BansheeEngine/Source/BansheeUtility/Utility/BsBitwise.h

//********************************** Banshee Engine (www.banshee3d.com) **************************************************//
//**************** Copyright (c) 2016 Marko Pintera ([email protected]). All rights reserved. **********************//
#pragma once

#include "Prerequisites/BsPrerequisitesUtil.h"

namespace bs 
{
	/** @addtogroup General
	 *  @{
	 */

	/** Floating point number broken down into components for easier access. */
	union Float754 
	{
		UINT32 raw;
		float value;
		struct {
#if BS_ENDIAN == BS_ENDIAN_BIG
			UINT32 negative : 1;
			UINT32 exponent : 8;
			UINT32 mantissa : 23;
#else
			UINT32 mantissa : 23;
			UINT32 exponent : 8;
			UINT32 negative : 1;
#endif
		} field;
	};

	/** 10-bit floating point number broken down into components for easier access. */
	union Float10
	{
		UINT32 raw;
		struct {
#if BS_ENDIAN == BS_ENDIAN_BIG
			UINT32 exponent : 5;
			UINT32 mantissa : 5;
#else
			UINT32 mantissa : 5;
			UINT32 exponent : 5;
#endif
		} field;
	};

	/** 11-bit floating point number broken down into components for easier access. */
	union Float11
	{
		UINT32 raw;
		struct {
#if BS_ENDIAN == BS_ENDIAN_BIG
			UINT32 exponent : 5;
			UINT32 mantissa : 6;
#else
			UINT32 mantissa : 6;
			UINT32 exponent : 5;
#endif
		} field;
	};

	/** Class for manipulating bit patterns. */
	class Bitwise
	{
	public:
		/** Returns the most significant bit set in a value. */
		static UINT32 mostSignificantBitSet(unsigned int value)
		{
			UINT32 result = 0;
			while (value != 0) {
				++result;
				value >>= 1;
			}
			return result - 1;
		}

		/** Returns the power-of-two number greater or equal to the provided value. */
		static UINT32 nextPow2(UINT32 n)
		{
			--n;
			n |= n >> 16;
			n |= n >> 8;
			n |= n >> 4;
			n |= n >> 2;
			n |= n >> 1;
			++n;
			return n;
		}

		/** Returns the power-of-two number closest to the provided value. */
		static UINT32 closestPow2(UINT32 n)
		{
			UINT32 next = nextPow2(n);

			UINT32 prev = next >> 1;
			if (n - prev < next - n)
				return prev;
			
			return next;
		}

		/** Determines whether the number is power-of-two or not. */
		template<typename T>
		static bool isPow2(T n)
		{
			return (n & (n - 1)) == 0;
		}

		/** Returns the number of bits a pattern must be shifted right by to remove right-hand zeros. */
		template<typename T>
		static unsigned int getBitShift(T mask)
		{
			if (mask == 0)
				return 0;

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

		/** Takes a value with a given src bit mask, and produces another value with a desired bit mask. */
		template<typename SrcT, typename DestT>
		static 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);
		}

		/** 
		 * Convert N bit color channel value to P bits. It fills P bits with the bit pattern repeated. 
		 * (this is /((1<<n)-1) in fixed point).
		 */
		static 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;
		}

		/** 
		 * Converts floating point value in range [0, 1] to an unsigned integer of a certain number of bits. Works for any
		 * value of bits between 0 and 31.
		 */
		static unsigned int unormToUint(float value, 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));
		}

		/** 
		 * Converts floating point value in range [-1, 1] to an unsigned integer of a certain number of bits. Works for any
		 * value of bits between 0 and 31.
		 */
		static unsigned int snormToUint(float value, unsigned int bits)
		{
			return unormToUint((value + 1.0f) * 0.5f, bits);
		}

		/** Converts an unsigned integer to a floating point in range [0, 1]. */
		static float uintToUnorm(unsigned value, unsigned int bits)
		{
			return (float)value / (float)((1 << bits) - 1);
		}

		/** Converts an unsigned integer to a floating point in range [-1, 1]. */
		static float uintToSnorm(unsigned value, unsigned int bits)
		{
			return uintToUnorm(value, bits) * 2.0f - 1.0f;
		}

		/** Write a n*8 bits integer value to memory in native endian. */
		static 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 BS_ENDIAN == BS_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;                
			}        
		}

		/** Read a n*8 bits integer value to memory in native endian. */
		static 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 BS_ENDIAN == BS_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; // ?
		}

		/** Convert a float32 to a float16 (NV_half_float). */
		static UINT16 floatToHalf(float i)
		{
			union { float f; UINT32 i; } v;
			v.f = i;
			return floatToHalfI(v.i);
		}

		/** Converts float in UINT32 format to a a half in UINT16 format. */
		static UINT16 floatToHalfI(UINT32 i)
		{
			int s =  (i >> 16) & 0x00008000;
			int e = ((i >> 23) & 0x000000ff) - (127 - 15);
			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));
			}
		}
		
		/** Convert a float16 (NV_half_float) to a float32. */
		static float halfToFloat(UINT16 y)
		{
			union { float f; UINT32 i; } v;
			v.i = halfToFloatI(y);
			return v.f;
		}

