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      1 
      2 /* @(#)s_ceil.c 1.3 95/01/18 */
      3 /*
      4  * ====================================================
      5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      6  *
      7  * Developed at SunSoft, 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  * ieee_ceil(x)
     16  * Return x rounded toward -inf to integral value
     17  * Method:
     18  *	Bit twiddling.
     19  * Exception:
     20  *	Inexact flag raised if x not equal to ieee_ceil(x).
     21  */
     22 
     23 #include "fdlibm.h"
     24 
     25 #ifdef __STDC__
     26 static const double huge = 1.0e300;
     27 #else
     28 static double huge = 1.0e300;
     29 #endif
     30 
     31 #ifdef __STDC__
     32 	double ieee_ceil(double x)
     33 #else
     34 	double ieee_ceil(x)
     35 	double x;
     36 #endif
     37 {
     38 	int i0,i1,j0;
     39 	unsigned i,j;
     40 	i0 =  __HI(x);
     41 	i1 =  __LO(x);
     42 	j0 = ((i0>>20)&0x7ff)-0x3ff;
     43 	if(j0<20) {
     44 	    if(j0<0) { 	/* raise inexact if x != 0 */
     45 		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
     46 		    if(i0<0) {i0=0x80000000;i1=0;}
     47 		    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
     48 		}
     49 	    } else {
     50 		i = (0x000fffff)>>j0;
     51 		if(((i0&i)|i1)==0) return x; /* x is integral */
     52 		if(huge+x>0.0) {	/* raise inexact flag */
     53 		    if(i0>0) i0 += (0x00100000)>>j0;
     54 		    i0 &= (~i); i1=0;
     55 		}
     56 	    }
     57 	} else if (j0>51) {
     58 	    if(j0==0x400) return x+x;	/* inf or NaN */
     59 	    else return x;		/* x is integral */
     60 	} else {
     61 	    i = ((unsigned)(0xffffffff))>>(j0-20);
     62 	    if((i1&i)==0) return x;	/* x is integral */
     63 	    if(huge+x>0.0) { 		/* raise inexact flag */
     64 		if(i0>0) {
     65 		    if(j0==20) i0+=1;
     66 		    else {
     67 			j = i1 + (1<<(52-j0));
     68 			if(j<i1) i0+=1;	/* got a carry */
     69 			i1 = j;
     70 		    }
     71 		}
     72 		i1 &= (~i);
     73 	    }
     74 	}
     75 	__HI(x) = i0;
     76 	__LO(x) = i1;
     77 	return x;
     78 }
     79