expressionVariablesSource.h

//
// Copyright 2023 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_USD_PCP_EXPRESSION_VARIABLES_SOURCE_H
#define PXR_USD_PCP_EXPRESSION_VARIABLES_SOURCE_H
 
#include "pxr/pxr.h"
#include "pxr/usd/pcp/api.h"
 
#include <memory>
 
PXR_NAMESPACE_OPEN_SCOPE
 
class PcpCache;
class PcpLayerStackIdentifier;
 
class PcpExpressionVariablesSource
{
public:
    PCP_API
    PcpExpressionVariablesSource();
 
    PCP_API
    PcpExpressionVariablesSource(
        const PcpLayerStackIdentifier& layerStackIdentifier,
        const PcpLayerStackIdentifier& rootLayerStackIdentifier);
 
    PCP_API
    ~PcpExpressionVariablesSource();
 
    PCP_API
    bool operator==(const PcpExpressionVariablesSource& rhs) const;
 
    PCP_API 
    bool operator!=(const PcpExpressionVariablesSource& rhs) const;
 
    PCP_API 
    bool operator<(const PcpExpressionVariablesSource& rhs) const;
 
    PCP_API
    size_t GetHash() const;
 
    bool IsRootLayerStack() const
    {
        return !static_cast<bool>(_identifier);
    }
 
    const PcpLayerStackIdentifier* GetLayerStackIdentifier() const
    {
        return _identifier ? _identifier.get() : nullptr;
    }
 
    PCP_API
    const PcpLayerStackIdentifier& ResolveLayerStackIdentifier(
        const PcpLayerStackIdentifier& rootLayerStackIdentifier) const;
 
    PCP_API
    const PcpLayerStackIdentifier& ResolveLayerStackIdentifier(
        const PcpCache& cache) const;
 
    // Avoid possibly returning a const-reference to a temporary.
    const PcpLayerStackIdentifier& ResolveLayerStackIdentifier(
        PcpLayerStackIdentifier&&) const = delete;
    const PcpLayerStackIdentifier& ResolveLayerStackIdentifier(
        PcpCache&&) const = delete;
 
private:
    // The identifier of the layer stack providing the associated
    // expression variables. A null value indicates the root layer stack.
    std::shared_ptr<PcpLayerStackIdentifier> _identifier;
};
 
template <typename HashState>
void
TfHashAppend(HashState& h, const PcpExpressionVariablesSource& x)
{
    h.Append(x.GetHash());
}
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif