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Bug 819523 part 2. Allow Nullable<> of various array types to work sanely. r=jlebar

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This commit is contained in:
Boris Zbarsky 2012-12-18 20:16:05 -05:00
parent 6efc316628
commit 3dfc80459c
2 changed files with 38 additions and 4 deletions
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4
dom/bindings/BindingUtils.h
View File

@ -1370,6 +1370,10 @@ public:
return mImpl.ref();
}
// If we ever decide to add conversion operators for optional arrays
// like the ones Nullable has, we'll need to ensure that Maybe<> has
// the boolean before the actual data.
private:
// Forbid copy-construction and assignment
Optional(const Optional& other) MOZ_DELETE;

38
dom/bindings/Nullable.h
View File

@ -9,6 +9,10 @@
#include "mozilla/Assertions.h"
template<typename E, class Allocator> class nsTArray;
template<typename E> class InfallibleTArray;
template<typename E> class FallibleTArray;
namespace mozilla {
namespace dom {
@ -17,17 +21,19 @@ template <typename T>
struct Nullable
{
private:
T mValue;
// mIsNull MUST COME FIRST because otherwise the casting in our array
// conversion operators would shift where it is found in the struct.
bool mIsNull;
T mValue;
public:
Nullable()
: mIsNull(true)
{}
Nullable(T aValue)
: mValue(aValue)
, mIsNull(false)
explicit Nullable(T aValue)
: mIsNull(false)
, mValue(aValue)
{}
void SetValue(T aValue) {
@ -60,6 +66,30 @@ public:
bool IsNull() const {
return mIsNull;
}
// Make it possible to use a const Nullable of an array type with other
// array types.
template<typename U, typename Allocator>
operator const Nullable< nsTArray<U, Allocator> >&() const {
// Make sure that T is ok to reinterpret to nsTArray<U, Allocator>
const nsTArray<U, Allocator>& arr = mValue;
(void)arr;
return *reinterpret_cast<const Nullable< nsTArray<U, Allocator> >*>(this);
}
template<typename U>
operator const Nullable< InfallibleTArray<U> >&() const {
// Make sure that T is ok to reinterpret to InfallibleTArray<U>
const InfallibleTArray<U>& arr = mValue;
(void)arr;
return *reinterpret_cast<const Nullable< InfallibleTArray<U> >*>(this);
}
template<typename U>
operator const Nullable< FallibleTArray<U> >&() const {
// Make sure that T is ok to reinterpret to FallibleTArray<U>
const FallibleTArray<U>& arr = mValue;
(void)arr;
return *reinterpret_cast<const Nullable< FallibleTArray<U> >*>(this);
}
};
} // namespace dom