s_floor.c (1833B)
1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 /* 13 * floor(x) 14 * Return x rounded toward -inf to integral value 15 * Method: 16 * Bit twiddling. 17 * Exception: 18 * Inexact flag raised if x not equal to floor(x). 19 */ 20 21 /*#include <features.h>*/ 22 /* Prevent math.h from defining a colliding inline */ 23 #undef __USE_EXTERN_INLINES 24 #include "math_libm.h" 25 #include "math_private.h" 26 27 #ifdef __WATCOMC__ /* Watcom defines huge=__huge */ 28 #undef huge 29 #endif 30 31 static const double huge = 1.0e300; 32 33 double floor(double x) 34 { 35 int32_t i0,i1,j0; 36 u_int32_t i,j; 37 EXTRACT_WORDS(i0,i1,x); 38 j0 = ((i0>>20)&0x7ff)-0x3ff; 39 if(j0<20) { 40 if(j0<0) { /* raise inexact if x != 0 */ 41 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 42 if(i0>=0) {i0=i1=0;} 43 else if(((i0&0x7fffffff)|i1)!=0) 44 { i0=0xbff00000;i1=0;} 45 } 46 } else { 47 i = (0x000fffff)>>j0; 48 if(((i0&i)|i1)==0) return x; /* x is integral */ 49 if(huge+x>0.0) { /* raise inexact flag */ 50 if(i0<0) i0 += (0x00100000)>>j0; 51 i0 &= (~i); i1=0; 52 } 53 } 54 } else if (j0>51) { 55 if(j0==0x400) return x+x; /* inf or NaN */ 56 else return x; /* x is integral */ 57 } else { 58 i = ((u_int32_t)(0xffffffff))>>(j0-20); 59 if((i1&i)==0) return x; /* x is integral */ 60 if(huge+x>0.0) { /* raise inexact flag */ 61 if(i0<0) { 62 if(j0==20) i0+=1; 63 else { 64 j = i1+(1<<(52-j0)); 65 if(j<(u_int32_t)i1) i0 +=1 ; /* got a carry */ 66 i1=j; 67 } 68 } 69 i1 &= (~i); 70 } 71 } 72 INSERT_WORDS(x,i0,i1); 73 return x; 74 } 75 libm_hidden_def(floor)