code review 159120044: compress/gzip: allow stopping at end of first stream

compress/gzip: allow stopping at end of first stream

Allows parsing some file formats that assign special
meaning to which stream data is found in.

Will do the same for compress/bzip2 once this is
reviewed and submitted.

Fixes issue 6486.

[rsc, 2014-10-20 21:34:17]

Hello nigeltao (cc: adg, bradfitz, golang-codereviews@googlegroups.com, r),

I'd like you to review this change to
https://code.google.com/p/go/

[kortschak, 2014-10-20 22:50:44]

Very nice. Thank you.

[nigeltao, 2014-10-21 01:20:02]

LGTM.

[rsc, 2014-10-21 02:03:51]

*** Submitted as https://code.google.com/p/go/source/detail?r=c31876cc01e9 ***

compress/gzip: allow stopping at end of first stream

Allows parsing some file formats that assign special
meaning to which stream data is found in.

Will do the same for compress/bzip2 once this is
reviewed and submitted.

Fixes issue 6486.

LGTM=nigeltao
R=nigeltao, dan.kortschak
CC=adg, bradfitz, golang-codereviews, r
https://codereview.appspot.com/159120044

[rsc, 2014-10-21 02:10:52]

I take it back. I am NOT making the same change to bzip2.
There is no Reader type there to add methods to. Not worth it.

Russ

[gobot, 2014-10-21 04:04:40]

This changed caused perf changes on windows-amd64-perf:


json-1                    old          new      delta
rss                  62550016     68612096      +9.69
sys-gc                3107388      3463740     +11.47
sys-total            57448760     63510840     +10.55

json-8                    old          new      delta
rss                 181248000    201818112     +11.35
sys-gc               10086972     11356732     +12.59
sys-total           174905656    196856120     +12.55

json-16                   old          new      delta
rss                 324767744    390537216     +20.25
sys-gc               18631228     22444604     +20.47
sys-total           318378280    383849192     +20.56

http://build.golang.org/perfdetail?commit=c31876cc01e949e1be6f707f51b980d3963...



—gobot