StdLib/LibC/Math/s_floor.c

   1 /* @(#)s_floor.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_floor.c,v 1.11 2002/05/26 22:01:56 wiz Exp $");
  16 #endif
  17
  18 /*
  19  * floor(x)
  20  * Return x rounded toward -inf to integral value
  21  * Method:
  22  *  Bit twiddling.
  23  * Exception:
  24  *  Inexact flag raised if x not equal to floor(x).
  25  */
  26
  27 #include "math.h"
  28 #include "math_private.h"
  29
  30 static const double huge = 1.0e300;
  31
  32 double
  33 floor(double x)
  34 {
  35   int32_t i0,i1,j0;
  36   u_int32_t i,j;
  37   EXTRACT_WORDS(i0,i1,x);
  38   j0 = ((i0>>20)&0x7ff)-0x3ff;
  39   if(j0<20) {
  40       if(j0<0) {  /* raise inexact if x != 0 */
  41     if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
  42         if(i0>=0) {i0=i1=0;}
  43         else if(((i0&0x7fffffff)|i1)!=0)
  44       { i0=0xbff00000;i1=0;}
  45     }
  46       } else {
  47     i = (0x000fffff)>>j0;
  48     if(((i0&i)|i1)==0) return x; /* x is integral */
  49     if(huge+x>0.0) {  /* raise inexact flag */
  50         if(i0<0) i0 += (0x00100000)>>j0;
  51         i0 &= (~i); i1=0;
  52     }
  53       }
  54   } else if (j0>51) {
  55       if(j0==0x400) return x+x; /* inf or NaN */
  56       else return x;    /* x is integral */
  57   } else {
  58       i = ((u_int32_t)(0xffffffff))>>(j0-20);
  59       if((i1&i)==0) return x; /* x is integral */
  60       if(huge+x>0.0) {    /* raise inexact flag */
  61     if(i0<0) {
  62         if(j0==20) i0+=1;
  63         else {
  64       j = i1+(1<<(52-j0));
  65       if((int32_t)j<i1) i0 +=1 ;   /* got a carry */
  66       i1=j;
  67         }
  68     }
  69     i1 &= (~i);
  70       }
  71   }
  72   INSERT_WORDS(x,i0,i1);
  73   return x;
  74 }