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Author vstinner
Recipients Ankur.Ankan, berker.peksag, brandon-rhodes, eric.araujo, ezio.melotti, kyle, larry, lars.gustaebel, rhettinger, serhiy.storchaka, vstinner
Date 2013-03-20.11:27:10
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I don't think that we need to support compressing/decompressing using
the standard input/output.

2013/3/20 Brandon Craig Rhodes <>:
> Brandon Craig Rhodes added the comment:
> Larry Hastings <> writes:
>> Huh.  tar *can* infer it from the data itself.  On the other hand, it
>> chooses explicitly not to.  I guess "tar" knows explicit is better
>> than implicit too ;-)
> I am told that the refusal of "tar" to introspect the data is because:
> (a) Tar runs "gunzip -c" (for example) as an external program; it does
> not actually compile against libz.
> (b) Streams in UNIX cannot be rewound.  Tar cannot look at the first
> block of an input pipe and then "put the block back" so that the same
> input can be fed directly to "gunzip" as its input.
> (c) Given (a) and (b), tar could only support data introspection of
> input from a pipe if it were willing to be a pass-through that, after
> reading and introspecting the first block, then fired up "gunzip" and
> sent ALL of the blocks through.  Which would require multiprocessing,
> threading, or async I/O so that tar could both read and write, which
> would make tar more complicated.
> (d) Therefore, tar refuses to even look.
> Since Python does bundle compression in its standard library, it can
> quite trivially step forward and actually do the data introspection that
> tar insists on not doing; the first few bytes of a tar archive are quite
> demonstrably different from the first bytes of a gzip stream, if I
> recall.
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Date User Action Args
2013-03-20 11:27:10vstinnersetrecipients: + vstinner, rhettinger, lars.gustaebel, larry, ezio.melotti, eric.araujo, kyle, brandon-rhodes, berker.peksag, serhiy.storchaka, Ankur.Ankan
2013-03-20 11:27:10vstinnerlinkissue13477 messages
2013-03-20 11:27:10vstinnercreate