__cxx03/__memory_resource/monotonic_buffer_resource.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___CXX03___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
0010 #define _LIBCPP___CXX03___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
0011
0012 #include <__cxx03/__config>
0013 #include <__cxx03/__memory/addressof.h>
0014 #include <__cxx03/__memory_resource/memory_resource.h>
0015 #include <__cxx03/cstddef>
0016
0017 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0018 #  pragma GCC system_header
0019 #endif
0020
0021 #if _LIBCPP_STD_VER >= 17
0022
0023 _LIBCPP_BEGIN_NAMESPACE_STD
0024
0025 namespace pmr {
0026
0027 // [mem.res.monotonic.buffer]
0028
0029 class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resource : public memory_resource {
0030   static const size_t __default_buffer_capacity  = 1024;
0031   static const size_t __default_buffer_alignment = 16;
0032
0033   struct __chunk_footer {
0034     __chunk_footer* __next_;
0035     char* __start_;
0036     char* __cur_;
0037     size_t __align_;
0038     _LIBCPP_HIDE_FROM_ABI size_t __allocation_size() {
0039       return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this);
0040     }
0041     void* __try_allocate_from_chunk(size_t, size_t);
0042   };
0043
0044   struct __initial_descriptor {
0045     char* __start_;
0046     char* __cur_;
0047     union {
0048       char* __end_;
0049       size_t __size_;
0050     };
0051     void* __try_allocate_from_chunk(size_t, size_t);
0052   };
0053
0054 public:
0055   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource()
0056       : monotonic_buffer_resource(nullptr, __default_buffer_capacity, get_default_resource()) {}
0057
0058   _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(size_t __initial_size)
0059       : monotonic_buffer_resource(nullptr, __initial_size, get_default_resource()) {}
0060
0061   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size)
0062       : monotonic_buffer_resource(__buffer, __buffer_size, get_default_resource()) {}
0063
0064   _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(memory_resource* __upstream)
0065       : monotonic_buffer_resource(nullptr, __default_buffer_capacity, __upstream) {}
0066
0067   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(size_t __initial_size, memory_resource* __upstream)
0068       : monotonic_buffer_resource(nullptr, __initial_size, __upstream) {}
0069
0070   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size, memory_resource* __upstream)
0071       : __res_(__upstream) {
0072     __initial_.__start_ = static_cast<char*>(__buffer);
0073     if (__buffer != nullptr) {
0074       __initial_.__cur_ = static_cast<char*>(__buffer) + __buffer_size;
0075       __initial_.__end_ = static_cast<char*>(__buffer) + __buffer_size;
0076     } else {
0077       __initial_.__cur_  = nullptr;
0078       __initial_.__size_ = __buffer_size;
0079     }
0080     __chunks_ = nullptr;
0081   }
0082
0083   monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
0084
0085   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~monotonic_buffer_resource() override { release(); }
0086
0087   monotonic_buffer_resource& operator=(const monotonic_buffer_resource&) = delete;
0088
0089   _LIBCPP_HIDE_FROM_ABI void release() {
0090     if (__initial_.__start_ != nullptr)
0091       __initial_.__cur_ = __initial_.__end_;
0092     while (__chunks_ != nullptr) {
0093       __chunk_footer* __next = __chunks_->__next_;
0094       __res_->deallocate(__chunks_->__start_, __chunks_->__allocation_size(), __chunks_->__align_);
0095       __chunks_ = __next;
0096     }
0097   }
0098
0099   _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
0100
0101 protected:
0102   void* do_allocate(size_t __bytes, size_t __alignment) override; // key function
0103
0104   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void do_deallocate(void*, size_t, size_t) override {}
0105
0106   _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
0107     return this == std::addressof(__other);
0108   }
0109
0110 private:
0111   __initial_descriptor __initial_;
0112   __chunk_footer* __chunks_;
0113   memory_resource* __res_;
0114 };
0115
0116 } // namespace pmr
0117
0118 _LIBCPP_END_NAMESPACE_STD
0119
0120 #endif // _LIBCPP_STD_VER >= 17
0121
0122 #endif // _LIBCPP___CXX03___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H