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small_vector.hpp
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/** small_vector.hpp
* An implementation of `small_vector` (a vector with a small
* buffer optimization). I would probably have preferred to
* call this `inline_vector`, but I'll just go with the canonical
* name for now.
*
* Copyright © 2020-2021 Gene Harvey
*
* This software may be modified and distributed under the terms
* of the MIT license. See the LICENSE file for details.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#ifndef GCH_SMALL_VECTOR_HPP
#define GCH_SMALL_VECTOR_HPP
#ifdef __clang__
# ifndef GCH_CLANG
# define GCH_CLANG
# endif
# if defined (__cplusplus) && __cplusplus >= 201103L
# ifndef GCH_CLANG_11
# define GCH_CLANG_11
# endif
# endif
# if defined (__cplusplus) && __cplusplus >= 201402L
# ifndef GCH_CLANG_14
# define GCH_CLANG_14
# endif
# endif
# if defined (__cplusplus) && __cplusplus >= 201703L
# ifndef GCH_CLANG_17
# define GCH_CLANG_17
# endif
# endif
# if defined (__cplusplus) && __cplusplus >= 202002L
# ifndef GCH_CLANG_20
# define GCH_CLANG_20
# endif
# endif
#endif
#ifndef GCH_CPP14_CONSTEXPR
# if defined (__cpp_constexpr) && __cpp_constexpr >= 201304L
# define GCH_CPP14_CONSTEXPR constexpr
# ifndef GCH_HAS_CPP14_CONSTEXPR
# define GCH_HAS_CPP14_CONSTEXPR
# endif
# else
# define GCH_CPP14_CONSTEXPR
# endif
#endif
#ifndef GCH_CPP17_CONSTEXPR
# if defined (__cpp_constexpr) && __cpp_constexpr >= 201603L
# define GCH_CPP17_CONSTEXPR constexpr
# ifndef GCH_HAS_CPP17_CONSTEXPR
# define GCH_HAS_CPP17_CONSTEXPR
# endif
# else
# define GCH_CPP17_CONSTEXPR
# endif
#endif
#ifndef GCH_CPP20_CONSTEXPR
# if defined (__cpp_constexpr) && __cpp_constexpr >= 201907L
# define GCH_CPP20_CONSTEXPR constexpr
# ifndef GCH_HAS_CPP20_CONSTEXPR
# define GCH_HAS_CPP20_CONSTEXPR
# endif
# else
# define GCH_CPP20_CONSTEXPR
# endif
#endif
#ifndef GCH_NORETURN
# if defined (__has_cpp_attribute) && __has_cpp_attribute (noreturn) >= 200809L
# define GCH_NORETURN [[noreturn]]
# else
# define GCH_NORETURN
# endif
#endif
#ifndef GCH_NODISCARD
# if defined (__has_cpp_attribute) && __has_cpp_attribute (nodiscard) >= 201603L
# if ! defined (__clang__) || defined (GCH_CLANG_17)
# define GCH_NODISCARD [[nodiscard]]
# else
# define GCH_NODISCARD
# endif
# else
# define GCH_NODISCARD
# endif
#endif
#ifndef GCH_INLINE_VARIABLE
# if defined (__cpp_inline_variables) && __cpp_inline_variables >= 201606L
# define GCH_INLINE_VARIABLE inline
# else
# define GCH_INLINE_VARIABLE
# endif
#endif
#ifndef GCH_EMPTY_BASE
# if defined (_MSC_FULL_VER) && _MSC_FULL_VER >= 190023918L
# define GCH_EMPTY_BASE __declspec (empty_bases)
# else
# define GCH_EMPTY_BASE
# endif
#endif
#ifndef GCH_IMPLICIT_CONVERSION
# if defined (__cpp_conditional_explicit) && __cpp_conditional_explicit >= 201806L
# define GCH_IMPLICIT_CONVERSION explicit (false)
# else
# define GCH_IMPLICIT_CONVERSION /* implicit */
# endif
#endif
#if defined (__cpp_variable_templates) && __cpp_variable_templates >= 201304L
# ifndef GCH_VARIABLE_TEMPLATES
# define GCH_VARIABLE_TEMPLATES
# endif
#endif
#if defined (__cpp_deduction_guides) && __cpp_deduction_guides >= 201703L
# ifndef GCH_CTAD_SUPPORT
# define GCH_CTAD_SUPPORT
# endif
#endif
