anchor.diff:  , openssl
   , zlib
   , libuv
  -, fetchpatch
   # External poll is required for e.g. mosquitto, but discouraged by the maintainer.
   , withExternalPoll ? false
   }:
   
   let
  -  generic = { version, sha256, patches ? [] }: stdenv.mkDerivation rec {
  +  generic = { version, hash, patches ? [] }: stdenv.mkDerivation rec {
       pname = "libwebsockets";
       inherit version;
   
  
positive.code:       owner = "warmcat";
        repo = "libwebsockets";
        rev = "v${version}";
        inherit sha256;
      };
  
      inherit patches;
  
negative.code: 
  in {
    libwebsockets_4_3 = generic {
      version = "4.3.2";
      hash = "sha256-why8LAcc4XN0JdTJ1JoNWijKENL5mOHBsi9K4wpYr2c=";
    };
  }
  