From mboxrd@z Thu Jan  1 00:00:00 1970
From: Junio C Hamano <junkio@cox.net>
Subject: Re: [RFH] zlib gurus out there?
Date: Tue, 07 Mar 2006 17:22:59 -0800
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To: Linus Torvalds <torvalds@osdl.org>
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Linus Torvalds <torvalds@osdl.org> writes:

> On Tue, 7 Mar 2006, Junio C Hamano wrote:
>> 
>> However, I am stuck with the first step, which is to do a full
>> flush after the header.  An obvious change to the code quoted
>> above writes out a corrupt object:
>> 
>> 	/* First header.. */
>> 	stream.next_in = hdr;
>> 	stream.avail_in = hdrlen;
>> -	while (deflate(&stream, 0) == Z_OK)
>> +	while (deflate(&stream, Z_FULL_FLUSH) == Z_OK)
>> 		/* nothing */;
>
> No, I don't think that's good. You're only doing a partial deflate, you 
> can't ask for a Z_FULL_FLUSH. That only works if you give it the whole 
> buffer, and you don't.

So, in short there is no way to create:

    hdr part deflated.
    flush.
    data part deflated independently.

and have the current sha1_read_file() not to notice that flush,
while I can inspect the deflated stream to find the "flush", and
copy only the defalted data part into a pack?  Bummer...  I was
really shooting for full backward compatibility.