collectionCache.h

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//
// Copyright 2018 Pixar
//
// Licensed under the Apache License, Version 2.0 (the "Apache License")
// with the following modification; you may not use this file except in
// compliance with the Apache License and the following modification to it:
// Section 6. Trademarks. is deleted and replaced with:
//
// 6. Trademarks. This License does not grant permission to use the trade
//    names, trademarks, service marks, or product names of the Licensor
//    and its affiliates, except as required to comply with Section 4(c) of
//    the License and to reproduce the content of the NOTICE file.
//
// You may obtain a copy of the Apache License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the Apache License with the above modification is
// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the Apache License for the specific
// language governing permissions and limitations under the Apache License.
//
#ifndef PXR_USD_IMAGING_USD_IMAGING_COLLECTION_CACHE_H
#define PXR_USD_IMAGING_USD_IMAGING_COLLECTION_CACHE_H


#include "pxr/pxr.h"
#include "pxr/usdImaging/usdImaging/api.h"
#include "pxr/usd/usd/collectionAPI.h"

#include <boost/noncopyable.hpp>
#include <tbb/concurrent_unordered_map.h>
#include <tbb/concurrent_queue.h>
#include <mutex>
#include <unordered_map>

PXR_NAMESPACE_OPEN_SCOPE

class UsdImaging_CollectionCache : boost::noncopyable {
public:
    typedef UsdCollectionAPI::MembershipQuery Query;

    bool
    UpdateCollection(UsdCollectionAPI const& collection);
 
    size_t
    RemoveCollection(UsdStageWeakPtr const& stage, SdfPath const& path);

    TfToken
    GetIdForCollection(UsdCollectionAPI const& collection);

    // the given path.
    VtArray<TfToken>
    ComputeCollectionsContainingPath(SdfPath const& path) const;

    SdfPathSet const&
    GetDirtyPaths() const;

    void
    ClearDirtyPaths();

private:
    // The cache boils down to tracking the correspondence of
    // collection paths, their computed queries, and the id
    // assigned to each unique query:
    //
    // CollectionPath <=> MembershipQuery <=> AssignedId
    //
    // In this scheme, the assigned id provides a compact but
    // potentially human-meaningful reference to the query,
    // which we can pass to the renderer. 
    //
    std::unordered_map<Query, TfToken, Query::Hash> _idForQuery;
    std::unordered_map<TfToken, Query, TfToken::HashFunctor> _queryForId;
    std::unordered_map<SdfPath, TfToken, SdfPath::Hash> _idForPath;
    std::unordered_map<Query, SdfPathSet, Query::Hash> _pathsForQuery;

    void
    _MarkCollectionContentDirty(
        UsdStageWeakPtr const& stage, 
        UsdCollectionAPI::MembershipQuery const& query);

    SdfPathSet _dirtyPaths;

    std::mutex _mutex;
};


PXR_NAMESPACE_CLOSE_SCOPE

#endif // PXR_USD_IMAGING_USD_IMAGING_COLLECTION_CACHE_H