Testing Archives

This feature does not work on disk images, because they don't have any sort of checksum or CRC on the files.  Every file on a disk archive is scanned when the disk is opened, and any obviously damaged files are labeled as such in the file list.

Files in ShrinkIt, Binary II, and AppleLink Compression Utility archives can be tested, but not all of those have CRCs either.  In those cases CiderPress will read the data to verify that the archive hasn't been truncated.  Errors in compressed data can sometimes be detected without a CRC.  The overall structure of the archive, including any CRCs on header fields, is verified when the archive is opened.

For files that do have checksums or CRCs, CiderPress will use the appropriate error detection algorithm, uncompressing the data when necessary.  Testing an archive essentially does a full extraction, doing everything except write the data to disk.