memory_resource
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// <memory_resource> -*- C++ -*-
// Copyright (C) 2018-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file include/memory_resource
* This is a Standard C++ Library header.
*/
#ifndef _GLIBCXX_MEMORY_RESOURCE
#define _GLIBCXX_MEMORY_RESOURCE 1
#pragma GCC system_header
#if __cplusplus >= 201703L
#include <vector> // vector
#include <cstddef> // size_t, max_align_t, byte
#include <shared_mutex> // shared_mutex
#include <bits/align.h> // align
#include <bits/functexcept.h> // __throw_bad_array_new_length
#include <bits/uses_allocator.h> // __use_alloc
#include <bits/uses_allocator_args.h> // uninitialized_construct_using_alloc
#include <ext/numeric_traits.h>
#include <debug/assertions.h>
#if ! __cpp_lib_make_obj_using_allocator
# include <utility> // pair, index_sequence
# include <tuple> // tuple, forward_as_tuple
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace pmr
{
#ifdef _GLIBCXX_HAS_GTHREADS
// Header and all contents are present.
# define __cpp_lib_memory_resource 201603L
#else
// The pmr::synchronized_pool_resource type is missing.
# define __cpp_lib_memory_resource 1
#endif
class memory_resource;
#if __cplusplus == 201703L
template<typename _Tp>
class polymorphic_allocator;
#else // C++20
# define __cpp_lib_polymorphic_allocator 201902L
template<typename _Tp = std::byte>
class polymorphic_allocator;
#endif
// Global memory resources
memory_resource* new_delete_resource() noexcept;
memory_resource* null_memory_resource() noexcept;
memory_resource* set_default_resource(memory_resource* __r) noexcept;
memory_resource* get_default_resource() noexcept
__attribute__((__returns_nonnull__));
// Pool resource classes
struct pool_options;
#ifdef _GLIBCXX_HAS_GTHREADS
class synchronized_pool_resource;
#endif
class unsynchronized_pool_resource;
class monotonic_buffer_resource;
/// Class memory_resource
class memory_resource
{
static constexpr size_t _S_max_align = alignof(max_align_t);
public:
memory_resource() = default;
memory_resource(const memory_resource&) = default;
virtual ~memory_resource(); // key function
memory_resource& operator=(const memory_resource&) = default;
[[nodiscard]]
void*
allocate(size_t __bytes, size_t __alignment = _S_max_align)
__attribute__((__returns_nonnull__,__alloc_size__(2),__alloc_align__(3)))
{ return do_allocate(__bytes, __alignment); }
void
deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
__attribute__((__nonnull__))
{ return do_deallocate(__p, __bytes, __alignment); }
bool
is_equal(const memory_resource& __other) const noexcept
{ return do_is_equal(__other); }
private:
virtual void*
do_allocate(size_t __bytes, size_t __alignment) = 0;
virtual void
do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
virtual bool
do_is_equal(const memory_resource& __other) const noexcept = 0;
};
inline bool
operator==(const memory_resource& __a, const memory_resource& __b) noexcept
{ return &__a == &__b || __a.is_equal(__b); }
#if __cpp_impl_three_way_comparison < 201907L
inline bool
operator!=(const memory_resource& __a, const memory_resource& __b) noexcept
{ return !(__a == __b); }
#endif
// C++17 23.12.3 Class template polymorphic_allocator
template<typename _Tp>
class polymorphic_allocator
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2975. Missing case for pair construction in polymorphic allocators
template<typename _Up>
struct __not_pair { using type = void; };
template<typename _Up1, typename _Up2>
struct __not_pair<pair<_Up1, _Up2>> { };
public:
using value_type = _Tp;
polymorphic_allocator() noexcept
: _M_resource(get_default_resource())
{ }
polymorphic_allocator(memory_resource* __r) noexcept
__attribute__((__nonnull__))
: _M_resource(__r)
