Implementation of RuntimeAssetCache

#codereview Robert.Manuszewski

[CL 2582347 by Mikolaj Sieluzycki in Main branch]

Engine/Source/Runtime/RuntimeAssetCache/Public/RuntimeAssetCacheInterface.h

@@ -0,0 +1,79 @@
+// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+/** Forward declarations */
+class FRuntimeAssetCacheBuilderInterface;
+
+/**
+* Interface for the Runtime Asset Cache. Cache is split into buckets to cache various assets separately.
+* Bucket names and maximum sizes are configure via Engine.ini config file using the following syntax
+* [RuntimeAssetCache]
+* +BucketConfigs=(Name="<Plugin name>", Size=<Maximum bucket size in bytes>)
+* This API is fully thread safe.
+**/
+class FRuntimeAssetCacheInterface
+{
+public:
+	/**
+	* Synchronously gets value from cache. If value is not found, builds entry using CacheBuilder and updates cache.
+	* @param CacheBuilder Builder to produce cache key and in the event of a miss.
+	* @param OutData Reference to serialized data.
+	* @return true if the data was retrieved from the cache or the deriver built the data successfully. false can only occur if the plugin returns false.
+	**/
+	virtual bool GetSynchronous(FRuntimeAssetCacheBuilderInterface* CacheBuilder, TArray<uint8>& OutData) = 0;
+
+	/**
+	* Asynchronously checks the cache. If value is not found, builds entry using CacheBuilder and updates cache.
+	* @param CacheBuilder Builder to produce cache key and in the event of a miss, return the data.
+	* @return Handle to worker.
+	**/
+	virtual uint32 GetAsynchronous(FRuntimeAssetCacheBuilderInterface* CacheBuilder) = 0;
+
+	/**
+	* Gets cache size.
+	* @param Bucket to check.
+	* @return Maximum allowed bucket size.
+	**/
+	virtual int32 GetCacheSize(FName Bucket) const = 0;
+
+	/**
+	* Removes all cache entries.
+	* @return true if cache was successfully cleaned.
+	*/
+	virtual bool ClearCache() = 0;
+
+	/**
+	* Removes all cache from given bucket.
+	* @param Bucket Bucket to clean.
+	* @return true if cache was successfully cleaned.
+	*/
+	virtual bool ClearCache(FName Bucket) = 0;
+
+	/**
+	* Waits until worker finishes execution.
+	* @param Handle Worker handle to wait for.
+	*/
+	virtual void WaitAsynchronousCompletion(uint32 Handle) = 0;
+
+	/**
+	* Gets asynchronous query results.
+	* @param Handle Worker handle to check.
+	* @param OutData Reference to serialized cache entry.
+	* @return True if successfully retrieved data, false otherwise.
+	*/
+	virtual bool GetAsynchronousResults(uint32 Handle, TArray<uint8>& OutData) = 0;
+
+	/**
+	* Checks if worker finished execution.
+	* @param Handle Worker handle to check.
+	* @return True if execution finished, false otherwise.
+	*/
+	virtual bool PollAsynchronousCompletion(uint32 Handle) = 0;
+
+	/**
+	 * Adds a number from the thread safe counter which tracks outstanding async requests. This is used to ensure everything is complete prior to shutdown.
+	 * @param Value to add to counter. Can be negative.
+	 */
+	virtual void AddToAsyncCompletionCounter(int32 Addend) = 0;
+};