1//===----------------------------------------------------------------------===//
  2//
  3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  4// See https://llvm.org/LICENSE.txt for license information.
  5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  6//
  7//===----------------------------------------------------------------------===//
  8
  9#ifndef _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
 10#define _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H
 11
 12#include <__config>
 13#include <__cstddef/size_t.h>
 14#include <__memory/addressof.h>
 15#include <__memory_resource/memory_resource.h>
 16
 17#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 18#  pragma GCC system_header
 19#endif
 20
 21#if _LIBCPP_STD_VER >= 17
 22
 23_LIBCPP_BEGIN_NAMESPACE_STD
 24
 25namespace pmr {
 26
 27// [mem.res.monotonic.buffer]
 28
 29class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resource : public memory_resource {
 30  static constexpr size_t __default_buffer_capacity = 1024;
 31
 32  struct __chunk_footer {
 33    __chunk_footer* __next_;
 34    char* __start_;
 35    char* __cur_;
 36    size_t __align_;
 37    _LIBCPP_HIDE_FROM_ABI size_t __allocation_size() {
 38      return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this);
 39    }
 40  };
 41
 42  struct __initial_descriptor {
 43    char* __start_;
 44    char* __cur_;
 45    union {
 46      char* __end_;
 47      size_t __size_;
 48    };
 49  };
 50
 51public:
 52  _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource()
 53      : monotonic_buffer_resource(nullptr, __default_buffer_capacity, get_default_resource()) {}
 54
 55  _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(size_t __initial_size)
 56      : monotonic_buffer_resource(nullptr, __initial_size, get_default_resource()) {}
 57
 58  _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size)
 59      : monotonic_buffer_resource(__buffer, __buffer_size, get_default_resource()) {}
 60
 61  _LIBCPP_HIDE_FROM_ABI explicit monotonic_buffer_resource(memory_resource* __upstream)
 62      : monotonic_buffer_resource(nullptr, __default_buffer_capacity, __upstream) {}
 63
 64  _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(size_t __initial_size, memory_resource* __upstream)
 65      : monotonic_buffer_resource(nullptr, __initial_size, __upstream) {}
 66
 67  _LIBCPP_HIDE_FROM_ABI monotonic_buffer_resource(void* __buffer, size_t __buffer_size, memory_resource* __upstream)
 68      : __res_(__upstream) {
 69    __initial_.__start_ = static_cast<char*>(__buffer);
 70    if (__buffer != nullptr) {
 71      __initial_.__cur_ = static_cast<char*>(__buffer) + __buffer_size;
 72      __initial_.__end_ = static_cast<char*>(__buffer) + __buffer_size;
 73    } else {
 74      __initial_.__cur_  = nullptr;
 75      __initial_.__size_ = __buffer_size;
 76    }
 77    __chunks_ = nullptr;
 78  }
 79
 80  monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
 81
 82  _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~monotonic_buffer_resource() override { release(); }
 83
 84  monotonic_buffer_resource& operator=(const monotonic_buffer_resource&) = delete;
 85
 86  _LIBCPP_HIDE_FROM_ABI void release() {
 87    if (__initial_.__start_ != nullptr)
 88      __initial_.__cur_ = __initial_.__end_;
 89    while (__chunks_ != nullptr) {
 90      __chunk_footer* __next = __chunks_->__next_;
 91      __res_->deallocate(__chunks_->__start_, __chunks_->__allocation_size(), __chunks_->__align_);
 92      __chunks_ = __next;
 93    }
 94  }
 95
 96  _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
 97
 98protected:
 99  void* do_allocate(size_t __bytes, size_t __alignment) override; // key function
100
101  _LIBCPP_HIDE_FROM_ABI_VIRTUAL void do_deallocate(void*, size_t, size_t) override {}
102
103  _LIBCPP_HIDE_FROM_ABI_VIRTUAL bool do_is_equal(const memory_resource& __other) const _NOEXCEPT override {
104    return this == std::addressof(__other);
105  }
106
107private:
108  __initial_descriptor __initial_;
109  __chunk_footer* __chunks_;
110  memory_resource* __res_;
111};
112
113} // namespace pmr
114
115_LIBCPP_END_NAMESPACE_STD
116
117#endif // _LIBCPP_STD_VER >= 17
118
119#endif // _LIBCPP___MEMORY_RESOURCE_MONOTONIC_BUFFER_RESOURCE_H