/******************************************************************************
 * $Id: tif_float.c 78b178fa5c7861a10b5eadda77c8e9e697f8fef3 2017-06-19 11:03:33Z Even Rouault $
 *
 * Project:  GeoTIFF Driver
 * Purpose:  Floating point conversion functions. Convert 16- and 24-bit
 *           floating point numbers into the 32-bit IEEE 754 compliant ones.
 * Author:   Andrey Kiselev, dron@remotesensing.org
 *
 ******************************************************************************
 * Copyright (c) 2005, Andrey Kiselev <dron@remotesensing.org>
 *
 * This code is based on the code from OpenEXR project with the following
 * copyright:
 *
 * 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.
 *
 ****************************************************************************/

#include "tif_float.h"

/************************************************************************/
/*                           HalfToFloat()                              */
/*                                                                      */
/*  16-bit floating point number to 32-bit one.                         */
/************************************************************************/

GUInt32 HalfToFloat( GUInt16 iHalf )
{

    GUInt32 iSign =     (iHalf >> 15) & 0x00000001;
    int iExponent = (iHalf >> 10) & 0x0000001f;
    GUInt32 iMantissa = iHalf         & 0x000003ff;

    if (iExponent == 0)
    {
        if (iMantissa == 0)
        {
/* -------------------------------------------------------------------- */
/*      Plus or minus zero.                                             */
/* -------------------------------------------------------------------- */

            return iSign << 31;
        }
        else
        {
/* -------------------------------------------------------------------- */
/*      Denormalized number -- renormalize it.                          */
/* -------------------------------------------------------------------- */

            while (!(iMantissa & 0x00000400))
            {
                iMantissa <<= 1;
                iExponent -=  1;
            }

            iExponent += 1;
            iMantissa &= ~0x00000400U;
        }
    }
    else if (iExponent == 31)
    {
        if (iMantissa == 0)
        {
/* -------------------------------------------------------------------- */
/*       Positive or negative infinity.                                 */
/* -------------------------------------------------------------------- */

            return (iSign << 31) | 0x7f800000;
        }
        else
        {
/* -------------------------------------------------------------------- */
/*       NaN -- preserve sign and significand bits.                     */
/* -------------------------------------------------------------------- */

            return (iSign << 31) | 0x7f800000 | (iMantissa << 13);
        }
    }

/* -------------------------------------------------------------------- */
/*       Normalized number.                                             */
/* -------------------------------------------------------------------- */

    iExponent = iExponent + (127 - 15);
    iMantissa = iMantissa << 13;

/* -------------------------------------------------------------------- */
/*       Assemble sign, exponent and mantissa.                          */
/* -------------------------------------------------------------------- */

    /* coverity[overflow_sink] */
    return (iSign << 31) | ((GUInt32)iExponent << 23) | iMantissa;
}

/************************************************************************/
/*                           TripleToFloat()                            */
/*                                                                      */
/*  24-bit floating point number to 32-bit one.                         */
/************************************************************************/

GUInt32 TripleToFloat( GUInt32 iTriple )
{

    GUInt32 iSign       = (iTriple >> 23) & 0x00000001;
    int iExponent   = (iTriple >> 16) & 0x0000007f;
    GUInt32 iMantissa   = iTriple         & 0x0000ffff;

    if (iExponent == 0)
    {
        if (iMantissa == 0)
        {
/* -------------------------------------------------------------------- */
/*      Plus or minus zero.                                             */
/* -------------------------------------------------------------------- */

            return iSign << 31;
        }
        else
        {
/* -------------------------------------------------------------------- */
/*      Denormalized number -- renormalize it.                          */
/* -------------------------------------------------------------------- */

            while (!(iMantissa & 0x00010000))
            {
                iMantissa <<= 1;
                iExponent -= 1;
            }

            iExponent += 1;
            iMantissa &= ~0x00010000U;
        }
    }
    else if (iExponent == 127)
    {
        if (iMantissa == 0)
        {
/* -------------------------------------------------------------------- */
/*       Positive or negative infinity.                                 */
/* -------------------------------------------------------------------- */

            return (iSign << 31) | 0x7f800000;
        }
        else
        {
/* -------------------------------------------------------------------- */
/*       NaN -- preserve sign and significand bits.                     */
/* -------------------------------------------------------------------- */

            return (iSign << 31) | 0x7f800000 | (iMantissa << 7);
        }
    }

/* -------------------------------------------------------------------- */
/*       Normalized number.                                             */
/* -------------------------------------------------------------------- */

    iExponent = iExponent + (127 - 63);
    iMantissa = iMantissa << 7;

/* -------------------------------------------------------------------- */
/*       Assemble sign, exponent and mantissa.                          */
/* -------------------------------------------------------------------- */

    /* coverity[overflow_sink] */
    return (iSign << 31) | ((GUInt32)iExponent << 23) | iMantissa;
}