1 /* sf_scalbn.c -- float version of s_scalbn.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5 /* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16 #include "fdlibm.h" 17 #include <limits.h> 18 #include <float.h> 19 20 #if INT_MAX > 50000 21 #define OVERFLOW_INT 50000 22 #else 23 #define OVERFLOW_INT 30000 24 #endif 25 26 #ifdef __STDC__ 27 static const float 28 #else 29 static float 30 #endif 31 two25 = 3.355443200e+07, /* 0x4c000000 */ 32 twom25 = 2.9802322388e-08, /* 0x33000000 */ 33 huge = 1.0e+30, 34 tiny = 1.0e-30; 35 36 #ifdef __STDC__ scalbnf(float x,int n)37 float scalbnf (float x, int n) 38 #else 39 float scalbnf (x,n) 40 float x; int n; 41 #endif 42 { 43 __int32_t k,ix; 44 __uint32_t hx; 45 46 GET_FLOAT_WORD(ix,x); 47 hx = ix&0x7fffffff; 48 k = hx>>23; /* extract exponent */ 49 if (FLT_UWORD_IS_ZERO(hx)) 50 return x; 51 if (!FLT_UWORD_IS_FINITE(hx)) 52 return x+x; /* NaN or Inf */ 53 if (FLT_UWORD_IS_SUBNORMAL(hx)) { 54 x *= two25; 55 GET_FLOAT_WORD(ix,x); 56 k = ((ix&0x7f800000)>>23) - 25; 57 if (n< -50000) return tiny*x; /*underflow*/ 58 } 59 k = k+n; 60 if (k > FLT_LARGEST_EXP) return huge*copysignf(huge,x); /* overflow */ 61 if (k > 0) /* normal result */ 62 {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;} 63 if (k < FLT_SMALLEST_EXP) { 64 if (n > OVERFLOW_INT) /* in case integer overflow in n+k */ 65 return huge*copysignf(huge,x); /*overflow*/ 66 else return tiny*copysignf(tiny,x); /*underflow*/ 67 } 68 k += 25; /* subnormal result */ 69 SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); 70 return x*twom25; 71 } 72 73 #ifdef _DOUBLE_IS_32BITS 74 75 #ifdef __STDC__ scalbn(double x,int n)76 double scalbn(double x, int n) 77 #else 78 double scalbn(x,n) 79 double x; 80 int n; 81 #endif 82 { 83 return (double) scalbnf((float) x, n); 84 } 85 86 #endif /* defined(_DOUBLE_IS_32BITS) */ 87