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//
// Copyright (c) Benjamin Kaufmann 2010
//
// This is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This file is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
//
// NOTE: ProgramOptions is inspired by Boost.Program_options
// see: www.boost.org/libs/program_options
//
#ifndef PROGRAM_OPTIONS_VALUE_STORE_H_INCLUDED
#define PROGRAM_OPTIONS_VALUE_STORE_H_INCLUDED
#include <typeinfo>
#include <new>
namespace ProgramOptions {
namespace detail {
typedef void (*vcall_type)(const void* in, void** out);
typedef vcall_type vtable_type[4];
typedef vtable_type* vptr_type;
// workaround: some compilers don't support
// out-of-class definition of member templates.
template <class T>
inline vptr_type vtable(const T* = 0);
template <class T>
inline vptr_type base_vtable(const T* = 0);
}
//! A type that can hold any kind of value type
class ValueStore {
public:
//! creates an empty object
ValueStore();
//! copies the value in other
ValueStore(const ValueStore& other);
//! stores a copy of obj
template <class T>
ValueStore(const T& obj)
: vptr_(detail::vtable(static_cast<const T*>(0)))
, value_(0) {
clone(&obj, &value_);
}
//! releases any stored value
~ValueStore();
//! stores a copy of other releasing any previous value
ValueStore& operator=(ValueStore other);
//! stores a copy of obj releasing any previous value
template <class T>
ValueStore& operator=(const T& obj) {
ValueStore(obj).swap(*this);
return *this;
}
//! stores obj in this and takes over ownership of obj
/*!
* \pre delete obj is valid
*/
template <class T>
ValueStore& assimilate(T* obj) {
clear();
vptr_ = detail::base_vtable(static_cast<const T*>(0));
value_= obj;
return *this;
}
//! swaps this with other
void swap(ValueStore& other);
//! Returns true if holder does not contain a value.
bool empty() const { return vptr_ == 0; }
//! Returns the type of the stored value.
const std::type_info&
type() const;
//! destroys and releases any stored value
void clear();
//! surrenders any stored value without destroying it
void surrender();
void* extract_raw() const {
return !empty()
? extract(const_cast<void**>(&value_))
: 0;
}
private:
enum { call_extract = 0, vcall_clone = 1, vcall_destroy = 2, vcall_typeid = 3 };
typedef detail::vptr_type vptr_type;
void clone(const void* obj, void** out) const;
void* extract(void** o) const;
vptr_type vptr_;
void* value_;
};
struct bad_value_cast : std::bad_cast {
const char * what() const throw() {
return "value_cast: invalid conversion on ValueStore";
}
};
//! Extracts a typed value from a ValueStore.
/*!
* \throw bad_value_cast if value is not of type T
*/
template <class T>
const T& value_cast(const ValueStore& v, const T* = 0) {
if (v.type() == typeid(T)) {
return *static_cast<const T*>(const_cast<const void*>(v.extract_raw()));
}
throw bad_value_cast();
}
//! Returns 0 on error
template <class T>
const T* value_cast(const ValueStore* v, const T* = 0) {
if (v->type() == typeid(T)) {
return static_cast<const T*>(const_cast<const void*>(v->extract_raw()));
}
return 0;
}
/*!
* \overload
*/
template <class T>
T& value_cast(ValueStore& v, const T* p = 0) {
return const_cast<T&>(value_cast(const_cast<const ValueStore&>(v), p));
}
template <class T>
T* value_cast(ValueStore* v, const T* p = 0) {
return const_cast<T*>(value_cast(const_cast<const ValueStore*>(v), p));
}
//! Extracts a typed value from a ValueStore *without* checking if the type matches
template <class T>
const T* unsafe_value_cast(const ValueStore* v, const T* = 0) {
return static_cast<const T*>(const_cast<const void*>(v->extract_raw()));
}
/*!
* \overload
*/
template <class T>
T* unsafe_value_cast(ValueStore* v, const T* p = 0) {
return const_cast<T*>(unsafe_value_cast(const_cast<const ValueStore*>(v), p));
}
#include "detail/value_store.h"
}
#endif
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