#include "jlib.h"

/* Read or write a buffer from file.  Usually you use dos_read() or dos_write()
   macros rather than calling this one directly */
long dos_rw(Jfile f,void *buf,long size,int ah)
{
union i86_regs reg;
long written;
unsigned s1;

written = 0;
while (size > 0)
	{
	reg.b.ah = ah;
	reg.w.bx = f;
	s1 = (size > 0x0c000L ?  0xc000 : size);
	reg.w.cx = s1;
	reg.w.dx = i86_ptr_offset(buf);
	reg.w.ds = i86_ptr_seg(buf);
	if ((i86_sysint(0x21,&reg,&reg))&1)	/* check carry */
		{
		goto OUT;
		}
	else
		{
		written += (unsigned)reg.w.ax;
		size -= (unsigned)reg.w.ax;
		if (s1 != reg.w.ax)
			goto OUT;
		}
	buf = i86_norm_ptr((char *)buf + s1);
	}
OUT:
return(written);
}