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multi_buffer improvements:

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fix #1345

* Revise documentation
* Add reserve() member
* Add max_size() member
* Add shrink_to_fit() member
* Respect Allocator max_size
* Specify exception safety
This commit is contained in:
Vinnie Falco
2018-12-07 17:08:02 -08:00
parent 11c71d118f
commit 8262405064
4 changed files with 385 additions and 157 deletions
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1
CHANGELOG.md
View File

@ -1,6 +1,7 @@
Version 198:
* flat_buffer improvements
* multi_buffer improvements
--------------------------------------------------------------------------------

210
include/boost/beast/core/impl/multi_buffer.ipp
View File

@ -446,17 +446,20 @@ basic_multi_buffer<Allocator>::
template<class Allocator>
basic_multi_buffer<Allocator>::
basic_multi_buffer(Allocator const& alloc) noexcept
: boost::empty_value<
base_alloc_type>(boost::empty_init_t(), alloc)
basic_multi_buffer(
Allocator const& alloc) noexcept
: boost::empty_value<base_alloc_type>(
boost::empty_init_t(), alloc)
, max_(alloc_traits::max_size(this->get()))
, out_(list_.end())
{
}
template<class Allocator>
basic_multi_buffer<Allocator>::
basic_multi_buffer(std::size_t limit,
Allocator const& alloc) noexcept
basic_multi_buffer(
std::size_t limit,
Allocator const& alloc) noexcept
: boost::empty_value<
base_alloc_type>(boost::empty_init_t(), alloc)
, max_(limit)
@ -466,9 +469,10 @@ basic_multi_buffer(std::size_t limit,
template<class Allocator>
basic_multi_buffer<Allocator>::
basic_multi_buffer(basic_multi_buffer&& other) noexcept
: boost::empty_value<
base_alloc_type>(boost::empty_init_t(), std::move(other.get()))
basic_multi_buffer(
basic_multi_buffer&& other) noexcept
: boost::empty_value<base_alloc_type>(
boost::empty_init_t(), std::move(other.get()))
, max_(other.max_)
, in_size_(boost::exchange(other.in_size_, 0))
, in_pos_(boost::exchange(other.in_pos_, 0))
@ -484,8 +488,9 @@ basic_multi_buffer(basic_multi_buffer&& other) noexcept
template<class Allocator>
basic_multi_buffer<Allocator>::
basic_multi_buffer(basic_multi_buffer&& other,
Allocator const& alloc)
basic_multi_buffer(
basic_multi_buffer&& other,
Allocator const& alloc)
: boost::empty_value<
base_alloc_type>(boost::empty_init_t(), alloc)
, max_(other.max_)
@ -494,7 +499,7 @@ basic_multi_buffer(basic_multi_buffer&& other,
{
out_ = list_.end();
copy_from(other);
other.reset();
other.clear();
}
else
{
@ -516,11 +521,12 @@ basic_multi_buffer(basic_multi_buffer&& other,
template<class Allocator>
basic_multi_buffer<Allocator>::
basic_multi_buffer(basic_multi_buffer const& other)
: boost::empty_value<
base_alloc_type>(boost::empty_init_t(), alloc_traits::
select_on_container_copy_construction(
other.get()))
basic_multi_buffer(
basic_multi_buffer const& other)
: boost::empty_value<base_alloc_type>(
boost::empty_init_t(), alloc_traits::
select_on_container_copy_construction(
other.get()))
, max_(other.max_)
, out_(list_.end())
{
@ -529,10 +535,11 @@ basic_multi_buffer(basic_multi_buffer const& other)
template<class Allocator>
basic_multi_buffer<Allocator>::
basic_multi_buffer(basic_multi_buffer const& other,
Allocator const& alloc)
: boost::empty_value<
base_alloc_type>(boost::empty_init_t(), alloc)
basic_multi_buffer(
basic_multi_buffer const& other,
Allocator const& alloc)
: boost::empty_value<base_alloc_type>(
boost::empty_init_t(), alloc)
, max_(other.max_)
, out_(list_.end())
{
