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diff --git a/security/manager/ssl/CryptoTask.h b/security/manager/ssl/CryptoTask.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=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 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