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Diffstat (limited to 'include/pybind11/detail/descr.h')
-rw-r--r-- | include/pybind11/detail/descr.h | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h new file mode 100644 index 0000000..8d404e5 --- /dev/null +++ b/include/pybind11/detail/descr.h @@ -0,0 +1,100 @@ +/* + pybind11/detail/descr.h: Helper type for concatenating type signatures at compile time + + Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch> + + All rights reserved. Use of this source code is governed by a + BSD-style license that can be found in the LICENSE file. +*/ + +#pragma once + +#include "common.h" + +NAMESPACE_BEGIN(PYBIND11_NAMESPACE) +NAMESPACE_BEGIN(detail) + +#if !defined(_MSC_VER) +# define PYBIND11_DESCR_CONSTEXPR static constexpr +#else +# define PYBIND11_DESCR_CONSTEXPR const +#endif + +/* Concatenate type signatures at compile time */ +template <size_t N, typename... Ts> +struct descr { + char text[N + 1]; + + constexpr descr() : text{'\0'} { } + constexpr descr(char const (&s)[N+1]) : descr(s, make_index_sequence<N>()) { } + + template <size_t... Is> + constexpr descr(char const (&s)[N+1], index_sequence<Is...>) : text{s[Is]..., '\0'} { } + + template <typename... Chars> + constexpr descr(char c, Chars... cs) : text{c, static_cast<char>(cs)..., '\0'} { } + + static constexpr std::array<const std::type_info *, sizeof...(Ts) + 1> types() { + return {{&typeid(Ts)..., nullptr}}; + } +}; + +template <size_t N1, size_t N2, typename... Ts1, typename... Ts2, size_t... Is1, size_t... Is2> +constexpr descr<N1 + N2, Ts1..., Ts2...> plus_impl(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b, + index_sequence<Is1...>, index_sequence<Is2...>) { + return {a.text[Is1]..., b.text[Is2]...}; +} + +template <size_t N1, size_t N2, typename... Ts1, typename... Ts2> +constexpr descr<N1 + N2, Ts1..., Ts2...> operator+(const descr<N1, Ts1...> &a, const descr<N2, Ts2...> &b) { + return plus_impl(a, b, make_index_sequence<N1>(), make_index_sequence<N2>()); +} + +template <size_t N> +constexpr descr<N - 1> _(char const(&text)[N]) { return descr<N - 1>(text); } +constexpr descr<0> _(char const(&)[1]) { return {}; } + +template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { }; +template <size_t...Digits> struct int_to_str<0, Digits...> { + static constexpr auto digits = descr<sizeof...(Digits)>(('0' + Digits)...); +}; + +// Ternary description (like std::conditional) +template <bool B, size_t N1, size_t N2> +constexpr enable_if_t<B, descr<N1 - 1>> _(char const(&text1)[N1], char const(&)[N2]) { + return _(text1); +} +template <bool B, size_t N1, size_t N2> +constexpr enable_if_t<!B, descr<N2 - 1>> _(char const(&)[N1], char const(&text2)[N2]) { + return _(text2); +} + +template <bool B, typename T1, typename T2> +constexpr enable_if_t<B, T1> _(const T1 &d, const T2 &) { return d; } +template <bool B, typename T1, typename T2> +constexpr enable_if_t<!B, T2> _(const T1 &, const T2 &d) { return d; } + +template <size_t Size> auto constexpr _() -> decltype(int_to_str<Size / 10, Size % 10>::digits) { + return int_to_str<Size / 10, Size % 10>::digits; +} + +template <typename Type> constexpr descr<1, Type> _() { return {'%'}; } + +constexpr descr<0> concat() { return {}; } + +template <size_t N, typename... Ts> +constexpr descr<N, Ts...> concat(const descr<N, Ts...> &descr) { return descr; } + +template <size_t N, typename... Ts, typename... Args> +constexpr auto concat(const descr<N, Ts...> &d, const Args &...args) + -> decltype(std::declval<descr<N + 2, Ts...>>() + concat(args...)) { + return d + _(", ") + concat(args...); +} + +template <size_t N, typename... Ts> +constexpr descr<N + 2, Ts...> type_descr(const descr<N, Ts...> &descr) { + return _("{") + descr + _("}"); +} + +NAMESPACE_END(detail) +NAMESPACE_END(PYBIND11_NAMESPACE) |