var skipLength int64
	var cumulativeActualSize int64
	var firstPartIdx int
	for i, part := range oi.Parts {
		cumulativeActualSize += part.ActualSize
		if cumulativeActualSize <= offset {
			compressedOffset += part.Size
		} else {
			firstPartIdx = i
			skipLength = cumulativeActualSize - part.ActualSize
			break
		}
	}
	partSkip = offset - skipLength