gecko-dev/dom/bindings/DOMJSProxyHandler.h

248 lines
9.0 KiB
C++

/* -*- 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 "jsapi.h"
#include "js/Proxy.h"
#include "nsString.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.)
*/
template<typename T> struct Prefable;
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<JS::PropertyDescriptor> desc) const override;
virtual bool ownPropertyKeys(JSContext* cx, JS::Handle<JSObject*> proxy,
JS::AutoIdVector &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::AutoIdVector &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::AutoIdVector& 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<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 *defined) 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 ExpandoAndGeneration.
class ShadowingDOMProxyHandler : public DOMProxyHandler
{
virtual void trace(JSTracer* trc, JSObject* proxy) const override;
};
inline bool IsDOMProxy(JSObject *obj)
{
const js::Class* clasp = js::GetObjectClass(obj);
return clasp->isProxy() &&
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(JSContext* cx, 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...
if (MOZ_LIKELY(JSID_IS_INT(id))) {
return JSID_TO_INT(id);
}
if (MOZ_LIKELY(id == s_length_id)) {
return UINT32_MAX;
}
if (MOZ_UNLIKELY(!JSID_IS_ATOM(id))) {
return UINT32_MAX;
}
JSLinearString* str = js::AtomToLinearString(JSID_TO_ATOM(id));
char16_t s;
{
JS::AutoCheckCannotGC nogc;
if (js::LinearStringHasLatin1Chars(str)) {
s = *js::GetLatin1LinearStringChars(nogc, str);
} else {
s = *js::GetTwoByteLinearStringChars(nogc, str);
}
}
if (MOZ_LIKELY((unsigned)s >= 'a' && (unsigned)s <= 'z'))
return UINT32_MAX;
uint32_t i;
return js::StringIsArrayIndex(str, &i) ? i : UINT32_MAX;
}
inline bool
IsArrayIndex(uint32_t index)
{
return index < UINT32_MAX;
}
inline void
FillPropertyDescriptor(JS::MutableHandle<JS::PropertyDescriptor> desc,
JSObject* obj, bool readonly, bool enumerable = true)
{
desc.object().set(obj);
desc.setAttributes((readonly ? JSPROP_READONLY : 0) |
(enumerable ? JSPROP_ENUMERATE : 0));
desc.setGetter(nullptr);
desc.setSetter(nullptr);
}
inline void
FillPropertyDescriptor(JS::MutableHandle<JS::PropertyDescriptor> desc,
JSObject* obj, const JS::Value& v,
bool readonly, bool enumerable = true)
{
desc.value().set(v);
FillPropertyDescriptor(desc, obj, readonly, enumerable);
}
inline void
FillPropertyDescriptor(JS::MutableHandle<JS::PropertyDescriptor> desc,
JSObject* obj, unsigned attributes, const JS::Value& v)
{
desc.object().set(obj);
desc.value().set(v);
desc.setAttributes(attributes);
desc.setGetter(nullptr);
desc.setSetter(nullptr);
}
} // namespace dom
} // namespace mozilla
#endif /* mozilla_dom_DOMProxyHandler_h */