These files are used to test for proper use of Unicode Path extra fields (zip specification §4.6.9) when unarchiving zip archives.
Both contain three empty files, one without a Unicode Path extra field, one with a good extra field (CRC matches the header file name), one with a stale extra field (mismatched CRC). By using different values in the header file name and the Unicode path, it can be distinguished which one was used. A compliant unarchiver will use the names marked in bold.
| File name in header | CRC | Unicode Path |
|---|---|---|
| nameonly-name | ||
| goodextra-name | CRC("goodextra-name") | goodextra-extra |
| badextra-name | CRC("bogus") | badextra-extra |
The difference between the two archives is whether the Language Encoding Flag (EFS) is set, which indicates that the header file names are already in UTF-8. The specification is not explicit about which one wins when both the flag is set and a Unicode Path extra field is present (it only says archivers shouldn’t do that). In practice, all unarchivers I have seen (including Apache Commons Compress used by Plexus-Archiver) ignore the extra field when the flag is set, which is why only efsclear.zip is useful for testing.
The archives were created by the included GenerateZips.java using Commons Compress.