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106 lines
3.4 KiB
C++
106 lines
3.4 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla__CryptoTask_h
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#define mozilla__CryptoTask_h
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#include "mozilla/Attributes.h"
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#include "nsThreadUtils.h"
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#include "nsNSSShutDown.h"
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namespace mozilla {
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/**
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* Frequently we need to run a task on a background thread without blocking
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* the main thread, and then call a callback on the main thread with the
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* result. This class provides the framework for that. Subclasses must:
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*
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* (1) Override CalculateResult for the off-the-main-thread computation.
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* NSS functionality may only be accessed within CalculateResult.
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* (2) Override ReleaseNSSResources to release references to all NSS
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* resources (that do implement nsNSSShutDownObject themselves).
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* (3) Override CallCallback() for the on-the-main-thread call of the
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* callback.
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*
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* CalculateResult, ReleaseNSSResources, and CallCallback are called in order,
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* except CalculateResult might be skipped if NSS is shut down before it can
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* be called; in that case ReleaseNSSResources will be called and then
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* CallCallback will be called with an error code.
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*
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* That sequence of events is what happens if you call Dispatch. If for
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* some reason, you decide not to run the task (e.g., due to an error in the
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* constructor), you may call Skip, in which case the task is cleaned up and
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* not run. In that case, only ReleaseNSSResources is called. (So a
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* subclass must be prepared for ReleaseNSSResources to be run without
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* CalculateResult having been called first.)
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*
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* Once a CryptoTask is created, the calling code must call either
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* Dispatch or Skip.
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*
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*/
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class CryptoTask : public nsRunnable,
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public nsNSSShutDownObject
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{
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public:
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template <size_t LEN>
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nsresult Dispatch(const char (&taskThreadName)[LEN])
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{
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static_assert(LEN <= 15,
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"Thread name must be no more than 15 characters");
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return Dispatch(nsDependentCString(taskThreadName, LEN - 1));
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}
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nsresult Dispatch(const nsACString& taskThreadName);
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void Skip()
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{
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virtualDestroyNSSReference();
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}
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protected:
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CryptoTask()
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: mRv(NS_ERROR_NOT_INITIALIZED),
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mReleasedNSSResources(false)
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{
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}
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virtual ~CryptoTask();
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/**
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* Called on a background thread (never the main thread). If CalculateResult
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* is called, then its result will be passed to CallCallback on the main
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* thread.
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*/
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virtual nsresult CalculateResult() = 0;
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/**
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* Called on the main thread during NSS shutdown or just before CallCallback
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* has been called. All NSS resources must be released. Usually, this just
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* means assigning nullptr to the ScopedNSSType-based memory variables.
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*/
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virtual void ReleaseNSSResources() = 0;
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/**
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* Called on the main thread with the result from CalculateResult() or
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* with an error code if NSS was shut down before CalculateResult could
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* be called.
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*/
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virtual void CallCallback(nsresult rv) = 0;
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private:
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NS_IMETHOD Run() override final;
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virtual void virtualDestroyNSSReference() override final;
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nsresult mRv;
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bool mReleasedNSSResources;
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nsCOMPtr<nsIThread> mThread;
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};
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} // namespace mozilla
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#endif // mozilla__CryptoTask_h
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