Read flags stored in one byte

Intermediate · C#. Portable allocates these bitfields from the low bits. The one-bit enabled field comes before the three-bit mode.

Run this example

Prerequisites: the repository's .NET 10 SDK and a checkout of this source. Run from the repository root:

dotnet run --project docs/examples/CStructSharp.Docs.Examples.csproj -c Release -- bit-flags

The runner checks 0B stores enabled 1, mode 5, reserved 0. Success includes PASS bit-flags.

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Complete program

The layout, options, input bytes, helper methods, and required types are all included. To adapt it outside the repository, create a .NET 10 console project, add CStructSharp, and replace Program.cs with this complete file. These examples follow the source version; use a matching package when testing a release.

Download the complete C# source.

// Generated from executable documentation examples. Edit the source region, then regenerate.
using System;
using System.IO;
using System.IO.Pipelines;
using System.Linq;
using System.Buffers;
using System.Collections.Generic;
using System.Dynamic;
using System.Globalization;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using CStructSharp;
using CStructSharp.Codecs;
using CStructSharp.Diagnostics;
using CStructSharp.Introspection;
using CStructSharp.Values;

internal static partial class Program
{
    public static void Main()
    {
        BitFlags();
        Console.WriteLine("PASS bit-flags");
    }

    private static void BitFlags()
    {
        var layout = new CStruct("struct flags { uint8 enabled : 1; uint8 mode : 3; uint8 reserved : 4; };");
        byte[] bytes = [0x0B];
        StructValue flags = layout.Parse(bytes.AsSpan(), "flags");
        Equal(1, flags.Get<int>("enabled"));
        Equal(5, flags.Get<int>("mode"));
        SequenceEqual(bytes, layout.Serialize("flags", flags));
    }

    private static void Equal<T>(T expected, T actual)
    {
        if (!EqualityComparer<T>.Default.Equals(expected, actual))
        {
            throw new InvalidOperationException($"Expected '{expected}', received '{actual}'.");
        }
    }

    private static void SequenceEqual(byte[] expected, byte[] actual)
    {
        if (!expected.AsSpan().SequenceEqual(actual))
        {
            throw new InvalidOperationException(
                $"Expected {Convert.ToHexString(expected)}, received {Convert.ToHexString(actual)}.");
        }
    }
}

Try it and diagnose mistakes

Change 0B to 0A.

Answer: enabled becomes 0; mode stays 5. Update the assertion before running the modified example. The program contains assertions for its original inputs. When changing an input intentionally, update the expected assertion too; an unchanged assertion is not evidence that the new value is wrong.

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