libcruft-util/introspection.hpp

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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2015-2016 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_INTROSPECTION_HPP
#define __UTIL_INTROSPECTION_HPP
#include "./preprocessor.hpp"
#include "./variadic.hpp"
#include <cstddef>
#include <cstdint>
#include <string>
#include <tuple>
namespace util {
// XXX: we should be using a const char[] here, but clang-3.9 will not
// instantiate array values within template specialisations.
template <typename T>
struct type_name;
template <> struct type_name<bool> { static constexpr const char *value = "bool"; };
template <> struct type_name<char> { static constexpr const char *value = "char"; };
template <> struct type_name<void*> { static constexpr const char *value = "void*"; };
template <> struct type_name< int8_t> { static constexpr const char *value = "int8"; };
template <> struct type_name< int16_t> { static constexpr const char *value = "int16"; };
template <> struct type_name< int32_t> { static constexpr const char *value = "int32"; };
template <> struct type_name< int64_t> { static constexpr const char *value = "int64"; };
template <> struct type_name< uint8_t> { static constexpr const char *value = "uint8"; };
template <> struct type_name<uint16_t> { static constexpr const char *value = "uint16"; };
template <> struct type_name<uint32_t> { static constexpr const char *value = "uint32"; };
template <> struct type_name<uint64_t> { static constexpr const char *value = "uint64"; };
template <> struct type_name<float > { static constexpr const char *value = "float32"; };
template <> struct type_name<double > { static constexpr const char *value = "float64"; };
template <> struct type_name<std::string> { static constexpr const char *value = "string"; };
template <> struct type_name<char*> { static constexpr const char *value = "cstring"; };
template <> struct type_name<const char*> { static constexpr const char *value = "cstring"; };
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template <typename T>
constexpr
const char* type_name_v = type_name<T>::value;
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template <typename T>
const char*
to_string (void)
{ return type_name_v<T>; }
///////////////////////////////////////////////////////////////////////////
/// Lists valid values of an enumeration
///
/// E: enumeration type
template <
typename E
>
struct enum_traits {
/// Specialisations must provide the following constexpr:
///
/// value_type: typename
/// value_count: size_t
/// values: static const std::array<value_type,value_count>
};
///////////////////////////////////////////////////////////////////////////
/// Defines specialisations for introspection data structures for an
/// enum E, in namespace NS, with variadic values __VA_ARGS__.
///
/// Expects to be caleld from outside all namespaces.
#define INTROSPECTION_ENUM_DECL(NS,E, ...) \
namespace util { \
template <> \
struct enum_traits<::NS::E> { \
using value_type = ::NS::E; \
\
static constexpr \
size_t value_count = VA_ARGS_COUNT(__VA_ARGS__); \
\
static constexpr \
std::array<value_type,value_count> \
values = { \
MAP1(NAMESPACE_LIST, ::NS::E, __VA_ARGS__) \
}; \
\
static constexpr \
std::array<const char*,value_count> \
names = { MAP(STRINGIZE_LIST, __VA_ARGS__) }; \
}; \
\
template <> \
struct type_name<::NS::E> { \
static constexpr const char ns[] = #NS; \
static constexpr const char value[] = #E; \
}; \
} \
///------------------------------------------------------------------------
/// Declares specialisations for introspection data structures for an
/// enum E, in namespace NS, with variadic values __VA_ARGS__.
///
/// Expects to be caleld from outside all namespaces.
#define INTROSPECTION_ENUM_IMPL(NS,E, ...) \
constexpr \
std::array< \
util::enum_traits<::NS::E>::value_type, \
util::enum_traits<::NS::E>::value_count \
> util::enum_traits<::NS::E>::values; \
\
constexpr \
std::array< \
const char*, \
util::enum_traits<::NS::E>::value_count \
> util::enum_traits<::NS::E>::names; \
\
constexpr \
const char util::type_name<::NS::E>::ns[]; \
\
constexpr \
const char util::type_name<::NS::E>::value[]; \
///------------------------------------------------------------------------
/// Defines an istream extraction operator for an enumeration E, within
/// namespace NS
///
/// Expects to be called from outside all namespaces.
///
/// The user is responsible for specialising the ::util::enum_traits<NS::E>
/// parameters which are used to drive the implementation (eg, through
/// INTROSPECTION_ENUM_DECL, and INTROSPECTION_ENUM_IMPL).
///
/// For trivial enumerations INTROSPECTION_ENUM may be easier to use.
#define INTROSPECTION_ENUM_ISTREAM(NS,E) \
std::istream& \
::NS::operator>> (std::istream &is, ::NS::E &e) \
{ \
using traits = util::enum_traits<::NS::E>; \
\
std::string name; \
is >> name; \
\
std::transform (std::begin (name), \
std::end (name), \
std::begin (name), \
::toupper); \
\
auto name_pos = std::find ( \
std::cbegin (traits::names), \
std::cend (traits::names), \
name \
); \
\
if (name_pos == std::cend (traits::names)) { \
is.setstate (std::istream::failbit); \
} else { \
auto d = std::distance ( \
std::begin (traits::names), \
name_pos \
); \
\
e = traits::values[d]; \
} \
\
return is; \
}
/// Defines an ostream insertion operator for an enumeration E, within
/// namespace NS.
///
/// Expects to be called from outside all namespaces.
