/* e_fmodf.c -- float version of e_fmod.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

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

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] =
  "$NetBSD: e_fmodf.c,v 1.4 1995/05/10 20:45:10 jtc Exp $";
#endif

/* 
 * __ieee754_fmodf(x,y)
 * Return x mod y in exact arithmetic
 * Method: shift and subtract
 */

#include <math.h>
#include <inttypes.h>
#include <unixlib/math.h>
#include <unixlib/types.h>

static const float one = 1.0, Zero[] = { 0.0, -0.0, };

float
fmodf (float x, float y)
{
  int32_t n, hx, hy, hz, ix, iy, sx, i;

  GET_FLOAT_WORD (hx, x);
  GET_FLOAT_WORD (hy, y);
  sx = hx & 0x80000000;		/* sign of x */
  hx ^= sx;			/* |x| */
  hy &= 0x7fffffff;		/* |y| */

  /* purge off exception values */
  if (hy == 0 || (hx >= 0x7f800000) ||	/* y=0,or x not finite */
      (hy > 0x7f800000))	/* or y is NaN */
    return (x * y) / (x * y);
  if (hx < hy)
    return x;			/* |x|<|y| return x */
  if (hx == hy)
    return Zero[(uint32_t) sx >> 31];	/* |x|=|y| return x*0 */

  /* determine ix = ilogb(x) */
  if (hx < 0x00800000)
    {				/* subnormal x */
      for (ix = -126, i = (hx << 8); i > 0; i <<= 1)
	ix -= 1;
    }
  else
    ix = (hx >> 23) - 127;

  /* determine iy = ilogb(y) */
  if (hy < 0x00800000)
    {				/* subnormal y */
      for (iy = -126, i = (hy << 8); i >= 0; i <<= 1)
	iy -= 1;
    }
  else
    iy = (hy >> 23) - 127;

  /* set up {hx,lx}, {hy,ly} and align y to x */
  if (ix >= -126)
    hx = 0x00800000 | (0x007fffff & hx);
  else
    {				/* subnormal x, shift x to normal */
      n = -126 - ix;
      hx = hx << n;
    }
  if (iy >= -126)
    hy = 0x00800000 | (0x007fffff & hy);
  else
    {				/* subnormal y, shift y to normal */
      n = -126 - iy;
      hy = hy << n;
    }

  /* fix point fmod */
  n = ix - iy;
  while (n--)
    {
      hz = hx - hy;
      if (hz < 0)
	{
	  hx = hx + hx;
	}
      else
	{
	  if (hz == 0)		/* return sign(x)*0 */
	    return Zero[(uint32_t) sx >> 31];
	  hx = hz + hz;
	}
    }
  hz = hx - hy;
  if (hz >= 0)
    {
      hx = hz;
    }

  /* convert back to floating value and restore the sign */
  if (hx == 0)			/* return sign(x)*0 */
    return Zero[(uint32_t) sx >> 31];
  while (hx < 0x00800000)
    {				/* normalize x */
      hx = hx + hx;
      iy -= 1;
    }
  if (iy >= -126)
    {				/* normalize output */
      hx = ((hx - 0x00800000) | ((iy + 127) << 23));
      SET_FLOAT_WORD (x, hx | sx);
    }
  else
    {				/* subnormal output */
      n = -126 - iy;
      hx >>= n;
      SET_FLOAT_WORD (x, hx | sx);
      x *= one;			/* create necessary signal */
    }
  return x;			/* exact output */
}
