contrib/openbsd_libm/src/ld80/s_ceill.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  * ceill(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
  24 #include "math_private.h"
  25
  26 static const long double huge = 1.0e4930L;
  27
  28 long double
  29 ceill(long double x)
  30 {
  31         int32_t i1,jj0;
  32         u_int32_t i,j,se,i0,sx;
  33         GET_LDOUBLE_WORDS(se,i0,i1,x);
  34         sx = (se>>15)&1;
  35         jj0 = (se&0x7fff)-0x3fff;
  36         if(jj0<31) {
  37             if(jj0<0) { /* raise inexact if x != 0 */
  38                 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
  39                     if(sx) {se=0x8000;i0=0;i1=0;}
  40                     else if((i0|i1)!=0) { se=0x3fff;i0=0x80000000;i1=0;}
  41                 }
  42             } else {
  43                 i = (0x7fffffff)>>jj0;
  44                 if(((i0&i)|i1)==0) return x; /* x is integral */
  45                 if(huge+x>0.0) {        /* raise inexact flag */
  46                     if(sx==0) {
  47                         if (jj0>0 && (i0+(0x80000000>>jj0))>i0)
  48                           i0+=0x80000000>>jj0;
  49                         else
  50                           {
  51                             i = 0x7fffffff;
  52                             ++se;
  53                           }
  54                     }
  55                     i0 &= (~i); i1=0;
  56                 }
  57             }
  58         } else if (jj0>62) {
  59             if(jj0==0x4000) return x+x; /* inf or NaN */
  60             else return x;              /* x is integral */
  61         } else {
  62             i = ((u_int32_t)(0xffffffff))>>(jj0-31);
  63             if((i1&i)==0) return x;     /* x is integral */
  64             if(huge+x>0.0) {            /* raise inexact flag */
  65                 if(sx==0) {
  66                     if(jj0==31) i0+=1;
  67                     else {
  68                         j = i1 + (1<<(63-jj0));
  69                         if(j<i1) i0+=1; /* got a carry */
  70                         i1 = j;
  71                     }
  72                 }
  73                 i1 &= (~i);
  74             }
  75         }
  76         SET_LDOUBLE_WORDS(x,se,i0,i1);
  77         return x;
  78 }