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/*****
* inst.h
* Tom Prince and John Bowman 2005/04/12
*
* Descibes the items that are used by the virtual machine.
*****/
#ifndef ITEM_H
#define ITEM_H
#include "common.h"
#include <typeinfo>
namespace vm {
class item;
class bad_item_value {};
template<typename T>
T get(const item&);
class item : public gc {
public:
bool empty()
{ return *kind == typeid(void); }
item()
: kind(&typeid(void)) {}
#ifndef Int
item(Int i)
: kind(&typeid(Int)), i(i) {}
#endif
item(int i)
: kind(&typeid(Int)), i(i) {}
item(double x)
: kind(&typeid(double)), x(x) {}
item(bool b)
: kind(&typeid(bool)), b(b) {}
#ifndef Int
item& operator= (int a)
{ kind=&typeid(Int); i=a; return *this; }
#endif
item& operator= (Int a)
{ kind=&typeid(Int); i=a; return *this; }
item& operator= (double a)
{ kind=&typeid(double); x=a; return *this; }
item& operator= (bool a)
{ kind=&typeid(bool); b=a; return *this; }
template<class T>
item(T *p)
: kind(&typeid(T)), p((void *) p) {}
template<class T>
item(const T &p)
: kind(&typeid(T)), p(new(UseGC) T(p)) {}
template<class T>
item& operator= (T *a)
{ kind=&typeid(T); p=(void *) a; return *this; }
template<class T>
item& operator= (const T &it)
{ kind=&typeid(T); p=new(UseGC) T(it); return *this; }
template<typename T>
friend inline T get(const item&);
friend inline bool isdefault(const item&);
friend inline bool isarray(const item&);
const std::type_info &type() const
{ return *kind; }
friend ostream& operator<< (ostream& out, const item& i);
private:
const std::type_info *kind;
union {
Int i;
double x;
bool b;
void *p;
};
template <typename T>
struct help;
template <typename T>
struct help<T*> {
static T* unwrap(const item& it)
{
if (*it.kind == typeid(T))
return (T*) it.p;
throw vm::bad_item_value();
}
};
template <typename T>
struct help {
static T& unwrap(const item& it)
{
if (*it.kind == typeid(T))
return *(T*) it.p;
throw vm::bad_item_value();
}
};
};
class frame : public gc {
typedef mem::vector<item> vars_t;
vars_t vars;
public:
frame(size_t size)
: vars(size)
{}
item& operator[] (size_t n)
{ return vars[n]; }
item operator[] (size_t n) const
{ return vars[n]; }
size_t size()
{ return vars.size(); }
// Extends vars to ensure it has a place for any variable indexed up to n.
void extend(size_t n) {
if (vars.size() < n)
vars.resize(n);
}
};
template<typename T>
inline T get(const item& it)
{
return item::help<T>::unwrap(it);
}
#ifndef Int
template <>
inline int get<int>(const item&)
{
throw vm::bad_item_value();
}
#endif
template <>
inline Int get<Int>(const item& it)
{
if (*it.kind == typeid(Int))
return it.i;
throw vm::bad_item_value();
}
template <>
inline double get<double>(const item& it)
{
if (*it.kind == typeid(double))
return it.x;
throw vm::bad_item_value();
}
template <>
inline bool get<bool>(const item& it)
{
if (*it.kind == typeid(bool))
return it.b;
throw vm::bad_item_value();
}
// This serves as the object for representing a default argument.
struct default_t : public gc {};
inline bool isdefault(const item& it)
{
return *it.kind == typeid(default_t);
}
inline ostream& operator<< (ostream& out, const item& i)
{
out << "type " << i.type().name();
if (i.type() == typeid(Int))
cout << ", value = " << get<Int>(i) << endl;
else if (i.type() == typeid(double))
cout << ", value = " << get<double>(i) << endl;
else if (i.type() == typeid(string))
cout << ", value = " << get<string>(i) << endl;
else out << endl;
return out;
}
} // namespace vm
GC_DECLARE_PTRFREE(vm::default_t);
#endif // ITEM_H
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