@ -571,10 +578,9 @@ operator=(basic_multi_buffer&& other) ->
{
if(this == &other)
return *this;
reset();
clear();
max_ = other.max_;
move_assign(other, std::integral_constant<bool,
alloc_traits::propagate_on_container_move_assignment::value>{});
move_assign(other, pocma{});
return *this;
}
@ -586,8 +592,7 @@ basic_multi_buffer&
{
if(this == &other)
return *this;
copy_assign(other, std::integral_constant<bool,
alloc_traits::propagate_on_container_copy_assignment::value>{});
copy_assign(other, pocca{});
return *this;
}
@ -599,8 +604,7 @@ operator=(
basic_multi_buffer<OtherAlloc> const& other) ->
basic_multi_buffer&
{
reset();
max_ = other.max_;
clear();
copy_from(other);
return *this;
}
@ -639,6 +643,56 @@ data() noexcept ->
return mutable_data_type(*this);
}
template<class Allocator>
void
basic_multi_buffer<Allocator>::
reserve(std::size_t n)
{
if(n > alloc_traits::max_size(this->get()))
BOOST_THROW_EXCEPTION(std::length_error(
"A basic_multi_buffer exceeded the allocator's maximum size"));
std::size_t total = in_size_;
if(n <= total)
return;
if(out_ != list_.end())
{
total += out_->size() - out_pos_;
if(n <= total)
return;
auto it = out_;
while(++it != list_.end())
{
total += it->size();
if(n <= total)
return;
}
}
BOOST_ASSERT(n > total);
(void)prepare(n - total);
}
template<class Allocator>
void
basic_multi_buffer<Allocator>::
shrink_to_fit() noexcept
{
if( out_ != list_.end() &&
out_ != list_.iterator_to(list_.back()))
{
list_type extra;
extra.splice(extra.end(), list_,
std::next(out_), list_.end());
for(auto it = extra.begin(); it != extra.end();)
{
auto& e = *it++;
auto const len = sizeof(e) + e.size();
e.~element();
alloc_traits::deallocate(this->get(),
reinterpret_cast<char*>(&e), len);
}
}
}
template<class Allocator>
auto
basic_multi_buffer<Allocator>::
@ -647,7 +701,7 @@ prepare(size_type n) ->
{
if(in_size_ + n > max_)
BOOST_THROW_EXCEPTION(std::length_error{
"dynamic buffer overflow"});
"A basic_multi_buffer exceeded its maximum size"});
list_type reuse;
std::size_t total = in_size_;
// put all empty buffers on reuse list
@ -707,7 +761,7 @@ prepare(size_type n) ->
auto& e = *it++;
reuse.erase(list_.iterator_to(e));
auto const len = sizeof(e) + e.size();
alloc_traits::destroy(this->get(), &e);
e.~element();
alloc_traits::deallocate(this->get(),
reinterpret_cast<char*>(&e), len);
}
@ -722,10 +776,8 @@ prepare(size_type n) ->
in_size_ * growth_factor - in_size_),
512,
n}));
auto& e = *reinterpret_cast<element*>(static_cast<
void*>(alloc_traits::allocate(this->get(),
sizeof(element) + size)));
alloc_traits::construct(this->get(), &e, size);
auto &e = *::new(alloc(
sizeof(element) + size)) element(size);
list_.push_back(e);
if(out_ == list_.end())
out_ = list_.iterator_to(e);
@ -813,7 +865,7 @@ consume(size_type n) noexcept
auto& e = list_.front();
list_.erase(list_.iterator_to(e));
auto const len = sizeof(e) + e.size();
alloc_traits::destroy(this->get(), &e);
e.~element();
alloc_traits::deallocate(this->get(),
reinterpret_cast<char*>(&e), len);
#if BOOST_BEAST_MULTI_BUFFER_DEBUG_CHECK
@ -854,45 +906,17 @@ consume(size_type n) noexcept
}
template<class Allocator>
template<class OtherAlloc>
void
basic_multi_buffer<Allocator>::
reset() noexcept
copy_from(basic_multi_buffer<OtherAlloc> const& other)
{
delete_list();
list_.clear();
out_ = list_.end();
in_size_ = 0;
in_pos_ = 0;
out_pos_ = 0;
out_end_ = 0;
}
template<class Allocator>
void
basic_multi_buffer<Allocator>::
delete_list() noexcept
{
for(auto iter = list_.begin(); iter != list_.end();)
{
auto& e = *iter++;
