dom/bindings/Nullable.h@97036ab72558
dom/bindings/Nullable.h
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
2 /* vim: set ts=2 sw=2 et tw=79: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
5 * You can obtain one at http://mozilla.org/MPL/2.0/. */
7 #ifndef mozilla_dom_Nullable_h
8 #define mozilla_dom_Nullable_h
10 #include "mozilla/Assertions.h"
11 #include "nsTArrayForwardDeclare.h"
12 #include "mozilla/Move.h"
14 namespace mozilla {
15 namespace dom {
17 // Support for nullable types
18 template <typename T>
19 struct Nullable
20 {
21 private:
22 // mIsNull MUST COME FIRST because otherwise the casting in our array
23 // conversion operators would shift where it is found in the struct.
24 bool mIsNull;
25 T mValue;
27 public:
28 Nullable()
29 : mIsNull(true)
30 {}
32 explicit Nullable(T aValue)
33 : mIsNull(false)
34 , mValue(aValue)
35 {}
37 explicit Nullable(Nullable<T>&& aOther)
38 : mIsNull(aOther.mIsNull)
39 , mValue(mozilla::Move(aOther.mValue))
40 {}
42 Nullable(const Nullable<T>& aOther)
43 : mIsNull(aOther.mIsNull)
44 , mValue(aOther.mValue)
45 {}
47 void operator=(const Nullable<T>& aOther)
48 {
49 mIsNull = aOther.mIsNull;
50 mValue = aOther.mValue;
51 }
53 void SetValue(T aValue) {
54 mValue = aValue;
55 mIsNull = false;
56 }
58 // For cases when |T| is some type with nontrivial copy behavior, we may want
59 // to get a reference to our internal copy of T and work with it directly
60 // instead of relying on the copying version of SetValue().
61 T& SetValue() {
62 mIsNull = false;
63 return mValue;
64 }
66 void SetNull() {
67 mIsNull = true;
68 }
70 const T& Value() const {
71 MOZ_ASSERT(!mIsNull);
72 return mValue;
73 }
75 T& Value() {
76 MOZ_ASSERT(!mIsNull);
77 return mValue;
78 }
80 bool IsNull() const {
81 return mIsNull;
82 }
84 bool Equals(const Nullable<T>& aOtherNullable) const
85 {
86 return (mIsNull && aOtherNullable.mIsNull) ||
87 (!mIsNull && !aOtherNullable.mIsNull &&
88 mValue == aOtherNullable.mValue);
89 }
91 bool operator==(const Nullable<T>& aOtherNullable) const
92 {
93 return Equals(aOtherNullable);
94 }
96 bool operator!=(const Nullable<T>& aOtherNullable) const
97 {
98 return !Equals(aOtherNullable);
99 }
101 // Make it possible to use a const Nullable of an array type with other
102 // array types.
103 template<typename U>
104 operator const Nullable< nsTArray<U> >&() const {
105 // Make sure that T is ok to reinterpret to nsTArray<U>
106 const nsTArray<U>& arr = mValue;
107 (void)arr;
108 return *reinterpret_cast<const Nullable< nsTArray<U> >*>(this);
109 }
110 template<typename U>
111 operator const Nullable< FallibleTArray<U> >&() const {
112 // Make sure that T is ok to reinterpret to FallibleTArray<U>
113 const FallibleTArray<U>& arr = mValue;
114 (void)arr;
115 return *reinterpret_cast<const Nullable< FallibleTArray<U> >*>(this);
116 }
117 };
119 } // namespace dom
120 } // namespace mozilla
122 #endif /* mozilla_dom_Nullable_h */
