sysdeps/ieee754/dbl-64/wordsize-64/s_ceil.c

   1 /* @(#)s_ceil.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
  13 /*
  14  * ceil(x)
  15  * Return x rounded toward -inf to integral value
  16  * Method:
  17  *      Bit twiddling.
  18  * Exception:
  19  *      Inexact flag raised if x not equal to ceil(x).
  20  */
  21
  22 #include "math.h"
  23 #include "math_private.h"
  24
  25 static const double huge = 1.0e300;
  26
  27 double
  28 __ceil(double x)
  29 {
  30         int64_t i0,i;
  31         int32_t j0;
  32         EXTRACT_WORDS64(i0,x);
  33         j0 = ((i0>>52)&0x7ff)-0x3ff;
  34         if(j0<=51) {
  35             if(j0<0) {  /* raise inexact if x != 0 */
  36                 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
  37                     if(i0<0) {i0=INT64_C(0x8000000000000000);}
  38                     else if(i0!=0) { i0=INT64_C(0x3ff0000000000000);}
  39                 }
  40             } else {
  41                 i = INT64_C(0x000fffffffffffff)>>j0;
  42                 if((i0&i)==0) return x; /* x is integral */
  43                 if(huge+x>0.0) {        /* raise inexact flag */
  44                     if(i0>0) i0 += UINT64_C(0x0010000000000000)>>j0;
  45                     i0 &= (~i);
  46                 }
  47             }
  48         } else {
  49             if(j0==0x400) return x+x;   /* inf or NaN */
  50             else return x;              /* x is integral */
  51         }
  52         INSERT_WORDS64(x,i0);
  53         return x;
  54 }
  55 #ifndef __ceil
  56 weak_alias (__ceil, ceil)
  57 # ifdef NO_LONG_DOUBLE
  58 strong_alias (__ceil, __ceill)
  59 weak_alias (__ceil, ceill)
  60 # endif
  61 #endif