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https://github.com/transmission/transmission
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2b917de65b
This refactoring is driven by the need to be able to do true queued RPC calls (where each successive call uses the result of the previous). Currently, such queueing of requests is done by assigning them special "magic" tag numbers, which are then intercepted in one big switch() statement and acted upon. This (aside from making code greatly unclear) effectively makes each such queue a singleton, because state passing is restricted to global variables. We refactor RpcClient to assign an unique tag to each remote call, and then abstract all the call<->response matching with Qt's future/promise mechanism. Finally, we introduce a "RPC request queue" class (RpcQueue) which is built on top of QFutureWatcher and C++11's <functional> library. This class maintains a queue of functions, where each function receives an RPC response, does necessary processing, performs another call and finally returns its future.
88 lines
1.9 KiB
C++
88 lines
1.9 KiB
C++
/*
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* This file Copyright (C) 2016 Mnemosyne LLC
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*
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* It may be used under the GNU GPL versions 2 or 3
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* or any future license endorsed by Mnemosyne LLC.
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*
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* $Id$
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*/
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#include <cassert>
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#include "RpcQueue.h"
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RpcQueue::RpcQueue (QObject * parent):
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QObject (parent),
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myTolerateErrors (false)
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{
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connect (&myFutureWatcher, SIGNAL (finished ()), SLOT (stepFinished ()));
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}
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RpcResponseFuture
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RpcQueue::future ()
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{
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return myPromise.future ();
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}
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void
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RpcQueue::stepFinished ()
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{
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RpcResponse result;
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if (myFutureWatcher.future ().isResultReadyAt (0))
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{
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result = myFutureWatcher.result ();
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RpcResponseFuture future = myFutureWatcher.future ();
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// we can't handle network errors, abort queue and pass the error upwards
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if (result.networkError != QNetworkReply::NoError)
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{
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assert (!result.success);
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myPromise.reportFinished (&result);
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deleteLater ();
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return;
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}
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// call user-handler for ordinary errors
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if (!result.success && myNextErrorHandler)
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{
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myNextErrorHandler (future);
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}
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// run next request, if we have one to run and there was no error (or if we tolerate errors)
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if ((result.success || myTolerateErrors) && !myQueue.isEmpty ())
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{
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runNext (future);
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return;
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}
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}
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else
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{
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assert (!myNextErrorHandler);
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assert (myQueue.isEmpty ());
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// one way or another, the last step returned nothing.
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// assume it is OK and ensure that we're not going to give an empty response object to any of the next steps.
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result.success = true;
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}
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myPromise.reportFinished (&result);
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deleteLater ();
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}
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void
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RpcQueue::runNext (const RpcResponseFuture& response)
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{
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assert (!myQueue.isEmpty ());
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auto next = myQueue.dequeue ();
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myNextErrorHandler = next.second;
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myFutureWatcher.setFuture ((next.first) (response));
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}
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void
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RpcQueue::run ()
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{
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runNext (RpcResponseFuture ());
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}
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