/*
 * ====================================================
 * 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.
 * ====================================================
 */

/*
 * modf(double x, double *iptr)
 * return fraction part of x, and return x's integral part in *iptr.
 * Method:
 *      Bit twiddling.
 *
 * Exception:
 *      No exception.
 */

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

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

#if BYTE_ORDER == BIG_ENDIAN

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

#endif

#if BYTE_ORDER == LITTLE_ENDIAN

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 a double from two 32 bit ints.  */

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

static const double one = 1.0;

double
modf(double x, double *iptr)
{
        int32_t i0,i1,j0;
        u_int32_t i;
        EXTRACT_WORDS(i0,i1,x);
        j0 = ((i0>>20)&0x7ff)-0x3ff;    /* exponent of x */
        if(j0<20) {                     /* integer part in high x */
            if(j0<0) {                  /* |x|<1 */
                INSERT_WORDS(*iptr,i0&0x80000000,0);    /* *iptr = +-0 */
                return x;
            } else {
                i = (0x000fffff)>>j0;
                if(((i0&i)|i1)==0) {            /* x is integral */
                    u_int32_t high;
                    *iptr = x;
                    GET_HIGH_WORD(high,x);
                    INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
                    return x;
                } else {
                    INSERT_WORDS(*iptr,i0&(~i),0);
                    return x - *iptr;
                }
            }
        } else if (j0>51) {             /* no fraction part */
            u_int32_t high;
            if (j0 == 0x400) {          /* inf/NaN */
                *iptr = x;
                return 0.0 / x;
            }
            *iptr = x*one;
            GET_HIGH_WORD(high,x);
            INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
            return x;
        } else {                        /* fraction part in low x */
            i = ((u_int32_t)(0xffffffff))>>(j0-20);
            if((i1&i)==0) {             /* x is integral */
                u_int32_t high;
                *iptr = x;
                GET_HIGH_WORD(high,x);
                INSERT_WORDS(x,high&0x80000000,0);      /* return +-0 */
                return x;
            } else {
                INSERT_WORDS(*iptr,i0,i1&(~i));
                return x - *iptr;
            }
        }
}