#if defined (__cpp_if_constexpr) && __cpp_if_constexpr >= 201606L
# ifndef GCH_CONSTEXPR_IF
# define GCH_CONSTEXPR_IF
# endif
#endif
#if defined (__cpp_exceptions) && __cpp_exceptions >= 199711L
# ifndef GCH_EXCEPTIONS
# define GCH_EXCEPTIONS
# endif
#endif
#ifndef GCH_TRY
# ifdef GCH_EXCEPTIONS
# define GCH_TRY try
# else
# ifdef GCH_CONSTEXPR_IF
# define GCH_TRY if constexpr (true)
# else
# define GCH_TRY if (true)
# endif
# endif
#endif
#ifndef GCH_CATCH
# ifdef GCH_EXCEPTIONS
# define GCH_CATCH(...) catch (__VA_ARGS__)
# else
# ifdef GCH_CONSTEXPR_IF
# define GCH_CATCH(...) else if constexpr (false)
# else
# define GCH_CATCH(...) else if (false)
# endif
# endif
#endif
#ifndef GCH_THROW
# ifdef GCH_EXCEPTIONS
# define GCH_THROW throw
# else
# define GCH_THROW
# endif
#endif
#ifndef GCH_CONSTEVAL
# if defined (__cpp_consteval) && __cpp_consteval >= 201811L
# define GCH_CONSTEVAL consteval
# ifndef GCH_HAS_CONSTEVAL
# define GCH_HAS_CONSTEVAL
# endif
# else
# define GCH_CONSTEVAL constexpr
# endif
#endif
#if defined (__cpp_impl_three_way_comparison) && __cpp_impl_three_way_comparison >= 201907L
# ifndef GCH_IMPL_THREE_WAY_COMPARISON
# define GCH_IMPL_THREE_WAY_COMPARISON
# endif
#endif
#if defined (__cpp_concepts) && __cpp_concepts >= 201907L
# ifndef GCH_CONCEPTS
# define GCH_CONCEPTS
# endif
#endif
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <initializer_list>
#include <iterator>
#include <limits>
#include <memory>
#include <new>
#include <type_traits>
#include <utility>
#ifdef GCH_IMPL_THREE_WAY_COMPARISON
# if defined (__has_include) && __has_include (<compare>)
# include <compare>
# endif
#endif
#ifdef GCH_CONCEPTS
# if defined (__has_include) && __has_include (<concepts>)
# include <concepts>
# endif
#endif
#ifdef GCH_STDLIB_INTEROP
# include <array>
# include <valarray>
# include <vector>
#endif
#ifdef GCH_EXCEPTIONS
# include <stdexcept>
#else
# include <cstdio>
# include <cstdlib>
#endif
#if defined (__cpp_lib_three_way_comparison) && __cpp_lib_three_way_comparison >= 201907L
# ifndef GCH_LIB_THREE_WAY_COMPARISON
# define GCH_LIB_THREE_WAY_COMPARISON
# endif
#endif
#if defined (__cpp_lib_concepts) && __cpp_lib_concepts >= 202002L
# if ! defined (GCH_LIB_CONCEPTS) && ! defined (GCH_DISABLE_CONCEPTS)
# define GCH_LIB_CONCEPTS
# endif
#endif
#if defined (__cpp_lib_is_final) && __cpp_lib_is_final >= 201402L
# ifndef GCH_LIB_IS_FINAL
# define GCH_LIB_IS_FINAL
# endif
#endif
#if defined (__cpp_lib_is_constant_evaluated) && __cpp_lib_is_constant_evaluated >= 201811L
# ifndef GCH_LIB_IS_CONSTANT_EVALUATED
# define GCH_LIB_IS_CONSTANT_EVALUATED
# endif
#endif
#if defined (__cpp_lib_is_swappable) && __cpp_lib_is_swappable >= 201603L
# ifndef GCH_LIB_IS_SWAPPABLE
# define GCH_LIB_IS_SWAPPABLE
# endif
#endif
#if defined (__cpp_lib_allocator_traits_is_always_equal)
# if __cpp_lib_allocator_traits_is_always_equal >= 201411L
# ifndef GCH_LIB_IS_ALWAYS_EQUAL
# define GCH_LIB_IS_ALWAYS_EQUAL
# endif
# endif
#endif
#if defined (__cpp_lib_constexpr_memory) && __cpp_lib_constexpr_memory >= 201811L
# ifndef GCH_LIB_CONSTEXPR_MEMORY
# define GCH_LIB_CONSTEXPR_MEMORY
# endif
#endif
// TODO:
// Make sure we don't need any laundering in the internal class functions.
