Taking advantage of BitMasks

Ian Parr — Fri, 13 Oct 2017 17:11:43 +0000

Recently I needed a way to store a finite list or error messages that could potentially occur during an async process.

I could have implemented something like - creating a relational table structure, store them as a JSON file etc. All of the alternatives felt a bit like 'overkill' for reasons I won't go into here. So I decided to opt for a Bitmask. Why? Well, essentially, bitmasks are a great way to store a large amount of 'information' in a small space.

Here are the potential errors that I needed to log.

invalidName
invalidDate
invalidTime
invalidType
invalidRange
invalidState

So what Bitmasking allowed me to do was to assign an integer value to each of the potential errors. So:

invalidName = 1
invalidDate = 2
invalidTime = 4
invalidType = 8
invalidRange = 16
invalidState = 32

Usage
In C# land we would implement something like this:

using System;

public class Program
{
    static int _errorTotal = 0;

    public static void Main()
    {           
        //simulate some errors
        _errorTotal += (int)Errors.Name;
        _errorTotal += (int)Errors.Date;
        _errorTotal += (int)Errors.Time;
        _errorTotal += (int)Errors.Type;

        Console.WriteLine("Error total: {0}", _errorTotal); // this is what we persist
        Console.WriteLine("Error list: {0}", (Errors)_errorTotal); // this is how we read the data back out
    }

    // Holds the value of each of the error types
    [Flags]
        public enum Errors 
    {
        Name = 1,
        Date = 2,
        Time = 4,
        Type = 8,
        Range = 16,
        State = 32
    }
}

Output:
Error total: 15 Error list: Name, Date, Time, Type

We can now see how storing just one integer value, you can gain access to any combination of errors that occurred during the async process.

Note: Like I said at the start, this is a great way of storing a finite list of 'stuff' - for particularly long lists of 'stuff', you might want to cast your [Flag] enum to (long):

[Flags]
public enum Errors : long
{
    Name = (long)1,
    Date = (long)2,
    Time = (long)4,
        ...

Forem: Ian Parr

Taking advantage of BitMasks