1 /* derived from /netlib/fdlibm */ 2 3 /* @(#)s_ceil.c 1.3 95/01/18 */ 4 /* 5 * ==================================================== 6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 7 * 8 * Developed at SunSoft, a Sun Microsystems, Inc. business. 9 * Permission to use, copy, modify, and distribute this 10 * software is freely granted, provided that this notice 11 * is preserved. 12 * ==================================================== 13 */ 14 15 /* 16 * ceil(x) 17 * Return x rounded toward -inf to integral value 18 * Method: 19 * Bit twiddling. 20 * Exception: 21 * Inexact flag raised if x not equal to ceil(x). 22 */ 23 24 #include "fdlibm.h" 25 26 static const double Huge = 1.0e300; 27 28 double ceil(double x) 29 { 30 int i0,i1,j0; 31 unsigned i,j; 32 i0 = __HI(x); 33 i1 = __LO(x); 34 j0 = ((i0>>20)&0x7ff)-0x3ff; 35 if(j0<20) { 36 if(j0<0) { /* raise inexact if x != 0 */ 37 if(Huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 38 if(i0<0) {i0=0x80000000;i1=0;} 39 else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;} 40 } 41 } else { 42 i = (0x000fffff)>>j0; 43 if(((i0&i)|i1)==0) return x; /* x is integral */ 44 if(Huge+x>0.0) { /* raise inexact flag */ 45 if(i0>0) i0 += (0x00100000)>>j0; 46 i0 &= (~i); i1=0; 47 } 48 } 49 } else if (j0>51) { 50 if(j0==0x400) return x+x; /* inf or NaN */ 51 else return x; /* x is integral */ 52 } else { 53 i = ((unsigned)(0xffffffff))>>(j0-20); 54 if((i1&i)==0) return x; /* x is integral */ 55 if(Huge+x>0.0) { /* raise inexact flag */ 56 if(i0>0) { 57 if(j0==20) i0+=1; 58 else { 59 j = i1 + (1<<(52-j0)); 60 if(j<i1) i0+=1; /* got a carry */ 61 i1 = j; 62 } 63 } 64 i1 &= (~i); 65 } 66 } 67 __HI(x) = i0; 68 __LO(x) = i1; 69 return x; 70 } 71