template method specialisation problem - c++

Question

Can anyone help me with this code. I'm trying to specialise a method. At the moment it doesn't work with one specialisation (1) but I'd like to ultimately have lots of specialisations (2, 3, 4, 5 etc)
class X
{
public:
// declaration
template< int FLD >
void set_native( char *ptr, unsigned int length );
// specialisations
template<> void set_native< 1 >( char *ptr, unsigned int length )
{
}
};
The error messages I'm getting are..
x.cpp:13: error: explicit specialization in non-namespace scope 'class X'
x.cpp:13: error: template-id 'set_native<1>' for 'void set_native(char*, unsigned int)' does not match any template declaration
x.cpp:13: error: invalid function declaration

Answer 1

As Benoit proposed, you have to specialize the member function in the surrounding namespace:
struct X {
template<int N> void f() {}
};
template<> void X::f<1>() {} // explicit specialization at namespace scope
This is because of §14.7.3 (C++03):
An explicit specialization shall be declared in the namespace of which the template is a member, or, for member templates, in the namespace of which the enclosing class or enclosing class template is a member.
VC however doesn't conform to the standard in that regard and thus creates some portability headaches.

Answer 2

Try the following
class X
{
public:
// declaration
template< int FLD >
void set_native( char *ptr, unsigned int length );
};
// specialisations
template<> void X::set_native< 1 >( char *ptr, unsigned int length )
{
}
If it does not work, try adding a templated class behind set_native
template<int FLD> class SetNative;
class X
{
public:
// declaration
template< int FLD >
void set_native( char *ptr, unsigned int length )
{ return SetNative()(ptr, length); }
};
template<> class SetNative<1>
{
void operator()( char *ptr, unsigned int length ){...}
};