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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 #include <sys/cdefs.h>
     14 #if defined(LIBM_SCCS) && !defined(lint)
     15 __RCSID("$NetBSD: s_ceil.c,v 1.14 2013/11/11 23:57:34 joerg Exp $");
     16 #endif
     17 
     18 /*
     19  * ceil(x)
     20  * Return x rounded toward -inf to integral value
     21  * Method:
     22  *	Bit twiddling.
     23  * Exception:
     24  *	Inexact flag raised if x not equal to ceil(x).
     25  */
     26 
     27 #include "math.h"
     28 #include "math_private.h"
     29 
     30 static const double huge = 1.0e300;
     31 
     32 #ifndef __HAVE_LONG_DOUBLE
     33 __strong_alias(_ceill, ceil)
     34 __weak_alias(ceill, ceil)
     35 #endif
     36 
     37 double
     38 ceil(double x)
     39 {
     40 	int32_t i0,i1,jj0;
     41 	u_int32_t i,j;
     42 	EXTRACT_WORDS(i0,i1,x);
     43 	jj0 = ((i0>>20)&0x7ff)-0x3ff;
     44 	if(jj0<20) {
     45 	    if(jj0<0) { 	/* raise inexact if x != 0 */
     46 		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
     47 		    if(i0<0) {i0=0x80000000;i1=0;}
     48 		    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
     49 		}
     50 	    } else {
     51 		i = (0x000fffff)>>jj0;
     52 		if(((i0&i)|i1)==0) return x; /* x is integral */
     53 		if(huge+x>0.0) {	/* raise inexact flag */
     54 		    if(i0>0) i0 += (0x00100000)>>jj0;
     55 		    i0 &= (~i); i1=0;
     56 		}
     57 	    }
     58 	} else if (jj0>51) {
     59 	    if(jj0==0x400) return x+x;	/* inf or NaN */
     60 	    else return x;		/* x is integral */
     61 	} else {
     62 	    i = ((u_int32_t)(0xffffffff))>>(jj0-20);
     63 	    if((i1&i)==0) return x;	/* x is integral */
     64 	    if(huge+x>0.0) { 		/* raise inexact flag */
     65 		if(i0>0) {
     66 		    if(jj0==20) i0+=1;
     67 		    else {
     68 			j = i1 + (1<<(52-jj0));
     69 			if(j<(u_int32_t)i1) i0+=1;	/* got a carry */
     70 			i1 = j;
     71 		    }
     72 		}
     73 		i1 &= (~i);
     74 	    }
     75 	}
     76 	INSERT_WORDS(x,i0,i1);
     77 	return x;
     78 }
     79