v1/__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___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
0010 #define _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
0011
0012 #include <__config>
0013 #include <__cstddef/size_t.h>
0014 #include <__memory/addressof.h>
0015 #include <__memory_resource/memory_resource.h>
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 constexpr size_t __default_buffer_capacity = 1024;
0031
0032   struct __chunk_footer {
0033     __chunk_footer* __next_;
0034     char* __start_;
0035     char* __cur_;
0036     size_t __align_;
0037     _LIBCPP_HIDE_FROM_ABI size_t __allocation_size() {
0038       return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this);
0039     }
0040   };
0041
0042   struct __initial_descriptor {
0043     char* __start_;
0044     char* __cur_;
0045     union {
0046       char* __end_;
0047       size_t __size_;
0048     };
0049   };
0050
0051 public:
0052   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource()
0053       : monotonic_buffer_resource(nullptr, __default_buffer_capacity, get_default_resource()) {}
0054
0055   _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(size_t __initial_size)
0056       : monotonic_buffer_resource(nullptr, __initial_size, get_default_resource()) {}
0057
0058   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size)
0059       : monotonic_buffer_resource(__buffer, __buffer_size, get_default_resource()) {}
0060
0061   _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(memory_resource* __upstream)
0062       : monotonic_buffer_resource(nullptr, __default_buffer_capacity, __upstream) {}
0063
0064   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(size_t __initial_size, memory_resource* __upstream)
0065       : monotonic_buffer_resource(nullptr, __initial_size, __upstream) {}
0066
0067   _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size, memory_resource* __upstream)
0068       : __res_(__upstream) {
0069     __initial_.__start_ = static_cast<char*>(__buffer);
0070     if (__buffer != nullptr) {
0071       __initial_.__cur_ = static_cast<char*>(__buffer) + __buffer_size;
0072       __initial_.__end_ = static_cast<char*>(__buffer) + __buffer_size;
0073     } else {
0074       __initial_.__cur_  = nullptr;
0075       __initial_.__size_ = __buffer_size;
0076     }
0077     __chunks_ = nullptr;
0078   }
0079
0080   monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
0081
0082   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~monotonic_buffer_resource() override { release(); }
0083
0084   monotonic_buffer_resource& operator=(const monotonic_buffer_resource&) = delete;
0085
0086   _LIBCPP_HIDE_FROM_ABI void release() {
0087     if (__initial_.__start_ != nullptr)
0088       __initial_.__cur_ = __initial_.__end_;
0089     while (__chunks_ != nullptr) {
0090       __chunk_footer* __next = __chunks_->__next_;
0091       __res_->deallocate(__chunks_->__start_, __chunks_->__allocation_size(), __chunks_->__align_);
0092       __chunks_ = __next;
0093     }
0094   }
0095
0096   _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
0097
0098 protected:
0099   void* do_allocate(size_t __bytes, size_t __alignment) override; // key function
0100
0101   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void do_deallocate(void*, size_t, size_t) override {}
0102
0103   _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
0104     return this == std::addressof(__other);
0105   }
0106
0107 private:
0108   __initial_descriptor __initial_;
0109   __chunk_footer* __chunks_;
0110   memory_resource* __res_;
0111 };
0112
0113 } // namespace pmr
0114
0115 _LIBCPP_END_NAMESPACE_STD
0116
0117 #endif // _LIBCPP_STD_VER >= 17
0118
0119 #endif // _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H