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Re: [Duplicity-talk] zfec vs. par2 (and, hello there!)

From: zooko
Subject: Re: [Duplicity-talk] zfec vs. par2 (and, hello there!)
Date: Tue, 4 Nov 2008 06:48:13 -0700

On Nov 4, 2008, at 4:34 AM, address@hidden wrote:

At least the command line interface do not support to file the redundancy information separately... it always creates a set of files, of which a definable count is necessary to recreate the source file.

In that set of files, the first 3 of them actually contain the contents of the input file (plus each file has a couple of bytes of header). You can inspect the files that zfec produces to see what I mean. Make a file with contents "0123456789" and then run "zfec" on it. Then run "less" on the resulting output files.

only one file can be processed at a time.

It would be easy to change the cmdline zfec tool to process multiple files, but what should it do with them? I guess maybe "for FILE in a b c d e ; do zfec $FILE ; done" or else "tar cjf a.tar.bz2 a b c d e && zfec a.tar.bz2" would probably be the best way to handle multiple files.

I don't know about the inner API as I am not python literate ... regards ede

The zfec README.txt describes the API. There is a function called "encode()". You tell it which block numbers to produce. If you tell it numbers which are >= K then it produces only "check blocks" a.k.a. "parity blocks" a.k.a. "secondary blocks", and produces no file data blocks.



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