js/src/fdlibm/s_ceil.c

   1 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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  15  *
  16  * The Original Code is Mozilla Communicator client code, released
  17  * March 31, 1998.
  18  *
  19  * The Initial Developer of the Original Code is
  20  * Sun Microsystems, Inc.
  21  * Portions created by the Initial Developer are Copyright (C) 1998
  22  * the Initial Developer. All Rights Reserved.
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  39
  40 /* @(#)s_ceil.c 1.3 95/01/18 */
  41 /*
  42  * ====================================================
  43  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  44  *
  45  * Developed at SunSoft, a Sun Microsystems, Inc. business.
  46  * Permission to use, copy, modify, and distribute this
  47  * software is freely granted, provided that this notice
  48  * is preserved.
  49  * ====================================================
  50  */
  51
  52 /*
  53  * ceil(x)
  54  * Return x rounded toward -inf to integral value
  55  * Method:
  56  *      Bit twiddling.
  57  * Exception:
  58  *      Inexact flag raised if x not equal to ceil(x).
  59  */
  60
  61 #include "fdlibm.h"
  62
  63 #ifdef __STDC__
  64 static const double really_big = 1.0e300;
  65 #else
  66 static double really_big = 1.0e300;
  67 #endif
  68
  69 #ifdef __STDC__
  70         double fd_ceil(double x)
  71 #else
  72         double fd_ceil(x)
  73         double x;
  74 #endif
  75 {
  76         fd_twoints u;
  77         int i0,i1,j0;
  78         unsigned i,j;
  79         u.d = x;
  80         i0 =  __HI(u);
  81         i1 =  __LO(u);
  82         j0 = ((i0>>20)&0x7ff)-0x3ff;
  83         if(j0<20) {
  84             if(j0<0) {  /* raise inexact if x != 0 */
  85                 if(really_big+x>0.0) {/* return 0*sign(x) if |x|<1 */
  86                     if(i0<0) {i0=0x80000000;i1=0;}
  87                     else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
  88                 }
  89             } else {
  90                 i = (0x000fffff)>>j0;
  91                 if(((i0&i)|i1)==0) return x; /* x is integral */
  92                 if(really_big+x>0.0) {  /* raise inexact flag */
  93                     if(i0>0) i0 += (0x00100000)>>j0;
  94                     i0 &= (~i); i1=0;
  95                 }
  96             }
  97         } else if (j0>51) {
  98             if(j0==0x400) return x+x;   /* inf or NaN */
  99             else return x;              /* x is integral */
 100         } else {
 101             i = ((unsigned)(0xffffffff))>>(j0-20);
 102             if((i1&i)==0) return x;     /* x is integral */
 103             if(really_big+x>0.0) {              /* raise inexact flag */
 104                 if(i0>0) {
 105                     if(j0==20) i0+=1;
 106                     else {
 107                         j = i1 + (1<<(52-j0));
 108                         if((int)j<i1) i0+=1;    /* got a carry */
 109                         i1 = j;
 110                     }
 111                 }
 112                 i1 &= (~i);
 113             }
 114         }
 115         u.d = x;
 116         __HI(u) = i0;
 117         __LO(u) = i1;
 118         x = u.d;
 119         return x;
 120 }