The Tor Browser: comparison js/xpconnect/src/nsCxPusher.h

--1:000000000000
+:c76a40a6b4ae
+/* -*- 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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comparison: js/xpconnect/src/nsCxPusher.h

js/xpconnect/src/nsCxPusher.h