// I also need some sort of test case to actually show where UB is occurring,
// because it's still a bit unclear to me.
#if defined (__cpp_lib_launder) && __cpp_lib_launder >= 201606L
# ifndef GCH_LIB_LAUNDER
# define GCH_LIB_LAUNDER
# endif
#endif
// defined if the entire thing is available for constexpr
#ifndef GCH_SMALL_VECTOR_CONSTEXPR
# if defined (GCH_HAS_CPP20_CONSTEXPR) && defined (GCH_LIB_IS_CONSTANT_EVALUATED) \
&& defined (GCH_LIB_CONSTEXPR_MEMORY)
# define GCH_SMALL_VECTOR_CONSTEXPR constexpr
# ifndef GCH_HAS_CONSTEXPR_SMALL_VECTOR
# define GCH_HAS_CONSTEXPR_SMALL_VECTOR
# endif
# else
# define GCH_SMALL_VECTOR_CONSTEXPR
# endif
#endif
#ifndef GCH_SMALL_VECTOR_DEFAULT_SIZE
# define GCH_SMALL_VECTOR_DEFAULT_SIZE 64
#endif
namespace gch
{
#ifdef GCH_LIB_CONCEPTS
namespace concepts
{
template <typename T>
concept Complete = requires { sizeof (T); };
// Note: this mirrors the named requirements, not the standard concepts, so we don't require
// the destructor to be noexcept for Destructible.
template <typename T>
concept Destructible = std::is_destructible<T>::value;
template <typename T>
concept TriviallyDestructible = std::is_trivially_destructible<T>::value;
template <typename T>
concept NoThrowDestructible = std::is_nothrow_destructible<T>::value;
// Note: this mirrors the named requirements, not the standard library concepts,
// so we don't require Destructible here.
template <typename T, typename... Args>
concept ConstructibleFrom = std::is_constructible<T, Args...>::value;
template <typename T, typename... Args>
concept NoThrowConstructibleFrom = std::is_nothrow_constructible<T, Args...>::value;
template <typename From, typename To>
concept ConvertibleTo =
std::is_convertible<From, To>::value
&& requires (typename std::add_rvalue_reference<From>::type (&f) (void))
{
static_cast<To> (f ());
};
template <typename From, typename To>
concept NoThrowConvertibleTo =
std::is_nothrow_convertible<From, To>::value
&& requires (typename std::add_rvalue_reference<From>::type (&f) (void) noexcept)
{
{ static_cast<To> (f ()) } noexcept;
};
// Note: std::default_initializable requires std::destructible.
