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| -rw-r--r-- | dom/bindings/DOMJSProxyHandler.h | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/dom/bindings/DOMJSProxyHandler.h b/dom/bindings/DOMJSProxyHandler.h new file mode 100644 index 0000000000..8e68b32980 --- /dev/null +++ b/dom/bindings/DOMJSProxyHandler.h @@ -0,0 +1,163 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this file, + * You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef mozilla_dom_DOMJSProxyHandler_h +#define mozilla_dom_DOMJSProxyHandler_h + +#include "mozilla/Assertions.h" +#include "mozilla/Maybe.h" + +#include "jsapi.h" +#include "js/Object.h" // JS::GetClass +#include "js/Proxy.h" + +namespace mozilla::dom { + +/** + * DOM proxies store the expando object in the private slot. + * + * The expando object is a plain JSObject whose properties correspond to + * "expandos" (custom properties set by the script author). + * + * The exact value stored in the proxy's private slot depends on whether the + * interface is annotated with the [OverrideBuiltins] extended attribute. + * + * If it is, the proxy is initialized with a PrivateValue, which contains a + * pointer to a JS::ExpandoAndGeneration object; this contains a pointer to + * the actual expando object as well as the "generation" of the object. The + * proxy handler will trace the expando object stored in the + * JS::ExpandoAndGeneration while the proxy itself is alive. + * + * If it is not, the proxy is initialized with an UndefinedValue. In + * EnsureExpandoObject, it is set to an ObjectValue that points to the + * expando object directly. (It is set back to an UndefinedValue only when + * the object is about to die.) + */ + +class BaseDOMProxyHandler : public js::BaseProxyHandler { + public: + explicit constexpr BaseDOMProxyHandler(const void* aProxyFamily, + bool aHasPrototype = false) + : js::BaseProxyHandler(aProxyFamily, aHasPrototype) {} + + // Implementations of methods that can be implemented in terms of + // other lower-level methods. + bool getOwnPropertyDescriptor( + JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id, + JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc) const override; + virtual bool ownPropertyKeys( + JSContext* cx, JS::Handle<JSObject*> proxy, + JS::MutableHandleVector<jsid> props) const override; + + virtual bool getPrototypeIfOrdinary( + JSContext* cx, JS::Handle<JSObject*> proxy, bool* isOrdinary, + JS::MutableHandle<JSObject*> proto) const override; + + // We override getOwnEnumerablePropertyKeys() and implement it directly + // instead of using the default implementation, which would call + // ownPropertyKeys and then filter out the non-enumerable ones. This avoids + // unnecessary work during enumeration. + virtual bool getOwnEnumerablePropertyKeys( + JSContext* cx, JS::Handle<JSObject*> proxy, + JS::MutableHandleVector<jsid> props) const override; + + protected: + // Hook for subclasses to implement shared ownPropertyKeys()/keys() + // functionality. The "flags" argument is either JSITER_OWNONLY (for keys()) + // or JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS (for + // ownPropertyKeys()). + virtual bool ownPropNames(JSContext* cx, JS::Handle<JSObject*> proxy, + unsigned flags, + JS::MutableHandleVector<jsid> props) const = 0; + + // Hook for subclasses to allow set() to ignore named props while other things + // that look at property descriptors see them. This is intentionally not + // named getOwnPropertyDescriptor to avoid subclasses that override it hiding + // our public getOwnPropertyDescriptor. + virtual bool getOwnPropDescriptor( + JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id, + bool ignoreNamedProps, + JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc) const = 0; +}; + +class DOMProxyHandler : public BaseDOMProxyHandler { + public: + constexpr DOMProxyHandler() : BaseDOMProxyHandler(&family) {} + + bool defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy, + JS::Handle<jsid> id, + JS::Handle<JS::PropertyDescriptor> desc, + JS::ObjectOpResult& result) const override { + bool unused; + return defineProperty(cx, proxy, id, desc, result, &unused); + } + virtual bool defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy, + JS::Handle<jsid> id, + JS::Handle<JS::PropertyDescriptor> desc, + JS::ObjectOpResult& result, bool* done) const; + bool delete_(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id, + JS::ObjectOpResult& result) const override; + bool preventExtensions(JSContext* cx, JS::Handle<JSObject*> proxy, + JS::ObjectOpResult& result) const override; + bool isExtensible(JSContext* cx, JS::Handle<JSObject*> proxy, + bool* extensible) const override; + bool set(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id, + JS::Handle<JS::Value> v, JS::Handle<JS::Value> receiver, + JS::ObjectOpResult& result) const override; + + /* + * If assigning to proxy[id] hits a named setter with OverrideBuiltins or + * an indexed setter, call it and set *done to true on success. Otherwise, set + * *done to false. + */ + virtual bool setCustom(JSContext* cx, JS::Handle<JSObject*> proxy, + JS::Handle<jsid> id, JS::Handle<JS::Value> v, + bool* done) const; + + /* + * Get the expando object for the given DOM proxy. + */ + static JSObject* GetExpandoObject(JSObject* obj); + + /* + * Clear the expando object for the given DOM proxy and return it. This + * function will ensure that the returned object is exposed to active JS if + * the given object is exposed. + * + * GetAndClearExpandoObject does not DROP or clear the preserving wrapper + * flag. + */ + static JSObject* GetAndClearExpandoObject(JSObject* obj); + + /* + * Ensure that the given proxy (obj) has an expando object, and return it. + * Returns null on failure. + */ + static JSObject* EnsureExpandoObject(JSContext* cx, + JS::Handle<JSObject*> obj); + + static const char family; +}; + +// Class used by shadowing handlers (the ones that have [OverrideBuiltins]. +// This handles tracing the expando in JS::ExpandoAndGeneration. +class ShadowingDOMProxyHandler : public DOMProxyHandler { + virtual void trace(JSTracer* trc, JSObject* proxy) const override; +}; + +inline bool IsDOMProxy(JSObject* obj) { + return js::IsProxy(obj) && + js::GetProxyHandler(obj)->family() == &DOMProxyHandler::family; +} + +inline const DOMProxyHandler* GetDOMProxyHandler(JSObject* obj) { + MOZ_ASSERT(IsDOMProxy(obj)); + return static_cast<const DOMProxyHandler*>(js::GetProxyHandler(obj)); +} + +} // namespace mozilla::dom + +#endif /* mozilla_dom_DOMProxyHandler_h */ |