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