requiredInputsPredicate.h

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//
// Copyright 2025 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_EXEC_VDF_REQUIRED_INPUTS_PREDICATE_H
#define PXR_EXEC_VDF_REQUIRED_INPUTS_PREDICATE_H
 
 
#include "pxr/pxr.h"
 
#include "pxr/exec/vdf/input.h"
 
PXR_NAMESPACE_OPEN_SCOPE
 
class VdfRequiredInputsPredicate
{
public:
    static VdfRequiredInputsPredicate AllReads(const VdfNode &node) {
        return VdfRequiredInputsPredicate(_Selector::AllReads, node, nullptr);
    }
 
    static VdfRequiredInputsPredicate NoReads(const VdfNode &node) {
        return VdfRequiredInputsPredicate(_Selector::NoReads, node, nullptr);
    }
 
    static VdfRequiredInputsPredicate OneRead(
        const VdfNode &node,
        const VdfInput &input) {
        return VdfRequiredInputsPredicate(_Selector::OneRead, node, &input);
    }
 
    bool IsRequiredRead(const VdfInput &input) const {
        return
            _selector != _Selector::NoReads &&
            !input.GetAssociatedOutput() &&
            !input.GetSpec().IsPrerequisite() &&
            (_selector == _Selector::AllReads ||
                (_oneRead == &input && &input.GetNode() == &_node));
    }
 
    bool HasRequiredReads() const {
        return _selector != _Selector::NoReads;
    }
 
    bool RequiresAllReads() const {
        return _selector == _Selector::AllReads;
    }
 
private:
    // Denotes how inputs are selected.
    enum class _Selector {
        NoReads,
        AllReads,
        OneRead
    };
 
    // Constructor. \p oneRead is only relevant if \p selector equals
    // _Selector::OneRead. Otherwise \p oneRead may be \c nullptr.
    VdfRequiredInputsPredicate(
        _Selector selector,
        const VdfNode &node,
        const VdfInput *oneRead) :
        _selector(selector),
        _node(node),
        _oneRead(oneRead)
    {}
 
    // Select inputs based on this choice of selector.
    _Selector _selector;
 
    // The owning node.
    const VdfNode &_node;
 
    // The input, if _selector is OneRead.
    const VdfInput *_oneRead;
};
 
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif