Large flags enumerations in C#

Question

Hey everyone, got a quick question that I can't seem to find anything about...

I'm working on a project that requires flag enumerations with a large number of flags (up to 40-ish), and I don't really feel like typing in the exact mask for each enumeration value:

public enum MyEnumeration : ulong
{
    Flag1 = 1,
    Flag2 = 2,
    Flag3 = 4,
    Flag4 = 8,
    Flag5 = 16,
    // ...
    Flag16 = 65536,
    Flag17 = 65536 * 2,
    Flag18 = 65536 * 4,
    Flag19 = 65536 * 8,
    // ...
    Flag32 = 65536 * 65536,
    Flag33 = 65536 * 65536 * 2
    // right about here I start to get really pissed off
}

Moreover, I'm also hoping that there is an easy(ier) way for me to control the actual arrangement of bits on different endian machines, since these values will eventually be serialized over a network:

public enum MyEnumeration : uint
{
    Flag1 = 1,     // BIG: 0x00000001, LITTLE:0x01000000
    Flag2 = 2,     // BIG: 0x00000002, LITTLE:0x02000000
    Flag3 = 4,     // BIG: 0x00000004, LITTLE:0x03000000
    // ...
    Flag9 = 256,   // BIG: 0x00000010, LITTLE:0x10000000
    Flag10 = 512,  // BIG: 0x00000011, LITTLE:0x11000000
    Flag11 = 1024  // BIG: 0x00000012, LITTLE:0x12000000
}

So, I'm kind of wondering if there is some cool way I can set my enumerations up like:

public enum MyEnumeration : uint
{
     Flag1 = flag(1), // BOTH: 0x80000000
     Flag2 = flag(2), // BOTH: 0x40000000
     Flag3 = flag(3), // BOTH: 0x20000000
     // ...
     Flag9 = flag(9), // BOTH: 0x00800000
}

What I've Tried:

// this won't work because Math.Pow returns double
// and because C# requires constants for enum values
public enum MyEnumeration : uint
{
    Flag1 = Math.Pow(2, 0),
    Flag2 = Math.Pow(2, 1)
}

// this won't work because C# requires constants for enum values
public enum MyEnumeration : uint
{
    Flag1 = Masks.MyCustomerBitmaskGeneratingFunction(0)
}

// this is my best solution so far, but is definitely
// quite clunkie
public struct EnumWrapper<TEnum> where TEnum
{
    private BitVector32 vector;
    public bool this[TEnum index]
    {
         // returns whether the index-th bit is set in vector
    }
    // all sorts of overriding using TEnum as args
}

Just wondering if anyone has any cool ideas, thanks!

Gallantry

You typed a few hundred lines of text here. Why didn't you just bite the bullet and type the original 40 lines? (You might have used 1<<1, 1<<2, ... instead of the multiplies but anyway...) – Healey

Umm... I did want to present the solutions I had tried, "<<" and ">>" would have worked, but I don't exactly see the difference when they are only evaluated once. Its not like it takes me half an hour to type this out, a few hundred lines of text isn't much... I'd rather provide too much information than too little... – Gallantry

you can use the full range of the ulong with the shift operator, you will just need to indicate to the compiler that the 1 you are shifting is a ulong. 1ul << 63, notice the 'ul' afer the 1. – Forelady

Answer 1

You could write a T4 template to generate the enum :

Template (MyEnumeration.tt)

<#@ template language="C#" #>
<#@ output extension=".cs" #>
using System;

namespace MyNamespace
{
    [Flags]
    public enum MyEnumeration : ulong
    {
<#
    ulong value = 1;
    for(int i = 1; i <= 64; i++)
    {
#>
        Flag<#= i #> = <#= string.Format("0x{0:X8}", value) #>,
<#
        value = value << 1;
    }
#>
    }
}

Resulting C# code (MyEnumeration.cs)

using System;

