dom/bindings/DOMJSProxyHandler.h
author Bob Owen <bobowencode@gmail.com>
Tue, 05 Jan 2016 10:08:57 +0000
changeset 278418 d765b7934fae4c1389ec4d860988a21437aed075
parent 242147 bd079aadd3feeee3f9b9f73c5e0bc4bd6a870722
child 282071 114ec4ff6d65378cfe3d86f1af3e5c7aae855a09
permissions -rw-r--r--
Bug 1156742 Part 7: Refactor nsDeviceContext.cpp to use printing surface for size and nsIDeviceContextSpec for DPI and scale. r=roc These changes are to make using an off screen surface behind our DrawTarget in the child easier. It still creates the real printing surface for some of the calculations, removing this will be required for future tightening of the sandbox.

/* -*- 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"

#define DOM_PROXY_OBJECT_SLOT js::PROXY_PRIVATE_SLOT

namespace mozilla {
namespace dom {

enum {
  /**
   * DOM proxies have an extra slot for the expando object at index
   * JSPROXYSLOT_EXPANDO.
   *
   * 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 JSPROXYSLOT_EXPANDO 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.
   *
   * 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.)
   */
  JSPROXYSLOT_EXPANDO = 0
};

template<typename T> struct Prefable;

class BaseDOMProxyHandler : public js::BaseProxyHandler
{
public:
  explicit MOZ_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<JSPropertyDescriptor> desc) const override;
  virtual bool ownPropertyKeys(JSContext* cx, JS::Handle<JSObject*> proxy,
                               JS::AutoIdVector &props) const override;

  virtual bool enumerate(JSContext *cx, JS::Handle<JSObject*> proxy,
                         JS::MutableHandle<JSObject*> objp) 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;

  bool watch(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,
             JS::Handle<JSObject*> callable) const override;
  bool unwatch(JSContext* cx, JS::Handle<JSObject*> proxy,
               JS::Handle<jsid> id) 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<JSPropertyDescriptor> desc) const = 0;
};

class DOMProxyHandler : public BaseDOMProxyHandler
{
public:
  MOZ_CONSTEXPR DOMProxyHandler()
    : BaseDOMProxyHandler(&family)
  {}

  bool defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,
                      JS::Handle<JSPropertyDescriptor> 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<JSPropertyDescriptor> 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 has(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,
           bool* bp) 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;

  static JSObject* GetExpandoObject(JSObject* obj);

  /* GetAndClearExpandoObject does not DROP or clear the preserving wrapper flag. */
  static JSObject* GetAndClearExpandoObject(JSObject* obj);
  static JSObject* EnsureExpandoObject(JSContext* cx,
                                       JS::Handle<JSObject*> obj);

  static const char family;
};

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;

int32_t IdToInt32(JSContext* cx, JS::Handle<jsid> id);

// XXXbz this should really return uint32_t, with the maximum value
// meaning "not an index"...
inline int32_t
GetArrayIndexFromId(JSContext* cx, JS::Handle<jsid> id)
{
  if (MOZ_LIKELY(JSID_IS_INT(id))) {
    return JSID_TO_INT(id);
  }
  if (MOZ_LIKELY(id == s_length_id)) {
    return -1;
  }
  if (MOZ_LIKELY(JSID_IS_ATOM(id))) {
    JSAtom* atom = JSID_TO_ATOM(id);
    char16_t s;
    {
      JS::AutoCheckCannotGC nogc;
      if (js::AtomHasLatin1Chars(atom)) {
        s = *js::GetLatin1AtomChars(nogc, atom);
      } else {
        s = *js::GetTwoByteAtomChars(nogc, atom);
      }
    }
    if (MOZ_LIKELY((unsigned)s >= 'a' && (unsigned)s <= 'z'))
      return -1;

    uint32_t i;
    JSLinearString* str = js::AtomToLinearString(JSID_TO_ATOM(id));
    return js::StringIsArrayIndex(str, &i) ? i : -1;
  }
  return IdToInt32(cx, id);
}

inline bool
IsArrayIndex(int32_t index)
{
  return index >= 0;
}

inline void
FillPropertyDescriptor(JS::MutableHandle<JSPropertyDescriptor> 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<JSPropertyDescriptor> desc,
                       JSObject* obj, JS::Value v,
                       bool readonly, bool enumerable = true)
{
  desc.value().set(v);
  FillPropertyDescriptor(desc, obj, readonly, enumerable);
}

inline void
FillPropertyDescriptor(JS::MutableHandle<JSPropertyDescriptor> desc,
                       JSObject* obj, unsigned attributes, 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 */