Revision control
Copy as Markdown
Other Tools
/**
* Useful concepts that are available throughout the library
* (C) 2023 Jack Lloyd
* 2023 René Meusel - Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_CONCEPTS_H_
#define BOTAN_CONCEPTS_H_
#include <botan/exceptn.h>
#include <concepts>
#include <cstdint>
#include <iosfwd>
#include <ranges>
#include <span>
#include <type_traits>
namespace Botan {
template <typename T, typename Tag, typename... Capabilities>
class Strong;
template <typename... Ts>
struct is_strong_type : std::false_type {};
template <typename... Ts>
struct is_strong_type<Strong<Ts...>> : std::true_type {};
template <typename... Ts>
constexpr bool is_strong_type_v = is_strong_type<std::remove_const_t<Ts>...>::value;
template <typename T0 = void, typename... Ts>
struct all_same {
static constexpr bool value = (std::is_same_v<T0, Ts> && ... && true);
};
template <typename... Ts>
static constexpr bool all_same_v = all_same<Ts...>::value;
namespace detail {
/**
* Helper type to indicate that a certain type should be automatically
* detected based on the context.
*/
struct AutoDetect {
constexpr AutoDetect() = delete;
};
} // namespace detail
namespace ranges {
/**
* Models a std::ranges::contiguous_range that (optionally) restricts its
* value_type to ValueT. In other words: a stretch of contiguous memory of
* a certain type (optional ValueT).
*/
template <typename T, typename ValueT = std::ranges::range_value_t<T>>
concept contiguous_range = std::ranges::contiguous_range<T> && std::same_as<ValueT, std::ranges::range_value_t<T>>;
/**
* Models a std::ranges::contiguous_range that satisfies
* std::ranges::output_range with an arbitrary value_type. In other words: a
* stretch of contiguous memory of a certain type (optional ValueT) that can be
* written to.
*/
template <typename T, typename ValueT = std::ranges::range_value_t<T>>
concept contiguous_output_range = contiguous_range<T, ValueT> && std::ranges::output_range<T, ValueT>;
/**
* Models a range that can be turned into a std::span<>. Typically, this is some
* form of ranges::contiguous_range.
*/
template <typename T>
concept spanable_range = std::constructible_from<std::span<const std::ranges::range_value_t<T>>, T>;
/**
* Models a range that can be turned into a std::span<> with a static extent.
* Typically, this is a std::array or a std::span derived from an array.
*/
// clang-format off
template <typename T>
concept statically_spanable_range = spanable_range<T> &&
decltype(std::span{std::declval<T&>()})::extent != std::dynamic_extent;
// clang-format on
/**
* Find the length in bytes of a given contiguous range @p r.
*/
inline constexpr size_t size_bytes(spanable_range auto&& r) {
return std::span{r}.size_bytes();
}
/**
* Check that a given range @p r has a certain statically-known byte length. If
* the range's extent is known at compile time, this is a static check,
* otherwise a runtime argument check will be added.
*
* @throws Invalid_Argument if range @p r has a dynamic extent and does not
* feature the expected byte length.
*/
template <size_t expected, spanable_range R>
inline constexpr void assert_exact_byte_length(R&& r) {
const std::span s{r};
if constexpr(statically_spanable_range<R>) {
static_assert(s.size_bytes() == expected, "memory region does not have expected byte lengths");
} else {
if(s.size_bytes() != expected) {
throw Invalid_Argument("Memory regions did not have expected byte lengths");
}
}
}
/**
* Check that a list of ranges (in @p r0 and @p rs) all have the same byte
* lengths. If the first range's extent is known at compile time, this will be a
* static check for all other ranges whose extents are known at compile time,
* otherwise a runtime argument check will be added.
*
* @throws Invalid_Argument if any range has a dynamic extent and not all
* ranges feature the same byte length.
*/
template <spanable_range R0, spanable_range... Rs>
inline constexpr void assert_equal_byte_lengths(R0&& r0, Rs&&... rs)
requires(sizeof...(Rs) > 0)
{
const std::span s0{r0};
if constexpr(statically_spanable_range<R0>) {
constexpr size_t expected_size = s0.size_bytes();
(assert_exact_byte_length<expected_size>(rs), ...);
} else {
const size_t expected_size = s0.size_bytes();
const bool correct_size =
((std::span<const std::ranges::range_value_t<Rs>>{rs}.size_bytes() == expected_size) && ...);
if(!correct_size) {
throw Invalid_Argument("Memory regions did not have equal lengths");
}
}
}
} // namespace ranges
namespace concepts {
// TODO: C++20 provides concepts like std::ranges::range or ::sized_range
// but at the time of this writing clang had not caught up on all
// platforms. E.g. clang 14 on Xcode does not support ranges properly.
template <typename IterT, typename ContainerT>
concept container_iterator =
std::same_as<IterT, typename ContainerT::iterator> || std::same_as<IterT, typename ContainerT::const_iterator>;
template <typename PtrT, typename ContainerT>
concept container_pointer =
std::same_as<PtrT, typename ContainerT::pointer> || std::same_as<PtrT, typename ContainerT::const_pointer>;
template <typename T>
concept container = requires(T a) {
{ a.begin() } -> container_iterator<T>;
{ a.end() } -> container_iterator<T>;
{ a.cbegin() } -> container_iterator<T>;
{ a.cend() } -> container_iterator<T>;
{ a.size() } -> std::same_as<typename T::size_type>;
typename T::value_type;
};
template <typename T>
concept contiguous_container = container<T> && requires(T a) {
{ a.data() } -> container_pointer<T>;
};
template <typename T>
concept has_empty = requires(T a) {
{ a.empty() } -> std::same_as<bool>;
};
// clang-format off
template <typename T>
concept has_bounds_checked_accessors = container<T> && (
requires(T a, const T ac, typename T::size_type s) {
{ a.at(s) } -> std::same_as<typename T::value_type&>;
{ ac.at(s) } -> std::same_as<const typename T::value_type&>;
} ||
requires(T a, const T ac, typename T::key_type k) {
{ a.at(k) } -> std::same_as<typename T::mapped_type&>;
{ ac.at(k) } -> std::same_as<const typename T::mapped_type&>;
});
// clang-format on
template <typename T>
concept resizable_container = container<T> && requires(T& c, typename T::size_type s) {
T(s);
c.resize(s);
};
template <typename T>
concept reservable_container = container<T> && requires(T& c, typename T::size_type s) { c.reserve(s); };
template <typename T>
concept resizable_byte_buffer =
contiguous_container<T> && resizable_container<T> && std::same_as<typename T::value_type, uint8_t>;
template <typename T>
concept streamable = requires(std::ostream& os, T a) { os << a; };
template <class T>
concept strong_type = is_strong_type_v<T>;
template <class T>
concept contiguous_strong_type = strong_type<T> && contiguous_container<T>;
template <class T>
concept integral_strong_type = strong_type<T> && std::integral<typename T::wrapped_type>;
template <class T>
concept unsigned_integral_strong_type = strong_type<T> && std::unsigned_integral<typename T::wrapped_type>;
template <typename T, typename Capability>
concept strong_type_with_capability = T::template has_capability<Capability>();
} // namespace concepts
} // namespace Botan
#endif