template <typename T>
concept DefaultConstructible =
ConstructibleFrom<T>
&& requires { T { }; }
&& requires { ::new (static_cast<void *> (nullptr)) T; };
template <typename T>
concept MoveAssignable = std::assignable_from<T&, T>;
template <typename T>
concept CopyAssignable =
MoveAssignable<T>
&& std::assignable_from<T&, T&>
&& std::assignable_from<T&, const T&>
&& std::assignable_from<T&, const T>;
template <typename T>
concept MoveConstructible = ConstructibleFrom<T, T> && ConvertibleTo<T, T>;
template <typename T>
concept NoThrowMoveConstructible =
NoThrowConstructibleFrom<T, T>
&& NoThrowConvertibleTo<T, T>;
template <typename T>
concept CopyConstructible =
MoveConstructible<T>
&& ConstructibleFrom<T, T&> && ConvertibleTo< T&, T>
&& ConstructibleFrom<T, const T&> && ConvertibleTo<const T&, T>
&& ConstructibleFrom<T, const T > && ConvertibleTo<const T , T>;
template <typename T>
concept NoThrowCopyConstructible =
NoThrowMoveConstructible<T>
&& NoThrowConstructibleFrom<T, T&> && NoThrowConvertibleTo< T&, T>
&& NoThrowConstructibleFrom<T, const T&> && NoThrowConvertibleTo<const T&, T>
&& NoThrowConstructibleFrom<T, const T > && NoThrowConvertibleTo<const T , T>;
template <typename T>
concept Swappable = std::swappable<T>;
template <typename T>
concept EqualityComparable = std::equality_comparable<T>;
// T is a type
// X is a Container
// A is an Allocator
// if X::allocator_type then
// std::same_as<typename X::allocator_type,
// typename std::allocator_traits<A>::template rebind_alloc<T>>
// otherwise
// no condition; we use std::allocator<T> regardless of A
//
// see [22.2.1].16
template <typename T, typename X, typename A, typename ...Args>
concept EmplaceConstructible =
std::same_as<typename X::value_type, T>
&& ( ( requires { typename X::allocator_type; } // only perform this check if X is
&& std::same_as<typename X::allocator_type, // allocator-aware
typename std::allocator_traits<A>::template rebind_alloc<T>>
&& ( requires (A m, T *p, Args&&... args)
{
m.construct (p, std::forward<Args> (args)...);
}
|| requires (T *p, Args&&... args)
{
#if __cplusplus >= 202002L // c++20 fully featured
{ std::construct_at (p, std::forward<Args> (args)...) } -> std::same_as<T *>;
#else
::new (std::declval<void *> ()) T (std::declval<Args> ()...);
#endif
}))
|| (! requires { typename X::allocator_type; }
&& requires (T *p, Args&&... args)
{
#if __cplusplus >= 202002L // c++20 fully featured
{ std::construct_at (p, std::forward<Args> (args)...) } -> std::same_as<T *>;
#else
::new (std::declval<void *> ()) T (std::declval<Args> ()...);
#endif
}));
template <typename T, typename X,
typename A = typename std::conditional<requires { typename X::allocator_type; },
typename X::allocator_type,
std::allocator<T>>::type>
concept DefaultInsertable = EmplaceConstructible<T, X, A>;
template <typename T, typename X,
typename A = typename std::conditional<requires { typename X::allocator_type; },
typename X::allocator_type,
std::allocator<T>>::type>
concept MoveInsertable = EmplaceConstructible<T, X, A, T>;
template <typename T, typename X,
typename A = typename std::conditional<requires { typename X::allocator_type; },
typename X::allocator_type,
std::allocator<T>>::type>
concept CopyInsertable = MoveInsertable<T, X, A>
&& EmplaceConstructible<T, X, A, T&>
&& EmplaceConstructible<T, X, A, const T&>;
// same method as with EmplaceConstructible
template <typename T, typename X,
typename A = typename std::conditional<requires { typename X::allocator_type; },
typename X::allocator_type,
std::allocator<T>>::type>
concept Erasable =
std::same_as<typename X::value_type, T>
&& ( ( requires { typename X::allocator_type; } // if X is allocator aware
&& std::same_as<typename X::allocator_type,
typename std::allocator_traits<A>::template rebind_alloc<T>>
&& ( requires (A m, T *p)
{
m.destroy (p);
}
|| std::is_destructible<T>::value))
|| (! requires { typename X::allocator_type; }
&& std::is_destructible<T>::value));
template <typename T>
