FModel/FModel/Extensions/StreamExtensions.cs

using System;
using System.IO;
using System.Runtime.CompilerServices;

namespace FModel.Extensions
{
    public enum Endianness
    {
        LittleEndian,
        BigEndian,
    }

    public static class StreamExtensions
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static uint ReadUInt32(this Stream s, Endianness endian = Endianness.LittleEndian)
        {
            var b1 = s.ReadByte();
            var b2 = s.ReadByte();
            var b3 = s.ReadByte();
            var b4 = s.ReadByte();

            return endian switch
            {
                Endianness.LittleEndian => (uint) (b4 << 24 | b3 << 16 | b2 << 8 | b1),
                Endianness.BigEndian => (uint) (b1 << 24 | b2 << 16 | b3 << 8 | b4),
                _ => throw new Exception("unknown endianness")
            };
        }
    }
}