lib/float/cfi.c

   1 /*
   2   (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
   3   See the copyright notice in the ACK home directory, in the file "Copyright".
   4 */
   5
   6 /* $Header$ */
   7
   8 /*
   9                 CONVERT FLOAT TO SIGNED (CFI m n)
  10
  11                 N.B. The caller must know what it is getting.
  12                      A LONG is always returned. If it is an
  13                      integer the high byte is cleared first.
  14 */
  15
  16 #include "FP_trap.h"
  17 #include "FP_types.h"
  18 #include "FP_shift.h"
  19
  20 long
  21 cfi(ds,ss,src)
  22 int     ds;     /* destination size (2 or 4) */
  23 int     ss;     /* source size      (4 or 8) */
  24 DOUBLE  src;    /* assume worst case */
  25 {
  26         EXTEND  buf;
  27         long    new;
  28         short   max_exp;
  29
  30         extend(&src.d[0],&buf,ss);      /* get extended format */
  31         if (buf.exp < 0) {      /* no conversion needed */
  32                 src.d[ss == 8] = 0L;
  33                 return(0L);
  34         }
  35         max_exp = (ds << 3) - 2;        /* signed numbers */
  36                                 /* have more limited max_exp */
  37         if (buf.exp > max_exp) {
  38                 if (buf.exp == max_exp+1 && buf.sign && buf.m1 == NORMBIT &&
  39                     buf.m2 == 0L) {
  40                 }
  41                 else {
  42                         trap(EIOVFL);   /* integer overflow     */
  43                         buf.exp %= max_exp; /* truncate */
  44                 }
  45         }
  46         new = buf.m1 >> (31-buf.exp);
  47         if (buf.sign)
  48                 new = -new;
  49 done:
  50         src.d[ss == 8] = new;
  51         return(new);
  52 }