toolchain/gcc/newlib/libm/math/s_floor.c

   1
   2 /* @(#)s_floor.c 5.1 93/09/24 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunPro, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  */
  13
  14 /*
  15 FUNCTION
  16 <<floor>>, <<floorf>>, <<ceil>>, <<ceilf>>---floor and ceiling
  17 INDEX
  18         floor
  19 INDEX
  20         floorf
  21 INDEX
  22         ceil
  23 INDEX
  24         ceilf
  25
  26 ANSI_SYNOPSIS
  27         #include <math.h>
  28         double floor(double <[x]>);
  29         float floorf(float <[x]>);
  30         double ceil(double <[x]>);
  31         float ceilf(float <[x]>);
  32
  33 TRAD_SYNOPSIS
  34         #include <math.h>
  35         double floor(<[x]>)
  36         double <[x]>;
  37         float floorf(<[x]>)
  38         float <[x]>;
  39         double ceil(<[x]>)
  40         double <[x]>;
  41         float ceilf(<[x]>)
  42         float <[x]>;
  43
  44 DESCRIPTION
  45 <<floor>> and <<floorf>> find
  46 @tex
  47 $\lfloor x \rfloor$,
  48 @end tex
  49 the nearest integer less than or equal to <[x]>.
  50 <<ceil>> and <<ceilf>> find
  51 @tex
  52 $\lceil x\rceil$,
  53 @end tex
  54 the nearest integer greater than or equal to <[x]>.
  55
  56 RETURNS
  57 <<floor>> and <<ceil>> return the integer result as a double.
  58 <<floorf>> and <<ceilf>> return the integer result as a float.
  59
  60 PORTABILITY
  61 <<floor>> and <<ceil>> are ANSI.
  62 <<floorf>> and <<ceilf>> are extensions.
  63
  64
  65 */
  66
  67 /*
  68  * floor(x)
  69  * Return x rounded toward -inf to integral value
  70  * Method:
  71  *      Bit twiddling.
  72  * Exception:
  73  *      Inexact flag raised if x not equal to floor(x).
  74  */
  75
  76 #include "fdlibm.h"
  77
  78 #ifndef _DOUBLE_IS_32BITS
  79
  80 #ifdef __STDC__
  81 static const double huge = 1.0e300;
  82 #else
  83 static double huge = 1.0e300;
  84 #endif
  85
  86 #ifdef __STDC__
  87         double floor(double x)
  88 #else
  89         double floor(x)
  90         double x;
  91 #endif
  92 {
  93         __int32_t i0,i1,j0;
  94         __uint32_t i,j;
  95         EXTRACT_WORDS(i0,i1,x);
  96         j0 = ((i0>>20)&0x7ff)-0x3ff;
  97         if(j0<20) {
  98             if(j0<0) {  /* raise inexact if x != 0 */
  99                 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
 100                     if(i0>=0) {i0=i1=0;}
 101                     else if(((i0&0x7fffffff)|i1)!=0)
 102                         { i0=0xbff00000;i1=0;}
 103                 }
 104             } else {
 105                 i = (0x000fffff)>>j0;
 106                 if(((i0&i)|i1)==0) return x; /* x is integral */
 107                 if(huge+x>0.0) {        /* raise inexact flag */
 108                     if(i0<0) i0 += (0x00100000)>>j0;
 109                     i0 &= (~i); i1=0;
 110                 }
 111             }
 112         } else if (j0>51) {
 113             if(j0==0x400) return x+x;   /* inf or NaN */
 114             else return x;              /* x is integral */
 115         } else {
 116             i = ((__uint32_t)(0xffffffff))>>(j0-20);
 117             if((i1&i)==0) return x;     /* x is integral */
 118             if(huge+x>0.0) {            /* raise inexact flag */
 119                 if(i0<0) {
 120                     if(j0==20) i0+=1;
 121                     else {
 122                         j = i1+(1<<(52-j0));
 123                         if(j<i1) i0 +=1 ;       /* got a carry */
 124                         i1=j;
 125                     }
 126                 }
 127                 i1 &= (~i);
 128             }
 129         }
 130         INSERT_WORDS(x,i0,i1);
 131         return x;
 132 }
 133
 134 #endif /* _DOUBLE_IS_32BITS */