public async Task Save(RecordRefRun run, string targetFileName, bool returnBuffer = true)
        {
            using var output = new FileStream(
                      path: targetFileName,
                      FileMode.CreateNew,
                      FileAccess.Write,
                      FileShare.None,
                      bufferSize: 1024 * (int)Units.BytesPerKiB);

            const int capacity = 900 * 1000;

            ValueTask writeTask = ValueTask.CompletedTask;

            var buffer1 = new ArrayBufferWriter <byte>(capacity);
            var buffer2 = new ArrayBufferWriter <byte>(capacity);

            var buffer = buffer1;

            foreach (var item in run.Records)
            {
                if (buffer.FreeCapacity < item.length)
                {
                    await writeTask;
                    writeTask = output.WriteAsync(buffer.WrittenMemory);

                    buffer = buffer == buffer1 ? buffer2 : buffer1;
                    buffer.Clear();
                }
                buffer.Write(run.Buffer.AsSpan().Slice(item.offset, item.length));
            }
            await writeTask;
            await output.WriteAsync(buffer.WrittenMemory);

            if (returnBuffer)
            {
                ReturnBuffer(run.Buffer);
            }
        }
        public void Sort(RecordRefRun run)
        {
            var comparer = new RecordRefComparer(run.Buffer, run.Limit);

            run.Records.Sort(comparer.Compare);
        }