ConstantValue.hxx

//--------------------------------------------------------------
//
// Microsoft Edge Implementation
// Copyright(c) Microsoft Corporation
// All rights reserved.
//
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files(the ""Software""),
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//
//--------------------------------------------------------------
#pragma once

#include "ConstantValue.hxx"

//+-----------------------------------------------------------------------------
//
//  Class:      ConstantValue
//
//  Synopsis:   Class to store a constant expression value. This is stored
//              as the initialized value of an identifier for those that have
//              an initializer, or passed around when a constant is required.
//
//              Currently only int and double values are supported.
//
//              This stores both a basic type and (optionally) a value. It is
//              possible to have a type without a value.
//
//------------------------------------------------------------------------------
class ConstantValue
{
public:
    ConstantValue();

    void SetTypeOnly(int type);
    HRESULT GetBasicType(__out int* pBasicType) const;

    template<typename T> 
    void SetValue(T val) { AssertSz(false, "Invalid template of ConstantValue::SetValue used"); }

    template<>
    void SetValue<int>(int val);

    template<>
    void SetValue<double>(double val);

    template<typename T>
    HRESULT GetValue(__out T* pValue) const { return E_FAIL; }

    template<>
    HRESULT GetValue<int>(__out int* pValue) const;

    template<>
    HRESULT GetValue<double>(__out double* pValue) const;

    // Conversions
    HRESULT AsInt(__out int* pValue) const;
    HRESULT AsDouble(__out double* pValue) const;

private:
    int _type;                                                      // The type stored in the struct
    bool _fSet;                                                     // Whether a value is set or not

    union
    {
        int _intValue;                                              // The value if this is an int
        double _doubleValue;                                        // The value if this is a double
    };
};