How to read variable in C code?

[Witold Filipczyk]

Hi,

there is map:
map $http_host $hosts {
  hostnames;
  default 0;
  .example.com 1;
  .example.net 1;
  ...
  .example.org 1;
}

How to read the value of $hosts in C module code?
How to make it right, that's mean do not evaluate it more than once per request?

I want to do some modifications of body response based on 'type' of host and map
would simplify the code, at least hope so.