{ _GLIBCXX_DEBUG_ASSERT(__r); }
polymorphic_allocator(const polymorphic_allocator& __other) = default;
template<typename _Up>
polymorphic_allocator(const polymorphic_allocator<_Up>& __x) noexcept
: _M_resource(__x.resource())
{ }
polymorphic_allocator&
operator=(const polymorphic_allocator&) = delete;
[[nodiscard]]
_Tp*
allocate(size_t __n)
__attribute__((__returns_nonnull__))
{
if ((__gnu_cxx::__int_traits<size_t>::__max / sizeof(_Tp)) < __n)
std::__throw_bad_array_new_length();
return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
alignof(_Tp)));
}
void
deallocate(_Tp* __p, size_t __n) noexcept
__attribute__((__nonnull__))
{ _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
#if __cplusplus > 201703L
[[nodiscard]] void*
allocate_bytes(size_t __nbytes,
size_t __alignment = alignof(max_align_t))
{ return _M_resource->allocate(__nbytes, __alignment); }
void
deallocate_bytes(void* __p, size_t __nbytes,
size_t __alignment = alignof(max_align_t))
{ _M_resource->deallocate(__p, __nbytes, __alignment); }
template<typename _Up>
[[nodiscard]] _Up*
allocate_object(size_t __n = 1)
{
if ((__gnu_cxx::__int_traits<size_t>::__max / sizeof(_Up)) < __n)
std::__throw_bad_array_new_length();
return static_cast<_Up*>(allocate_bytes(__n * sizeof(_Up),
alignof(_Up)));
}
template<typename _Up>
void
deallocate_object(_Up* __p, size_t __n = 1)
{ deallocate_bytes(__p, __n * sizeof(_Up), alignof(_Up)); }
template<typename _Up, typename... _CtorArgs>
[[nodiscard]] _Up*
new_object(_CtorArgs&&... __ctor_args)
{
_Up* __p = allocate_object<_Up>();
__try
{
construct(__p, std::forward<_CtorArgs>(__ctor_args)...);
}
__catch (...)
{
deallocate_object(__p);
__throw_exception_again;
}
return __p;
}
template<typename _Up>
void
delete_object(_Up* __p)
{
destroy(__p);
deallocate_object(__p);
}
#endif // C++2a
#if ! __cpp_lib_make_obj_using_allocator
template<typename _Tp1, typename... _Args>
__attribute__((__nonnull__))
typename __not_pair<_Tp1>::type
construct(_Tp1* __p, _Args&&... __args)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2969. polymorphic_allocator::construct() shouldn't pass resource()
using __use_tag
= std::__uses_alloc_t<_Tp1, polymorphic_allocator, _Args...>;
if constexpr (is_base_of_v<__uses_alloc0, __use_tag>)
::new(__p) _Tp1(std::forward<_Args>(__args)...);
else if constexpr (is_base_of_v<__uses_alloc1_, __use_tag>)
::new(__p) _Tp1(allocator_arg, *this,
std::forward<_Args>(__args)...);
else
::new(__p) _Tp1(std::forward<_Args>(__args)..., *this);
}
template<typename _Tp1, typename _Tp2,
typename... _Args1, typename... _Args2>
__attribute__((__nonnull__))
void
construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
tuple<_Args1...> __x, tuple<_Args2...> __y)
{
auto __x_tag =
__use_alloc<_Tp1, polymorphic_allocator, _Args1...>(*this);
auto __y_tag =
__use_alloc<_Tp2, polymorphic_allocator, _Args2...>(*this);
index_sequence_for<_Args1...> __x_i;
index_sequence_for<_Args2...> __y_i;
::new(__p) pair<_Tp1, _Tp2>(piecewise_construct,
_S_construct_p(__x_tag, __x_i, __x),
_S_construct_p(__y_tag, __y_i, __y));
}
template<typename _Tp1, typename _Tp2>
__attribute__((__nonnull__))
void
construct(pair<_Tp1, _Tp2>* __p)
{ this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
template<typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
__attribute__((__nonnull__))
void
construct(pair<_Tp1, _Tp2>* __p, _Up&& __x, _Vp&& __y)
{
this->construct(__p, piecewise_construct,
std::forward_as_tuple(std::forward<_Up>(__x)),
std::forward_as_tuple(std::forward<_Vp>(__y)));
}
template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
__attribute__((__nonnull__))
void
construct(pair<_Tp1, _Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
{
this->construct(__p, piecewise_construct,
