C++ – How to concat two or more gzip files/streams

I want to concat two or more gzip streams without recompressing them.

I mean I have A compressed to A.gz and B to B.gz, I want to compress them to single gzip (A+B).gz without compressing once again, using C or C++.

Several notes:

• Even you can just concat two files and gunzip would know how to deal with them, most of programs would not be able to deal with two chunks.
• I had seen once an example of code that does this just by decompression of the files and then manipulating original and this significantly faster then normal re-compression, but still requires O(n) CPU operation.
• Unfortunaly I can't found this example I had found once (concatenation using decompression only), if someone can point it I would be greatful.

Note: it is not duplicate of this because proposed solution is not fits my needs.

Clearification edit:

I want to concate several compressed HTML pices and send them to browser as one page, as per request: "Accept-Encoding: gzip", with respnse "Content-Encoding: gzip"

If the stream is concated as simple as cat a.gz b.gz >ab.gz, Gecko (firefox) and KHTML web engines gets only first part (a); IE6 does not display anything and Google Chrome displays first part (a) correctly and the second part (b) as garbage (does not decompress at all).

Only Opera handles this well.

So I need to create a single gzip stream of several chunks and send them without re-compressing.

Update: I had found gzjoin.c in the examples of zlib, it does it using only decompression. The problem is that decompression is still slower them simple memcpy.

It is still faster 4 times then fastest gzip compression. But it is not enough.

What I need is to find the data I need to save together with gzip file in order to
not run decompression procedure, and how do I find this data during compression.