Re: template class and non-template class
On Sep 24, 3:38 pm, ThosRTanner <ttann...@bloomberg.net> wrote:
I have a template class which I'd like to have a non-templated version
of - it's templated on a size_t which is currently a compile time
constant. I now need to make an almost identical class, except with
the size_t being a constructor parameter instead. This
template <size_t Size> class SomeClass {
char data[Size];
....
public:
SomeClass() { };
};
and
class SomeClass {
char *data;
....
public:
explicit SomeClass(size_t size) :
data(new char[Size]) { }
};
more or less. The rest of the methods and implementation would be
exactly (for an appropriate meaning of exact) the same.
But I'd like to avoid having 2 copies of the code.
Any suggestions on how to go about this? (avoiding implementing the
template in terms of the non-template because the template class
shouldn't allocate memory dynamically)
Use a proxy class size of 0 as a marker. Comeau and g++ are both
quite happy with the below:
-- CUT HERE --
typedef unsigned size_t;
template< size_t Size > class FooData {
char data[Size];
public:
FooData(size_t) { }
operator char*() { return data; }
operator char const * () const { return data; }
};
template<> struct FooData<0> {
char *data;
public:
FooData(size_t sz) : data(new char[sz]) { }
~FooData() { delete[] data; }
operator char*() { return data; }
operator char const * () const { return data; }
};
template< size_t Size > struct Foo {
FooData<Size> data;
Foo(size_t sz = Size) : data(FooData<Size>(sz)) { }
};
void f()
{
Foo<3> x;
Foo<0> y(3);
x.data[1] = 7;
y.data[2] = x.data[1];
}
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