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