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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/Attributes.h"
#include "mozilla/Likely.h"
#include "mozilla/Maybe.h"
#include "mozilla/TextUtils.h"
#include "jsapi.h"
#include "js/Object.h" // JS::GetClass
#include "js/Proxy.h"
#include "js/String.h" // JS::AtomToLinearString, JS::GetLinearString{CharAt,Length}
#include "nsString.h"
// XXX Avoid including this (and maybe some of those above by moving inline
// function bodies out)
#include "jsfriendapi.h"
namespace mozilla {
namespace 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;
// Use the DOMProxyExpando object for private fields, rather than the proxy
// expando object.
virtual bool useProxyExpandoObjectForPrivateFields() const override {
return false;
}
/*
* 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));
}
extern jsid s_length_id;
// A return value of UINT32_MAX indicates "not an array index". Note, in
// particular, that UINT32_MAX itself is not a valid array index in general.
inline uint32_t GetArrayIndexFromId(JS::Handle<jsid> id) {
// Much like js::IdIsIndex, except with a fast path for "length" and another
// fast path for starting with a lowercase ascii char. Is that second one
// really needed? I guess it is because StringIsArrayIndex is out of line...
// as of now, use id.get() instead of id otherwise operands mismatch error
// occurs.
if (MOZ_LIKELY(id.isInt())) {
return id.toInt();
}
if (MOZ_LIKELY(id.get() == s_length_id)) {
return UINT32_MAX;
}
if (MOZ_UNLIKELY(!id.isAtom())) {
return UINT32_MAX;
}
JSLinearString* str = JS::AtomToLinearString(id.toAtom());
if (MOZ_UNLIKELY(JS::GetLinearStringLength(str) == 0)) {
return UINT32_MAX;
}
char16_t firstChar = JS::GetLinearStringCharAt(str, 0);
if (MOZ_LIKELY(IsAsciiLowercaseAlpha(firstChar))) {
return UINT32_MAX;
}
uint32_t i;
return js::StringIsArrayIndex(str, &i) ? i : UINT32_MAX;
}
inline bool IsArrayIndex(uint32_t index) { return index < UINT32_MAX; }
} // namespace dom
} // namespace mozilla
#endif /* mozilla_dom_DOMProxyHandler_h */