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[] = "$FreeBSD$"; 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