57 lines
1.7 KiB
C++
57 lines
1.7 KiB
C++
#ifndef __horrible_cast_h__
|
|
#define __horrible_cast_h__
|
|
|
|
|
|
// horrible_union is used by {safe|dangerous}_horrible_cast to copy one arbitrary type to another
|
|
template <typename t_out, typename t_in>
|
|
union horrible_union
|
|
{
|
|
t_in in;
|
|
t_out out;
|
|
};
|
|
|
|
|
|
// dangerous_horrible_cast uses horrible_union to blindly copy one arbitrary type to another
|
|
//
|
|
// the data is zeroed out (via memset) before copying, in the case that he input type is smaller
|
|
// than the output type
|
|
template <typename t_out, typename t_in>
|
|
inline t_out dangerous_horrible_cast(t_in in)
|
|
{
|
|
// instance the union
|
|
horrible_union<t_out,t_in> data;
|
|
|
|
// zero out the output part of the union (only if the input is actually smaller than the output)
|
|
if ( sizeof(t_in) < sizeof(t_out) )
|
|
{
|
|
memset(&data.out,0,sizeof(data.out));
|
|
}
|
|
|
|
// copy the input into the union
|
|
data.in = in;
|
|
|
|
// return the output part out of the union
|
|
return data.out;
|
|
}
|
|
|
|
|
|
// safe_horrible_cast is exactly like dangerous_horrible_cast, except it statically checks to make
|
|
// certain that the output type (t_out) is at least large enough (in size) to store an instance of
|
|
// the input type (t_in)
|
|
//
|
|
// note: if you use safe_horrible_cast to copy an instance of A to B, then you may safely use
|
|
// dangerous_horrible_cast to copy an instance of B back to A.
|
|
template <typename t_out, typename t_in>
|
|
inline t_out safe_horrible_cast(t_in in)
|
|
{
|
|
// statically (compile-time) test if t_out is at least as big as t_in
|
|
typedef int ERROR___horrible_union_is_too_small_to_store_input_type[(sizeof(t_in) <= sizeof(t_out)) ? 1 : -1];
|
|
|
|
// now just do the regular horrible_cast
|
|
return dangerous_horrible_cast<t_out,t_in>(in);
|
|
}
|
|
|
|
|
|
#endif // __horrible_cast_h__
|
|
|