allEmpty := true
	for _, tag := range c.PartETags {
		if len(tag) != 0 {
			allEmpty = false
			break
		}
	}
	if allEmpty {
		c.PartETags = nil
	}
	if len(c.PartActualSizes) == 0 {
		c.PartActualSizes = nil
	}

	// Get a 64 bit CRC
	crc := hashDeterministicString(c.MetaUser)
	crc ^= hashDeterministicBytes(c.MetaSys)

	// Nil fields.
	c.MetaSys = nil
	c.MetaUser = nil