namespace MyNamespace
{
    [Flags]
    public enum MyEnumeration : ulong
    {
        Flag1 = 0x00000001,
        Flag2 = 0x00000002,
        Flag3 = 0x00000004,
        Flag4 = 0x00000008,
        Flag5 = 0x00000010,
        Flag6 = 0x00000020,
        Flag7 = 0x00000040,
        Flag8 = 0x00000080,
        Flag9 = 0x00000100,
        Flag10 = 0x00000200,
        Flag11 = 0x00000400,
        Flag12 = 0x00000800,
        Flag13 = 0x00001000,
        Flag14 = 0x00002000,
        Flag15 = 0x00004000,
        Flag16 = 0x00008000,
        Flag17 = 0x00010000,
        Flag18 = 0x00020000,
        Flag19 = 0x00040000,
        Flag20 = 0x00080000,
        Flag21 = 0x00100000,
        Flag22 = 0x00200000,
        Flag23 = 0x00400000,
        Flag24 = 0x00800000,
        Flag25 = 0x01000000,
        Flag26 = 0x02000000,
        Flag27 = 0x04000000,
        Flag28 = 0x08000000,
        Flag29 = 0x10000000,
        Flag30 = 0x20000000,
        Flag31 = 0x40000000,
        Flag32 = 0x80000000,
        Flag33 = 0x100000000,
        Flag34 = 0x200000000,
        Flag35 = 0x400000000,
        Flag36 = 0x800000000,
        Flag37 = 0x1000000000,
        Flag38 = 0x2000000000,
        Flag39 = 0x4000000000,
        Flag40 = 0x8000000000,
        Flag41 = 0x10000000000,
        Flag42 = 0x20000000000,
        Flag43 = 0x40000000000,
        Flag44 = 0x80000000000,
        Flag45 = 0x100000000000,
        Flag46 = 0x200000000000,
        Flag47 = 0x400000000000,
        Flag48 = 0x800000000000,
        Flag49 = 0x1000000000000,
        Flag50 = 0x2000000000000,
        Flag51 = 0x4000000000000,
        Flag52 = 0x8000000000000,
        Flag53 = 0x10000000000000,
        Flag54 = 0x20000000000000,
        Flag55 = 0x40000000000000,
        Flag56 = 0x80000000000000,
        Flag57 = 0x100000000000000,
        Flag58 = 0x200000000000000,
        Flag59 = 0x400000000000000,
        Flag60 = 0x800000000000000,
        Flag61 = 0x1000000000000000,
        Flag62 = 0x2000000000000000,
        Flag63 = 0x4000000000000000,
        Flag64 = 0x8000000000000000,
    }
}

In order to edit T4 templates, I recommend you use a T4 editor plugin like this one (this gives you syntax highlighting and Intellisense)

Medullated

You hardly need a T4 system to do this. A simple loop in any scripting programming language can print the core of this. – Healey

Yes, but T4 in built into Visual Studio, which makes it very convenient for that kind of things... – Medullated

Nice. Is it possible to go above 64? – Rialto

@arao6, no. For that you would need an integer type with more than 64bits... and there isn't one (well, there is BigInteger of course, but it can't be used in an enum) – Medullated

Answer 2

Why not just do:

public enum MyEnumeration : ulong 
{ 
    Flag1 = 1, 
    Flag2 = 1 << 1, 
    Flag3 = 1 << 2, 
    Flag4 = 1 << 3, 
    .
    .
    .
    Flag30 = 1 << 29, 
    Flag31 = 1 << 30, 
    Flag32 = 1 << 31
}

Dressel

hmm... bit shifting behind 8 bits seems weird to me... I'm not sure if the compiler handles this automatically, but technically, shouldn't (1 << 8) == 0 regardless of the size of the datatype on little endian systems? I may be completely out to lunch, I'm not sure – Gallantry

@LorenVS, you can use the full range of the ulong with the shift operator, you will just need to indicate to the compiler that the 1 you are shifting is a ulong. 1ul << 63, notice the 'ul' afer the 1. – Forelady

@Gallantry - The compiler is fine with that. It is, however, wrapped to the data-size. So actually for int/Int32, 1 << 33 is the same as 1 << 1. Since (note Chris's comment, though) we're using ulong in this case it is % 64, so 1 << 65 is the same as 1 << 1 – Muscarine

Answer 3

Use 1UL like this

[Flags]    
    public enum EventType : ulong
    {
        f1= 1,
        f2= 1 << 1,
        f3= 1 << 2,
        ......

        f... = 1 << 30,
        f... = 1UL << 31,
        f...  = 1UL << 32        
    }

Boscage

This is by far the easiest solution to implement and use. Not sure why it doesn't have more votes. – Vasiliu

Answer 4

Well to address the endianes you have two options that I can think of off the top of my head

1- Handle the serialization your self and use System.Net.IPAddress.HostToNetworkOrder to ensure consistent byte ordering on the wire and of course do the reverse with System.Net.IPAddress.NetworkToHostOrder when you deserialize.

I have two old blog posts on the topic of binary serialization, they could do with an update but it is a starting point.

http://taylorza.blogspot.com/2010/04/archive-binary-data-from-structure.html
http://taylorza.blogspot.com/2010/04/archive-structure-from-binary-data.html

2- Serialize to XML, in which case endianes is not an issue but of course there are other downsides such as payload size and general performance.

Forelady