[Bug-tar] Feature request: Include support for lz4 (patch included)

[Pascal Ernster]

Would it be possible to include support for lz4 and zstd into the GNU
tar implementation?

To the best of my knowledge, lz4 seems to be the fastest mature FOSS
compression tool/algorithm available right know (for both compression
and decompression). While compression is only a few percent faster than
LZO/lzop or Snappy (yet still achieving better compression rates when
applied to the Silesia Corpus), decompression is almost twice as fast as
Snappy, and thrice as fast as LZO. The only thing which I know to be
able to achieve even faster decompression rates is lz4 in HC mode - but
LZ4-HC only achieves a compression throughput and compression ratio
comparable to zlib.

https://github.com/Cyan4973/lz4

lz4 should be mostly compatible to gzip, as it supports the parameters
-d, -f, -1 and -9 just the same way as gzip does.

I've written a patch to implement LZ4 support for tar (see attachment),
but as I'm not really accustomed to fiddling with GNU tar code, you
should definitely double check it for any mistakes before merging it.

regards
Pascal Ernster

lz4.diff
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