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 #ifndef lint 14 static char rcsid[] = "$FreeBSD$"; 15 #endif 16 17 /* 18 * floor(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 floor(x). 24 */ 25 26 #include "math.h" 27 #include "math_private.h" 28 29 #ifdef __STDC__ 30 static const double huge = 1.0e300; 31 #else 32 static double huge = 1.0e300; 33 #endif 34 35 #ifdef __STDC__ 36 double floor(double x) 37 #else 38 double floor(x) 39 double x; 40 #endif 41 { 42 int32_t i0,i1,j0; 43 u_int32_t i,j; 44 EXTRACT_WORDS(i0,i1,x); 45 j0 = ((i0>>20)&0x7ff)-0x3ff; 46 if(j0<20) { 47 if(j0<0) { /* raise inexact if x != 0 */ 48 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 49 if(i0>=0) {i0=i1=0;} 50 else if(((i0&0x7fffffff)|i1)!=0) 51 { i0=0xbff00000;i1=0;} 52 } 53 } else { 54 i = (0x000fffff)>>j0; 55 if(((i0&i)|i1)==0) return x; /* x is integral */ 56 if(huge+x>0.0) { /* raise inexact flag */ 57 if(i0<0) i0 += (0x00100000)>>j0; 58 i0 &= (~i); i1=0; 59 } 60 } 61 } else if (j0>51) { 62 if(j0==0x400) return x+x; /* inf or NaN */ 63 else return x; /* x is integral */ 64 } else { 65 i = ((u_int32_t)(0xffffffff))>>(j0-20); 66 if((i1&i)==0) return x; /* x is integral */ 67 if(huge+x>0.0) { /* raise inexact flag */ 68 if(i0<0) { 69 if(j0==20) i0+=1; 70 else { 71 j = i1+(1<<(52-j0)); 72 if(j<i1) i0 +=1 ; /* got a carry */ 73 i1=j; 74 } 75 } 76 i1 &= (~i); 77 } 78 } 79 INSERT_WORDS(x,i0,i1); 80 return x; 81 } 82