variableExpression.h

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//
// Copyright 2023 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_SDF_VARIABLE_EXPRESSION
#define PXR_USD_SDF_VARIABLE_EXPRESSION
 
 
#include "pxr/pxr.h"
#include "pxr/usd/sdf/api.h"
 
#include "pxr/base/vt/array.h"
#include "pxr/base/vt/dictionary.h"
#include "pxr/base/vt/value.h"
 
#include <memory>
#include <string>
#include <unordered_set>
#include <vector>
 
PXR_NAMESPACE_OPEN_SCOPE
 
namespace Sdf_VariableExpressionImpl {
    class Node;
}
 
class SdfVariableExpression
{
public:
    SDF_API
    explicit SdfVariableExpression(const std::string& expr);
 
    SDF_API
    SdfVariableExpression();
 
    SDF_API
    ~SdfVariableExpression();
 
    SDF_API
    static bool IsExpression(const std::string& s);
 
    SDF_API
    static bool IsValidVariableType(const VtValue& value);
 
    SDF_API
    explicit operator bool() const;
 
    SDF_API
    const std::string& GetString() const;
 
    SDF_API
    const std::vector<std::string>& GetErrors() const;
 
    class EmptyList { };
 
    class Result
    {
    public:
        VtValue value;
 
        std::vector<std::string> errors;
 
        std::unordered_set<std::string> usedVariables;
    };
 
    SDF_API
    Result Evaluate(const VtDictionary& variables) const;
 
    template <class ResultType>
    Result EvaluateTyped(const VtDictionary& variables) const
    {
        Result r = Evaluate(variables);
 
        if (VtIsArray<ResultType>::value && r.value.IsHolding<EmptyList>()) {
            r.value = VtValue(ResultType());
        }
        else if (!r.value.IsEmpty() && !r.value.IsHolding<ResultType>()) {
            r.errors.push_back(
                _FormatUnexpectedTypeError(r.value, VtValue(ResultType())));
            r.value = VtValue();
        }
        return r;
    }
 
private:
    SDF_API
    static std::string
    _FormatUnexpectedTypeError(const VtValue& got, const VtValue& expected);
 
    std::vector<std::string> _errors;
    std::shared_ptr<Sdf_VariableExpressionImpl::Node> _expression;
    std::string _expressionStr;
};
 
inline bool
operator==(
    const SdfVariableExpression::EmptyList&,
    const SdfVariableExpression::EmptyList&)
{
    return true;
}
 
inline bool
operator!=(
    const SdfVariableExpression::EmptyList&,
    const SdfVariableExpression::EmptyList&)
{
    return false;
}
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif