tree 0c246ada7da7723353ec38b5e22bd3d833f07c16
parent e14dc8d6f1c277603822760b74eab711609ac1bf
author Maxim Dounin <mdounin@mdounin.ru> 1510967007 +0300
committer Maxim Dounin <mdounin@mdounin.ru> 1510967007 +0300

Gzip: support for a zlib variant from Intel.

A zlib variant from Intel as available from https://github.com/jtkukunas/zlib
uses 64K hash instead of scaling it from the specified memory level, and
also uses 16-byte padding in one of the window-sized memory buffers, and can
force window bits to 13 if compression level is set to 1 and appropriate
compile options are used.  As a result, nginx complained with "gzip filter
failed to use preallocated memory" alerts.

This change improves deflate_state allocation detection by testing that
items is 1 (deflate_state is the only allocation where items is 1).
Additionally, on first failure to use preallocated memory we now assume
that we are working with the Intel's modified zlib, and switch to using
appropriate preallocations.  If this does not help, we complain with the
usual alerts.

Previous version of this patch was published at
http://mailman.nginx.org/pipermail/nginx/2014-July/044568.html.
The zlib variant in question is used by default in ClearLinux from Intel,
see http://mailman.nginx.org/pipermail/nginx-ru/2017-October/060421.html,
http://mailman.nginx.org/pipermail/nginx-ru/2017-November/060544.html.