///
/// The user is responsible for specialising the ::util::enum_traits<NS::E>
/// parameters which are used to drive the implementation (eg, through
/// INTROSPECTION_ENUM_DECL, and INTROSPECTION_ENUM_IMPL).
///
/// For trivial enumerations INTROSPECTION_ENUM may be easier to use.
#define INTROSPECTION_ENUM_OSTREAM(NS,E) \
std::ostream& \
::NS::operator<< (std::ostream &os, ::NS::E e) \
{ \
using traits = ::util::enum_traits<::NS::E>; \
\
auto val_pos = std::find ( \
std::cbegin (traits::values), \
std::cend (traits::values), \
e \
); \
\
if (val_pos == std::cend (traits::values)) { \
os.setstate (std::ostream::failbit); \
} else { \
auto d = std::distance ( \
std::cbegin (traits::values), \
val_pos \
); \
\
os << traits::names[d]; \
} \
\
return os; \
}
/// Defines an enum, its values, associated introspection structures, and
/// istream and ostream operators.
///
/// This must be called from outside all namespaces as
/// INTROSPECTION_ENUM_DECL and INTROSPECTION_ENUM_IMPL need to declare
/// and define structures outside the user's namespace.
///
/// The enum will be defined inside an inline namespace to simplify the
/// passing of parameters to functions which require some namespace
/// prefixing. This shouldn't have a practical effect on user code.
#define INTROSPECTION_ENUM(E, ...) \
inline namespace detail_intr_enum { \
enum E { __VA_ARGS__ }; \
std::ostream& operator<< (std::ostream&, E); \
std::istream& operator>> (std::istream&, E&); \
} \
INTROSPECTION_ENUM_DECL(detail_intr_enum,E,__VA_ARGS__) \
INTROSPECTION_ENUM_IMPL(detail_intr_enum,E,__VA_ARGS__) \
INTROSPECTION_ENUM_ISTREAM(detail_intr_enum,E) \
INTROSPECTION_ENUM_OSTREAM(detail_intr_enum,E)
#define INTROSPECTION_ENUM_CLASS(E, ...) \
inline namespace detail_intr_enum { \
enum class E { __VA_ARGS__ }; \
std::ostream& operator<< (std::ostream&, E); \
std::istream& operator>> (std::istream&, E&); \
} \
INTROSPECTION_ENUM_DECL(detail_intr_enum,E,__VA_ARGS__) \
INTROSPECTION_ENUM_IMPL(detail_intr_enum,E,__VA_ARGS__) \
INTROSPECTION_ENUM_ISTREAM(detail_intr_enum,E) \
INTROSPECTION_ENUM_OSTREAM(detail_intr_enum,E)
///////////////////////////////////////////////////////////////////////////
/// Describes a single member variable in a type availabe for introspection
///
/// K: target class
/// R: member type
/// M: pointer-to-member
template <
class K,
typename R,
R K::*M
>
struct field
{
typedef K klass;
typedef R type;
static const std::string name;
static const R& get (const K &k) { return k.*M; }
static R& get ( K &k) { return k.*M; }
static R& get ( K &&) = delete;
};
///////////////////////////////////////////////////////////////////////////
/// Holds the fields of a type available for introspection
///
/// Specialise the following type struct with a 'fields' tuple of the
/// members that should be accessed like below:
///
/// struct foo { int a; int b; };
///
/// template <> struct type<foo>
/// {
/// typedef std::tuple<
/// field<foo,int,&foo::a>,
/// field<foo,int,&foo::b>
/// > fields;
/// };
///
/// template <> const std::string field<foo,int,&foo::a>::name = "a";
/// template <> const std::string field<foo,int,&foo::b>::name = "b";
template <class K>
struct type { };
///////////////////////////////////////////////////////////////////////////
/// traits class which converts an introspected type to a tuple
///
/// K: target class
template <typename K>
struct type_tuple;
template <
typename ...T
> struct type_tuple<
std::tuple<T...>
> {
typedef std::tuple<T...> type;
};
template <
typename K,
typename I = typename make_indices<
std::tuple_size<
typename type<K>::fields
>::value
>::type
> struct _type_tuple;
template <
typename K,
size_t ...I
> struct _type_tuple <
K,
indices<I...>
> {
typedef std::tuple<
typename std::tuple_element<
I,
typename type<K>::fields
>::type::type...
> type;
};
template <
typename K
> struct type_tuple {
typedef typename _type_tuple<K>::type type;
};
///////////////////////////////////////////////////////////////////////////
namespace detail {
template <
typename K,
typename I = typename make_indices<
std::tuple_size<
typename type<K>::fields
>::value
>::type
>
struct _as_tuple;
template <
typename K,
size_t ...I
>
struct _as_tuple <
K,
indices<I...>
>
{
static typename type_tuple<K>::type
make (const K &k)
{
return std::make_tuple (
std::tuple_element<I, typename type<K>::fields>::type::get (k)...
);
}
static auto make (K&&) = delete;
};
}
/// Convert an introspection capable class instance into a tuple instance
///
/// K: source class
template <typename K>
auto
as_tuple (const K &k)
{
return detail::_as_tuple<K>::make (k);
}
template <typename K>
auto as_tuple (K &_k)
{
const K &k = _k;
return as_tuple (k);
}
template <typename K>
auto as_tuple (K&&) = delete;
}
#endif