AssetRipper_AssetRipper/Source/AssetRipper.IO.Files/BundleFiles/BundleHeader.cs

using AssetRipper.IO.Endian;
using AssetRipper.IO.Files.BundleFiles.FileStream;
using AssetRipper.IO.Files.BundleFiles.RawWeb.Raw;
using AssetRipper.IO.Files.BundleFiles.RawWeb.Web;
using AssetRipper.IO.Files.Streams.Smart;
using System.Diagnostics;

namespace AssetRipper.IO.Files.BundleFiles
{
	public abstract record class BundleHeader : IEndianWritable
	{
		internal BundleHeader() { }
		protected abstract string MagicString { get; }
		public BundleVersion Version { get; set; }
		/// <summary>
		/// Generation version
		/// </summary>
		public string? UnityWebBundleVersion { get; set; }
		/// <summary>
		/// Actual engine version
		/// </summary>
		public string? UnityWebMinimumRevision { get; set; }

		public virtual void Read(EndianReader reader)
		{
			string signature = reader.ReadStringZeroTerm();
			Debug.Assert(signature == MagicString);
			Version = (BundleVersion)reader.ReadInt32();
			Debug.Assert(Version >= 0);
			UnityWebBundleVersion = reader.ReadStringZeroTerm();
			UnityWebMinimumRevision = reader.ReadStringZeroTerm();
		}

		public virtual void Write(EndianWriter writer)
		{
			writer.WriteStringZeroTerm(MagicString);
			writer.Write((int)Version);
			writer.WriteStringZeroTerm(UnityWebBundleVersion ?? throw new NullReferenceException(nameof(UnityWebBundleVersion)));
			writer.WriteStringZeroTerm(UnityWebMinimumRevision ?? throw new NullReferenceException(nameof(UnityWebMinimumRevision)));
		}

		private protected static bool IsBundleHeader(EndianReader reader, string magicString)
		{
			const int MaxLength = 0x20;
			if (reader.BaseStream.Length >= MaxLength)
			{
				long position = reader.BaseStream.Position;
				bool isRead = reader.ReadStringZeroTerm(MaxLength, out string? signature);
				reader.BaseStream.Position = position;
				return isRead && signature == magicString;
			}
			return false;
		}

		public static bool IsBundleHeader(string path)
		{
			using SmartStream stream = SmartStream.OpenRead(path);
			using EndianReader reader = new EndianReader(stream, EndianType.BigEndian);
			return FileStreamBundleHeader.IsBundleHeader(reader)
				|| RawBundleHeader.IsBundleHeader(reader)
				|| WebBundleHeader.IsBundleHeader(reader);
		}
	}
}