		/** Converts a half in UINT16 format to a float in UINT32 format. */
		static UINT32 halfToFloatI(UINT16 y)
		{
			int s = (y >> 15) & 0x00000001;
			int e = (y >> 10) & 0x0000001f;
			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;
		}

		/** Converts a 32-bit float to a 10-bit float according to OpenGL packed_float extension. */
		static UINT32 floatToFloat10(float v)
		{
			Float754 f;
			f.value = v;

			if (f.field.exponent == 0xFF)
			{
				// NAN or INF
				if (f.field.mantissa > 0)
					return 0x3E0 | (((f.raw >> 18) | (f.raw >> 13) | (f.raw >> 3) | f.raw) & 0x1F);
				else if (f.field.negative)
					return 0; // Negative infinity clamped to 0
				else
					return 0x3E0; // Positive infinity

			}
			else if (f.field.negative)
				return 0; // Negative clamped to 0, no negatives allowed
			else if (f.raw > 0x477C0000)
				return 0x3DF; // Too large, clamp to max value
			else
			{
				UINT32 val;
				if (f.raw < 0x38800000U)
				{
					// Too small to be represented as a normalized float, convert to denormalized value
					UINT32 shift = 113 - f.field.exponent;
					val = (0x800000U | f.field.mantissa) >> shift;
				}
				else
				{
					// Rebias exponent
					val = f.raw + 0xC8000000;
				}

				return  ((val + 0x1FFFFU + ((val >> 18) & 1)) >> 18) & 0x3FF;
			}
		}

		/** Converts a 32-bit float to a 11-bit float according to OpenGL packed_float extension. */
		static UINT32 floatToFloat11(float v)
		{
			Float754 f;
			f.value = v;

			if (f.field.exponent == 0xFF)
			{
				// NAN or INF
				if (f.field.mantissa > 0)
					return 0x7C0 | (((f.raw >> 17) | (f.raw >> 11) | (f.raw >> 6) | f.raw) & 0x3F);
				else if (f.field.negative)
					return 0; // Negative infinity clamped to 0
				else
					return 0x7C0; // Positive infinity

			}
			else if (f.field.negative)
				return 0; // Negative clamped to 0, no negatives allowed
			else if (f.raw > 0x477E0000)
				return 0x7BF; // Too large, clamp to max value
			else
			{
				UINT32 val;
				if(f.raw < 0x38800000U)
				{
					// Too small to be represented as a normalized float, convert to denormalized value
					UINT32 shift = 113 - f.field.exponent;
					val = (0x800000U | f.field.mantissa) >> shift;
				}
				else
				{
					// Rebias exponent
					val = f.raw + 0xC8000000;
				}

				return  ((val + 0xFFFFU + ((val >> 17) & 1)) >> 17) & 0x7FF;
			}
		}

		/** Converts a 10-bit float to a 32-bit float according to OpenGL packed_float extension. */
		static float float10ToFloat(UINT32 v)
		{
			Float10 f;
			f.raw = v;

			UINT32 output;
			if (f.field.exponent == 0x1F) // INF or NAN
			{
				output = 0x7f800000 | (f.field.mantissa << 17);
			}
			else
			{
				UINT32 exponent;
				UINT32 mantissa = f.field.mantissa;

				if (f.field.exponent != 0) // The value is normalized
					exponent = f.field.exponent;
				else if (mantissa != 0) // The value is denormalized
				{
					// Normalize the value in the resulting float
					exponent = 1;

					do
					{
						exponent--;
						mantissa <<= 1;
					} while ((mantissa & 0x20) == 0);

					mantissa &= 0x1F;
				}
				else // The value is zero
					exponent = (UINT32)-112;

				output = ((exponent + 112) << 23) | (mantissa << 18);
			}

			return *(float*)&output;
		}

		/** Converts a 11-bit float to a 32-bit float according to OpenGL packed_float extension. */
		static float float11ToFloat(UINT32 v)
		{
			Float11 f;
			f.raw = v;

			UINT32 output;
			if (f.field.exponent == 0x1F) // INF or NAN
			{
				output = 0x7f800000 | (f.field.mantissa << 17);
			}
			else
			{
				UINT32 exponent;
				UINT32 mantissa = f.field.mantissa;

				if (f.field.exponent != 0) // The value is normalized
					exponent = f.field.exponent;
				else if (mantissa != 0) // The value is denormalized
				{
					// Normalize the value in the resulting float
					exponent = 1;

					do
					{
						exponent--;
						mantissa <<= 1;
					} while ((mantissa & 0x40) == 0);

					mantissa &= 0x3F;
				}
				else // The value is zero
					exponent = (UINT32)-112;

				output = ((exponent + 112) << 23) | (mantissa << 17);
			}

			return *(float*)&output;
		}

		/** Converts a float in range [-1,1] into an unsigned 8-bit integer. */
		static UINT8 quantize8BitSigned(float v)
		{
			return quantize8BitUnsigned(v * 0.5f + 0.5f);
		}

		/** Converts a float in range [0,1] into an unsigned 8-bit integer. */
		static UINT8 quantize8BitUnsigned(float v)
		{
			return (UINT8)(v * 255.999f);
		}
	};

	/** @} */
}