The Tor Browser: js/xpconnect/src/nsCxPusher.h@a63d609f5ebe (annotated)

js/xpconnect/src/nsCxPusher.h@a63d609f5ebe (annotated)

js/xpconnect/src/nsCxPusher.h

Thu, 15 Jan 2015 15:55:04 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:55:04 +0100
branch: TOR_BUG_9701
changeset 9: a63d609f5ebe
permissions: -rw-r--r--

Back out 97036ab72558 which inappropriately compared turds to third parties.

 /* -*- 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 nsCxPusher_h
 #define nsCxPusher_h
 #include "jsapi.h"
 #include "mozilla/Maybe.h"
 #include "nsCOMPtr.h"
 namespace mozilla {
 namespace dom {
 class EventTarget;
 }
 }
 class nsIScriptContext;
 namespace mozilla {
 /**
  * Fundamental cx pushing class. All other cx pushing classes are implemented
  * in terms of this class.
  */
 class MOZ_STACK_CLASS AutoCxPusher
 {
 public:
   AutoCxPusher(JSContext *aCx, bool aAllowNull = false);
   // XPCShell uses an nsCxPusher, which contains an AutoCxPusher.
   ~AutoCxPusher();
   nsIScriptContext* GetScriptContext() { return mScx; }
   // Returns true if this AutoCxPusher performed the push that is currently at
   // the top of the cx stack.
   bool IsStackTop();
 private:
   mozilla::Maybe<JSAutoRequest> mAutoRequest;
   mozilla::Maybe<JSAutoCompartment> mAutoCompartment;
   nsCOMPtr<nsIScriptContext> mScx;
   uint32_t mStackDepthAfterPush;
 #ifdef DEBUG
   JSContext* mPushedContext;
   unsigned mCompartmentDepthOnEntry;
 #endif
 };
 } /* namespace mozilla */
 /**
  * Legacy cx pushing class.
  *
  * This class provides a rather wonky interface, with the following quirks:
  *   * The constructor is a no-op, and callers must explicitly call one of
  *     the Push() methods.
  *   * Null must be pushed with PushNull().
  *   * The cx pusher can be reused multiple times with RePush().
  *
  * This class implements this interface in terms of the much simpler
  * AutoCxPusher class below.
  */
 class MOZ_STACK_CLASS nsCxPusher
 {
 public:
   // Returns false if something erroneous happened.
   bool Push(mozilla::dom::EventTarget *aCurrentTarget);
   // If nothing has been pushed to stack, this works like Push.
   // Otherwise if context will change, Pop and Push will be called.
   bool RePush(mozilla::dom::EventTarget *aCurrentTarget);
   // If a null JSContext is passed to Push(), that will cause no
   // push to happen and false to be returned.
   void Push(JSContext *cx);
   // Explicitly push a null JSContext on the the stack
   void PushNull();
   // Pop() will be a no-op if Push() or PushNull() fail
   void Pop();
   nsIScriptContext* GetCurrentScriptContext() {
     return mPusher.empty() ? nullptr : mPusher.ref().GetScriptContext();
   }
 private:
   mozilla::Maybe<mozilla::AutoCxPusher> mPusher;
 };
 namespace mozilla {
 /**
  * Use AutoJSContext when you need a JS context on the stack but don't have one
  * passed as a parameter. AutoJSContext will take care of finding the most
  * appropriate JS context and release it when leaving the stack.
  */
 class MOZ_STACK_CLASS AutoJSContext {
 public:
   AutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
   operator JSContext*() const;
 protected:
   AutoJSContext(bool aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
   // We need this Init() method because we can't use delegating constructor for
   // the moment. It is a C++11 feature and we do not require C++11 to be
   // supported to be able to compile Gecko.
   void Init(bool aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
   JSContext* mCx;
   Maybe<AutoCxPusher> mPusher;
   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
 };
 /**
  * Use ThreadsafeAutoJSContext when you want an AutoJSContext but might be
  * running on a worker thread.
  */
 class MOZ_STACK_CLASS ThreadsafeAutoJSContext {
 public:
   ThreadsafeAutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
   operator JSContext*() const;
 private:
   JSContext* mCx; // Used on workers.  Null means mainthread.
   Maybe<JSAutoRequest> mRequest; // Used on workers.
   Maybe<AutoJSContext> mAutoJSContext; // Used on main thread.
   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
 };
 /**
  * AutoSafeJSContext is similar to AutoJSContext but will only return the safe
  * JS context. That means it will never call ::GetCurrentJSContext().
  */
 class MOZ_STACK_CLASS AutoSafeJSContext : public AutoJSContext {
 public:
   AutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
 private:
   JSAutoCompartment mAc;
 };
 /**
  * Like AutoSafeJSContext but can be used safely on worker threads.
  */
 class MOZ_STACK_CLASS ThreadsafeAutoSafeJSContext {
 public:
   ThreadsafeAutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
   operator JSContext*() const;
 private:
   JSContext* mCx; // Used on workers.  Null means mainthread.
   Maybe<JSAutoRequest> mRequest; // Used on workers.
   Maybe<AutoSafeJSContext> mAutoSafeJSContext; // Used on main thread.
   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
 };
 /**
  * Use AutoPushJSContext when you want to use a specific JSContext that may or
  * may not be already on the stack. This differs from nsCxPusher in that it only
  * pushes in the case that the given cx is not the active cx on the JSContext
  * stack, which avoids an expensive JS_SaveFrameChain in the common case.
  *
  * Most consumers of this should probably just use AutoJSContext. But the goal
  * here is to preserve the existing behavior while ensure proper cx-stack
  * semantics in edge cases where the context being used doesn't match the active
  * context.
  *
  * NB: This will not push a null cx even if aCx is null. Make sure you know what
  * you're doing.
  */
 class MOZ_STACK_CLASS AutoPushJSContext {
   Maybe<AutoCxPusher> mPusher;
   JSContext* mCx;
 public:
   AutoPushJSContext(JSContext* aCx);
   operator JSContext*() { return mCx; }
 };
 } // namespace mozilla
 #endif /* nsCxPusher_h */

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js/xpconnect/src/nsCxPusher.h@a63d609f5ebe (annotated)

js/xpconnect/src/nsCxPusher.h