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Re: [PATCH 5/5] archive-zip: stream large blobs into zip file

From
René Scharfe <rene.scharfe@lsrfire.ath.cx>
Date
Apr 30, 2012, 22:54 UTC
Message-ID
<4F9F1809.1060803@lsrfire.ath.cx>
In-Reply-To
<7vipghf2z0.fsf@alter.siamese.dyndns.org>
Am 30.04.2012 21:12, schrieb Junio C Hamano:
Show 10 quoted lines
> Nguyễn Thái Ngọc Duy<pclouds@gmail.com>  writes:
>
>> A large blob will be read twice. One for calculating crc32, one for
>> actual writing.
>
> Is that because you need the checksum before the payload?  That is
> unfortunate.  It would be nice (read: not a rejection of this patch---it
> is a good first step to do it stupid but correct way before trying to
> optimize it) to avoid it when the output is seekable, especially because
> we are talking about a *large* payload.

The ZIP format optionally allows writing the CRC and the sizes after the data. This adds a data descriptor with a size of 16 bytes to each streamed entry. Seeking back and correcting these values in an output file would avoid that.

Show 15 quoted lines
>> diff --git a/t/t1050-large.sh b/t/t1050-large.sh
>> index fe47554..458fdde 100755
>> --- a/t/t1050-large.sh
>> +++ b/t/t1050-large.sh
>> @@ -138,4 +138,8 @@ test_expect_success 'tar achiving' '
>>   	git archive --format=tar HEAD>/dev/null
>>   '
>>
>> +test_expect_success 'zip achiving' '
>> +	git archive --format=zip HEAD>/dev/null
>> +'
>
> Can't we do better than "we only check if it finishes without barfing; we
> cannot afford to check the correctness of the output"?  The same comment
> applies to all the tests you added to this file in the past 3 months.

Streaming to tar can be tested by setting core.big_file_threshold big enough, creating a non-streamed version of the archive and comparing it to the streamed one. With the seek trick, this would work for ZIP as well. For streaming with an added data descriptor we'd need to actually unpack the ZIP file, though.

René
Previous: Junio C HamanoNext: René Scharfe
Message 15 of 23 in “Large file support for git-archive”
  1. 0/5 Large file support for git-archiveNguyễn Thái Ngọc Duy, Apr 30, 2012
  2. 1/5 archive-tar: turn write_tar_entry into blob-writing onlyNguyễn Thái Ngọc Duy, Apr 30, 2012
  3. Junio C HamanoApr 30, 2012
  4. René ScharfeApr 30, 2012
  5. 2/5 archive-tar: unindent write_tar_entry by one levelNguyễn Thái Ngọc Duy, Apr 30, 2012
  6. 3/5 archive: delegate blob reading to backendNguyễn Thái Ngọc Duy, Apr 30, 2012
  7. René ScharfeApr 30, 2012
  8. 4/5 archive-tar: stream large blobs to tar fileNguyễn Thái Ngọc Duy, Apr 30, 2012
  9. Junio C HamanoApr 30, 2012
  10. René ScharfeApr 30, 2012
  11. Junio C HamanoApr 30, 2012
  12. René ScharfeApr 30, 2012
  13. 5/5 archive-zip: stream large blobs into zip fileNguyễn Thái Ngọc Duy, Apr 30, 2012
  14. Junio C HamanoApr 30, 2012
  15. René ScharfeApr 30, 2012
  16. streaming: void pointer instead of char pointerRené Scharfe, Apr 30, 2012
  17. archive-zip: remove uncompressed_sizeRené Scharfe, Apr 30, 2012
  18. archive-zip: factor out helpers for writing sizes and CRCRené Scharfe, Apr 30, 2012
  19. archive-zip: streaming for stored filesRené Scharfe, Apr 30, 2012
  20. archive-zip: streaming for deflated filesRené Scharfe, Apr 30, 2012
  21. Junio C HamanoApr 30, 2012
  22. René ScharfeApr 30, 2012
  23. Nguyen Thai Ngoc DuyMay 1, 2012

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