StdLib/LibC/Math/s_modf.c

   1 /* @(#)s_modf.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12 #include  <LibConfig.h>
  13 #include  <sys/EfiCdefs.h>
  14 #if defined(LIBM_SCCS) && !defined(lint)
  15 __RCSID("$NetBSD: s_modf.c,v 1.11 2002/05/26 22:01:57 wiz Exp $");
  16 #endif
  17
  18 /*
  19  * modf(double x, double *iptr)
  20  * return fraction part of x, and return x's integral part in *iptr.
  21  * Method:
  22  *  Bit twiddling.
  23  *
  24  * Exception:
  25  *  No exception.
  26  */
  27
  28 #include "math.h"
  29 #include "math_private.h"
  30
  31 static const double one = 1.0;
  32
  33 double
  34 modf(double x, double *iptr)
  35 {
  36   int32_t i0,i1,j0;
  37   u_int32_t i;
  38   EXTRACT_WORDS(i0,i1,x);
  39   j0 = ((i0>>20)&0x7ff)-0x3ff;  /* exponent of x */
  40   if(j0<20) {     /* integer part in high x */
  41       if(j0<0) {      /* |x|<1 */
  42           INSERT_WORDS(*iptr,i0&0x80000000,0);  /* *iptr = +-0 */
  43     return x;
  44       } else {
  45     i = (0x000fffff)>>j0;
  46     if(((i0&i)|i1)==0) {    /* x is integral */
  47         u_int32_t high;
  48         *iptr = x;
  49         GET_HIGH_WORD(high,x);
  50         INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
  51         return x;
  52     } else {
  53         INSERT_WORDS(*iptr,i0&(~i),0);
  54         return x - *iptr;
  55     }
  56       }
  57   } else if (j0>51) {   /* no fraction part */
  58       u_int32_t high;
  59       *iptr = x*one;
  60       GET_HIGH_WORD(high,x);
  61       INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
  62       return x;
  63   } else {      /* fraction part in low x */
  64       i = ((u_int32_t)(0xffffffff))>>(j0-20);
  65       if((i1&i)==0) {     /* x is integral */
  66           u_int32_t high;
  67     *iptr = x;
  68     GET_HIGH_WORD(high,x);
  69     INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
  70     return x;
  71       } else {
  72           INSERT_WORDS(*iptr,i0,i1&(~i));
  73     return x - *iptr;
  74       }
  75   }
  76 }