The operations are the same in both directions. Here is some code for the common unsigned data types: Code: inline void endian_swap(unsigned short& x) { x = (x>>8) | (x<<8); } inline void endian_swap(unsigned int& x) { x = (x>>24) | ((x<<8) & 0x00FF0000) | ((x>>8) & 0x0000FF00) | (x<<24); } // __int64 for MSVC, "long long" for gcc inline void endian_swap(unsigned __int64& x) { x = (x>>56) | ((x<<40) & 0x00FF000000000000) | ((x<<24) & 0x0000FF0000000000) | ((x<<8) & 0x000000FF00000000) | ((x>>8) & 0x00000000FF000000) | ((x>>24) & 0x0000000000FF0000) | ((x>>40) & 0x000000000000FF00) | (x<<56); }