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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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_PreallocatedProcessManager_h
#define mozilla_PreallocatedProcessManager_h
#include "base/basictypes.h"
#include "nsCOMPtr.h"
#include "nsIObserver.h"
namespace mozilla {
namespace dom {
class ContentParent;
} // namespace dom
/**
* This class manages a ContentParent that it starts up ahead of any particular
* need. You can then call Take() to get this process and use it. Since we
* already started it up, it should be ready for use faster than if you'd
* created the process when you needed it.
*
* This class watches the dom.ipc.processPrelaunch.enabled pref. If it changes
* from false to true, it preallocates a process. If it changes from true to
* false, it kills the preallocated process, if any.
*
* We don't expect this pref to flip between true and false in production, but
* flipping the pref is important for tests.
*
* The static methods here are implemented by forwarding calls on to a
* PreallocatedProcessManagerImpl singleton class, so if you add a new static
* method here, you'll need to write a corresponding public method on the
* singleton.
*/
class PreallocatedProcessManager final
{
typedef mozilla::dom::ContentParent ContentParent;
public:
/**
* Create a process after a delay. We wait for a period of time (specified
* by the dom.ipc.processPrelaunch.delayMs pref), then wait for this process
* to go idle, then allocate the new process.
*
* If the dom.ipc.processPrelaunch.enabled pref is false, or if we already
* have a preallocated process, this function does nothing.
*/
static void AllocateAfterDelay();
/**
* Create a process once this process goes idle.
*
* If the dom.ipc.processPrelaunch.enabled pref is false, or if we already
* have a preallocated process, this function does nothing.
*/
static void AllocateOnIdle();
/**
* Create a process right now.
*
* If the dom.ipc.processPrelaunch.enabled pref is false, or if we already
* have a preallocated process, this function does nothing.
*/
static void AllocateNow();
/**
* Take the preallocated process, if we have one. If we don't have one, this
* returns null.
*
* If you call Take() twice in a row, the second call is guaranteed to return
* null.
*
* After you Take() the preallocated process, you need to call one of the
* Allocate* functions (or change the dom.ipc.processPrelaunch pref from
* false to true) before we'll create a new process.
*/
static already_AddRefed<ContentParent> Take();
private:
PreallocatedProcessManager();
DISALLOW_EVIL_CONSTRUCTORS(PreallocatedProcessManager);
};
} // namespace mozilla
#endif // defined mozilla_PreallocatedProcessManager_h
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