Re: [RFH] zlib gurus out there?

From: Junio C Hamano <junkio@cox.net>
Date: Mar 8, 2006, 01:22 UTC
Message-ID: <7vslptivbg.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.64.0603071658300.32577@g5.osdl.org>

Linus Torvalds <torvalds@osdl.org> writes:

Show 16 quoted lines

> 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.