1/* Copyright 2021 The TensorFlow Authors. All Rights Reserved.
2
3Licensed under the Apache License, Version 2.0 (the "License");
4you may not use this file except in compliance with the License.
5You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9Unless required by applicable law or agreed to in writing, software
10distributed under the License is distributed on an "AS IS" BASIS,
11WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12See the License for the specific language governing permissions and
13limitations under the License.
14==============================================================================*/
15#ifndef TENSORFLOW_TSL_PLATFORM_INTRUSIVE_PTR_H_
16#define TENSORFLOW_TSL_PLATFORM_INTRUSIVE_PTR_H_
17
18#include <algorithm>
19namespace tsl {
20namespace core {
21
22// A utility for managing the lifetime of ref-counted objects.
23//
24// Generally used for objects that derive from `tensorflow::RefCounted`.
25template <class T>
26class IntrusivePtr {
27 public:
28 // add_ref=false indicates that IntrusivePtr owns the underlying pointer.
29 //
30 // In most cases, we expect this to be called with add_ref=false, except in
31 // special circumstances where the lifetime of the underlying RefCounted
32 // object needs to be externally managed.
33 IntrusivePtr(T* h, bool add_ref) { reset(h, add_ref); }
34 IntrusivePtr(const IntrusivePtr& o) { reset(o.handle_, /*add_ref=*/true); }
35 IntrusivePtr(IntrusivePtr&& o) { *this = std::move(o); }
36 IntrusivePtr() {}
37 void reset(T* h, bool add_ref) {
38 if (h != handle_) {
39 if (add_ref && h) h->Ref();
40 if (handle_) handle_->Unref();
41 handle_ = h;
42 }
43 }
44 IntrusivePtr& operator=(const IntrusivePtr& o) {
45 reset(o.handle_, /*add_ref=*/true);
46 return *this;
47 }
48 IntrusivePtr& operator=(IntrusivePtr&& o) {
49 if (handle_ != o.handle_) {
50 // Must clear o.handle_ before calling reset to capture the case where
51 // handle_->member == o. In this case, calling handle_->Unref first would
52 // delete o.handle_ so we clear it out first.
53 reset(o.detach(), /*add_ref=*/false);
54 }
55 return *this;
56 }
57 bool operator==(const IntrusivePtr& o) const { return handle_ == o.handle_; }
58 T* operator->() const { return handle_; }
59 T& operator*() const { return *handle_; }
60 explicit operator bool() const noexcept { return get(); }
61 T* get() const { return handle_; }
62 // Releases ownership of the pointer without unreffing. Caller is responsible
63 // for calling Unref on the returned pointer.
64 T* detach() {
65 T* handle = handle_;
66 handle_ = nullptr;
67 return handle;
68 }
69
70 ~IntrusivePtr() {
71 if (handle_) handle_->Unref();
72 }
73
74 private:
75 T* handle_ = nullptr;
76};
77
78} // namespace core
79} // namespace tsl
80
81#endif // TENSORFLOW_TSL_PLATFORM_INTRUSIVE_PTR_H_
82