OgreBitwise.h

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/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2012 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-----------------------------------------------------------------------------
*/
#ifndef _Bitwise_H__
#define _Bitwise_H__

#include "OgrePrerequisites.h"

namespace Ogre {
    class Bitwise {
    public:
        static FORCEINLINE unsigned int mostSignificantBitSet(unsigned int value)
        {
            unsigned int result = 0;
            while (value != 0) {
                ++result;
                value >>= 1;
            }
            return result-1;
        }
        static FORCEINLINE uint32 firstPO2From(uint32 n)
        {
            --n;            
            n |= n >> 16;
            n |= n >> 8;
            n |= n >> 4;
            n |= n >> 2;
            n |= n >> 1;
            ++n;
            return n;
        }
        template<typename T>
        static FORCEINLINE bool isPO2(T n)
        {
            return (n & (n-1)) == 0;
        }
        template<typename T>
        static FORCEINLINE unsigned int getBitShift(T mask)
        {
            if (mask == 0)
                return 0;

            unsigned int result = 0;
            while ((mask & 1) == 0) {
                ++result;
                mask >>= 1;
            }
            return result;
        }

        template<typename SrcT, typename DestT>
        static inline DestT convertBitPattern(SrcT srcValue, SrcT srcBitMask, DestT destBitMask)
        {
            // Mask off irrelevant source value bits (if any)
            srcValue = srcValue & srcBitMask;

            // Shift source down to bottom of DWORD
            const unsigned int srcBitShift = getBitShift(srcBitMask);
            srcValue >>= srcBitShift;

            // Get max value possible in source from srcMask
            const SrcT srcMax = srcBitMask >> srcBitShift;

            // Get max available in dest
            const unsigned int destBitShift = getBitShift(destBitMask);
            const DestT destMax = destBitMask >> destBitShift;

            // Scale source value into destination, and shift back
            DestT destValue = (srcValue * destMax) / srcMax;
            return (destValue << destBitShift);
        }

        static inline unsigned int fixedToFixed(uint32 value, unsigned int n, unsigned int p) 
        {
            if(n > p) 
            {
                // Less bits required than available; this is easy
                value >>= n-p;
            } 
            else if(n < p)
            {
                // More bits required than are there, do the fill
                // Use old fashioned division, probably better than a loop
                if(value == 0)
                        value = 0;
                else if(value == (static_cast<unsigned int>(1)<<n)-1)
                        value = (1<<p)-1;
                else    value = value*(1<<p)/((1<<n)-1);
            }
            return value;    
        }

        static inline unsigned int floatToFixed(const float value, const unsigned int bits)
        {
            if(value <= 0.0f) return 0;
            else if (value >= 1.0f) return (1<<bits)-1;
            else return (unsigned int)(value * (1<<bits));     
        }

        static inline float fixedToFloat(unsigned value, unsigned int bits)
        {
            return (float)value/(float)((1<<bits)-1);
        }

        static inline void intWrite(void *dest, const int n, const unsigned int value)
        {
            switch(n) {
                case 1:
                    ((uint8*)dest)[0] = (uint8)value;
                    break;
                case 2:
                    ((uint16*)dest)[0] = (uint16)value;
                    break;
                case 3:
#if OGRE_ENDIAN == OGRE_ENDIAN_BIG      
                    ((uint8*)dest)[0] = (uint8)((value >> 16) & 0xFF);
                    ((uint8*)dest)[1] = (uint8)((value >> 8) & 0xFF);
                    ((uint8*)dest)[2] = (uint8)(value & 0xFF);
#else
                    ((uint8*)dest)[2] = (uint8)((value >> 16) & 0xFF);
                    ((uint8*)dest)[1] = (uint8)((value >> 8) & 0xFF);
                    ((uint8*)dest)[0] = (uint8)(value & 0xFF);
#endif
                    break;
                case 4:
                    ((uint32*)dest)[0] = (uint32)value;                
                    break;                
            }        
        }
        static inline unsigned int intRead(const void *src, int n) {
            switch(n) {
                case 1:
                    return ((uint8*)src)[0];
                case 2:
                    return ((uint16*)src)[0];
                case 3:
#if OGRE_ENDIAN == OGRE_ENDIAN_BIG      
                    return ((uint32)((uint8*)src)[0]<<16)|
                            ((uint32)((uint8*)src)[1]<<8)|
                            ((uint32)((uint8*)src)[2]);
#else
                    return ((uint32)((uint8*)src)[0])|
                            ((uint32)((uint8*)src)[1]<<8)|
                            ((uint32)((uint8*)src)[2]<<16);
#endif
                case 4:
                    return ((uint32*)src)[0];
            } 
            return 0; // ?
        }

        static inline uint16 floatToHalf(float i)
        {
            union { float f; uint32 i; } v;
            v.f = i;
            return floatToHalfI(v.i);
        }
        static inline uint16 floatToHalfI(uint32 i)
        {
            register int s =  (i >> 16) & 0x00008000;
            register int e = ((i >> 23) & 0x000000ff) - (127 - 15);
            register int m =   i        & 0x007fffff;
        
            if (e <= 0)
            {
                if (e < -10)
                {
                    return 0;
                }
                m = (m | 0x00800000) >> (1 - e);
        
                return static_cast<uint16>(s | (m >> 13));
            }
            else if (e == 0xff - (127 - 15))
            {
                if (m == 0) // Inf
                {
                    return static_cast<uint16>(s | 0x7c00);
                } 
                else    // NAN
                {
                    m >>= 13;
                    return static_cast<uint16>(s | 0x7c00 | m | (m == 0));
                }
            }
            else
            {
                if (e > 30) // Overflow
                {
                    return static_cast<uint16>(s | 0x7c00);
                }
        
                return static_cast<uint16>(s | (e << 10) | (m >> 13));
            }
        }
        
        static inline float halfToFloat(uint16 y)
        {
            union { float f; uint32 i; } v;
            v.i = halfToFloatI(y);
            return v.f;
        }
        static inline uint32 halfToFloatI(uint16 y)
        {
            register int s = (y >> 15) & 0x00000001;
            register int e = (y >> 10) & 0x0000001f;
            register int m =  y        & 0x000003ff;
        
            if (e == 0)
            {
                if (m == 0) // Plus or minus zero
                {
                    return s << 31;
                }
                else // Denormalized number -- renormalize it
                {
                    while (!(m & 0x00000400))
                    {
                        m <<= 1;
                        e -=  1;
                    }
        
                    e += 1;
                    m &= ~0x00000400;
                }
            }
            else if (e == 31)
            {
                if (m == 0) // Inf
                {
                    return (s << 31) | 0x7f800000;
                }
                else // NaN
                {
                    return (s << 31) | 0x7f800000 | (m << 13);
                }
            }
        
            e = e + (127 - 15);
            m = m << 13;
        
            return (s << 31) | (e << 23) | m;
        }
         

    };
}

#endif