1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/js/xpconnect/src/nsCxPusher.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,183 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set ts=8 sts=2 et sw=2 tw=80: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef nsCxPusher_h
1.11 +#define nsCxPusher_h
1.12 +
1.13 +#include "jsapi.h"
1.14 +#include "mozilla/Maybe.h"
1.15 +#include "nsCOMPtr.h"
1.16 +
1.17 +namespace mozilla {
1.18 +namespace dom {
1.19 +class EventTarget;
1.20 +}
1.21 +}
1.22 +
1.23 +class nsIScriptContext;
1.24 +
1.25 +namespace mozilla {
1.26 +
1.27 +/**
1.28 + * Fundamental cx pushing class. All other cx pushing classes are implemented
1.29 + * in terms of this class.
1.30 + */
1.31 +class MOZ_STACK_CLASS AutoCxPusher
1.32 +{
1.33 +public:
1.34 + AutoCxPusher(JSContext *aCx, bool aAllowNull = false);
1.35 + // XPCShell uses an nsCxPusher, which contains an AutoCxPusher.
1.36 + ~AutoCxPusher();
1.37 +
1.38 + nsIScriptContext* GetScriptContext() { return mScx; }
1.39 +
1.40 + // Returns true if this AutoCxPusher performed the push that is currently at
1.41 + // the top of the cx stack.
1.42 + bool IsStackTop();
1.43 +
1.44 +private:
1.45 + mozilla::Maybe<JSAutoRequest> mAutoRequest;
1.46 + mozilla::Maybe<JSAutoCompartment> mAutoCompartment;
1.47 + nsCOMPtr<nsIScriptContext> mScx;
1.48 + uint32_t mStackDepthAfterPush;
1.49 +#ifdef DEBUG
1.50 + JSContext* mPushedContext;
1.51 + unsigned mCompartmentDepthOnEntry;
1.52 +#endif
1.53 +};
1.54 +
1.55 +} /* namespace mozilla */
1.56 +
1.57 +/**
1.58 + * Legacy cx pushing class.
1.59 + *
1.60 + * This class provides a rather wonky interface, with the following quirks:
1.61 + * * The constructor is a no-op, and callers must explicitly call one of
1.62 + * the Push() methods.
1.63 + * * Null must be pushed with PushNull().
1.64 + * * The cx pusher can be reused multiple times with RePush().
1.65 + *
1.66 + * This class implements this interface in terms of the much simpler
1.67 + * AutoCxPusher class below.
1.68 + */
1.69 +class MOZ_STACK_CLASS nsCxPusher
1.70 +{
1.71 +public:
1.72 + // Returns false if something erroneous happened.
1.73 + bool Push(mozilla::dom::EventTarget *aCurrentTarget);
1.74 + // If nothing has been pushed to stack, this works like Push.
1.75 + // Otherwise if context will change, Pop and Push will be called.
1.76 + bool RePush(mozilla::dom::EventTarget *aCurrentTarget);
1.77 + // If a null JSContext is passed to Push(), that will cause no
1.78 + // push to happen and false to be returned.
1.79 + void Push(JSContext *cx);
1.80 + // Explicitly push a null JSContext on the the stack
1.81 + void PushNull();
1.82 +
1.83 + // Pop() will be a no-op if Push() or PushNull() fail
1.84 + void Pop();
1.85 +
1.86 + nsIScriptContext* GetCurrentScriptContext() {
1.87 + return mPusher.empty() ? nullptr : mPusher.ref().GetScriptContext();
1.88 + }
1.89 +
1.90 +private:
1.91 + mozilla::Maybe<mozilla::AutoCxPusher> mPusher;
1.92 +};
1.93 +
1.94 +namespace mozilla {
1.95 +
1.96 +/**
1.97 + * Use AutoJSContext when you need a JS context on the stack but don't have one
1.98 + * passed as a parameter. AutoJSContext will take care of finding the most
1.99 + * appropriate JS context and release it when leaving the stack.
1.100 + */
1.101 +class MOZ_STACK_CLASS AutoJSContext {
1.102 +public:
1.103 + AutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
1.104 + operator JSContext*() const;
1.105 +
1.106 +protected:
1.107 + AutoJSContext(bool aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
1.108 +
1.109 + // We need this Init() method because we can't use delegating constructor for
1.110 + // the moment. It is a C++11 feature and we do not require C++11 to be
1.111 + // supported to be able to compile Gecko.
1.112 + void Init(bool aSafe MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
1.113 +
1.114 + JSContext* mCx;
1.115 + Maybe<AutoCxPusher> mPusher;
1.116 + MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
1.117 +};
1.118 +
1.119 +/**
1.120 + * Use ThreadsafeAutoJSContext when you want an AutoJSContext but might be
1.121 + * running on a worker thread.
1.122 + */
1.123 +class MOZ_STACK_CLASS ThreadsafeAutoJSContext {
1.124 +public:
1.125 + ThreadsafeAutoJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
1.126 + operator JSContext*() const;
1.127 +
1.128 +private:
1.129 + JSContext* mCx; // Used on workers. Null means mainthread.
1.130 + Maybe<JSAutoRequest> mRequest; // Used on workers.
1.131 + Maybe<AutoJSContext> mAutoJSContext; // Used on main thread.
1.132 + MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
1.133 +};
1.134 +
1.135 +/**
1.136 + * AutoSafeJSContext is similar to AutoJSContext but will only return the safe
1.137 + * JS context. That means it will never call ::GetCurrentJSContext().
1.138 + */
1.139 +class MOZ_STACK_CLASS AutoSafeJSContext : public AutoJSContext {
1.140 +public:
1.141 + AutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
1.142 +private:
1.143 + JSAutoCompartment mAc;
1.144 +};
1.145 +
1.146 +/**
1.147 + * Like AutoSafeJSContext but can be used safely on worker threads.
1.148 + */
1.149 +class MOZ_STACK_CLASS ThreadsafeAutoSafeJSContext {
1.150 +public:
1.151 + ThreadsafeAutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
1.152 + operator JSContext*() const;
1.153 +
1.154 +private:
1.155 + JSContext* mCx; // Used on workers. Null means mainthread.
1.156 + Maybe<JSAutoRequest> mRequest; // Used on workers.
1.157 + Maybe<AutoSafeJSContext> mAutoSafeJSContext; // Used on main thread.
1.158 + MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
1.159 +};
1.160 +
1.161 +/**
1.162 + * Use AutoPushJSContext when you want to use a specific JSContext that may or
1.163 + * may not be already on the stack. This differs from nsCxPusher in that it only
1.164 + * pushes in the case that the given cx is not the active cx on the JSContext
1.165 + * stack, which avoids an expensive JS_SaveFrameChain in the common case.
1.166 + *
1.167 + * Most consumers of this should probably just use AutoJSContext. But the goal
1.168 + * here is to preserve the existing behavior while ensure proper cx-stack
1.169 + * semantics in edge cases where the context being used doesn't match the active
1.170 + * context.
1.171 + *
1.172 + * NB: This will not push a null cx even if aCx is null. Make sure you know what
1.173 + * you're doing.
1.174 + */
1.175 +class MOZ_STACK_CLASS AutoPushJSContext {
1.176 + Maybe<AutoCxPusher> mPusher;
1.177 + JSContext* mCx;
1.178 +
1.179 +public:
1.180 + AutoPushJSContext(JSContext* aCx);
1.181 + operator JSContext*() { return mCx; }
1.182 +};
1.183 +
1.184 +} // namespace mozilla
1.185 +
1.186 +#endif /* nsCxPusher_h */
