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      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 #ifndef lint
     14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_ceil.c,v 1.9 2003/07/23 04:53:46 peter Exp $";
     15 #endif
     16 
     17 /*
     18  * ceil(x)
     19  * Return x rounded toward -inf to integral value
     20  * Method:
     21  *	Bit twiddling.
     22  * Exception:
     23  *	Inexact flag raised if x not equal to ceil(x).
     24  */
     25 
     26 #include "math.h"
     27 #include "math_private.h"
     28 
     29 static const double huge = 1.0e300;
     30 
     31 double
     32 ceil(double x)
     33 {
     34 	int32_t i0,i1,j0;
     35 	u_int32_t i,j;
     36 	EXTRACT_WORDS(i0,i1,x);
     37 	j0 = ((i0>>20)&0x7ff)-0x3ff;
     38 	if(j0<20) {
     39 	    if(j0<0) { 	/* raise inexact if x != 0 */
     40 		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
     41 		    if(i0<0) {i0=0x80000000;i1=0;}
     42 		    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
     43 		}
     44 	    } else {
     45 		i = (0x000fffff)>>j0;
     46 		if(((i0&i)|i1)==0) return x; /* x is integral */
     47 		if(huge+x>0.0) {	/* raise inexact flag */
     48 		    if(i0>0) i0 += (0x00100000)>>j0;
     49 		    i0 &= (~i); i1=0;
     50 		}
     51 	    }
     52 	} else if (j0>51) {
     53 	    if(j0==0x400) return x+x;	/* inf or NaN */
     54 	    else return x;		/* x is integral */
     55 	} else {
     56 	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
     57 	    if((i1&i)==0) return x;	/* x is integral */
     58 	    if(huge+x>0.0) { 		/* raise inexact flag */
     59 		if(i0>0) {
     60 		    if(j0==20) i0+=1;
     61 		    else {
     62 			j = i1 + (1<<(52-j0));
     63 			if(j<i1) i0+=1;	/* got a carry */
     64 			i1 = j;
     65 		    }
     66 		}
     67 		i1 &= (~i);
     68 	    }
     69 	}
     70 	INSERT_WORDS(x,i0,i1);
     71 	return x;
     72 }
     73