libcruft-util/introspection.hpp

445 lines
18 KiB
C++

/*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* Copyright 2015-2017 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_INTROSPECTION_HPP
#define __UTIL_INTROSPECTION_HPP
#include "variadic.hpp"
#include <cruft/util/preprocessor.hpp>
#include <array>
#include <cstddef>
#include <cstdint>
#include <filesystem>
#include <ostream>
#include <string>
#include <tuple>
#include <utility>
namespace cruft {
// clang#18781: clang-3.9/clang-4.0 will not instantiate static constexpr
// member variables from class specialisations, so we have to use detail
// classes to hold the variables and instantiate _those_ members instead.
template <typename T>
struct type_name;
#define CLANG_WORKAROUND(TYPE,TAG,NAME) \
namespace detail { \
struct type_name_##TAG { \
static constexpr const char value[] = (NAME); \
}; \
} \
\
template <> \
struct type_name<TYPE> : public detail::type_name_##TAG { };
CLANG_WORKAROUND(bool,bool,"bool")
CLANG_WORKAROUND(char,char,"char")
CLANG_WORKAROUND(void*,voidp,"void*")
CLANG_WORKAROUND( uint8_t, u08, "u08")
CLANG_WORKAROUND(uint16_t, u16, "u16")
CLANG_WORKAROUND(uint32_t, u32, "u32")
CLANG_WORKAROUND(uint64_t, u64, "u64")
CLANG_WORKAROUND( int8_t, s08, "i08")
CLANG_WORKAROUND(int16_t, s16, "i16")
CLANG_WORKAROUND(int32_t, s32, "i32")
CLANG_WORKAROUND(int64_t, s64, "i64")
CLANG_WORKAROUND(float, f32, "f32")
CLANG_WORKAROUND(double, f64, "f64")
CLANG_WORKAROUND(const char*, const_cstring, "cstring")
CLANG_WORKAROUND(char*, cstring, "cstring")
CLANG_WORKAROUND(std::string, string, "string")
CLANG_WORKAROUND(std::filesystem::path, path, "path");
CLANG_WORKAROUND(std::byte, byte, "byte");
#undef CLANG_WORKAROUND
template <typename T>
constexpr
auto type_name_v = type_name<T>::value;
template <typename T>
const char*
to_string (void)
{ return type_name_v<T>; }
///////////////////////////////////////////////////////////////////////////
template <typename T>
struct type_char;
template <> struct type_char<float > { static constexpr char value = 'f'; };
template <> struct type_char<double> { static constexpr char value = 'd'; };
template <> struct type_char< int8_t> { static constexpr char value = 'i'; };
template <> struct type_char< int16_t> { static constexpr char value = 'i'; };
template <> struct type_char< int32_t> { static constexpr char value = 'i'; };
template <> struct type_char< int64_t> { static constexpr char value = 'i'; };
template <> struct type_char< uint8_t> { static constexpr char value = 'u'; };
template <> struct type_char<uint16_t> { static constexpr char value = 'u'; };
template <> struct type_char<uint32_t> { static constexpr char value = 'u'; };
template <> struct type_char<uint64_t> { static constexpr char value = 'u'; };
template <typename T>
constexpr auto type_char_v = type_char<T>::value;
///////////////////////////////////////////////////////////////////////////
/// Lists valid values of an enumeration
///
/// E: enumeration type
///
/// Specialisations must provide the following constexpr:
/// value_type: typename
/// value_count: size_t
/// values: static const std::array<value_type,value_count>
template <
typename E
>
struct enum_traits;
///////////////////////////////////////////////////////////////////////////
/// 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.
///
/// XXX: If we define the constexpr fields in a template specialised class
/// clang has trouble instantiating them (with std=c++1z) resulting in
/// undefined symbols at link time. By using a simple struct and inheriting
/// from it we can avoid this problem. Revist this solution at clang-4.0.
#define INTROSPECTION_ENUM_DECL(NS,E, ...) \
namespace cruft { \
struct PASTE(__enum_traits_,E) { \
using value_type = ::NS::E; \
\
static constexpr \
size_t value_count = VA_ARGS_COUNT(__VA_ARGS__); \
\
static const \
std::array<value_type,value_count> \
values; \
\
static const \
std::array<const char*,value_count> \
names; \
}; \
\
template <> \
struct enum_traits<::NS::E> : public PASTE(__enum_traits_,E) \
{ }; \
\
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 called from outside all namespaces.
#define INTROSPECTION_ENUM_IMPL(NS,E, ...) \
const \
std::array< \
cruft::enum_traits<::NS::E>::value_type, \
cruft::enum_traits<::NS::E>::value_count \
> PASTE(cruft::__enum_traits_,E)::values = { \
MAP1(NAMESPACE_LIST, ::NS::E, __VA_ARGS__) \
}; \
\
const \
std::array< \
const char*, \
cruft::enum_traits<::NS::E>::value_count \
> PASTE(cruft::__enum_traits_,E)::names = { \
MAP0(STRINGIZE_LIST, __VA_ARGS__) \
};
///------------------------------------------------------------------------
/// 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 ::cruft::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 = ::cruft::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 ::cruft::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 = ::cruft::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 std::make_index_sequence<
std::tuple_size<
typename type<K>::fields
>::value
>
> struct _type_tuple;
template <
typename K,
size_t ...I
> struct _type_tuple <
K,
std::index_sequence<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 std::make_index_sequence<
std::tuple_size<
typename type<K>::fields
>::value
>
>
struct _as_tuple;
template <
typename K,
size_t ...I
>
struct _as_tuple <
K,
std::index_sequence<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