///////////////////////////////////////////////////////////////////////////

//

// Copyright (c) 2002, Industrial Light & Magic, a division of Lucas

// Digital Ltd. LLC

// 

// All rights reserved.

// 

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// *       Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// *       Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// *       Neither the name of Industrial Light & Magic nor the names of

// its contributors may be used to endorse or promote products derived

// from this software without specific prior written permission. 

// 

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

///////////////////////////////////////////////////////////////////////////

// Primary authors:

//     Florian Kainz <kainz@ilm.com>

//     Rod Bogart <rgb@ilm.com>

//---------------------------------------------------------------------------

//

//	halfFunction<T> -- a class for fast evaluation

//			   of half --> T functions

//

//	The constructor for a halfFunction object,

//

//	    halfFunction (function,

//			  domainMin, domainMax,

//			  defaultValue,

//			  posInfValue, negInfValue,

//			  nanValue);

//

//	evaluates the function for all finite half values in the interval

//	[domainMin, domainMax], and stores the results in a lookup table.

//	For finite half values that are not in [domainMin, domainMax], the

//	constructor stores defaultValue in the table.  For positive infinity,

//	negative infinity and NANs, posInfValue, negInfValue and nanValue

//	are stored in the table.

//

//	The tabulated function can then be evaluated quickly for arbitrary

//	half values by calling the the halfFunction object's operator()

//	method.

//

//	Example:

//

//	    #include <math.h>

//	    #include <halfFunction.h>

//

//	    halfFunction<half> hsin (sin);

//

//	    halfFunction<half> hsqrt (sqrt,		// function

//				      0, HALF_MAX,	// domain

//				      half::qNan(),	// sqrt(x) for x < 0

//				      half::posInf(),	// sqrt(+inf)

//				      half::qNan(),	// sqrt(-inf)

//				      half::qNan());	// sqrt(nan)

//

//	    half x = hsin (1);

//	    half y = hsqrt (3.5);

//

//---------------------------------------------------------------------------

#ifndef _HALF_FUNCTION_H_

#define _HALF_FUNCTION_H_

#include "half.h"

#include "IlmBaseConfig.h"

#ifndef ILMBASE_HAVE_LARGE_STACK  

#include <string.h>     // need this for memset

#else 

#endif

#include <float.h>

template <class T>

class halfFunction

{

  public:

    //------------

    // Constructor

    //------------

    template <class Function>

    halfFunction (Function f,

		  half domainMin = -HALF_MAX,

		  half domainMax =  HALF_MAX,

		  T defaultValue = 0,

		  T posInfValue  = 0,

		  T negInfValue  = 0,

		  T nanValue     = 0);

#ifndef ILMBASE_HAVE_LARGE_STACK

    ~halfFunction () { delete [] _lut; }    

#endif

    //-----------

    // Evaluation

    //-----------

    T		operator () (half x) const;

  private:

#ifdef ILMBASE_HAVE_LARGE_STACK

    T		_lut[1 << 16];

#else

    T *         _lut;

#endif

};

//---------------

// Implementation

//---------------

template <class T>

template <class Function>

halfFunction<T>::halfFunction (Function f,

			       half domainMin,

			       half domainMax,

			       T defaultValue,

			       T posInfValue,

			       T negInfValue,

			       T nanValue)

{

#ifndef ILMBASE_HAVE_LARGE_STACK

    _lut = new T[1<<16];

    memset (_lut, 0 , (1<<16) * sizeof(T));

#endif

    for (int i = 0; i < (1 << 16); i++)

    {

	half x;

	x.setBits (i);

	if (x.isNan())

	    _lut[i] = nanValue;

	else if (x.isInfinity())

	    _lut[i] = x.isNegative()? negInfValue: posInfValue;

	else if (x < domainMin || x > domainMax)

	    _lut[i] = defaultValue;

	else

	    _lut[i] = f (x);

    }

}

template <class T>

inline T

halfFunction<T>::operator () (half x) const

{

    return _lut[x.bits()];

}

#endif