EnumAsByte.h

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// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "../BasicTypes.h"
#include "../Templates/IsPODType.h"
#include "../Templates/IsEnumClass.h"
 
template <bool> struct TEnumAsByte_EnumClass;
template <> struct TEnumAsByte_EnumClass<false> {};
 
/**
 * Template to store enumeration values as bytes in a type-safe way.
 */
template<class TEnum>
class TEnumAsByte
{
    typedef TEnumAsByte_EnumClass<TIsEnumClass<TEnum>::Value> Check;
 
public:
    typedef TEnum EnumType;
 
    /** Default Constructor (no initialization). */
    FORCEINLINE TEnumAsByte() { }
 
    /**
     * Copy constructor.
     *
     * @param InValue value to construct with.
     */
    FORCEINLINE TEnumAsByte( const TEnumAsByte &InValue )
        : Value(InValue.Value)
    { }
 
    /**
     * Constructor, initialize to the enum value.
     *
     * @param InValue value to construct with.
     */
    FORCEINLINE TEnumAsByte( TEnum InValue )
        : Value(static_cast<uint8>(InValue))
    { }
 
    /**
     * Constructor, initialize to the int32 value.
     *
     * @param InValue value to construct with.
     */
    explicit FORCEINLINE TEnumAsByte( int32 InValue )
        : Value(static_cast<uint8>(InValue))
    { }
 
    /**
     * Constructor, initialize to the int32 value.
     *
     * @param InValue value to construct with.
     */
    explicit FORCEINLINE TEnumAsByte( uint8 InValue )
        : Value(InValue)
    { }
 
public:
 
    /**
     * Assignment operator.
     *
     * @param InValue value to set.
     * @return This instance.
     */
    FORCEINLINE TEnumAsByte& operator=( TEnumAsByte InValue )
    {
        Value = InValue.Value;
        return *this;
    }
    /**
     * Assignment operator.
     *
     * @param InValue value to set.
     * @return This instance.
     */
    FORCEINLINE TEnumAsByte& operator=( TEnum InValue )
    {
        Value = static_cast<uint8>(InValue);
        return *this;
    }
 
    /**
     * Compares two enumeration values for equality.
     *
     * @param InValue The value to compare with.
     * @return true if the two values are equal, false otherwise.
     */
    bool operator==( TEnum InValue ) const
    {
        return static_cast<TEnum>(Value) == InValue;
    }
 
    /**
     * Compares two enumeration values for equality.
     *
     * @param InValue The value to compare with.
     * @return true if the two values are equal, false otherwise.
     */
    bool operator==(TEnumAsByte InValue) const
    {
        return Value == InValue.Value;
    }
 
    /** Implicit conversion to TEnum. */
    operator TEnum() const
    {
        return (TEnum)Value;
    }
 
public:
 
    /**
     * Gets the enumeration value.
     *
     * @return The enumeration value.
     */
    TEnum GetValue() const
    {
        return (TEnum)Value;
    }
 
private:
 
    /** Holds the value as a byte. **/
    uint8 Value;
 
 
    FORCEINLINE friend uint32 GetTypeHash(const TEnumAsByte& Enum)
    {
        return GetTypeHash(Enum.Value);
    }
};
 
 
template<class T> struct TIsPODType<TEnumAsByte<T>> { enum { Value = true }; };