// TODO: update when package unicode captures more of the properties.
func isSeparator(r rune) bool {
	// ASCII alphanumerics and underscore are not separators
	if r <= 0x7F {
		switch {
		case '0' <= r && r <= '9':
			return false
		case 'a' <= r && r <= 'z':
			return false
		case 'A' <= r && r <= 'Z':
			return false
		case r == '_':
			return false
		}

   * of reads and delaying a lock acquisition until the threshold is crossed or a mutation occurs.
   *
   * <p>This must be a (2^n)-1 as it is used as a mask.
   */
  static final int DRAIN_THRESHOLD = 0x3F;

  /**
   * Maximum number of entries to be drained in a single cleanup run. This applies independently to
   * the cleanup queue and both reference queues.
   */
  // TODO(fry): empirically optimize this

         <match value="0x00" type="string" mask="0xF8" offset="5"/>
         <match value="0x08" type="string" mask="0xF8" offset="5"/>
         <match value="0x10" type="string" mask="0xF8" offset="5"/>
         <match value="0x18" type="string" mask="0xF8" offset="5"/>
         <match value="0x20" type="string" mask="0xF8" offset="5"/>
         <match value="0x28" type="string" mask="0xF8" offset="5"/>

   * of reads and delaying a lock acquisition until the threshold is crossed or a mutation occurs.
   *
   * <p>This must be a (2^n)-1 as it is used as a mask.
   */
  static final int DRAIN_THRESHOLD = 0x3F;

  /**
   * Maximum number of entries to be drained in a single cleanup run. This applies independently to
   * the cleanup queue and both reference queues.
   */
  // TODO(fry): empirically optimize this