Diagnose the wrong byte order

Beginner · C#. Changing byte order changes the value, not the field width. A read may succeed even when the chosen byte order is wrong.

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 -- byte-order

The runner checks little-endian kind 2; big-endian kind 512 and length 100663296. Success includes PASS byte-order.

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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()
    {
        ByteOrder();
        Console.WriteLine("PASS byte-order");
    }

    private static void ByteOrder()
    {
        const string definition = "struct header { uint16 kind; uint32 length; };";
        byte[] bytes = [2, 0, 6, 0, 0, 0];
        var little = new CStruct(definition, isLittleEndian: true);
        var big = new CStruct(definition, isLittleEndian: false);
        Equal((ushort)2, (ushort)little.ReadValue(bytes.AsSpan(), "header.kind")!);
        Equal((ushort)512, (ushort)big.ReadValue(bytes.AsSpan(), "header.kind")!);
        Equal(100663296U, (uint)big.ReadValue(bytes.AsSpan(), "header.length")!);
    }

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

Try it and diagnose mistakes

Swap the two kind bytes and read with big-endian order.

Answer: 00 02 gives kind 2 in big-endian order. 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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