concept ContextuallyConvertibleToBool = std::constructible_from<bool, T>;
template <typename T>
concept BoolConstant = std::derived_from<T, std::true_type>
|| std::derived_from<T, std::false_type>;
template <typename T>
concept NullablePointer =
EqualityComparable<T>
&& DefaultConstructible<T>
&& CopyConstructible<T>
&& CopyAssignable<T>
&& Destructible<T>
&& ConstructibleFrom<T, std::nullptr_t>
&& ConvertibleTo<std::nullptr_t, T>
&& requires (T p, T q, std::nullptr_t np)
{
T (np);
{ p = np } -> std::same_as<T&>;
{ p != q } -> ContextuallyConvertibleToBool;
{ p == np } -> ContextuallyConvertibleToBool;
{ np == p } -> ContextuallyConvertibleToBool;
{ p != np } -> ContextuallyConvertibleToBool;
{ np != p } -> ContextuallyConvertibleToBool;
};
static_assert ( NullablePointer<int *>);
static_assert (! NullablePointer<int>);
template <typename A, typename T, typename U = T *>
concept AllocatorFor =
NoThrowCopyConstructible<A>
&& requires (A a,
typename std::allocator_traits<A>::template rebind_alloc<U> b,
U xp,
typename std::allocator_traits<A>::pointer p,
typename std::allocator_traits<A>::const_pointer cp,
typename std::allocator_traits<A>::void_pointer vp,
typename std::allocator_traits<A>::const_void_pointer cvp,
typename std::allocator_traits<A>::value_type& r,
typename std::allocator_traits<A>::size_type n)
{
/** Inner types **/
// A::pointer
requires NullablePointer< typename std::allocator_traits<A>::pointer>;
requires std::random_access_iterator<typename std::allocator_traits<A>::pointer>;
requires std::contiguous_iterator< typename std::allocator_traits<A>::pointer>;
// A::const_pointer
requires NullablePointer< typename std::allocator_traits<A>::const_pointer>;
requires std::random_access_iterator<typename std::allocator_traits<A>::const_pointer>;
requires std::contiguous_iterator< typename std::allocator_traits<A>::const_pointer>;
requires std::convertible_to<typename std::allocator_traits<A>::pointer,
typename std::allocator_traits<A>::const_pointer>;
// A::void_pointer
requires NullablePointer<typename std::allocator_traits<A>::void_pointer>;
requires std::convertible_to<typename std::allocator_traits<A>::pointer,
typename std::allocator_traits<A>::void_pointer>;
requires std::same_as<typename std::allocator_traits<A>::void_pointer,
typename std::allocator_traits<decltype (b)>::void_pointer>;
// A::const_void_pointer
requires NullablePointer<typename std::allocator_traits<A>::const_void_pointer>;
requires std::convertible_to<typename std::allocator_traits<A>::pointer,
typename std::allocator_traits<A>::const_void_pointer>;
requires std::convertible_to<typename std::allocator_traits<A>::const_pointer,
typename std::allocator_traits<A>::const_void_pointer>;
requires std::convertible_to<typename std::allocator_traits<A>::void_pointer,
typename std::allocator_traits<A>::const_void_pointer>;
requires std::same_as<typename std::allocator_traits<A>::const_void_pointer,
typename std::allocator_traits<decltype (b)>::const_void_pointer>;
// A::value_type
typename A::value_type;
requires std::same_as<typename A::value_type, T>;
requires std::same_as<typename A::value_type,
typename std::allocator_traits<A>::value_type>;
// A::size_type
requires std::unsigned_integral<typename std::allocator_traits<A>::size_type>;
// A::difference_type
requires std::signed_integral<typename std::allocator_traits<A>::difference_type>;
// A::template rebind<U>::other [optional]
requires ! requires { typename A::template rebind<U>::other; }
|| requires
{
requires std::same_as<decltype (b), typename A::template rebind<U>::other>;
requires std::same_as<A, typename decltype (b)::template rebind<T>::other>;
};
/** Operations on pointers **/
{ *p } -> std::same_as<typename A::value_type&>;
{ *cp } -> std::same_as<const typename A::value_type&>;
// Language in the standard implies that `decltype (p)` must either
// be a raw pointer or implement `operator->`. There is no mention
// of `std::to_address` or `std::pointer_traits<Ptr>::to_address`.
