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250 lines
8.0 KiB
C++
250 lines
8.0 KiB
C++
//========= Copyright Valve Corporation, All rights reserved. ============//
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//
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// Purpose: Low level byte swapping routines.
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//
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// $NoKeywords: $
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//=============================================================================
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#ifndef BYTESWAP_H
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#define BYTESWAP_H
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#if defined(_WIN32)
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#pragma once
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#endif
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#include "datamap.h" // Needed for typedescription_t. Note datamap.h is tier1 as well.
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class CByteswap
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{
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public:
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CByteswap()
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{
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// Default behavior sets the target endian to match the machine native endian (no swap).
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SetTargetBigEndian( IsMachineBigEndian() );
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}
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//-----------------------------------------------------------------------------
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// Write a single field.
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//-----------------------------------------------------------------------------
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void SwapFieldToTargetEndian( void* pOutputBuffer, void *pData, typedescription_t *pField );
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//-----------------------------------------------------------------------------
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// Write a block of fields. Works a bit like the saverestore code.
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//-----------------------------------------------------------------------------
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void SwapFieldsToTargetEndian( void *pOutputBuffer, void *pBaseData, datamap_t *pDataMap );
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// Swaps fields for the templated type to the output buffer.
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template<typename T> inline void SwapFieldsToTargetEndian( T* pOutputBuffer, void *pBaseData, unsigned int objectCount = 1 )
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{
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for ( unsigned int i = 0; i < objectCount; ++i, ++pOutputBuffer )
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{
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SwapFieldsToTargetEndian( (void*)pOutputBuffer, pBaseData, &T::m_DataMap );
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pBaseData = (byte*)pBaseData + sizeof(T);
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}
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}
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// Swaps fields for the templated type in place.
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template<typename T> inline void SwapFieldsToTargetEndian( T* pOutputBuffer, unsigned int objectCount = 1 )
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{
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SwapFieldsToTargetEndian<T>( pOutputBuffer, (void*)pOutputBuffer, objectCount );
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}
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//-----------------------------------------------------------------------------
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// True if the current machine is detected as big endian.
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// (Endienness is effectively detected at compile time when optimizations are
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// enabled)
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//-----------------------------------------------------------------------------
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static bool IsMachineBigEndian()
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{
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short nIsBigEndian = 1;
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// if we are big endian, the first byte will be a 0, if little endian, it will be a one.
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return (bool)(0 == *(char *)&nIsBigEndian );
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}
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//-----------------------------------------------------------------------------
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// Sets the target byte ordering we are swapping to or from.
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//
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// Braindead Endian Reference:
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// x86 is LITTLE Endian
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// PowerPC is BIG Endian
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//-----------------------------------------------------------------------------
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inline void SetTargetBigEndian( bool bigEndian )
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{
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m_bBigEndian = bigEndian;
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m_bSwapBytes = IsMachineBigEndian() != bigEndian;
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}
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// Changes target endian
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inline void FlipTargetEndian( void )
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{
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m_bSwapBytes = !m_bSwapBytes;
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m_bBigEndian = !m_bBigEndian;
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}
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// Forces byte swapping state, regardless of endianess
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inline void ActivateByteSwapping( bool bActivate )
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{
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SetTargetBigEndian( IsMachineBigEndian() != bActivate );
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}
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//-----------------------------------------------------------------------------
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// Returns true if the target machine is the same as this one in endianness.
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//
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// Used to determine when a byteswap needs to take place.
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//-----------------------------------------------------------------------------
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inline bool IsSwappingBytes( void ) // Are bytes being swapped?
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{
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return m_bSwapBytes;
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}
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inline bool IsTargetBigEndian( void ) // What is the current target endian?
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{
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return m_bBigEndian;
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}
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//-----------------------------------------------------------------------------
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// IsByteSwapped()
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//
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// When supplied with a chunk of input data and a constant or magic number
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// (in native format) determines the endienness of the current machine in
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// relation to the given input data.
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//
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// Returns:
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// 1 if input is the same as nativeConstant.
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// 0 if input is byteswapped relative to nativeConstant.
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// -1 if input is not the same as nativeConstant and not byteswapped either.
