tor-browser

DOMJSProxyHandler.h (6807B)

---

/* -*- 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 "js/Proxy.h"
#include "jsapi.h"
#include "mozilla/Assertions.h"
#include "mozilla/Maybe.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 {
public:
 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 */