[COMPRESS-612] Support atime/ctime and higher time precision for TAR (original) (raw)

This is a proposal for some code I have already worked on.

Context

I'm coding a tool that requires extracting/compressing files. I noticed the following shortcomings:

• File size is limited to 8GB. This limitation was lifted as of POSIX.1-2001 and it also does not exist on GNU and old GNU formats. Bigger files are fully supported by some TAR archiving tools such as GNU TAR. Reference: https://lists.gnu.org/archive/html/help-tar/2015-04/msg00001.html
  • I think I was actually wrong here in that current implementation should support files >8GB if using BIGNUMBER_POSIX.
• Only modification date is available as a time type.
• Maximum granularity is seconds, even though the PAX header contains 100ns intervals
• Other time-related PAX headers are considered extra headers (ctime and atime)

My proposal is as follows:

• Migrate time fields from java.util.Date to java.nio.file.attribute.FileTime
• Keep backwards compatibility through getter/setter methods and add new ones for FileTime
• Parse times in with a maximal granularity of 100ns intervals from PAX headers
• Read/write ctime and atime and add corresponding fields
• Write times to PAX headers using a maximum granularity of 100ns intervals when in BIGNUMBER_POSIX mode.
• Add a new mode BIGNUMBER_POSIX_2001 for writing big numbers, allowing for the bigger size, mtime, ctime and atime to be written
• Lift the 8GB limit when using BIGNUMBER_POSIX_2001

I already have some code for that in https://github.com/andrebrait/commons-compress/tree/COMPRESS-612

Since compatibility with Android now requires API level 26 and that includes FileTime, I think we can do that here as well.

This will bring tar in line with Zip in this regard.