class HTTPClient::BasicAuth

Used in WWWAuth and ProxyAuth.
Authentication filter for handling BasicAuth negotiation.

def challenge(uri, param_str = nil)

Challenge handler: remember URL for response. 
def challenge(uri, param_str = nil)
  synchronize {
    @challenge[urify(uri)] = true
    true
  }
end

def get(req)

* child page of defined credential
* child page of challengeable(got *Authenticate before) uri and,
It sends cred only when a given uri is;
Response handler: returns credential. 
def get(req)
  target_uri = req.header.request_uri
  synchronize {
    return nil if !@force_auth and !@challenge.any? { |uri, ok|
      Util.uri_part_of(target_uri, uri) and ok
    }
    return @cred if @cred
    Util.hash_find_value(@auth) { |uri, cred|
      Util.uri_part_of(target_uri, uri)
    }
  }
end

def initialize

Creates new BasicAuth filter. 
def initialize
  super('Basic')
  @cred = nil
  @auth = {}
  @force_auth = false
end

def set(uri, user, passwd)

uri == nil for generic purpose (allow to use user/password for any URL).
Set authentication credential. 
def set(uri, user, passwd)
  synchronize do
    if uri.nil?
      @cred = ["#{user}:#{passwd}"].pack('m').tr("\n", '')
    else
      uri = Util.uri_dirname(uri)
      @auth[uri] = ["#{user}:#{passwd}"].pack('m').tr("\n", '')
    end
  end
end

def set?

have we marked this as set - ie that it's valid to use in this context? 
def set?
  @cred || @auth.any?
end