compare_tar_header.cs

void Main()
{
	var fileInfoOriginal = new FileInfo(@"C:\Development\project-dev-12345-67890-abcdefg.tar.gz"); // unmodified
	var fileInfoModified = new FileInfo(@"C:\Development\project-dev-12345-67890-abcdefg-modified.tar.gz"); // modified

	using var fileStreamOriginal = fileInfoOriginal.OpenRead();
	using var decompresssionStreamOriginal = new GZipStream(fileStreamOriginal, CompressionMode.Decompress);
	var original = InspectTarHeader(decompresssionStreamOriginal);

	using var fileStreamModified = fileInfoModified.OpenRead();
	using var decompresssionStreamModified = new GZipStream(fileStreamModified, CompressionMode.Decompress);
	var modified = InspectTarHeader(decompresssionStreamModified);
	
	foreach (var originalEntry in original)
	{
		var modifiedEntry = modified[originalEntry.Key];
		originalEntry.Key.Dump();
		Util.Dif(originalEntry.Value, modifiedEntry, depth: 3, true).Dump();
	}
}


public static Dictionary<string, byte[]> InspectTarHeader(Stream stream)
{
	var readBuffer = new byte[1024];
	var readBufferSpan = readBuffer.AsMemory();
	
	var bufferArray = new byte[512];
	var buffer = bufferArray.AsMemory();
	
	var dict = new Dictionary<string, byte[]>();
	
	var deduper = 0;
	
	while (true)
	{
		var header = buffer.Slice(0, 512);
		stream.Read(header.Span);
		
		var name = Encoding.ASCII.GetString(header.Slice(0, 100).Span).Trim('\0');
		if (String.IsNullOrWhiteSpace(name))
			break;
		
		header = header.Slice(100);
		
		header = header.Slice(8 + 8 + 8); // Skip mode, uid, gid
		
		var size = (int)Convert.ToInt64(Encoding.UTF8.GetString(header.Slice(0, 12).Span).Trim().Trim('\0'), 8);
		
		// Put the files 512 byte header into the output dictionary
		if(!dict.TryAdd(name, bufferArray.ToArray()))
		{
			name = $"{name}{deduper++}";
			dict.TryAdd(name, bufferArray.ToArray());
		}
		
		header = header.Slice(12);
		
		header = header.Slice(12 + 8); // Skip mtime, chksum
		
		var mode = (char)header.Span[0];
		
		header = header.Slice(1);
		
		if(mode == '5' ) // Directory
		{
			continue;
		}
		
				
		if(mode == '0' || mode == 'L') // Process it
		{
			var chunks = Math.DivRem(size, readBuffer.Length, out int remainder);
						
			for (int i = 0; i <= chunks; i++)
			{
				stream.Read(readBufferSpan.Slice(0, i == chunks ? remainder : readBuffer.Length).Span);
			}
			
			var emptyDataCount = 512 - (remainder % 512);
			if (emptyDataCount > 0 && emptyDataCount < 512)
			{
				stream.Read(readBufferSpan.Slice(0, emptyDataCount).Span);
			}
			continue;
		}
		
		return dict;
	}
	return dict;
}