1*37da2899SCharles.Forsyth /* derived from /netlib/fdlibm */ 2*37da2899SCharles.Forsyth 3*37da2899SCharles.Forsyth /* @(#)s_ceil.c 1.3 95/01/18 */ 4*37da2899SCharles.Forsyth /* 5*37da2899SCharles.Forsyth * ==================================================== 6*37da2899SCharles.Forsyth * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 7*37da2899SCharles.Forsyth * 8*37da2899SCharles.Forsyth * Developed at SunSoft, a Sun Microsystems, Inc. business. 9*37da2899SCharles.Forsyth * Permission to use, copy, modify, and distribute this 10*37da2899SCharles.Forsyth * software is freely granted, provided that this notice 11*37da2899SCharles.Forsyth * is preserved. 12*37da2899SCharles.Forsyth * ==================================================== 13*37da2899SCharles.Forsyth */ 14*37da2899SCharles.Forsyth 15*37da2899SCharles.Forsyth /* 16*37da2899SCharles.Forsyth * ceil(x) 17*37da2899SCharles.Forsyth * Return x rounded toward -inf to integral value 18*37da2899SCharles.Forsyth * Method: 19*37da2899SCharles.Forsyth * Bit twiddling. 20*37da2899SCharles.Forsyth * Exception: 21*37da2899SCharles.Forsyth * Inexact flag raised if x not equal to ceil(x). 22*37da2899SCharles.Forsyth */ 23*37da2899SCharles.Forsyth 24*37da2899SCharles.Forsyth #include "fdlibm.h" 25*37da2899SCharles.Forsyth 26*37da2899SCharles.Forsyth static const double Huge = 1.0e300; 27*37da2899SCharles.Forsyth ceil(double x)28*37da2899SCharles.Forsyth double ceil(double x) 29*37da2899SCharles.Forsyth { 30*37da2899SCharles.Forsyth int i0,i1,j0; 31*37da2899SCharles.Forsyth unsigned i,j; 32*37da2899SCharles.Forsyth i0 = __HI(x); 33*37da2899SCharles.Forsyth i1 = __LO(x); 34*37da2899SCharles.Forsyth j0 = ((i0>>20)&0x7ff)-0x3ff; 35*37da2899SCharles.Forsyth if(j0<20) { 36*37da2899SCharles.Forsyth if(j0<0) { /* raise inexact if x != 0 */ 37*37da2899SCharles.Forsyth if(Huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 38*37da2899SCharles.Forsyth if(i0<0) {i0=0x80000000;i1=0;} 39*37da2899SCharles.Forsyth else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;} 40*37da2899SCharles.Forsyth } 41*37da2899SCharles.Forsyth } else { 42*37da2899SCharles.Forsyth i = (0x000fffff)>>j0; 43*37da2899SCharles.Forsyth if(((i0&i)|i1)==0) return x; /* x is integral */ 44*37da2899SCharles.Forsyth if(Huge+x>0.0) { /* raise inexact flag */ 45*37da2899SCharles.Forsyth if(i0>0) i0 += (0x00100000)>>j0; 46*37da2899SCharles.Forsyth i0 &= (~i); i1=0; 47*37da2899SCharles.Forsyth } 48*37da2899SCharles.Forsyth } 49*37da2899SCharles.Forsyth } else if (j0>51) { 50*37da2899SCharles.Forsyth if(j0==0x400) return x+x; /* inf or NaN */ 51*37da2899SCharles.Forsyth else return x; /* x is integral */ 52*37da2899SCharles.Forsyth } else { 53*37da2899SCharles.Forsyth i = ((unsigned)(0xffffffff))>>(j0-20); 54*37da2899SCharles.Forsyth if((i1&i)==0) return x; /* x is integral */ 55*37da2899SCharles.Forsyth if(Huge+x>0.0) { /* raise inexact flag */ 56*37da2899SCharles.Forsyth if(i0>0) { 57*37da2899SCharles.Forsyth if(j0==20) i0+=1; 58*37da2899SCharles.Forsyth else { 59*37da2899SCharles.Forsyth j = i1 + (1<<(52-j0)); 60*37da2899SCharles.Forsyth if(j<i1) i0+=1; /* got a carry */ 61*37da2899SCharles.Forsyth i1 = j; 62*37da2899SCharles.Forsyth } 63*37da2899SCharles.Forsyth } 64*37da2899SCharles.Forsyth i1 &= (~i); 65*37da2899SCharles.Forsyth } 66*37da2899SCharles.Forsyth } 67*37da2899SCharles.Forsyth __HI(x) = i0; 68*37da2899SCharles.Forsyth __LO(x) = i1; 69*37da2899SCharles.Forsyth return x; 70*37da2899SCharles.Forsyth } 71