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

using AssetRipper.IO.Files.Streams;
using ZstdSharp;

namespace AssetRipper.IO.Files.BundleFiles
{
	public static class ZstdCompression
	{
		private static readonly byte[] Signature = [0x28, 0xB5, 0x2F, 0xFD];
		public static bool IsZstd(Stream Stream)
		{
			Span<byte> buffer = stackalloc byte[4];

			long pos = Stream.Position;
			Stream.ReadExactly(buffer);
			Stream.Position = pos;

			return buffer.SequenceEqual(Signature);
		}

		public static void DecompressStream(Stream compressedStream, long compressedSize, Stream decompressedStream, long decompressedSize)
		{
			using PartialStream compressedPartialStream = new PartialStream(compressedStream, compressedStream.Position, compressedSize, true);
			using PartialStream decompressedPartialStream = new PartialStream(decompressedStream, decompressedStream.Position, decompressedSize, true);
			using DecompressionStream zstdStream = new DecompressionStream(compressedPartialStream);
			zstdStream.CopyTo(decompressedPartialStream);
		}
	}
}