DDC: Extracted FHttpCacheStoreRequestQueue for reuse by Zen

#rb Zousar.Shaker
#rnx

[CL 33843384 by devin doucette in ue5-main branch]

Engine/Source/Developer/DerivedDataCache/Private/DerivedDataHttpRequestQueue.cpp

@@ -0,0 +1,132 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include "DerivedDataHttpRequestQueue.h"
+
+#include "Async/ManualResetEvent.h"
+#include "DerivedDataRequest.h"
+#include "DerivedDataRequestOwner.h"
+#include "Misc/ScopeExit.h"
+
+namespace UE::DerivedData
+{
+
+class FHttpRequestQueue::FQueueRequest : FRequestBase
+{
+public:
+	FQueueRequest(IRequestOwner& InOwner, FOnRequest&& InOnRequest)
+		: Owner(InOwner)
+		, OnRequest(MoveTemp(InOnRequest))
+	{
+		AddRef(); // Release() is called by ClaimRequest()
+		Owner.Begin(this);
+	}
+
+	bool TryClaimRequest(THttpUniquePtr<IHttpRequest>&& Request)
+	{
+		ON_SCOPE_EXIT{ Release(); };
+		return TryComplete(MoveTemp(Request));
+	}
+
+private:
+	bool TryComplete(THttpUniquePtr<IHttpRequest>&& Request)
+	{
+		if (bComplete.exchange(true))
+		{
+			return false;
+		}
+		Owner.End(this, [this](THttpUniquePtr<IHttpRequest>&& Request)
+		{
+			OnRequest(MoveTemp(Request));
+			OnComplete.Notify();
+		}, MoveTemp(Request));
+		return true;
+	}
+
+	void SetPriority(EPriority Priority) final
+	{
+	}
+
+	void Cancel() final
+	{
+		if (!TryComplete({}))
+		{
+			TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_CancelOperation);
+			OnComplete.Wait();
+		}
+	}
+
+	void Wait() final
+	{
+		TRACE_CPUPROFILER_EVENT_SCOPE(HttpDDC_WaitOperation);
+		OnComplete.Wait();
+	}
+
+	IRequestOwner& Owner;
+	FOnRequest OnRequest;
+	FManualResetEvent OnComplete;
+	std::atomic<bool> bComplete = false;
+};
+
+void FHttpRequestQueue::Initialize(IHttpConnectionPool& ConnectionPool, const FHttpClientParams& ClientParams)
+{
+	FHttpClientParams QueueParams = ClientParams;
+	QueueParams.OnDestroyRequest = [this, OnDestroyRequest = MoveTemp(QueueParams.OnDestroyRequest)]
+		{
+			if (OnDestroyRequest)
+			{
+				OnDestroyRequest();
+			}
+			if (!Queue.IsEmpty())
+			{
+				if (THttpUniquePtr<IHttpRequest> Request = Client->TryCreateRequest({}))
+				{
+					TryGiveRequestToQueue(MoveTemp(Request));
+				}
+			}
+		};
+	Client = ConnectionPool.CreateClient(QueueParams);
+}
+
+void FHttpRequestQueue::CreateRequestAsync(IRequestOwner& Owner, const FHttpRequestParams& Params, FOnRequest&& OnRequest)
+{
+	if (Params.bIgnoreMaxRequests)
+	{
+		THttpUniquePtr<IHttpRequest> Request = Client->TryCreateRequest(Params);
+		checkf(Request, TEXT("IHttpClient::TryCreateRequest returned null in spite of bIgnoreMaxRequests."));
+		OnRequest(MoveTemp(Request));
+		return;
+	}
+
+	while (THttpUniquePtr<IHttpRequest> Request = Client->TryCreateRequest(Params))
+	{
+		if (!TryGiveRequestToQueue(MoveTemp(Request)))
+		{
+			OnRequest(MoveTemp(Request));
+			return;
+		}
+	}
+
+	Queue.Push(new FQueueRequest(Owner, MoveTemp(OnRequest)));
+
+	while (THttpUniquePtr<IHttpRequest> Request = Client->TryCreateRequest(Params))
+	{
+		if (!TryGiveRequestToQueue(MoveTemp(Request)))
+		{
+			return;
+		}
+	}
+}
+
+bool FHttpRequestQueue::TryGiveRequestToQueue(THttpUniquePtr<IHttpRequest>&& Request)
+{
+	while (FQueueRequest* Waiter = Queue.Pop())
+	{
+		if (Waiter->TryClaimRequest(MoveTemp(Request)))
+		{
+			return true;
+		}
+	}
+	return false;
+}
+
+} // UE::DerivedData