mirror of
https://github.com/ncblakely/GiantsTools
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110 lines
3.7 KiB
C++
110 lines
3.7 KiB
C++
//--------------------------------------------------------------------------------------
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// File: SharedResourcePool.h
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// Licensed under the MIT License.
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//
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// http://go.microsoft.com/fwlink/?LinkId=248929
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// http://go.microsoft.com/fwlink/?LinkID=615561
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//--------------------------------------------------------------------------------------
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#pragma once
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#include <map>
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#include <memory>
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#include "PlatformHelpers.h"
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namespace DirectX
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{
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// Pool manager ensures that only a single TData instance is created for each unique TKey.
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// This is used to avoid duplicate resource creation, so that for instance a caller can
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// create any number of SpriteBatch instances, but these can internally share shaders and
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// vertex buffer if more than one SpriteBatch uses the same underlying D3D device.
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template<typename TKey, typename TData, typename... TConstructorArgs>
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class SharedResourcePool
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{
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public:
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SharedResourcePool() noexcept(false)
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: mResourceMap(std::make_shared<ResourceMap>())
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{ }
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SharedResourcePool(SharedResourcePool const&) = delete;
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SharedResourcePool& operator= (SharedResourcePool const&) = delete;
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// Allocates or looks up the shared TData instance for the specified key.
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std::shared_ptr<TData> DemandCreate(TKey key, TConstructorArgs... args)
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{
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std::lock_guard<std::mutex> lock(mResourceMap->mutex);
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// Return an existing instance?
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auto pos = mResourceMap->find(key);
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if (pos != mResourceMap->end())
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{
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auto existingValue = pos->second.lock();
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if (existingValue)
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return existingValue;
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else
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mResourceMap->erase(pos);
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}
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// Allocate a new instance.
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auto newValue = std::make_shared<WrappedData>(key, mResourceMap, args...);
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auto entry = std::make_pair(key, newValue);
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mResourceMap->insert(entry);
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return std::move(newValue);
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}
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private:
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// Keep track of all allocated TData instances.
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struct ResourceMap : public std::map<TKey, std::weak_ptr<TData>>
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{
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std::mutex mutex;
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};
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std::shared_ptr<ResourceMap> mResourceMap;
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// Wrap TData with our own subclass, so we can hook the destructor
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// to remove instances from our pool before they are freed.
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struct WrappedData : public TData
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{
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WrappedData(TKey key, std::shared_ptr<ResourceMap> const& resourceMap, TConstructorArgs... args)
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: TData(key, args...),
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mKey(key),
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mResourceMap(resourceMap)
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{ }
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WrappedData(WrappedData&&) = default;
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WrappedData& operator= (WrappedData&&) = default;
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WrappedData(WrappedData const&) = delete;
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WrappedData& operator= (WrappedData const&) = delete;
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~WrappedData()
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{
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std::lock_guard<std::mutex> lock(mResourceMap->mutex);
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auto pos = mResourceMap->find(mKey);
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// Check for weak reference expiry before erasing, in case DemandCreate runs on
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// a different thread at the same time as a previous instance is being destroyed.
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// We mustn't erase replacement objects that have just been added!
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if (pos != mResourceMap->end() && pos->second.expired())
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{
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mResourceMap->erase(pos);
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}
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}
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TKey mKey;
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std::shared_ptr<ResourceMap> mResourceMap;
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};
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};
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}
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