0,0 → 1,86 |
/* sf_scalbn.c -- float version of s_scalbn.c. |
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
*/ |
|
/* |
* ==================================================== |
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
* |
* Developed at SunPro, a Sun Microsystems, Inc. business. |
* Permission to use, copy, modify, and distribute this |
* software is freely granted, provided that this notice |
* is preserved. |
* ==================================================== |
*/ |
|
#include "fdlibm.h" |
#include <limits.h> |
#include <float.h> |
|
#if INT_MAX > 50000 |
#define OVERFLOW_INT 50000 |
#else |
#define OVERFLOW_INT 30000 |
#endif |
|
#ifdef __STDC__ |
static const float |
#else |
static float |
#endif |
two25 = 3.355443200e+07, /* 0x4c000000 */ |
twom25 = 2.9802322388e-08, /* 0x33000000 */ |
huge = 1.0e+30, |
tiny = 1.0e-30; |
|
#ifdef __STDC__ |
float scalbnf (float x, int n) |
#else |
float scalbnf (x,n) |
float x; int n; |
#endif |
{ |
__int32_t k,ix; |
__uint32_t hx; |
|
GET_FLOAT_WORD(ix,x); |
hx = ix&0x7fffffff; |
k = hx>>23; /* extract exponent */ |
if (FLT_UWORD_IS_ZERO(hx)) |
return x; |
if (!FLT_UWORD_IS_FINITE(hx)) |
return x+x; /* NaN or Inf */ |
if (FLT_UWORD_IS_SUBNORMAL(hx)) { |
x *= two25; |
GET_FLOAT_WORD(ix,x); |
k = ((ix&0x7f800000)>>23) - 25; |
if (n< -50000) return tiny*x; /*underflow*/ |
} |
k = k+n; |
if (k > FLT_LARGEST_EXP) return huge*copysignf(huge,x); /* overflow */ |
if (k > 0) /* normal result */ |
{SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;} |
if (k < FLT_SMALLEST_EXP) { |
if (n > OVERFLOW_INT) /* in case integer overflow in n+k */ |
return huge*copysignf(huge,x); /*overflow*/ |
else return tiny*copysignf(tiny,x); /*underflow*/ |
} |
k += 25; /* subnormal result */ |
SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); |
return x*twom25; |
} |
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#ifdef _DOUBLE_IS_32BITS |
|
#ifdef __STDC__ |
double scalbn(double x, int n) |
#else |
double scalbn(x,n) |
double x; |
int n; |
#endif |
{ |
return (double) scalbnf((float) x, n); |
} |
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#endif /* defined(_DOUBLE_IS_32BITS) */ |