double val1 = someVal; // little endian, for example // ... double val2 = little_endian_cast<double>(big_endian_cast<double>(val1));
For many values, val1 != val2; (For all integral types in the above casting functions, all possible values will have val1 == val2.)
This is a good point. And this is not as unusual as you may think, even on IEEE 754 machines. For example, on some compilers on Intel machines, sizeof(long comes in at 12 bytes (even though long double is only 80 bits), essentially meaning that the last two bytes are garbage when the data is in memory. However, I am not completely sure that this falls within the realm of an endian library. If, as in your example, the program cannot move the data from its internal registers to memory without modifying it, what would you suggest the endian should library do?