/*      $OpenBSD: ldexp.c,v 1.10 2015/10/27 05:54:49 guenther Exp $     */
/* @(#)s_scalbn.c 5.1 93/09/24 */
/* @(#)fdlibm.h 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.
 * ====================================================
 */

#include <sys/types.h>
#include <endian.h>
#include <float.h>
#include <math.h>

/* Bit fiddling routines copied from msun/src/math_private.h,v 1.15 */

#if (BYTE_ORDER == BIG_ENDIAN) || (defined(__arm__) && !defined(__VFP_FP__))

typedef union
{
  double value;
  struct
  {
    u_int32_t msw;
    u_int32_t lsw;
  } parts;
} ieee_double_shape_type;

#endif

#if (BYTE_ORDER == LITTLE_ENDIAN) && !(defined(__arm__) && !defined(__VFP_FP__))

typedef union
{
  double value;
  struct
  {
    u_int32_t lsw;
    u_int32_t msw;
  } parts;
} ieee_double_shape_type;

#endif

/* Get two 32 bit ints from a double.  */

#define EXTRACT_WORDS(ix0,ix1,d)                                \
do {                                                            \
  ieee_double_shape_type ew_u;                                  \
  ew_u.value = (d);                                             \
  (ix0) = ew_u.parts.msw;                                       \
  (ix1) = ew_u.parts.lsw;                                       \
} while (0)

/* Get the more significant 32 bit int from a double.  */

#define GET_HIGH_WORD(i,d)                                      \
do {                                                            \
  ieee_double_shape_type gh_u;                                  \
  gh_u.value = (d);                                             \
  (i) = gh_u.parts.msw;                                         \
} while (0)

/* Set the more significant 32 bits of a double from an int.  */

#define SET_HIGH_WORD(d,v)                                      \
do {                                                            \
  ieee_double_shape_type sh_u;                                  \
  sh_u.value = (d);                                             \
  sh_u.parts.msw = (v);                                         \
  (d) = sh_u.value;                                             \
} while (0)


static const double
two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
huge   = 1.0e+300,
tiny   = 1.0e-300;

static double
_copysign(double x, double y)
{
        u_int32_t hx,hy;
        GET_HIGH_WORD(hx,x);
        GET_HIGH_WORD(hy,y);
        SET_HIGH_WORD(x,(hx&0x7fffffff)|(hy&0x80000000));
        return x;
}

double
ldexp(double x, int n)
{
        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;
}
DEF_STRONG(ldexp);

#if     LDBL_MANT_DIG == DBL_MANT_DIG
__strong_alias(ldexpl, ldexp);
#endif  /* LDBL_MANT_DIG == DBL_MANT_DIG */