auto const len = sizeof(e) + e.size();
alloc_traits::destroy(this->get(), &e);
alloc_traits::deallocate(this->get(),
reinterpret_cast<char*>(&e), len);
}
}
template<class Allocator>
template<class DynamicBuffer>
void
basic_multi_buffer<Allocator>::
copy_from(DynamicBuffer const& buffer)
{
if(buffer.size() == 0)
clear();
max_ = other.max_;
if(other.size() == 0)
return;
using net::buffer_copy;
commit(buffer_copy(
prepare(buffer.size()), buffer.data()));
commit(net::buffer_copy(
prepare(other.size()), other.data()));
}
template<class Allocator>
@ -903,7 +927,7 @@ move_assign(basic_multi_buffer& other, std::false_type)
if(this->get() != other.get())
{
copy_from(other);
other.reset();
other.clear();
}
else
{
@ -926,6 +950,7 @@ move_assign(basic_multi_buffer& other, std::true_type) noexcept
in_pos_ = other.in_pos_;
out_pos_ = other.out_pos_;
out_end_ = other.out_end_;
max_ = other.max_;
other.in_size_ = 0;
other.out_ = other.list_.end();
@ -940,8 +965,6 @@ basic_multi_buffer<Allocator>::
copy_assign(
basic_multi_buffer const& other, std::false_type)
{
reset();
max_ = other.max_;
copy_from(other);
}
@ -951,8 +974,7 @@ basic_multi_buffer<Allocator>::
copy_assign(
basic_multi_buffer const& other, std::true_type)
{
reset();
max_ = other.max_;
clear();
this->get() = other.get();
copy_from(other);
}
@ -1021,6 +1043,46 @@ swap(
lhs.swap(rhs);
}
template<class Allocator>
void
basic_multi_buffer<Allocator>::
delete_list() noexcept
{
for(auto it = list_.begin(); it != list_.end();)
{
auto& e = *it++;
auto const len = sizeof(e) + e.size();
e.~element();
alloc_traits::deallocate(this->get(),
reinterpret_cast<char*>(&e), len);
}
}
template<class Allocator>
char*
basic_multi_buffer<Allocator>::
alloc(std::size_t n)
{
if(n > alloc_traits::max_size(this->get()))
BOOST_THROW_EXCEPTION(std::length_error(
"A basic_multi_buffer exceeded the allocator's maximum size"));
return alloc_traits::allocate(this->get(), n);
}
template<class Allocator>
void
basic_multi_buffer<Allocator>::
clear() noexcept
{
delete_list();
list_.clear();
out_ = list_.end();
in_size_ = 0;
in_pos_ = 0;
out_pos_ = 0;
out_end_ = 0;
}
template<class Allocator>
void
basic_multi_buffer<Allocator>::

283
include/boost/beast/core/multi_buffer.hpp
View File

@ -43,16 +43,16 @@ namespace beast {
Objects of this type meet the requirements of @b DynamicBuffer
and have the following additional properties:
@li The buffer sequence representing the readable bytes
returned by @ref data is mutable.
@li A mutable buffer sequence representing the readable
bytes is returned by @ref data when `this` is non-const.
@li Buffer sequences representing the readable and writable
bytes, returned by @ref data and @ref prepare, may have
length greater than one.
@li A configurable maximum buffer size may be set upon
construction. Attempts to exceed the buffer size will throw
`std::length_error`.
@li A configurable maximum size may be set upon construction
and adjusted afterwards. Calls to @ref prepare that would
exceed this size will throw `std::length_error`.
@li Sequences previously obtained using @ref data remain
valid after calls to @ref prepare or @ref commit.
@ -71,6 +71,9 @@ class basic_multi_buffer
detail::allocator_traits<Allocator>::
template rebind_alloc<char>;
static bool constexpr default_nothrow =
std::is_nothrow_default_constructible<Allocator>::value;
// Storage for the list of buffers representing the input
// and output sequences. The allocation for each element
// contains `element` followed by raw storage bytes.
