1 2 /* @(#)s_floor.c 1.3 95/01/18 */ 3 /* 4 * ==================================================== 5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6 * 7 * Developed at SunSoft, a Sun Microsystems, Inc. business. 8 * Permission to use, copy, modify, and distribute this 9 * software is freely granted, provided that this notice 10 * is preserved. 11 * ==================================================== 12 */ 13 14 /* 15 * floor(x) 16 * Return x rounded toward -inf to integral value 17 * Method: 18 * Bit twiddling. 19 * Exception: 20 * Inexact flag raised if x not equal to floor(x). 21 */ 22 23 #include "fdlibm.h" 24 25 #ifndef _DOUBLE_IS_32BITS 26 27 #ifdef __STDC__ 28 static const double huge = 1.0e300; 29 #else 30 static double huge = 1.0e300; 31 #endif 32 33 #ifdef __STDC__ floor(double x)34 double floor(double x) 35 #else 36 double floor(x) 37 double x; 38 #endif 39 { 40 int32_t i0,i1,j0; 41 uint32_t i,j; 42 EXTRACT_WORDS(i0,i1,x); 43 j0 = ((i0>>20)&0x7ff)-0x3ff; 44 if(j0<20) { 45 if(j0<0) { /* raise inexact if x != 0 */ 46 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 47 if(i0>=0) {i0=i1=0;} 48 else if(((i0&0x7fffffff)|i1)!=0) 49 { i0=0xbff00000;i1=0;} 50 } 51 } else { 52 i = (0x000fffff)>>j0; 53 if(((i0&i)|i1)==0) return x; /* x is integral */ 54 if(huge+x>0.0) { /* raise inexact flag */ 55 if(i0<0) i0 += (0x00100000)>>j0; 56 i0 &= (~i); i1=0; 57 } 58 } 59 } else if (j0>51) { 60 if(j0==0x400) return x+x; /* inf or NaN */ 61 else return x; /* x is integral */ 62 } else { 63 i = ((uint32_t)(0xffffffff))>>(j0-20); 64 if((i1&i)==0) return x; /* x is integral */ 65 if(huge+x>0.0) { /* raise inexact flag */ 66 if(i0<0) { 67 if(j0==20) i0+=1; 68 else { 69 j = i1+(1<<(52-j0)); 70 if(j<(uint32_t)i1) i0 +=1 ; /* got a carry */ 71 i1=j; 72 } 73 } 74 i1 &= (~i); 75 } 76 } 77 INSERT_WORDS(x,i0,i1); 78 return x; 79 } 80 #endif /* _DOUBLE_IS_32BITS */ 81