lib/ack/libfp/fif8.fc

   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         MULTIPLY AND DISMEMBER PARTS (FIF 8)
  10 */
  11
  12 #include "FP_types.h"
  13 #include "FP_shift.h"
  14
  15 void
  16 fif8(p,x,y)
  17 DOUBLE  x,y;
  18 struct fif8_returns *p;
  19 {
  20
  21         EXTEND  e1,e2;
  22
  23         extend(&y.d[0],&e1,sizeof(DOUBLE));
  24         extend(&x.d[0],&e2,sizeof(DOUBLE));
  25                 /* do a multiply */
  26         mul_ext(&e1,&e2);
  27         e2 = e1;
  28         compact(&e2, &y.d[0], sizeof(DOUBLE));
  29         if (e1.exp < 0) {
  30                 p->ipart.d[0] = 0;
  31                 p->ipart.d[1] = 0;
  32                 p->fpart = y;
  33                 return;
  34         }
  35         if (e1.exp > 62 - DBL_M1LEFT) {
  36                 p->ipart = y;
  37                 p->fpart.d[0] = 0;
  38                 p->fpart.d[1] = 0;
  39                 return;
  40         }
  41         b64_sft(&e1.mantissa, 63 - e1.exp);
  42         b64_sft(&e1.mantissa, e1.exp - 63);     /* "loose" low order bits */
  43         compact(&e1, &(p->ipart.d[0]), sizeof(DOUBLE));
  44         extend(&(p->ipart.d[0]), &e2, sizeof(DOUBLE));
  45         extend(&y.d[0], &e1, sizeof(DOUBLE));
  46         sub_ext(&e1, &e2);
  47         compact(&e1, &(p->fpart.d[0]), sizeof(DOUBLE));
  48 }