ExpressionEvaluator.hpp

Go to the documentation of this file.

//
//  CeresEngine - A game development framework
//
//  Created by Rogiel Sulzbach.
//  Copyright (c) 2018-2022 Rogiel Sulzbach. All rights reserved.
//
 
#pragma once
 
#include "CeresEngine/DataTypes.hpp"
 
#include "CeresEngine/Foundation/Flags.hpp"
#include "CeresEngine/Foundation/Function.hpp"
#include "CeresEngine/Foundation/Container/Stack.hpp"
 
#include "CeresEngine/Material/ShaderCompiler/Variant.hpp"
 
#include "CeresEngine/Material/ShaderCompiler/AST/Visitor/Visitor.hpp"
 
#include <functional>
 
namespace CeresEngine::ShaderCompiler {
 
    // Constant expression evaluator AST visitor.
    class ExpressionEvaluator : private Visitor {
    public:
        using OnObjectExpressionCallback = Function<Variant(ObjectExpression* expression) const>;
 
    private:
        Stack<Variant> mVariantStack;
 
        OnObjectExpressionCallback mOnObjectExpressionCallback;
 
        bool mThrowOnFailure = true;
        bool mAbort = false;
 
        RawFlags mFlags;
 
    public:
        // Evaluation flags enumeration.
        enum : UInt32 {
            // Evaluates only the sub expressions of a BinaryExpression that are necessary (especially for logical AND and OR).
            EvaluateReducedBinaryExpression = (1 << 0),
        };
 
        ExpressionEvaluator(RawFlags flags = 0);
 
        // Evaluates the specified expression and returns the result as variant, or throws a runtime error on failure.
        Variant evaluate(Expression& expression, const OnObjectExpressionCallback& onObjectExpressionCallback = nullptr);
 
        // Evaluates the specified expression and returns the result as variant, or returns the default value on failure.
        Variant evaluateOrDefault(Expression& expression, const Variant& defaultValue = {}, const OnObjectExpressionCallback& onObjectExpressionCallback = nullptr);
 
        // Abort expression evaluation process.
        void abort();
 
    private:
        void push(const Variant& v);
        Variant pop();
 
        void setObjectExpressionCallback(const OnObjectExpressionCallback& callback);
 
        Variant evaluateBinaryOp(const BinaryExpression* ast, Variant lhs, Variant rhs);
        Variant evaluateUnaryOp(const UnaryExpression* ast, Variant rhs);
 
    private: // Visitor implementation
        DECLARATION_VISIT_PROC(NullExpression);
        DECLARATION_VISIT_PROC(SequenceExpression);
        DECLARATION_VISIT_PROC(LiteralExpression);
        DECLARATION_VISIT_PROC(TypeSpecifierExpression);
        DECLARATION_VISIT_PROC(TernaryExpression);
        DECLARATION_VISIT_PROC(BinaryExpression);
        DECLARATION_VISIT_PROC(UnaryExpression);
        DECLARATION_VISIT_PROC(PostUnaryExpression);
        DECLARATION_VISIT_PROC(CallExpression);
        DECLARATION_VISIT_PROC(BracketExpression);
        DECLARATION_VISIT_PROC(AssignExpression);
        DECLARATION_VISIT_PROC(ObjectExpression);
        DECLARATION_VISIT_PROC(ArrayExpression);
        DECLARATION_VISIT_PROC(CastExpression);
        DECLARATION_VISIT_PROC(InitializerExpression);
    };
 
} // namespace CeresEngine::ShaderCompiler