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Refactor move constructor and swap implementations for small_vector a…
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…s in some cass unnecesary heap allocation was performed. Add tests for this.
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@igaztanaga
igaztanaga committed Jun 2, 2024
1 parent 4142050 commit 9da5dc4
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Showing 3 changed files with 425 additions and 79 deletions.
66 changes: 36 additions & 30 deletions include/boost/container/small_vector.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -283,7 +283,7 @@ class small_vector_allocator
{ return !(l == r); }

#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
private:
public:

typedef small_vector_base<value_type, allocator_type, Options> derived_type;
typedef typename dtl::vector_for_small_vector
Expand Down Expand Up @@ -357,6 +357,7 @@ class small_vector_base
typedef typename allocator_traits<allocator_type>::const_pointer const_pointer;
typedef typename allocator_traits<allocator_type>::void_pointer void_pointer;
typedef typename allocator_traits<allocator_type>::const_void_pointer const_void_pointer;
typedef typename base_type::size_type size_type;


private:
Expand All @@ -378,38 +379,54 @@ class small_vector_base

public:

BOOST_CONTAINER_ATTRIBUTE_NODISCARD bool is_small() const
{ return this->internal_storage() == this->data(); }

protected:

inline explicit small_vector_base(initial_capacity_t, std::size_t initial_capacity)
inline explicit small_vector_base(initial_capacity_t, size_type initial_capacity)
: base_type(initial_capacity_t(), this->internal_storage(), initial_capacity)
{}

template<class AllocFwd>
inline explicit small_vector_base(initial_capacity_t, std::size_t capacity, BOOST_FWD_REF(AllocFwd) a)
inline explicit small_vector_base(initial_capacity_t, size_type capacity, BOOST_FWD_REF(AllocFwd) a)
: base_type(initial_capacity_t(), this->internal_storage(), capacity, ::boost::forward<AllocFwd>(a))
{}

inline explicit small_vector_base(maybe_initial_capacity_t, std::size_t initial_capacity, std::size_t initial_size)
template<class AllocFwd>
inline explicit small_vector_base(initial_capacity_t, size_type capacity, BOOST_FWD_REF(AllocFwd) a, small_vector_base &x)
: base_type(initial_capacity_t(), this->internal_storage(), capacity, ::boost::forward<AllocFwd>(a), x)
{}

inline explicit small_vector_base(maybe_initial_capacity_t, size_type initial_capacity, size_type initial_size)
: base_type( maybe_initial_capacity_t()
, (initial_capacity >= initial_size) ? this->internal_storage() : pointer()
, (initial_capacity >= initial_size) ? initial_capacity : initial_size
)
{}

template<class AllocFwd>
inline explicit small_vector_base(maybe_initial_capacity_t, std::size_t initial_capacity, std::size_t initial_size, BOOST_FWD_REF(AllocFwd) a)
inline explicit small_vector_base(maybe_initial_capacity_t, size_type initial_capacity, size_type initial_size, BOOST_FWD_REF(AllocFwd) a)
: base_type(maybe_initial_capacity_t()
, (initial_capacity >= initial_size) ? this->internal_storage() : pointer()
, (initial_capacity >= initial_size) ? initial_capacity : initial_size
, ::boost::forward<AllocFwd>(a)
)
{}

void prot_shrink_to_fit_small(const size_type small_capacity)
{
this->base_type::prot_shrink_to_fit_small(this->internal_storage(), small_capacity);
}

using base_type::protected_set_size;

//~small_vector_base(){}
#endif //#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED

inline void prot_swap(small_vector_base& other, size_type internal_capacity_value)
{ this->base_type::prot_swap_small(other, internal_capacity_value); }

public:
inline small_vector_base& operator=(BOOST_COPY_ASSIGN_REF(small_vector_base) other)
{ return static_cast<small_vector_base&>(this->base_type::operator=(static_cast<base_type const&>(other))); }
Expand All @@ -418,24 +435,8 @@ class small_vector_base
{ return static_cast<small_vector_base&>(this->base_type::operator=(BOOST_MOVE_BASE(base_type, other))); }

inline void swap(small_vector_base &other)
{ return this->base_type::swap(other); }
{ return this->base_type::prot_swap_small(other, 0u); }

#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
protected:
void move_construct_impl(base_type &x)
{
if(base_type::is_propagable_from(x.get_stored_allocator(), x.data(), this->base_type::get_stored_allocator(), true)){
this->steal_resources(x);
}
else{
const typename base_type::size_type sz = x.size();
::boost::container::uninitialized_move_alloc_n_source
(this->base_type::get_stored_allocator(), x.begin(), sz, this->begin());
this->protected_set_size(sz);
x.clear();
}
}
#endif //#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
};

#ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
Expand Down Expand Up @@ -550,7 +551,7 @@ class small_vector
typedef typename base_type::size_type size_type;
typedef typename base_type::value_type value_type;

inline static std::size_t internal_capacity()
inline static size_type internal_capacity()
{ return static_capacity; }

typedef allocator_traits<typename base_type::allocator_type> allocator_traits_type;
Expand Down Expand Up @@ -627,17 +628,17 @@ class small_vector
{ this->assign(other.cbegin(), other.cend()); }

inline explicit small_vector(BOOST_RV_REF(base_type) other)
: base_type(initial_capacity_t(), internal_capacity(), ::boost::move(other.get_stored_allocator()))
{ this->base_type::move_construct_impl(other); }
: base_type(initial_capacity_t(), internal_capacity(), ::boost::move(other.get_stored_allocator()), other)
{}

inline small_vector(BOOST_RV_REF(small_vector) other)
BOOST_NOEXCEPT_IF(boost::container::dtl::is_nothrow_move_constructible<value_type>::value)
: base_type(initial_capacity_t(), internal_capacity(), ::boost::move(other.get_stored_allocator()))
{ this->base_type::move_construct_impl(other); }
: base_type(initial_capacity_t(), internal_capacity(), ::boost::move(other.get_stored_allocator()), other)
{}

inline small_vector(BOOST_RV_REF(small_vector) other, const allocator_type &a)
: base_type(initial_capacity_t(), internal_capacity(), a)
{ this->base_type::move_construct_impl(other); }
: base_type(initial_capacity_t(), internal_capacity(), a, other)
{}

#if !defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST)
inline small_vector(std::initializer_list<value_type> il, const allocator_type& a = allocator_type())
Expand All @@ -663,7 +664,12 @@ class small_vector
{ return static_cast<small_vector&>(this->base_type::operator=(boost::move(other))); }

inline void swap(small_vector &other)
{ return this->base_type::swap(other); }
{ return this->base_type::prot_swap(other, static_capacity); }

inline void shrink_to_fit()
{
this->base_type::prot_shrink_to_fit_small(this->internal_capacity());
}
};

}}
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