vectorSchema.h

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//
// Copyright 2022 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//

#ifndef PXR_IMAGING_HD_VECTOR_SCHEMA_H
#define PXR_IMAGING_HD_VECTOR_SCHEMA_H

#include "pxr/imaging/hd/api.h"

#include "pxr/imaging/hd/dataSource.h"

PXR_NAMESPACE_OPEN_SCOPE

// ----------------------------------------------------------------------------

/// Base class wrapping a vector data source.
///
class HdVectorSchema
{
public:
    HdVectorSchema(HdVectorDataSourceHandle const &vector)
      : _vector(vector) {}

    HD_API
    static HdVectorDataSourceHandle
    BuildRetained(
        size_t count,
        const HdDataSourceBaseHandle *values);

    /// Returns the vector data source that this schema is interpreting.
    HD_API
    HdVectorDataSourceHandle GetVector();
    HD_API
    bool IsDefined() const;

    /// Returns \c true if this schema is applied on top of a non-null
    /// vector.
    explicit operator bool() const { return IsDefined(); }

    /// Number of elements in the vector.
    HD_API
    size_t GetNumElements() const;

    using UnderlyingDataSource = HdVectorDataSource;

protected:
    template<typename T>
    typename T::Handle _GetTyped(const size_t element) const {
        return
            _vector
            ? T::Cast(_vector->GetElement(element))
            : nullptr;
    }

    HdVectorDataSourceHandle _vector;
};

/// Template class wrapping a vector data source whose children are
/// data source of an expected type.
///
template<typename T>
class HdTypedVectorSchema : public HdVectorSchema
{
public:
    HdTypedVectorSchema(HdVectorDataSourceHandle const &vector)
      : HdVectorSchema(vector) {}

    typename T::Handle GetElement(const size_t element) const {
        return _GetTyped<T>(element);
    }
};

/// Template class wrapping a vector data source whose children are
/// container data source conforming to an expected schema.
///
template<typename Schema>
class HdSchemaBasedVectorSchema : public HdVectorSchema
{
public:
    HdSchemaBasedVectorSchema(HdVectorDataSourceHandle const &vector)
      : HdVectorSchema(vector) {}
    
    Schema GetElement(const size_t element) const {
        using DataSource = typename Schema::UnderlyingDataSource;
        return Schema(_GetTyped<DataSource>(element));
    }
};

PXR_NAMESPACE_CLOSE_SCOPE

#endif