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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__CryptoTask_h
#define mozilla__CryptoTask_h
#include "mozilla/Attributes.h"
#include "nsThreadUtils.h"
#include "nsNSSShutDown.h"
namespace mozilla {
/**
* Frequently we need to run a task on a background thread without blocking
* the main thread, and then call a callback on the main thread with the
* result. This class provides the framework for that. Subclasses must:
*
* (1) Override CalculateResult for the off-the-main-thread computation.
* NSS functionality may only be accessed within CalculateResult.
* (2) Override ReleaseNSSResources to release references to all NSS
* resources (that do implement nsNSSShutDownObject themselves).
* (3) Override CallCallback() for the on-the-main-thread call of the
* callback.
*
* CalculateResult, ReleaseNSSResources, and CallCallback are called in order,
* except CalculateResult might be skipped if NSS is shut down before it can
* be called; in that case ReleaseNSSResources will be called and then
* CallCallback will be called with an error code.
*
* That sequence of events is what happens if you call Dispatch. If for
* some reason, you decide not to run the task (e.g., due to an error in the
* constructor), you may call Skip, in which case the task is cleaned up and
* not run. In that case, only ReleaseNSSResources is called. (So a
* subclass must be prepared for ReleaseNSSResources to be run without
* CalculateResult having been called first.)
*
* Once a CryptoTask is created, the calling code must call either
* Dispatch or Skip.
*
*/
class CryptoTask : public Runnable,
public nsNSSShutDownObject
{
public:
template <size_t LEN>
nsresult Dispatch(const char (&taskThreadName)[LEN])
{
static_assert(LEN <= 15,
"Thread name must be no more than 15 characters");
return Dispatch(nsDependentCString(taskThreadName, LEN - 1));
}
nsresult Dispatch(const nsACString& taskThreadName);
void Skip()
{
virtualDestroyNSSReference();
}
protected:
CryptoTask()
: mRv(NS_ERROR_NOT_INITIALIZED),
mReleasedNSSResources(false)
{
}
virtual ~CryptoTask();
/**
* Called on a background thread (never the main thread). If CalculateResult
* is called, then its result will be passed to CallCallback on the main
* thread.
*/
virtual nsresult CalculateResult() = 0;
/**
* Called on the main thread during NSS shutdown or just before CallCallback
* has been called. All NSS resources must be released. Usually, this just
* means assigning nullptr to the ScopedNSSType-based memory variables.
*/
virtual void ReleaseNSSResources() = 0;
/**
* Called on the main thread with the result from CalculateResult() or
* with an error code if NSS was shut down before CalculateResult could
* be called.
*/
virtual void CallCallback(nsresult rv) = 0;
private:
NS_IMETHOD Run() override final;
virtual void virtualDestroyNSSReference() override final;
nsresult mRv;
bool mReleasedNSSResources;
nsCOMPtr<nsIThread> mThread;
};
} // namespace mozilla
#endif // mozilla__CryptoTask_h
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