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+/* -*- 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 */