@ -89,6 +92,12 @@ class basic_multi_buffer
using const_buffer = net::const_buffer;
using mutable_buffer = net::mutable_buffer;
using pocma = typename
alloc_traits::propagate_on_container_move_assignment;
using pocca = typename
alloc_traits::propagate_on_container_copy_assignment;
static_assert(std::is_base_of<std::bidirectional_iterator_tag,
typename std::iterator_traits<iter>::iterator_category>::value,
"BidirectionalIterator requirements not met");
@ -97,8 +106,7 @@ class basic_multi_buffer
typename std::iterator_traits<const_iter>::iterator_category>::value,
"BidirectionalIterator requirements not met");
std::size_t max_ =
(std::numeric_limits<std::size_t>::max)();
std::size_t max_;
list_type list_; // list of allocated buffers
iter out_; // element that contains out_pos_
size_type in_size_ = 0; // size of the input sequence
@ -115,24 +123,26 @@ public:
/** Constructor
Upon construction, @ref capacity will return zero.
After construction, @ref capacity will return zero, and
@ref max_size will return the largest value which may
be passed to the allocator's `allocate` function.
*/
basic_multi_buffer() noexcept(
std::is_nothrow_default_constructible<Allocator>::value)
:
out_(list_.end())
basic_multi_buffer() noexcept(default_nothrow)
: max_(alloc_traits::max_size(this->get()))
, out_(list_.end())
{
}
/** Constructor
Upon construction, @ref capacity will return zero.
After construction, @ref capacity will return zero, and
@ref max_size will return the specified value of `limit`.
@param limit The setting for @ref max_size.
@param limit The desired maximum size.
*/
explicit
basic_multi_buffer(std::size_t limit) noexcept(
std::is_nothrow_default_constructible<Allocator>::value)
basic_multi_buffer(
std::size_t limit) noexcept(default_nothrow)
: max_(limit)
, out_(list_.end())
{
@ -140,87 +150,116 @@ public:
/** Constructor
Upon construction, @ref capacity will return zero.
After construction, @ref capacity will return zero, and
@ref max_size will return the largest value which may
be passed to the allocator's `allocate` function.
@param alloc The allocator to use.
@param alloc The allocator to use for the object.
@par Exception Safety
No-throw guarantee.
*/
explicit
basic_multi_buffer(Allocator const& alloc) noexcept;
/** Constructor
Upon construction, @ref capacity will return zero.
After construction, @ref capacity will return zero, and
@ref max_size will return the specified value of `limit`.
@param limit The setting for @ref max_size.
@param limit The desired maximum size.
@param alloc The allocator to use.
@param alloc The allocator to use for the object.
@par Exception Safety
No-throw guarantee.
*/
basic_multi_buffer(
std::size_t limit, Allocator const& alloc) noexcept;
/** Move Constructor
Constructs the container with the contents of other
using move semantics. After the move, other is
guaranteed to be empty.
The container is constructed with the contents of `other`
using move semantics. The maximum size will be the same
as the moved-from object.
Buffer sequences previously obtained using @ref data
or @ref prepare are not invalidated after the move.
Buffer sequences previously obtained from `other` using
@ref data or @ref prepare remain valid after the move.
@param other The object to move from. After the move,
the moved-from object's state will be as if default
constructed using its current allocator and limit.
@param other The object to move from. After the move, the
moved-from object will have zero capacity, zero readable
bytes, and zero writable bytes.
@par Exception Safety
No-throw guarantee.
*/
basic_multi_buffer(basic_multi_buffer&& other) noexcept;
/** Move Constructor
Using alloc as the allocator for the new container, the
contents of other are moved. If `alloc != other.get_allocator()`,
this results in a copy. After the move, other is
guaranteed to be empty.
Using `alloc` as the allocator for the new container, the
contents of `other` are moved. If `alloc != other.get_allocator()`,
this results in a copy. The maximum size will be the same
as the moved-from object.
All buffers sequences previously obtained using
@ref data or @ref prepare are invalidated.
Buffer sequences previously obtained from `other` using
@ref data or @ref prepare become invalid after the move.
@param other The object to move from. After the move,
the moved-from object's state will be as if default
constructed using its current allocator and limit.
the moved-from object will have zero capacity, zero readable
bytes, and zero writable bytes.
@param alloc The allocator to use for the newly
constructed object.
@param alloc The allocator to use for the object.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of `alloc`.
*/
basic_multi_buffer(basic_multi_buffer&& other,
basic_multi_buffer(
basic_multi_buffer&& other,
Allocator const& alloc);
/** Copy Constructor
The newly constructed object will have a copy of the
allocator and contents of other, and zero writable bytes.
This container is constructed with the contents of `other`
using copy semantics. The maximum size will be the same
as the copied object.
@param other The object to copy from.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of the allocator.
*/
basic_multi_buffer(basic_multi_buffer const& other);
/** Copy Constructor
The newly constructed object will have a copy of the
specified allocator, a copy of the contents of other,
and zero writable bytes.
This container is constructed with the contents of `other`
using copy semantics and the specified allocator. The maximum
size will be the same as the copied object.
@param other The object to copy from.
@param alloc The allocator to use.
@param alloc The allocator to use for the object.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of `alloc`.
*/
basic_multi_buffer(basic_multi_buffer const& other,
Allocator const& alloc);
/** Copy Constructor
The newly constructed object will have a copy of the
contents of other, and zero writable bytes.
This container is constructed with the contents of `other`
using copy semantics. The maximum size will be the same
as the copied object.
@param other The object to copy from.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of the allocator.
*/
template<class OtherAlloc>
basic_multi_buffer(basic_multi_buffer<
@ -228,52 +267,66 @@ public:
/** Copy Constructor
The newly constructed object will have a copy of the
specified allocator, a copy of the contents of other,
and zero writable bytes.
This container is constructed with the contents of `other`
using copy semantics. The maximum size will be the same
as the copied object.
@param other The object to copy from.
@param alloc The allocator to use.
@param alloc The allocator to use for the object.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of `alloc`.
*/
template<class OtherAlloc>
basic_multi_buffer(basic_multi_buffer<
OtherAlloc> const& other, allocator_type const& alloc);
basic_multi_buffer(
basic_multi_buffer<OtherAlloc> const& other,
allocator_type const& alloc);
/** Move Assignment
Assigns the container with the contents of other
using move semantics. After the move, other is
guaranteed to be empty. The previous contents of
this container are deleted.
The container is assigned with the contents of `other`
using move semantics. The maximum size will be the same
as the moved-from object.
Buffer sequences previously obtained using @ref data
or @ref prepare are not invalidated after the move.
Buffer sequences previously obtained from `other` using
@ref data or @ref prepare remain valid after the move.
@param other The object to move from. After the move,
the moved-from object's state will be as if default
constructed using its current allocator and limit.
the moved-from object will have zero capacity, zero readable
bytes, and zero writable bytes.
*/
basic_multi_buffer&
operator=(basic_multi_buffer&& other);
/** Copy Assignment
The assigned object will have a copy of the allocator
and contents of other, and zero writable bytes. The
previous contents of this container are deleted.
The container is assigned with the contents of `other`
using copy semantics. The maximum size will be the same
as the copied object.
After the copy, `this` will have zero writable bytes.
@param other The object to copy from.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of the allocator.
*/
basic_multi_buffer& operator=(basic_multi_buffer const& other);
basic_multi_buffer& operator=(
basic_multi_buffer const& other);
/** Copy assignment
/** Copy Assignment
The assigned object will have a copy of the contents
of other, and zero writable bytes. The previous contents
of this container are deleted.
The container is assigned with the contents of `other`
using copy semantics. The maximum size will be the same
as the copied object.
After the copy, `this` will have zero writable bytes.
@param other The object to copy from.
@throws std::length_error if `other.size()` exceeds the
maximum allocation size of the allocator.
*/
template<class OtherAlloc>
basic_multi_buffer& operator=(
@ -286,6 +339,66 @@ public:
return this->get();
}
/** Set the maximum allowed capacity
This function changes the currently configured upper limit
on capacity to the specified value.
@param n The maximum number of bytes ever allowed for capacity.
@par Exception Safety
No-throw guarantee.
*/
void
max_size(std::size_t n) noexcept
{
max_ = n;
}
/** Guarantee a minimum capacity
This function adjusts the internal storage (if necessary)
to guarantee space for at least `n` bytes.
Buffer sequences previously obtained using @ref data remain
valid, while buffer sequences previously obtained using
@ref prepare become invalid.
