/**
* Negotiate permessage-deflate settings with the server using the given handshake HTTP response.
*
* @param HttpResponse $response
* @return PerMessageDeflate Or null when the server did not enable the extension.
*/
protected function negotiatePerMessageDeflate(HttpResponse $response)
{
static $zlib;
$extension = null;
if ($zlib ?? ($zlib = \function_exists('inflate_init'))) {
foreach ($response->getHeaderTokens('Sec-WebSocket-Extensions') as $ext) {
if (\strtolower($ext->getValue()) === 'permessage-deflate') {
$extension = $ext;
break;
}
}
}
if ($extension === null) {
return;
}
try {
return PerMessageDeflate::fromHeaderToken($extension);
} catch (\OutOfRangeException $e) {
return;
}
}