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s_scalbn.c
Package: vxwork_src.rar [view]
Upload User: nvosite88
Upload Date: 2007-01-17
Package Size: 4983k
Code Size: 3k
Category:
VxWorks
Development Platform:
C/C++
- /* @(#)s_scalbn.c 5.1 93/09/24 */
- /*
- * ====================================================
- * 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.
- * ====================================================
- */
- /*
- FUNCTION
- <<scalbn>>, <<scalbnf>>---scale by integer
- INDEX
- scalbn
- INDEX
- scalbnf
- ANSI_SYNOPSIS
- #include <math.h>
- double scalbn(double <[x]>, int <[y]>);
- float scalbnf(float <[x]>, int <[y]>);
- TRAD_SYNOPSIS
- #include <math.h>
- double scalbn(<[x]>,<[y]>)
- double <[x]>;
- int <[y]>;
- float scalbnf(<[x]>,<[y]>)
- float <[x]>;
- int <[y]>;
- DESCRIPTION
- <<scalbn>> and <<scalbnf>> scale <[x]> by <[n]>, returning <[x]> times
- 2 to the power <[n]>. The result is computed by manipulating the
- exponent, rather than by actually performing an exponentiation or
- multiplication.
- RETURNS
- <[x]> times 2 to the power <[n]>.
- PORTABILITY
- Neither <<scalbn>> nor <<scalbnf>> is required by ANSI C or by the System V
- Interface Definition (Issue 2).
- */
- /*
- * scalbn (double x, int n)
- * scalbn(x,n) returns x* 2**n computed by exponent
- * manipulation rather than by actually performing an
- * exponentiation or a multiplication.
- */
- #include "fdlibm.h"
- #ifndef _DOUBLE_IS_32BITS
- #ifdef __STDC__
- static const double
- #else
- static double
- #endif
- two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
- twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
- huge = 1.0e+300,
- tiny = 1.0e-300;
- #ifdef __STDC__
- double scalbn (double x, int n)
- #else
- double scalbn (x,n)
- double x; int n;
- #endif
- {
- __int32_t k,hx,lx;
- EXTRACT_WORDS(hx,lx,x);
- k = (hx&0x7ff00000)>>20; /* extract exponent */
- if (k==0) { /* 0 or subnormal x */
- if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
- x *= two54;
- GET_HIGH_WORD(hx,x);
- k = ((hx&0x7ff00000)>>20) - 54;
- if (n< -50000) return tiny*x; /*underflow*/
- }
- if (k==0x7ff) return x+x; /* NaN or Inf */
- k = k+n;
- if (k > 0x7fe) return huge*copysign(huge,x); /* overflow */
- if (k > 0) /* normal result */
- {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
- if (k <= -54)
- if (n > 50000) /* in case integer overflow in n+k */
- return huge*copysign(huge,x); /*overflow*/
- else return tiny*copysign(tiny,x); /*underflow*/
- k += 54; /* subnormal result */
- SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
- return x*twom54;
- }
- #endif /* _DOUBLE_IS_32BITS */