requires std::same_as<decltype (p), typename A::value_type *>
|| requires
{
{ p.operator-> () } -> std::same_as<typename A::value_type *>;
};
requires std::same_as<decltype (cp), const typename A::value_type *>
|| requires
{
{ cp.operator-> () } -> std::same_as<const typename A::value_type *>;
};
{ static_cast<decltype (p)> (vp) } -> std::same_as<decltype (p)>;
{ static_cast<decltype (cp)> (cvp) } -> std::same_as<decltype (cp)>;
{ std::pointer_traits<decltype (p)>::pointer_to (r) } -> std::same_as<decltype (p)>;
/** Storage and lifetime operations **/
// a.allocate (n)
{ a.allocate (n) } -> std::same_as<decltype (p)>;
// a.allocate (n, cvp) [optional]
requires ! requires { a.allocate (n, cvp); }
|| requires { { a.allocate (n, cvp) } -> std::same_as<decltype (p)>; };
// a.deallocate (p, n)
{ a.deallocate (p, n) } -> std::convertible_to<void>;
// a.max_size () [optional]
requires ! requires { a.max_size (); }
|| requires { { a.max_size () } -> std::same_as<decltype (n)>; };
// a.construct (xp, args) [optional]
requires ! requires { a.construct (xp); }
|| requires { { a.construct (xp) } -> std::convertible_to<void>; };
// a.destroy (xp) [optional]
requires ! requires { a.destroy (xp); }
|| requires { { a.destroy (xp) } -> std::convertible_to<void>; };
/** Relationship between instances **/
requires NoThrowConstructibleFrom<A, decltype (b)>;
requires NoThrowConstructibleFrom<A, decltype (std::move (b))>;
requires BoolConstant<typename std::allocator_traits<A>::is_always_equal>;
/** Influence on container operations **/
// a.select_on_container_copy_construction () [optional]
requires ! requires { a.select_on_container_copy_construction (); }
|| requires
{
{ a.select_on_container_copy_construction () } -> std::same_as<A>;
};
requires BoolConstant<
typename std::allocator_traits<A>::propagate_on_container_copy_assignment>;
requires BoolConstant<
typename std::allocator_traits<A>::propagate_on_container_move_assignment>;
requires BoolConstant<
typename std::allocator_traits<A>::propagate_on_container_swap>;
{ a == b } -> std::same_as<bool>;
{ a != b } -> std::same_as<bool>;
}
&& requires (A a1, A a2)
{
{ a1 == a2 } -> std::same_as<bool>;
{ a1 != a2 } -> std::same_as<bool>;
};
static_assert (AllocatorFor<std::allocator<int>, int>,
"std::allocator<int> failed to meet Allocator concept requirements.");
template <typename A>
concept Allocator = AllocatorFor<A, typename A::value_type>;
namespace small_vector
{
// Basically, these shut off the concepts if we have an incomplete type.
// This namespace is only needed because of issues on Clang
// preventing us from short-circuiting for incomplete types.
