source: trunk/minix/lib/float/cfi.c@ 15

/*
  (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
  See the copyright notice in the ACK home directory, in the file "Copyright".
*/

/* $Header: /cvsup/minix/src/lib/float/cfi.c,v 1.1.1.1 2005/04/21 14:56:10 beng Exp $ */

/*
                CONVERT FLOAT TO SIGNED (CFI m n)

                N.B. The caller must know what it is getting.
                     A LONG is always returned. If it is an
                     integer the high byte is cleared first.
*/

#include "FP_trap.h"
#include "FP_types.h"
#include "FP_shift.h"

long
cfi(ds,ss,src)
int     ds;     /* destination size (2 or 4) */
int     ss;     /* source size      (4 or 8) */
DOUBLE  src;    /* assume worst case */
{
        EXTEND  buf;
        long    new;
        short   max_exp;

        extend(&src.d[0],&buf,ss);      /* get extended format */
        if (buf.exp < 0) {      /* no conversion needed */
                src.d[ss == 8] = 0L;
                return(0L);
        }
        max_exp = (ds << 3) - 2;        /* signed numbers */
                                /* have more limited max_exp */
        if (buf.exp > max_exp) {
                if (buf.exp == max_exp+1 && buf.sign && buf.m1 == NORMBIT &&
                    buf.m2 == 0L) {
                }
                else {
                        trap(EIOVFL);   /* integer overflow     */
                        buf.exp %= max_exp; /* truncate */
                }
        }
        new = buf.m1 >> (31-buf.exp);
        if (buf.sign)
                new = -new;
done:
        src.d[ss == 8] = new;
        return(new);
}