static void Cache <T>()
where T : struct, Enum
{
var type = typeof(T);
var underlyingType = Enum.GetUnderlyingType(type);
var values = ((T[])Enum.GetValues(type)).AsReadOnly();
var names = Enum.GetNames(type).ToReadOnlyArray();
var members = names.Select(x => new Member <T>(x)).ToReadOnlyArray();
var minValue = values.DefaultIfEmpty().Min();
var maxValue = values.DefaultIfEmpty().Max();
var isEmpty = values.Count == 0;
var isFlags = Attribute.IsDefined(type, typeof(FlagsAttribute));
var distinctedMembers = members.Distinct(new Member <T> .ValueComparer()).ToArray();
var memberByValue = distinctedMembers.ToFrozenDictionary(x => x.Value);
var memberByName = members.ToFrozenStringKeyDictionary(x => x.Name);
var underlyingOperation
= Type.GetTypeCode(type) switch
{
TypeCode.SByte => SByteOperation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.Byte => ByteOperation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.Int16 => Int16Operation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.UInt16 => UInt16Operation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.Int32 => Int32Operation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.UInt32 => UInt32Operation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.Int64 => Int64Operation <T> .Create(minValue, maxValue, distinctedMembers),
TypeCode.UInt64 => UInt64Operation <T> .Create(minValue, maxValue, distinctedMembers),
_ => throw new InvalidOperationException(),
};
}
static Cache()
{
Type = typeof(T);
UnderlyingType = Enum.GetUnderlyingType(Type);
Values = (Enum.GetValues(Type) as T[]).AsReadOnly();
Names = Enum.GetNames(Type).Select(string.Intern).ToReadOnlyArray();
Members = Names.Select(x => new Member <T>(x)).ToReadOnlyArray();
MinValue = Values.DefaultIfEmpty().Min();
MaxValue = Values.DefaultIfEmpty().Max();
IsEmpty = Values.Count == 0;
IsFlags = Attribute.IsDefined(Type, typeof(FlagsAttribute));
var distinctedMember = Members.OrderBy(x => x.Value).Distinct(new Member <T> .ValueComparer()).ToArray();
MemberByName = Members.ToFrozenStringKeyDictionary(x => x.Name);
UnderlyingOperation
= Type.GetTypeCode(Type) switch
{
TypeCode.SByte => SByteOperation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.Byte => ByteOperation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.Int16 => Int16Operation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.UInt16 => UInt16Operation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.Int32 => Int32Operation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.UInt32 => UInt32Operation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.Int64 => Int64Operation <T> .Create(MinValue, MaxValue, distinctedMember),
TypeCode.UInt64 => UInt64Operation <T> .Create(MinValue, MaxValue, distinctedMember),
_ => throw new InvalidOperationException(),
};
}
/// <summary>
/// Returns an indication whether a constant with a specified value exists in a specified enumeration.
/// </summary>
/// <param name="value"></param>
/// <typeparam name="T">Enum type</typeparam>
/// <returns></returns>
public static bool IsDefined <T>(int value)
where T : struct, Enum
{
if (Cache_UnderlyingOperation <T> .UnderlyingType == typeof(int))
{
return(Int32Operation <T> .IsDefined(ref value));
}
throw new ArgumentException(IsDefinedTypeMismatchMessage);
}
static void Main(string[] args)
{
Int32Operation op = new Int32Operation(AddNumbers);
Console.WriteLine(op(3, 4)); // Prints 7
op = SubtractNumbers; // Method group conversion
Console.WriteLine(op(3, 4)); // Prints -1
}
static Cache_UnderlyingOperation()
{
var type = Cache_Type <T> .Type;
var min = Cache_MinMaxValues <T> .MinValue;
var max = Cache_MinMaxValues <T> .MaxValue;
var distincted = Cache_Members <T> .Members.OrderBy(x => x.Value).Distinct(new Member <T> .ValueComparer()).ToArray();
UnderlyingType = Cache_Type <T> .UnderlyingType;
UnderlyingOperation
= Type.GetTypeCode(type) switch
{
TypeCode.SByte => SByteOperation <T> .Create(min, max, distincted),
TypeCode.Byte => ByteOperation <T> .Create(min, max, distincted),
TypeCode.Int16 => Int16Operation <T> .Create(min, max, distincted),
TypeCode.UInt16 => UInt16Operation <T> .Create(min, max, distincted),
TypeCode.Int32 => Int32Operation <T> .Create(min, max, distincted),
TypeCode.UInt32 => UInt32Operation <T> .Create(min, max, distincted),
TypeCode.Int64 => Int64Operation <T> .Create(min, max, distincted),
TypeCode.UInt64 => UInt64Operation <T> .Create(min, max, distincted),
_ => throw new InvalidOperationException(),
};
}
static CacheUnderlyingOperation()
{
Type type = CacheType <T> .Type;
T min = CacheMinMaxValues <T> .MinValue;
T max = CacheMinMaxValues <T> .MaxValue;
EnumMember <T>[] distincted = CacheMembers <T> .Members.OrderBy(x => x.Value).Distinct(new EnumMember <T> .ValueComparer()).ToArray();
UnderlyingType = CacheType <T> .UnderlyingType;
// ReSharper disable once SwitchExpressionHandlesSomeKnownEnumValuesWithExceptionInDefault
UnderlyingOperation = Type.GetTypeCode(type) switch
{
TypeCode.SByte => SByteOperation <T> .Create(min, max, distincted),
TypeCode.Byte => ByteOperation <T> .Create(min, max, distincted),
TypeCode.Int16 => Int16Operation <T> .Create(min, max, distincted),
TypeCode.UInt16 => UInt16Operation <T> .Create(min, max, distincted),
TypeCode.Int32 => Int32Operation <T> .Create(min, max, distincted),
TypeCode.UInt32 => UInt32Operation <T> .Create(min, max, distincted),
TypeCode.Int64 => Int64Operation <T> .Create(min, max, distincted),
TypeCode.UInt64 => UInt64Operation <T> .Create(min, max, distincted),
_ => throw new InvalidOperationException()
};
}
}
