Алгоритм работает весьма быстро, тут полный респект с моей стороны.
Но иногда не может раскодировать корректно закодированную строчку. Просто виснет.
Причём это даже не зависит от размера обрабатываемых данных. Иногда всё ОК, а иногда - мёртвое зависание.
Вот, например, на этой картинке:
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Другими алгоритмами декодирования (например, на php) строчка раскодируется совершенно без проблем.