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//
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// ( This is useful for detecting byteswapping in magic numbers in structure
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// headers for example. )
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//-----------------------------------------------------------------------------
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template<typename T> inline int SourceIsNativeEndian( T input, T nativeConstant )
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{
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// If it's the same, it isn't byteswapped:
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if( input == nativeConstant )
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return 1;
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int output;
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LowLevelByteSwap<T>( &output, &input );
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if( output == nativeConstant )
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return 0;
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assert( 0 ); // if we get here, input is neither a swapped nor unswapped version of nativeConstant.
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return -1;
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}
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//-----------------------------------------------------------------------------
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// Swaps an input buffer full of type T into the given output buffer.
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//
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// Swaps [count] items from the inputBuffer to the outputBuffer.
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// If inputBuffer is omitted or NULL, then it is assumed to be the same as
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// outputBuffer - effectively swapping the contents of the buffer in place.
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//-----------------------------------------------------------------------------
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template<typename T> inline void SwapBuffer( T* outputBuffer, T* inputBuffer = NULL, int count = 1 )
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{
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assert( count >= 0 );
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assert( outputBuffer );
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// Fail gracefully in release:
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if( count <=0 || !outputBuffer )
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return;
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// Optimization for the case when we are swapping in place.
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if( inputBuffer == NULL )
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{
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inputBuffer = outputBuffer;
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}
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// Swap everything in the buffer:
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for( int i = 0; i < count; i++ )
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{
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LowLevelByteSwap<T>( &outputBuffer[i], &inputBuffer[i] );
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}
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}
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//-----------------------------------------------------------------------------
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// Swaps an input buffer full of type T into the given output buffer.
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//
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// Swaps [count] items from the inputBuffer to the outputBuffer.
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// If inputBuffer is omitted or NULL, then it is assumed to be the same as
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// outputBuffer - effectively swapping the contents of the buffer in place.
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//-----------------------------------------------------------------------------
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template<typename T> inline void SwapBufferToTargetEndian( T* outputBuffer, T* inputBuffer = NULL, int count = 1 )
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{
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assert( count >= 0 );
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assert( outputBuffer );
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// Fail gracefully in release:
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if( count <=0 || !outputBuffer )
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return;
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// Optimization for the case when we are swapping in place.
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if( inputBuffer == NULL )
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{
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inputBuffer = outputBuffer;
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}
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// Are we already the correct endienness? ( or are we swapping 1 byte items? )
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if( !m_bSwapBytes || ( sizeof(T) == 1 ) )
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{
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// If we were just going to swap in place then return.
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if( !inputBuffer )
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return;
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// Otherwise copy the inputBuffer to the outputBuffer:
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memcpy( outputBuffer, inputBuffer, count * sizeof( T ) );
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return;
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}
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// Swap everything in the buffer:
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for( int i = 0; i < count; i++ )
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{
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LowLevelByteSwap<T>( &outputBuffer[i], &inputBuffer[i] );
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}
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}
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private:
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//-----------------------------------------------------------------------------
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// The lowest level byte swapping workhorse of doom. output always contains the
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// swapped version of input. ( Doesn't compare machine to target endianness )
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//-----------------------------------------------------------------------------
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template<typename T> static void LowLevelByteSwap( T *output, T *input )
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{
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T temp = *output;
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#if defined( _X360 )
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// Intrinsics need the source type to be fixed-point
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DWORD* word = (DWORD*)input;
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switch( sizeof(T) )
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{
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case 8:
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{
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__storewordbytereverse( *word, 0, &temp );
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__storewordbytereverse( *(word+1), 4, &temp );
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}
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break;
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case 4:
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__storewordbytereverse( *word, 0, &temp );
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break;
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case 2:
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__storeshortbytereverse( *input, 0, &temp );
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break;
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default:
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Assert( "Invalid size in CByteswap::LowLevelByteSwap" && 0 );
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}
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#else
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for( size_t i = 0; i < sizeof(T); i++ )
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{
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((unsigned char* )&temp)[i] = ((unsigned char*)input)[sizeof(T)-(i+1)];
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}
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#endif
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Q_memcpy( output, &temp, sizeof(T) );
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}
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unsigned int m_bSwapBytes : 1;
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unsigned int m_bBigEndian : 1;
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};
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#endif /* !BYTESWAP_H */
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