template <typename T>
concept Destructible =
! concepts::Complete<T> || concepts::Destructible<T>;
template <typename T>
concept MoveAssignable =
! concepts::Complete<T> || concepts::MoveAssignable<T>;
template <typename T>
concept CopyAssignable =
! concepts::Complete<T> || concepts::CopyAssignable<T>;
template <typename T>
concept MoveConstructible =
! concepts::Complete<T> || concepts::MoveConstructible<T>;
template <typename T>
concept CopyConstructible =
! concepts::Complete<T> || concepts::CopyConstructible<T>;
template <typename T>
concept Swappable =
! concepts::Complete<T> || concepts::Swappable<T>;
template <typename T, typename SmallVector, typename Alloc>
concept DefaultInsertable =
! concepts::Complete<T> || concepts::DefaultInsertable<T, SmallVector, Alloc>;
template <typename T, typename SmallVector, typename Alloc>
concept MoveInsertable =
! concepts::Complete<T> || concepts::MoveInsertable<T, SmallVector, Alloc>;
template <typename T, typename SmallVector, typename Alloc>
concept CopyInsertable =
! concepts::Complete<T> || concepts::CopyInsertable<T, SmallVector, Alloc>;
template <typename T, typename SmallVector, typename Alloc>
concept Erasable =
! concepts::Complete<T> || concepts::Erasable<T, SmallVector, Alloc>;
template <typename T, typename SmallVector, typename Alloc, typename ...Args>
concept EmplaceConstructible =
! concepts::Complete<T> || concepts::EmplaceConstructible<T, SmallVector, Alloc, Args...>;
template <typename Alloc, typename T>
concept AllocatorFor =
! concepts::Complete<T> || concepts::AllocatorFor<Alloc, T>;
template <typename Alloc>
concept Allocator = AllocatorFor<Alloc, typename Alloc::value_type>;
} // namespace gch::concepts::small_vector
} // namespace gch::concepts
#endif
template <typename Allocator>
#ifdef GCH_LIB_CONCEPTS
requires concepts::small_vector::Allocator<Allocator>
#endif
struct default_buffer_size;
template <typename T,
unsigned InlineCapacity = default_buffer_size<std::allocator<T>>::value,
typename Allocator = std::allocator<T>>
#ifdef GCH_LIB_CONCEPTS
requires concepts::small_vector::AllocatorFor<Allocator, T>
#endif
class small_vector;
template <typename Allocator>
#ifdef GCH_LIB_CONCEPTS
requires concepts::small_vector::Allocator<Allocator>
#endif
struct default_buffer_size
{
private:
template <typename, typename Enable = void>
struct is_complete
: std::false_type
{ };
template <typename U>
struct is_complete<U, decltype (static_cast<void> (sizeof (U)))>
: std::true_type
{ };
public:
using allocator_type = Allocator;
using value_type = typename std::allocator_traits<allocator_type>::value_type;
using empty_small_vector = small_vector<value_type, 0, allocator_type>;
static_assert (is_complete<value_type>::value,
"Calculation of a default number of elements requires that `T` be complete.");
static constexpr
unsigned
buffer_max = 256;
static constexpr
unsigned
ideal_total = GCH_SMALL_VECTOR_DEFAULT_SIZE;
#ifndef GCH_UNRESTRICTED_DEFAULT_BUFFER_SIZE
// FIXME: Some compilers will not emit the error from this static_assert
// while instantiating a small_vector, and attribute the mistake
// to some random other function.
// static_assert (sizeof (value_type) <= buffer_max, "`sizeof (T)` too large");
#endif
static constexpr
unsigned
ideal_buffer = ideal_total - sizeof (empty_small_vector);
static_assert (sizeof (empty_small_vector) != 0,
"Empty `small_vector` should not have size 0.");
static_assert (ideal_buffer < ideal_total,
"Empty `small_vector` is larger than ideal_total.");
static constexpr
unsigned
value = (sizeof (value_type) <= ideal_buffer) ? (ideal_buffer / sizeof (value_type)) : 1;
};
#ifdef GCH_VARIABLE_TEMPLATES
template <typename Allocator>
GCH_INLINE_VARIABLE constexpr
unsigned
default_buffer_size_v = default_buffer_size<Allocator>::value;
#endif
template <typename Pointer, typename DifferenceType>
class small_vector_iterator
{
public:
using difference_type = DifferenceType;
using value_type = typename std::iterator_traits<Pointer>::value_type;
