1 files changed, 165 insertions, 0 deletions
diff --git a/js/src/vm/ProxyObject.h b/js/src/vm/ProxyObject.h
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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 vm_ProxyObject_h
+#define vm_ProxyObject_h
+
+#include "js/Proxy.h"
+#include "js/shadow/Object.h"  // JS::shadow::Object
+#include "vm/JSObject.h"
+
+namespace js {
+
+/**
+ * This is the base class for the various kinds of proxy objects.  It's never
+ * instantiated.
+ *
+ * Proxy objects use their shape primarily to record flags. Property
+ * information, &c. is all dynamically computed.
+ *
+ * There is no class_ member to force specialization of JSObject::is<T>().
+ * The implementation in JSObject is incorrect for proxies since it doesn't
+ * take account of the handler type.
+ */
+class ProxyObject : public JSObject {
+  // GetProxyDataLayout computes the address of this field.
+  detail::ProxyDataLayout data;
+
+  void static_asserts() {
+    static_assert(sizeof(ProxyObject) == sizeof(JSObject_Slots0),
+                  "proxy object size must match GC thing size");
+    static_assert(offsetof(ProxyObject, data) == detail::ProxyDataOffset,
+                  "proxy object layout must match shadow interface");
+    static_assert(offsetof(ProxyObject, data.reservedSlots) ==
+                      offsetof(JS::shadow::Object, slots),
+                  "Proxy reservedSlots must overlay native object slots field");
+  }
+
+ public:
+  static ProxyObject* New(JSContext* cx, const BaseProxyHandler* handler,
+                          HandleValue priv, TaggedProto proto_,
+                          const JSClass* clasp);
+
+  void init(const BaseProxyHandler* handler, HandleValue priv, JSContext* cx);
+
+  // Proxies usually store their ProxyValueArray inline in the object.
+  // There's one unfortunate exception: when a proxy is swapped with another
+  // object, and the sizes don't match, we malloc the ProxyValueArray.
+  void* inlineDataStart() const {
+    return (void*)(uintptr_t(this) + sizeof(ProxyObject));
+  }
+  bool usingInlineValueArray() const {
+    return data.values() == inlineDataStart();
+  }
+  void setInlineValueArray() {
+    data.reservedSlots =
+        &reinterpret_cast<detail::ProxyValueArray*>(inlineDataStart())
+             ->reservedSlots;
+  }
+
+  // For use from JSObject::swap.
+  [[nodiscard]] bool prepareForSwap(JSContext* cx,
+                                    MutableHandleValueVector valuesOut);
+  [[nodiscard]] bool fixupAfterSwap(JSContext* cx, HandleValueVector values);
+
+  const Value& private_() const { return GetProxyPrivate(this); }
+  const Value& expando() const { return GetProxyExpando(this); }
+
+  void setExpando(JSObject* expando);
+
+  void setCrossCompartmentPrivate(const Value& priv);
+  void setSameCompartmentPrivate(const Value& priv);
+
+  JSObject* target() const { return private_().toObjectOrNull(); }
+
+  const BaseProxyHandler* handler() const { return GetProxyHandler(this); }
+
+  void setHandler(const BaseProxyHandler* handler) {
+    SetProxyHandler(this, handler);
+  }
+
+  static size_t offsetOfReservedSlots() {
+    return offsetof(ProxyObject, data.reservedSlots);
+  }
+  static size_t offsetOfHandler() {
+    return offsetof(ProxyObject, data.handler);
+  }
+
+  size_t numReservedSlots() const { return JSCLASS_RESERVED_SLOTS(getClass()); }
+  const Value& reservedSlot(size_t n) const {
+    return GetProxyReservedSlot(this, n);
+  }
+
+  void setReservedSlot(size_t n, const Value& extra) {
+    SetProxyReservedSlot(this, n, extra);
+  }
+
+  gc::AllocKind allocKindForTenure() const;
+
+ private:
+  GCPtr<Value>* reservedSlotPtr(size_t n) {
+    return reinterpret_cast<GCPtr<Value>*>(
+        &detail::GetProxyDataLayout(this)->reservedSlots->slots[n]);
+  }
+
+  GCPtr<Value>* slotOfPrivate() {
+    return reinterpret_cast<GCPtr<Value>*>(
+        &detail::GetProxyDataLayout(this)->values()->privateSlot);
+  }
+
+  GCPtr<Value>* slotOfExpando() {
+    return reinterpret_cast<GCPtr<Value>*>(
+        &detail::GetProxyDataLayout(this)->values()->expandoSlot);
+  }
+
+  void setPrivate(const Value& priv);
+
+  static bool isValidProxyClass(const JSClass* clasp) {
+    // Since we can take classes from the outside, make sure that they
+    // are "sane". They have to quack enough like proxies for us to belive
+    // they should be treated as such.
+
+    // Proxy classes are not allowed to have call or construct hooks directly.
+    // Their callability is instead decided by handler()->isCallable().
+    return clasp->isProxyObject() && clasp->isTrace(ProxyObject::trace) &&
+           !clasp->getCall() && !clasp->getConstruct();
+  }
+
+ public:
+  static unsigned grayLinkReservedSlot(JSObject* obj);
+
+  void renew(const BaseProxyHandler* handler, const Value& priv);
+
+  static void trace(JSTracer* trc, JSObject* obj);
+
+  static void traceEdgeToTarget(JSTracer* trc, ProxyObject* obj);
+
+  void nurseryProxyTenured(ProxyObject* old);
+
+  void nuke();
+};
+
+bool IsDerivedProxyObject(const JSObject* obj,
+                          const js::BaseProxyHandler* handler);
+
+}  // namespace js
+
+template <>
+inline bool JSObject::is<js::ProxyObject>() const {
+  // Note: this method is implemented in terms of the IsProxy() friend API
+  // functions to ensure the implementations are tied together.
+  // Note 2: this specialization isn't used for subclasses of ProxyObject
+  // which must supply their own implementation.
+  return js::IsProxy(this);
+}
+
+inline bool js::IsDerivedProxyObject(const JSObject* obj,
+                                     const js::BaseProxyHandler* handler) {
+  return obj->is<js::ProxyObject>() &&
+         obj->as<js::ProxyObject>().handler() == handler;
+}
+
+#endif /* vm_ProxyObject_h */