read.c

异步通讯C语言例行子程序

/* A module of ASYNCx.LIB version 1.20 */

#include <dos.h>
#include "asyncdef.h"

/************************************************************
 Receive n objects of size s from the port associated with p
 within t eighteenths of a second. Start puting them into
 memory starting at where buf points. Return the number of
 whole objects received.
************************************************************/
int a_read(void *buf,int s,int n,ASYNC *p,int t)
{unsigned i;
 byte *bp;
 unsigned long t0,far *t1;
 if (p)
  {t1=(unsigned long far *)MK_FP(0x40,0x6c);
   t0=*t1;
   bp=(byte *)buf;
   n*=s;
   for(i=0;i<n && (*t1)-t0<=(unsigned long)t;i++)
     if (a_icount(p))
       *bp++=a_getc(p);
     else
       i--;
   return(i/s);
  }
 return 0;
} /* end of a_read(buf,s,n,p,t) */