1 /* @(#)s_floor.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_floor.c,v 1.9 1997/10/09 11:32:01 lukem Exp $"); 16 #endif 17 18 /* 19 * floor(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 floor(x). 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 #ifdef __STDC__ 31 static const double huge = 1.0e300; 32 #else 33 static double huge = 1.0e300; 34 #endif 35 36 #ifdef __STDC__ 37 double floor(double x) 38 #else 39 double floor(x) 40 double x; 41 #endif 42 { 43 int32_t i0,i1,j0; 44 u_int32_t i,j; 45 EXTRACT_WORDS(i0,i1,x); 46 j0 = ((i0>>20)&0x7ff)-0x3ff; 47 if(j0<20) { 48 if(j0<0) { /* raise inexact if x != 0 */ 49 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 50 if(i0>=0) {i0=i1=0;} 51 else if(((i0&0x7fffffff)|i1)!=0) 52 { i0=0xbff00000;i1=0;} 53 } 54 } else { 55 i = (0x000fffff)>>j0; 56 if(((i0&i)|i1)==0) return x; /* x is integral */ 57 if(huge+x>0.0) { /* raise inexact flag */ 58 if(i0<0) i0 += (0x00100000)>>j0; 59 i0 &= (~i); i1=0; 60 } 61 } 62 } else if (j0>51) { 63 if(j0==0x400) return x+x; /* inf or NaN */ 64 else return x; /* x is integral */ 65 } else { 66 i = ((u_int32_t)(0xffffffff))>>(j0-20); 67 if((i1&i)==0) return x; /* x is integral */ 68 if(huge+x>0.0) { /* raise inexact flag */ 69 if(i0<0) { 70 if(j0==20) i0+=1; 71 else { 72 j = i1+(1<<(52-j0)); 73 if(j<i1) i0 +=1 ; /* got a carry */ 74 i1=j; 75 } 76 } 77 i1 &= (~i); 78 } 79 } 80 INSERT_WORDS(x,i0,i1); 81 return x; 82 } 83