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bzip2: fix bug with duplicate read of CRC32 when it overlaps end of buffer and 'bzip2-done is thrown. #12

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bzip2: fix bug with duplicate read of CRC32 when it overlaps end of buffer and 'bzip2-done is thrown. #12

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16 changes: 13 additions & 3 deletions bzip2.lisp
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Original file line number Diff line number Diff line change
Expand Up @@ -424,12 +424,22 @@
(unless (= byte #x59)
(error 'invalid-bzip2-data))
(incf (bzip2-state-current-block-number state))
(transition-to bzip2-block-crc32)))
(transition-to bzip2-block-crc32-1)))

(bzip2-block-crc32 (state)
(bzip2-block-crc32-1 (state)
(declare (type bzip2-state state))
(let ((crc32-hi (ensure-and-read-bits 16 state))
;; store first part of CRC32
;; (the 2 states should be split to avoid bug when
;; the state machine is restarted between reads of the hi & lo parts)
(setf (bzip2-state-stored-block-crc state)
(ensure-and-read-bits 16 state))
(transition-to bzip2-block-crc32-2))

(bzip2-block-crc32-2 (state)
(declare (type bzip2-state state))
(let ((crc32-hi (bzip2-state-stored-block-crc state))
(crc32-lo (ensure-and-read-bits 16 state)))
;; combine first and second part of CRC32
(setf (bzip2-state-stored-block-crc state)
(logior (ash crc32-hi 16) crc32-lo))
(transition-to bzip2-block-randombit)))
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