1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/dom/bindings/Nullable.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,122 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
1.5 +/* vim: set ts=2 sw=2 et tw=79: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this file,
1.8 + * You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef mozilla_dom_Nullable_h
1.11 +#define mozilla_dom_Nullable_h
1.12 +
1.13 +#include "mozilla/Assertions.h"
1.14 +#include "nsTArrayForwardDeclare.h"
1.15 +#include "mozilla/Move.h"
1.16 +
1.17 +namespace mozilla {
1.18 +namespace dom {
1.19 +
1.20 +// Support for nullable types
1.21 +template <typename T>
1.22 +struct Nullable
1.23 +{
1.24 +private:
1.25 + // mIsNull MUST COME FIRST because otherwise the casting in our array
1.26 + // conversion operators would shift where it is found in the struct.
1.27 + bool mIsNull;
1.28 + T mValue;
1.29 +
1.30 +public:
1.31 + Nullable()
1.32 + : mIsNull(true)
1.33 + {}
1.34 +
1.35 + explicit Nullable(T aValue)
1.36 + : mIsNull(false)
1.37 + , mValue(aValue)
1.38 + {}
1.39 +
1.40 + explicit Nullable(Nullable<T>&& aOther)
1.41 + : mIsNull(aOther.mIsNull)
1.42 + , mValue(mozilla::Move(aOther.mValue))
1.43 + {}
1.44 +
1.45 + Nullable(const Nullable<T>& aOther)
1.46 + : mIsNull(aOther.mIsNull)
1.47 + , mValue(aOther.mValue)
1.48 + {}
1.49 +
1.50 + void operator=(const Nullable<T>& aOther)
1.51 + {
1.52 + mIsNull = aOther.mIsNull;
1.53 + mValue = aOther.mValue;
1.54 + }
1.55 +
1.56 + void SetValue(T aValue) {
1.57 + mValue = aValue;
1.58 + mIsNull = false;
1.59 + }
1.60 +
1.61 + // For cases when |T| is some type with nontrivial copy behavior, we may want
1.62 + // to get a reference to our internal copy of T and work with it directly
1.63 + // instead of relying on the copying version of SetValue().
1.64 + T& SetValue() {
1.65 + mIsNull = false;
1.66 + return mValue;
1.67 + }
1.68 +
1.69 + void SetNull() {
1.70 + mIsNull = true;
1.71 + }
1.72 +
1.73 + const T& Value() const {
1.74 + MOZ_ASSERT(!mIsNull);
1.75 + return mValue;
1.76 + }
1.77 +
1.78 + T& Value() {
1.79 + MOZ_ASSERT(!mIsNull);
1.80 + return mValue;
1.81 + }
1.82 +
1.83 + bool IsNull() const {
1.84 + return mIsNull;
1.85 + }
1.86 +
1.87 + bool Equals(const Nullable<T>& aOtherNullable) const
1.88 + {
1.89 + return (mIsNull && aOtherNullable.mIsNull) ||
1.90 + (!mIsNull && !aOtherNullable.mIsNull &&
1.91 + mValue == aOtherNullable.mValue);
1.92 + }
1.93 +
1.94 + bool operator==(const Nullable<T>& aOtherNullable) const
1.95 + {
1.96 + return Equals(aOtherNullable);
1.97 + }
1.98 +
1.99 + bool operator!=(const Nullable<T>& aOtherNullable) const
1.100 + {
1.101 + return !Equals(aOtherNullable);
1.102 + }
1.103 +
1.104 + // Make it possible to use a const Nullable of an array type with other
1.105 + // array types.
1.106 + template<typename U>
1.107 + operator const Nullable< nsTArray<U> >&() const {
1.108 + // Make sure that T is ok to reinterpret to nsTArray<U>
1.109 + const nsTArray<U>& arr = mValue;
1.110 + (void)arr;
1.111 + return *reinterpret_cast<const Nullable< nsTArray<U> >*>(this);
1.112 + }
1.113 + template<typename U>
1.114 + operator const Nullable< FallibleTArray<U> >&() const {
1.115 + // Make sure that T is ok to reinterpret to FallibleTArray<U>
1.116 + const FallibleTArray<U>& arr = mValue;
1.117 + (void)arr;
1.118 + return *reinterpret_cast<const Nullable< FallibleTArray<U> >*>(this);
1.119 + }
1.120 +};
1.121 +
1.122 +} // namespace dom
1.123 +} // namespace mozilla
1.124 +
1.125 +#endif /* mozilla_dom_Nullable_h */