using pointer = typename std::iterator_traits<Pointer>::pointer;
using reference = typename std::iterator_traits<Pointer>::reference;
using iterator_category = typename std::iterator_traits<Pointer>::iterator_category;
#ifdef GCH_LIB_CONCEPTS
using iterator_concept = std::contiguous_iterator_tag;
#endif
// small_vector_iterator (void) = impl;
small_vector_iterator (const small_vector_iterator&) = default;
small_vector_iterator (small_vector_iterator&&) noexcept = default;
small_vector_iterator& operator= (const small_vector_iterator&) = default;
small_vector_iterator& operator= (small_vector_iterator&&) noexcept = default;
~small_vector_iterator (void) = default;
#ifdef NDEBUG
small_vector_iterator (void) = default;
#else
constexpr
small_vector_iterator (void) noexcept
: m_ptr ()
{ }
#endif
constexpr explicit
small_vector_iterator (const Pointer& p) noexcept
: m_ptr (p)
{ }
template <typename U, typename D,
typename std::enable_if<std::is_convertible<U, Pointer>::value>::type * = nullptr>
constexpr GCH_IMPLICIT_CONVERSION
small_vector_iterator (const small_vector_iterator<U, D>& other) noexcept
: m_ptr (other.base ())
{ }
GCH_CPP14_CONSTEXPR
small_vector_iterator&
operator++ (void) noexcept
{
++m_ptr;
return *this;
}
GCH_CPP14_CONSTEXPR
small_vector_iterator
operator++ (int) noexcept
{
return small_vector_iterator (m_ptr++);
}
GCH_CPP14_CONSTEXPR
small_vector_iterator&
operator-- (void) noexcept
{
--m_ptr;
return *this;
}
GCH_CPP14_CONSTEXPR
small_vector_iterator
operator-- (int) noexcept
{
return small_vector_iterator (m_ptr--);
}
GCH_CPP14_CONSTEXPR
small_vector_iterator&
operator+= (difference_type n) noexcept
{
m_ptr += n;
return *this;
}
constexpr
small_vector_iterator
operator+ (difference_type n) const noexcept
{
return small_vector_iterator (m_ptr + n);
}
GCH_CPP14_CONSTEXPR
small_vector_iterator&
operator-= (difference_type n) noexcept
{
m_ptr -= n;
return *this;
}
constexpr
small_vector_iterator
operator- (difference_type n) const noexcept
{
return small_vector_iterator (m_ptr - n);
}
constexpr
reference
operator* (void) const noexcept
{
#ifdef GCH_LIB_LAUNDER
return launder_and_dereference (m_ptr);
#else
return *m_ptr;
#endif
}
constexpr
pointer
operator-> (void) const noexcept
{
return get_pointer (m_ptr);
}
constexpr
reference
operator[] (difference_type n) const noexcept
{
#ifdef GCH_LIB_LAUNDER
return launder_and_dereference (m_ptr + n);
#else
return m_ptr[n];
#endif
}
constexpr
const Pointer&
base (void) const noexcept
{
return m_ptr;
}
private:
template <typename Ptr = Pointer,
typename std::enable_if<std::is_pointer<Ptr>::value, bool>::type = true>
static constexpr
pointer
get_pointer (Pointer ptr) noexcept
{
return ptr;
}
template <typename Ptr = Pointer,
typename std::enable_if<! std::is_pointer<Ptr>::value, bool>::type = false>
static constexpr
pointer
get_pointer (Pointer ptr) noexcept
{
// Given the requirements for Allocator, Pointer must either be a raw pointer, or
// have a defined operator-> which returns a raw pointer.
return ptr.operator-> ();
}
#ifdef GCH_LIB_LAUNDER
template <typename Ptr = Pointer,
typename std::enable_if<std::is_pointer<Ptr>::value, bool>::type = true>
static constexpr
reference
launder_and_dereference (Pointer ptr) noexcept
{
return *std::launder (ptr);
}
template <typename Ptr = Pointer,
typename std::enable_if<! std::is_pointer<Ptr>::value, bool>::type = false>
static constexpr
reference
launder_and_dereference (Pointer ptr) noexcept
{
return *ptr;
}
#endif
Pointer m_ptr;
};
#ifdef GCH_LIB_THREE_WAY_COMPARISON
template <typename PointerLHS, typename DifferenceTypeLHS,
typename PointerRHS, typename DifferenceTypeRHS>
constexpr
bool
operator== (const small_vector_iterator<PointerLHS, DifferenceTypeLHS>& lhs,
const small_vector_iterator<PointerRHS, DifferenceTypeRHS>& rhs)
noexcept (noexcept (lhs.base () == rhs.base ()))
requires requires { { lhs.base () == rhs.base () } -> std::convertible_to<bool>; }
{
return lhs.base () == rhs.base ();
}