std::forward_as_tuple(__pr.first),
std::forward_as_tuple(__pr.second));
}
template<typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
__attribute__((__nonnull__))
void
construct(pair<_Tp1, _Tp2>* __p, pair<_Up, _Vp>&& __pr)
{
this->construct(__p, piecewise_construct,
std::forward_as_tuple(std::forward<_Up>(__pr.first)),
std::forward_as_tuple(std::forward<_Vp>(__pr.second)));
}
#else // make_obj_using_allocator
template<typename _Tp1, typename... _Args>
__attribute__((__nonnull__))
void
construct(_Tp1* __p, _Args&&... __args)
{
std::uninitialized_construct_using_allocator(__p, *this,
std::forward<_Args>(__args)...);
}
#endif
template<typename _Up>
_GLIBCXX20_DEPRECATED_SUGGEST("allocator_traits::destroy")
__attribute__((__nonnull__))
void
destroy(_Up* __p)
{ __p->~_Up(); }
polymorphic_allocator
select_on_container_copy_construction() const noexcept
{ return polymorphic_allocator(); }
memory_resource*
resource() const noexcept
__attribute__((__returns_nonnull__))
{ return _M_resource; }
private:
using __uses_alloc1_ = __uses_alloc1<polymorphic_allocator>;
using __uses_alloc2_ = __uses_alloc2<polymorphic_allocator>;
#if ! __cpp_lib_make_obj_using_allocator
template<typename _Ind, typename... _Args>
static tuple<_Args&&...>
_S_construct_p(__uses_alloc0, _Ind, tuple<_Args...>& __t)
{ return std::move(__t); }
template<size_t... _Ind, typename... _Args>
static tuple<allocator_arg_t, polymorphic_allocator, _Args&&...>
_S_construct_p(__uses_alloc1_ __ua, index_sequence<_Ind...>,
tuple<_Args...>& __t)
{
return {
allocator_arg, *__ua._M_a, std::get<_Ind>(std::move(__t))...
};
}
template<size_t... _Ind, typename... _Args>
static tuple<_Args&&..., polymorphic_allocator>
_S_construct_p(__uses_alloc2_ __ua, index_sequence<_Ind...>,
tuple<_Args...>& __t)
{ return { std::get<_Ind>(std::move(__t))..., *__ua._M_a }; }
#endif
memory_resource* _M_resource;
};
template<typename _Tp1, typename _Tp2>
inline bool
operator==(const polymorphic_allocator<_Tp1>& __a,
const polymorphic_allocator<_Tp2>& __b) noexcept
{ return *__a.resource() == *__b.resource(); }
#if __cpp_impl_three_way_comparison < 201907L
template<typename _Tp1, typename _Tp2>
inline bool
operator!=(const polymorphic_allocator<_Tp1>& __a,
const polymorphic_allocator<_Tp2>& __b) noexcept
{ return !(__a == __b); }
#endif
/// Parameters for tuning a pool resource's behaviour.
struct pool_options
{
/** @brief Upper limit on number of blocks in a chunk.
*
* A lower value prevents allocating huge chunks that could remain mostly
* unused, but means pools will need to replenished more frequently.
*/
size_t max_blocks_per_chunk = 0;
/* @brief Largest block size (in bytes) that should be served from pools.
*
* Larger allocations will be served directly by the upstream resource,
* not from one of the pools managed by the pool resource.
*/
size_t largest_required_pool_block = 0;
};
// Common implementation details for un-/synchronized pool resources.
class __pool_resource
{
friend class synchronized_pool_resource;
friend class unsynchronized_pool_resource;
__pool_resource(const pool_options& __opts, memory_resource* __upstream);
~__pool_resource();
__pool_resource(const __pool_resource&) = delete;
__pool_resource& operator=(const __pool_resource&) = delete;
// Allocate a large unpooled block.
void*
allocate(size_t __bytes, size_t __alignment);
// Deallocate a large unpooled block.
void
deallocate(void* __p, size_t __bytes, size_t __alignment);
// Deallocate unpooled memory.
void release() noexcept;
memory_resource* resource() const noexcept
{ return _M_unpooled.get_allocator().resource(); }
struct _Pool;
_Pool* _M_alloc_pools();
const pool_options _M_opts;
struct _BigBlock;
// Collection of blocks too big for any pool, sorted by address.
