allowed.h

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//
// Copyright 2016 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_USD_SDF_ALLOWED_H
#define PXR_USD_SDF_ALLOWED_H
 
 
#include "pxr/pxr.h"
#include "pxr/usd/sdf/api.h"
#include "pxr/base/tf/diagnostic.h"
 
#include <optional>
#include <string>
#include <utility>
 
PXR_NAMESPACE_OPEN_SCOPE
 
class SdfAllowed {
private:
    typedef std::optional<std::string> _State;
 
public:
    typedef std::pair<bool, std::string> Pair;
 
    SdfAllowed() { }
    SdfAllowed(bool x) { TF_AXIOM(x); }
    SdfAllowed(const char* whyNot) : _state(std::string(whyNot)) { }
    SdfAllowed(const std::string& whyNot) : _state(whyNot) { }
    SdfAllowed(bool condition, const char* whyNot) :
        SdfAllowed(condition, std::string(whyNot)) { }
    SdfAllowed(bool condition, const std::string& whyNot) :
        _state(condition ? std::nullopt :
               std::make_optional(whyNot)) { }
    SdfAllowed(const Pair& x) : SdfAllowed(x.first, x.second) { }
    ~SdfAllowed() { }
 
#if !defined(doxygen)
    typedef _State SdfAllowed::*UnspecifiedBoolType;
#endif
 
    operator UnspecifiedBoolType() const
    {
        return _state ? NULL : &SdfAllowed::_state;
    }
 
    bool operator!() const
    {
        return static_cast<bool>(_state);
    }
 
    operator const std::string&() const
    {
        return GetWhyNot();
    }
 
    SDF_API const std::string& GetWhyNot() const;
 
    bool IsAllowed(std::string* whyNot) const
    {
        if (whyNot && _state) {
            *whyNot = *_state;
        }
        return !_state;
    }
 
    bool operator==(const SdfAllowed& other) const
    {
        return _state == other._state;
    }
 
    bool operator!=(const SdfAllowed& other) const
    {
        return !(*this == other);
    }
 
private:
    _State _state;
};
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif // PXR_USD_SDF_ALLOWED_H