@param n The minimum number of byte for the new capacity.
If this value is greater than the maximum size, then the
maximum size will be adjusted upwards to this value.
@throws std::length_error if n is larger than the maximum
allocation size of the allocator.
@par Exception Safety
Strong guarantee.
*/
void
reserve(std::size_t n);
/** Reallocate the buffer to fit the readable bytes exactly.
Buffer sequences previously obtained using @ref data or
@ref prepare become invalid.
@par Exception Safety
No-throw guarantee.
*/
void
shrink_to_fit() noexcept;
/// Exchange two dynamic buffers
template<class Alloc>
friend
void
swap(
basic_multi_buffer<Alloc>& lhs,
basic_multi_buffer<Alloc>& rhs) noexcept;
//--------------------------------------------------------------------------
#if BOOST_BEAST_DOXYGEN
@ -354,6 +467,10 @@ public:
sequence.
@throws std::length_error if `size() + n` exceeds `max_size()`.
@par Exception Safety
Strong guarantee.
*/
mutable_buffers_type
prepare(size_type n);
@ -372,6 +489,10 @@ public:
@param n The number of bytes to append. If this number
is greater than the number of writable bytes, all
writable bytes are appended.
@par Exception Safety
No-throw guarantee.
*/
void
commit(size_type n) noexcept;
@ -386,27 +507,20 @@ public:
@param n The number of bytes to remove. If this number
is greater than the number of readable bytes, all
readable bytes are removed.
@par Exception Safety
No-throw guarantee.
*/
void
consume(size_type n) noexcept;
/// Exchange two dynamic buffers
template<class Alloc>
friend
void
swap(
basic_multi_buffer<Alloc>& lhs,
basic_multi_buffer<Alloc>& rhs) noexcept;
private:
template<class OtherAlloc>
friend class basic_multi_buffer;
void reset() noexcept;
void delete_list() noexcept;
template<class DynamicBuffer>
void copy_from(DynamicBuffer const& other);
template<class OtherAlloc>
void copy_from(basic_multi_buffer<OtherAlloc> const&);
void move_assign(basic_multi_buffer& other, std::false_type);
void move_assign(basic_multi_buffer& other, std::true_type) noexcept;
void copy_assign(basic_multi_buffer const& other, std::false_type);
@ -414,6 +528,9 @@ private:
void swap(basic_multi_buffer&) noexcept;
void swap(basic_multi_buffer&, std::true_type) noexcept;
void swap(basic_multi_buffer&, std::false_type) noexcept;
void delete_list() noexcept;
char* alloc(std::size_t n);
void clear() noexcept;
void debug_check() const;
};

48
test/beast/core/multi_buffer.cpp
View File

@ -442,6 +442,14 @@ public:
}
}
// max_size
{
multi_buffer b{10};
BEAST_EXPECT(b.max_size() == 10);
b.max_size(32);
BEAST_EXPECT(b.max_size() == 32);
}
// prepare
{
{
@ -570,6 +578,46 @@ public:
BEAST_EXPECT(b.size() == 0);
}
// reserve
{
multi_buffer b;
BEAST_EXPECT(b.capacity() == 0);
b.reserve(50);
BEAST_EXPECT(b.capacity() >= 50);
b.prepare(20);
b.commit(20);
b.reserve(50);
BEAST_EXPECT(b.capacity() >= 50);
}
// shrink to fit
{
{
multi_buffer b;
BEAST_EXPECT(b.capacity() == 0);
b.prepare(50);
BEAST_EXPECT(b.capacity() >= 50);
b.commit(50);
BEAST_EXPECT(b.capacity() >= 50);
b.prepare(75);
BEAST_EXPECT(b.capacity() >= 125);
b.shrink_to_fit();
BEAST_EXPECT(b.capacity() >= b.size());
}
{
multi_buffer b;
b.prepare(2000);
BEAST_EXPECT(b.capacity() == 2000);
b.commit(1800);
BEAST_EXPECT(b.size() == 1800);
BEAST_EXPECT(b.capacity() == 2000);
b.prepare(5000);
BEAST_EXPECT(b.capacity() == 6800);
b.shrink_to_fit();
BEAST_EXPECT(b.capacity() == 2000);
}
}
// swap
{
{