// This also stores the only copy of the upstream memory resource pointer.
_GLIBCXX_STD_C::pmr::vector<_BigBlock> _M_unpooled;
const int _M_npools;
};
#ifdef _GLIBCXX_HAS_GTHREADS
/// A thread-safe memory resource that manages pools of fixed-size blocks.
class synchronized_pool_resource : public memory_resource
{
public:
synchronized_pool_resource(const pool_options& __opts,
memory_resource* __upstream)
__attribute__((__nonnull__));
synchronized_pool_resource()
: synchronized_pool_resource(pool_options(), get_default_resource())
{ }
explicit
synchronized_pool_resource(memory_resource* __upstream)
__attribute__((__nonnull__))
: synchronized_pool_resource(pool_options(), __upstream)
{ }
explicit
synchronized_pool_resource(const pool_options& __opts)
: synchronized_pool_resource(__opts, get_default_resource()) { }
synchronized_pool_resource(const synchronized_pool_resource&) = delete;
virtual ~synchronized_pool_resource();
synchronized_pool_resource&
operator=(const synchronized_pool_resource&) = delete;
void release();
memory_resource*
upstream_resource() const noexcept
__attribute__((__returns_nonnull__))
{ return _M_impl.resource(); }
pool_options options() const noexcept { return _M_impl._M_opts; }
protected:
void*
do_allocate(size_t __bytes, size_t __alignment) override;
void
do_deallocate(void* __p, size_t __bytes, size_t __alignment) override;
bool
do_is_equal(const memory_resource& __other) const noexcept override
{ return this == &__other; }
public:
// Thread-specific pools (only public for access by implementation details)
struct _TPools;
private:
_TPools* _M_alloc_tpools(lock_guard<shared_mutex>&);
_TPools* _M_alloc_shared_tpools(lock_guard<shared_mutex>&);
auto _M_thread_specific_pools() noexcept;
__pool_resource _M_impl;
__gthread_key_t _M_key;
// Linked list of thread-specific pools. All threads share _M_tpools[0].
_TPools* _M_tpools = nullptr;
mutable shared_mutex _M_mx;
};
#endif
/// A non-thread-safe memory resource that manages pools of fixed-size blocks.
class unsynchronized_pool_resource : public memory_resource
{
public:
[[__gnu__::__nonnull__]]
unsynchronized_pool_resource(const pool_options& __opts,
memory_resource* __upstream);
unsynchronized_pool_resource()
: unsynchronized_pool_resource(pool_options(), get_default_resource())
{ }
[[__gnu__::__nonnull__]]
explicit
unsynchronized_pool_resource(memory_resource* __upstream)
: unsynchronized_pool_resource(pool_options(), __upstream)
{ }
explicit
unsynchronized_pool_resource(const pool_options& __opts)
: unsynchronized_pool_resource(__opts, get_default_resource()) { }
unsynchronized_pool_resource(const unsynchronized_pool_resource&) = delete;
virtual ~unsynchronized_pool_resource();
unsynchronized_pool_resource&
operator=(const unsynchronized_pool_resource&) = delete;
void release();
[[__gnu__::__returns_nonnull__]]
memory_resource*
upstream_resource() const noexcept
{ return _M_impl.resource(); }
pool_options options() const noexcept { return _M_impl._M_opts; }
protected:
void*
do_allocate(size_t __bytes, size_t __alignment) override;
void
do_deallocate(void* __p, size_t __bytes, size_t __alignment) override;
bool
do_is_equal(const memory_resource& __other) const noexcept override
{ return this == &__other; }
private:
using _Pool = __pool_resource::_Pool;
auto _M_find_pool(size_t) noexcept;
__pool_resource _M_impl;
_Pool* _M_pools = nullptr;
};
class monotonic_buffer_resource : public memory_resource
{
public:
