Re: [RFH] zlib gurus out there?

Linus Torvalds [off-list ref] writes:

On Tue, 7 Mar 2006, Junio C Hamano wrote:

quoted

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.