)
{
Tcb[CurrentTcb].state=READY;
Tcb[CurrentTcb].ss=_SS;
Tcb[CurrentTcb].sp=_SP;
SeekNext();
Tcb[CurrentTcb].state=RUNNING;
_SS=Tcb[CurrentTcb].ss;
_SP=Tcb[CurrentTcb].sp;
}
else
{
SeekNext();
Tcb[CurrentTcb].state=RUNNING;
_SS=Tcb[CurrentTcb].ss;
_SP=Tcb[CurrentTcb].sp;
}enable();
}
void f1(void)
{
int i,j,k;
for(i=1;i<50;i++)
{
putchar('A');
for(j=0;j<1000;j++)
for(k=0;k<1000;k++);
}
putchar('/n');
}
void f2(void)
{
int i,j,k;
for(i=1;i<50;i++)
{
putchar('B');
for(j=0;j<1000;j++)
for(k=0;k<5000;k++);
}
putchar('/n');
}
void f3(void)
{
int i,j,k;
for(i=1;i<50;i++)
{
putchar('C');
for(j=0;j<1000;j++)
for(k=0;k<2000;k++);
}
putchar('/n');
}
void f4(void)
{
int i,j,k;
for(i=1;i<50;i++)
{
putchar('D');
for(j=0;j<1000;j++)
for(k=0;k<6000;k++);
}
putchar('/n');
}
void f5(void)
{
int i,j,k;
for(i=1;i<50;i++)
{
putchar('E');
for(j=0;j<1000;j++)
for(k=0;k<4000;k++);
}
putchar('/n');
}
void main()
{
disable();
InitInDos();
InitTcb();
old_int8=getvect(8);
old_int23=getvect(0x23);
strcpy(Tcb[0].name,"main");
Tcb[0].state=RUNNING;
CurrentTcb=0;
creat("f1",(codeptr) f1,1024,LOW);
creat("f2",(codeptr) f2,1024,HIGH);
creat("f3",(codeptr) f3,1024,NORMAL);
creat("f4",(codeptr) f4,1024,HIGH);
creat("f5",(codeptr) f5,1024,LOW);
setvect(8,new_int8);
setvect(0x23,new_int23);
clrscr();
swith();
enable();
while (!(all_finished()));
delay(5000);
Tcb[0].name[0]='/0';
Tcb[0].state=FINISHED;
setvect(8,old_int8);
setvect(0x23,old_int23);
printf("Multi_Task system terminated./n");
}

FROM: http://topic.csdn.net/t/20031202/21/2520263.html