explicit
monotonic_buffer_resource(memory_resource* __upstream) noexcept
__attribute__((__nonnull__))
: _M_upstream(__upstream)
{ _GLIBCXX_DEBUG_ASSERT(__upstream != nullptr); }
monotonic_buffer_resource(size_t __initial_size,
memory_resource* __upstream) noexcept
__attribute__((__nonnull__))
: _M_next_bufsiz(__initial_size),
_M_upstream(__upstream)
{
_GLIBCXX_DEBUG_ASSERT(__upstream != nullptr);
_GLIBCXX_DEBUG_ASSERT(__initial_size > 0);
}
monotonic_buffer_resource(void* __buffer, size_t __buffer_size,
memory_resource* __upstream) noexcept
__attribute__((__nonnull__(4)))
: _M_current_buf(__buffer), _M_avail(__buffer_size),
_M_next_bufsiz(_S_next_bufsize(__buffer_size)),
_M_upstream(__upstream),
_M_orig_buf(__buffer), _M_orig_size(__buffer_size)
{
_GLIBCXX_DEBUG_ASSERT(__upstream != nullptr);
_GLIBCXX_DEBUG_ASSERT(__buffer != nullptr || __buffer_size == 0);
}
monotonic_buffer_resource() noexcept
: monotonic_buffer_resource(get_default_resource())
{ }
explicit
monotonic_buffer_resource(size_t __initial_size) noexcept
: monotonic_buffer_resource(__initial_size, get_default_resource())
{ }
monotonic_buffer_resource(void* __buffer, size_t __buffer_size) noexcept
: monotonic_buffer_resource(__buffer, __buffer_size, get_default_resource())
{ }
monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
virtual ~monotonic_buffer_resource(); // key function
monotonic_buffer_resource&
operator=(const monotonic_buffer_resource&) = delete;
void
release() noexcept
{
if (_M_head)
_M_release_buffers();
// reset to initial state at contruction:
if ((_M_current_buf = _M_orig_buf))
{
_M_avail = _M_orig_size;
_M_next_bufsiz = _S_next_bufsize(_M_orig_size);
}
else
{
_M_avail = 0;
_M_next_bufsiz = _M_orig_size;
}
}
memory_resource*
upstream_resource() const noexcept
__attribute__((__returns_nonnull__))
{ return _M_upstream; }
protected:
void*
do_allocate(size_t __bytes, size_t __alignment) override
{
if (__builtin_expect(__bytes == 0, false))
__bytes = 1; // Ensures we don't return the same pointer twice.
void* __p = std::align(__alignment, __bytes, _M_current_buf, _M_avail);
if (__builtin_expect(__p == nullptr, false))
{
_M_new_buffer(__bytes, __alignment);
__p = _M_current_buf;
}
_M_current_buf = (char*)_M_current_buf + __bytes;
_M_avail -= __bytes;
return __p;
}
void
do_deallocate(void*, size_t, size_t) override
{ }
bool
do_is_equal(const memory_resource& __other) const noexcept override
{ return this == &__other; }
private:
// Update _M_current_buf and _M_avail to refer to a new buffer with
// at least the specified size and alignment, allocated from upstream.
void
_M_new_buffer(size_t __bytes, size_t __alignment);
// Deallocate all buffers obtained from upstream.
void
_M_release_buffers() noexcept;
static size_t
_S_next_bufsize(size_t __buffer_size) noexcept
{
if (__builtin_expect(__buffer_size == 0, false))
__buffer_size = 1;
return __buffer_size * _S_growth_factor;
}
static constexpr size_t _S_init_bufsize = 128 * sizeof(void*);
static constexpr float _S_growth_factor = 1.5;
void* _M_current_buf = nullptr;
size_t _M_avail = 0;
size_t _M_next_bufsiz = _S_init_bufsize;
// Initial values set at construction and reused by release():
memory_resource* const _M_upstream;
void* const _M_orig_buf = nullptr;
size_t const _M_orig_size = _M_next_bufsiz;
class _Chunk;
_Chunk* _M_head = nullptr;
};
} // namespace pmr
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++17
#endif // _GLIBCXX_MEMORY_RESOURCE