1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2 * vim: set ts=8 sts=2 et sw=2 tw=80:
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
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
10 #include "mozilla/Variant.h"
12 #include <type_traits>
14 #include "js/GCPolicyAPI.h"
15 #include "js/RootingAPI.h"
16 #include "js/TracingAPI.h"
20 // These template specializations allow Variant to be used inside GC wrappers.
22 // When matching on GC wrappers around Variants, matching should be done on
23 // the wrapper itself. The matcher class's methods should take Handles or
24 // MutableHandles. For example,
28 // using ReturnType = const char*;
29 // ReturnType match(HandleObject o) { return "object"; }
30 // ReturnType match(HandleScript s) { return "script"; }
33 // Rooted<Variant<JSObject*, JSScript*>> v(cx, someScript);
37 // If you get compile errors about inability to upcast subclasses (e.g., from
38 // NativeObject* to JSObject*) and are inside js/src, be sure to also include
43 template <typename
... Ts
>
44 struct GCVariantImplementation
;
48 struct GCVariantImplementation
<T
> {
49 template <typename ConcreteVariant
>
50 static void trace(JSTracer
* trc
, ConcreteVariant
* v
, const char* name
) {
51 T
& thing
= v
->template as
<T
>();
52 GCPolicy
<T
>::trace(trc
, &thing
, name
);
55 template <typename Matcher
, typename ConcreteVariant
>
56 static typename
Matcher::ReturnType
match(Matcher
& matcher
,
57 Handle
<ConcreteVariant
> v
) {
58 const T
& thing
= v
.get().template as
<T
>();
59 return matcher
.match(Handle
<T
>::fromMarkedLocation(&thing
));
62 template <typename Matcher
, typename ConcreteVariant
>
63 static typename
Matcher::ReturnType
match(Matcher
& matcher
,
64 MutableHandle
<ConcreteVariant
> v
) {
65 T
& thing
= v
.get().template as
<T
>();
66 return matcher
.match(MutableHandle
<T
>::fromMarkedLocation(&thing
));
70 // The inductive case.
71 template <typename T
, typename
... Ts
>
72 struct GCVariantImplementation
<T
, Ts
...> {
73 using Next
= GCVariantImplementation
<Ts
...>;
75 template <typename ConcreteVariant
>
76 static void trace(JSTracer
* trc
, ConcreteVariant
* v
, const char* name
) {
77 if (v
->template is
<T
>()) {
78 T
& thing
= v
->template as
<T
>();
79 GCPolicy
<T
>::trace(trc
, &thing
, name
);
81 Next::trace(trc
, v
, name
);
85 template <typename Matcher
, typename ConcreteVariant
>
86 static typename
Matcher::ReturnType
match(Matcher
& matcher
,
87 Handle
<ConcreteVariant
> v
) {
88 if (v
.get().template is
<T
>()) {
89 const T
& thing
= v
.get().template as
<T
>();
90 return matcher
.match(Handle
<T
>::fromMarkedLocation(&thing
));
92 return Next::match(matcher
, v
);
95 template <typename Matcher
, typename ConcreteVariant
>
96 static typename
Matcher::ReturnType
match(Matcher
& matcher
,
97 MutableHandle
<ConcreteVariant
> v
) {
98 if (v
.get().template is
<T
>()) {
99 T
& thing
= v
.get().template as
<T
>();
100 return matcher
.match(MutableHandle
<T
>::fromMarkedLocation(&thing
));
102 return Next::match(matcher
, v
);
106 } // namespace detail
108 template <typename
... Ts
>
109 struct GCPolicy
<mozilla::Variant
<Ts
...>> {
110 using Impl
= detail::GCVariantImplementation
<Ts
...>;
112 static void trace(JSTracer
* trc
, mozilla::Variant
<Ts
...>* v
,
114 Impl::trace(trc
, v
, name
);
117 static bool isValid(const mozilla::Variant
<Ts
...>& v
) {
118 return v
.match([](auto& v
) {
119 return GCPolicy
<std::remove_reference_t
<decltype(v
)>>::isValid(v
);
128 template <typename Wrapper
, typename
... Ts
>
129 class WrappedPtrOperations
<mozilla::Variant
<Ts
...>, Wrapper
> {
130 using Impl
= JS::detail::GCVariantImplementation
<Ts
...>;
131 using Variant
= mozilla::Variant
<Ts
...>;
133 const Variant
& variant() const {
134 return static_cast<const Wrapper
*>(this)->get();
138 template <typename T
>
140 return variant().template is
<T
>();
143 template <typename T
>
144 JS::Handle
<T
> as() const {
145 return JS::Handle
<T
>::fromMarkedLocation(&variant().template as
<T
>());
148 template <typename Matcher
>
149 typename
Matcher::ReturnType
match(Matcher
& matcher
) const {
150 return Impl::match(matcher
,
151 JS::Handle
<Variant
>::fromMarkedLocation(&variant()));
155 template <typename Wrapper
, typename
... Ts
>
156 class MutableWrappedPtrOperations
<mozilla::Variant
<Ts
...>, Wrapper
>
157 : public WrappedPtrOperations
<mozilla::Variant
<Ts
...>, Wrapper
> {
158 using Impl
= JS::detail::GCVariantImplementation
<Ts
...>;
159 using Variant
= mozilla::Variant
<Ts
...>;
161 const Variant
& variant() const {
162 return static_cast<const Wrapper
*>(this)->get();
164 Variant
& variant() { return static_cast<Wrapper
*>(this)->get(); }
167 template <typename T
>
168 JS::MutableHandle
<T
> as() {
169 return JS::MutableHandle
<T
>::fromMarkedLocation(
170 &variant().template as
<T
>());
173 template <typename Matcher
>
174 typename
Matcher::ReturnType
match(Matcher
& matcher
) {
176 matcher
, JS::MutableHandle
<Variant
>::fromMarkedLocation(&variant()));
182 #endif // js_GCVariant_h