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// Copyright 2018 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef ABSL_CONTAINER_INTERNAL_COUNTING_ALLOCATOR_H_
#define ABSL_CONTAINER_INTERNAL_COUNTING_ALLOCATOR_H_

#include <cstdint>
#include <memory>

#include "y_absl/base/config.h"

namespace y_absl {
ABSL_NAMESPACE_BEGIN
namespace container_internal {

// This is a stateful allocator, but the state lives outside of the
// allocator (in whatever test is using the allocator). This is odd
// but helps in tests where the allocator is propagated into nested
// containers - that chain of allocators uses the same state and is
// thus easier to query for aggregate allocation information.
template <typename T>
class CountingAllocator { 
 public:
  using Allocator = std::allocator<T>; 
  using AllocatorTraits = std::allocator_traits<Allocator>; 
  using value_type = typename AllocatorTraits::value_type; 
  using pointer = typename AllocatorTraits::pointer; 
  using const_pointer = typename AllocatorTraits::const_pointer; 
  using size_type = typename AllocatorTraits::size_type; 
  using difference_type = typename AllocatorTraits::difference_type; 

  CountingAllocator() = default; 
  explicit CountingAllocator(int64_t* bytes_used) : bytes_used_(bytes_used) {} 
  CountingAllocator(int64_t* bytes_used, int64_t* instance_count) 
      : bytes_used_(bytes_used), instance_count_(instance_count) {} 

  template <typename U>
  CountingAllocator(const CountingAllocator<U>& x)
      : bytes_used_(x.bytes_used_), instance_count_(x.instance_count_) {} 

  pointer allocate( 
      size_type n, 
      typename AllocatorTraits::const_void_pointer hint = nullptr) { 
    Allocator allocator; 
    pointer ptr = AllocatorTraits::allocate(allocator, n, hint); 
    if (bytes_used_ != nullptr) { 
      *bytes_used_ += n * sizeof(T); 
    } 
    return ptr; 
  }

  void deallocate(pointer p, size_type n) {
    Allocator allocator; 
    AllocatorTraits::deallocate(allocator, p, n); 
    if (bytes_used_ != nullptr) { 
      *bytes_used_ -= n * sizeof(T); 
    } 
  }

  template <typename U, typename... Args> 
  void construct(U* p, Args&&... args) { 
    Allocator allocator; 
    AllocatorTraits::construct(allocator, p, std::forward<Args>(args)...); 
    if (instance_count_ != nullptr) { 
      *instance_count_ += 1; 
    } 
  } 
 
  template <typename U> 
  void destroy(U* p) { 
    Allocator allocator; 
    AllocatorTraits::destroy(allocator, p); 
    if (instance_count_ != nullptr) { 
      *instance_count_ -= 1; 
    } 
  } 
 
  template <typename U> 
  class rebind {
   public:
    using other = CountingAllocator<U>;
  };

  friend bool operator==(const CountingAllocator& a,
                         const CountingAllocator& b) {
    return a.bytes_used_ == b.bytes_used_ && 
           a.instance_count_ == b.instance_count_; 
  }

  friend bool operator!=(const CountingAllocator& a,
                         const CountingAllocator& b) {
    return !(a == b);
  }

  int64_t* bytes_used_ = nullptr; 
  int64_t* instance_count_ = nullptr; 
};

}  // namespace container_internal
ABSL_NAMESPACE_END
}  // namespace y_absl

#endif  // ABSL_CONTAINER_INTERNAL_COUNTING_ALLOCATOR_H_