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/****************************************************************************
**
** Copyright (C) 2020 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt VS Tools.
**
** $QT_BEGIN_LICENSE:GPL-EXCEPT$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
namespace QtVsTools.Common
{
/// <summary>
/// Extended enum support:
/// * Customized cast of enum values to arbitrary types
/// </summary>
public static class EnumExt
{
/// <summary>
/// Wrapper for enum cast values.
/// </summary>
/// <typeparam name="T">Type of cast output</typeparam>
/// <remarks>
/// Cast attributes associated with enum values must implement this interface.
/// </remarks>
public interface ICast<T>
{
T Value { get; }
}
/// <summary>
/// String cast attribute associated to an enum value.
/// </summary>
/// <example>
/// enum Foobar {
/// Foo,
/// [EnumExt.String("Bahr")] Bar
/// }
/// </example>
[AttributeUsage(AttributeTargets.All)]
public sealed class StringAttribute : Attribute, ICast<string>
{
public string Value { get; }
public StringAttribute(string str) { Value = str; }
}
/// <summary>
/// Cast enum value to type T.
/// </summary>
/// <typeparam name="T">Cast output type.</typeparam>
/// <param name="value">Input enum value.</param>
/// <returns>
/// Value of type T associated to the enum value by an Attribute implementing
/// ICast<typeparamref name="T"/>. If no attribute is found, returns a default value.
/// </returns>
/// <example>
/// enum Foobar
/// {
/// Foo,
/// [EnumExt.String("Bahr")] Bar
/// }
/// Foobar foo = Foobar.Foo;
/// Foobar bar = Foobar.Bar;
/// string fooCastString = foo.Cast<string>(); // "Foo"
/// string barCastString = bar.Cast<string>(); // "Bahr"
/// string fooToString = foo.ToString(); // "Foo"
/// string barToString = bar.ToString(); // "Bar"
/// </example>
public static T Cast<T>(this Enum value)
{
if (FindCastAttrib<T>(value) is ICast<T> cast)
return cast.Value;
else
return Default<T>(value);
}
/// <summary>
/// Compare enum value with instance/value of type T.
/// </summary>
/// <typeparam name="T">Cast/comparison type.</typeparam>
/// <param name="valueT">Instance/value of type T to compare with.</param>
/// <param name="valueEnum">Enum value to compare with.</param>
/// <returns>true if cast of valueEnum is equal to valueT, false otherwise</returns>
public static bool EqualTo<T>(this T valueT, Enum valueEnum)
{
return valueT.Equals(valueEnum.Cast<T>());
}
/// <summary>
/// Convert type T to enum
/// </summary>
public static bool TryCast<T, TEnum>(this T valueT, out TEnum value) where TEnum : struct
{
value = default(TEnum);
IEnumerable<Enum> enumValues = Enum.GetValues(typeof(TEnum)).OfType<Enum>()
.Where((Enum valueEnum) => valueEnum.Cast<T>().Equals(valueT));
if (enumValues.Any())
value = (TEnum)Enum.ToObject(typeof(TEnum), enumValues.FirstOrDefault());
return enumValues.Any();
}
/// <summary>
/// Convert type T to enum
/// </summary>
public static TEnum Cast<T, TEnum>(this T valueT, TEnum defaultValue) where TEnum : struct
{
TEnum value;
return TryCast(valueT, out value) ? value : defaultValue;
}
/// <summary>
/// Get list of values of enum type
/// </summary>
public static IEnumerable<TEnum> GetValues<TEnum>() where TEnum : struct
{
Debug.Assert(typeof(TEnum).IsEnum);
return Enum.GetValues(typeof(TEnum)).OfType<TEnum>();
}
/// <summary>
/// Get list of values of enum type converted to type T
/// </summary>
public static IEnumerable<T> GetValues<T>(Type enumType)
{
return Enum.GetValues(enumType).OfType<Enum>()
.Select((Enum value) => value.Cast<T>());
}
/// <summary>
/// Default cast of enum value to type T.
/// </summary>
/// <typeparam name="T">Cast output type.</typeparam>
/// <param name="value">Input enum value.</param>
/// <returns>
/// Default value of type T associated with the enum value:
/// * if T is string: returns the enum value name as string;
/// * if T is an integer type: returns the underlying enum integer value;
/// * otherwise: default value for type T (e.g. null for reference types).
/// </returns>
static T Default<T>(Enum value)
{
Type enumType = value.GetType();
Type baseType = Enum.GetUnderlyingType(enumType);
Type outputType = typeof(T);
if (outputType.IsAssignableFrom(enumType) || outputType.IsAssignableFrom(baseType))
return (T)(object)value;
else if (outputType == typeof(string))
return (T)(object)Enum.GetName(value.GetType(), value);
else
return default(T);
}
/// <summary>
/// Find cast attribute.
/// </summary>
/// <typeparam name="T">Cast output type.</typeparam>
/// <param name="value">Input enum value.</param>
/// <returns>
/// First cast attribute of type T found associated with the enum value, or null in case a
/// suitable attribute is not found.
/// </returns>
static ICast<T> FindCastAttrib<T>(Enum value)
{
Type enumType = value.GetType();
string valueName = Enum.GetName(enumType, value);
if (string.IsNullOrEmpty(valueName))
return null;
FieldInfo enumField = enumType.GetField(valueName);
if (enumField == null)
return null;
return CastAttribTypes
.Where(type => typeof(ICast<T>).IsAssignableFrom(type))
.Select(type => Attribute.GetCustomAttribute(enumField, type) as ICast<T>)
.FirstOrDefault();
}
static IEnumerable<Type> _CastAttribTypes;
/// <summary>
/// List of cast attribute types.
/// </summary>
/// <remarks>
/// Future cast attribute types need to be added to this list.
/// </remarks>
static IEnumerable<Type> CastAttribTypes => _CastAttribTypes
?? (_CastAttribTypes = new[]
{
typeof(StringAttribute)
});
}
}
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