• Glenn Lewis (7/7) Jul 22 2009 If I'm not mistaken, I used to use std.zlib with DMD1, and it was compat...
• Vladimir Panteleev (12/20) Jul 22 2009 If you compare DMD1 and DMD2's zlib.d, you'll notice that the difference...
• grauzone (9/11) Jul 23 2009 zlib can do this for you. Then you don't need to put up so much pressure...

Glenn Lewis <nospam nospam.org> writes:

If I'm not mistaken, I used to use std.zlib with DMD1, and it was compatible
with gzip.
Now that Andrei's awesome book is available on RoughCuts, I finally figured I
would take the plunge and switch up to DMD2.

I tried writing a file with std.zlib.compress, and gzip could not uncompress it
(both level=6 and level=9).
I tried gzip'ing a file, and std.zlib.uncompress could not uncompress it (see
attached D file).

Note that writing with std.zlib then later reading with std.zlib works just
fine... but am I dreaming that I used to also be able to use 'gzip' on the
resulting files?

Thanks!
-- Glenn Lewis

"Vladimir Panteleev" <thecybershadow gmail.com> writes:

On Thu, 23 Jul 2009 08:40:48 +0300, Glenn Lewis <nospam nospam.org> wrote:

 If I'm not mistaken, I used to use std.zlib with DMD1, and it was  
 compatible with gzip.
 Now that Andrei's awesome book is available on RoughCuts, I finally  
 figured I would take the plunge and switch up to DMD2.

If you compare DMD1 and DMD2's zlib.d, you'll notice that the differences  
are trivial, and the zlib library itself hasn't changed at all, so nothing  
could have changed to affect this.

 I tried writing a file with std.zlib.compress, and gzip could not  
 uncompress it (both level=6 and level=9).
 I tried gzip'ing a file, and std.zlib.uncompress could not uncompress it  
 (see attached D file).

What you seem to be confusing is that zlib is a compression algorithm,  
while gzip is a compression utility and file format. You need to add a  
header to zlib-compressed data.

I've attached a simple module I use to encode/decode gzip files. Hope this  
helps.

-- 
Best regards,
  Vladimir                          mailto:thecybershadow gmail.com

grauzone <none example.net> writes:

 I've attached a simple module I use to encode/decode gzip files. Hope 
 this helps.

zlib can do this for you. Then you don't need to put up so much pressure 
on the GC, and there's no need for manual header parsing/generation.

Quoting the docs for deflateInit2:

"windowBits can also be greater than 15 for optional gzip encoding. Add
    16 to windowBits to write a simple gzip header and trailer around the
    compressed data instead of a zlib wrapper."

You can also enable automatic header detection for zlib/gzip decoding in 
inflateInit2.

But I think you'll have to stop using std.zlib to use this functionality.