Standard Libraries for EDK II.

[mirror_edk2.git] / StdLib / LibC / Math / s_scalbn.c

/* @(#)s_scalbn.c 5.1 93/09/24 */\r
/*\r
 * ====================================================\r
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r
 *\r
 * Developed at SunPro, a Sun Microsystems, Inc. business.\r
 * Permission to use, copy, modify, and distribute this\r
 * software is freely granted, provided that this notice\r
 * is preserved.\r
 * ====================================================\r
 */\r
#include  <LibConfig.h>\r
#include  <sys/EfiCdefs.h>\r
#if defined(LIBM_SCCS) && !defined(lint)\r
__RCSID("$NetBSD: s_scalbn.c,v 1.12 2002/05/26 22:01:58 wiz Exp $");\r
#endif\r
\r
/*\r
 * scalbn (double x, int n)\r
 * scalbn(x,n) returns x* 2**n  computed by  exponent\r
 * manipulation rather than by actually performing an\r
 * exponentiation or a multiplication.\r
 */\r
\r
#include "math.h"\r
#include "math_private.h"\r
\r
static const double\r
two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */\r
twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */\r
huge   = 1.0e+300,\r
tiny   = 1.0e-300;\r
\r
double\r
scalbn(double x, int n)\r
{\r
  int32_t k,hx,lx;\r
  EXTRACT_WORDS(hx,lx,x);\r
        k = (hx&0x7ff00000)>>20;    /* extract exponent */\r
        if (k==0) {       /* 0 or subnormal x */\r
            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */\r
      x *= two54;\r
      GET_HIGH_WORD(hx,x);\r
      k = ((hx&0x7ff00000)>>20) - 54;\r
            if (n< -50000) return tiny*x;   /*underflow*/\r
      }\r
        if (k==0x7ff) return x+x;   /* NaN or Inf */\r
        k = k+n;\r
        if (k >  0x7fe) return huge*copysign(huge,x); /* overflow  */\r
        if (k > 0)        /* normal result */\r
      {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}\r
        if (k <= -54) {\r
            if (n > 50000)  /* in case integer overflow in n+k */\r
    return huge*copysign(huge,x); /*overflow*/\r
      else return tiny*copysign(tiny,x);  /*underflow*/\r
  }\r
        k += 54;        /* subnormal result */\r
  SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));\r
        return x*twom54;\r
}\r