nsIURIChecker

 The URI checker is a component that can be used to verify the existance
 of a resource at the location specified by a given URI.  It will use
 protocol specific methods to verify the URI (e.g., use of HEAD request
 for HTTP URIs).
[scriptable, uuid(4660c1a1-be2d-4c78-9baf-c22984176c28)]
interface nsIURIChecker : nsIRequest

Attributes

 Returns the base channel that will be used to verify the URI.
readonly attribute nsIChannel baseChannel

Methods

 Begin asynchronous checking URI for validity.  Notification will be
 asynchronous through the nsIRequestObserver callback interface.  When
 OnStartRequest is fired, the baseChannel attribute will have been
 updated to reflect the final channel used (corresponding to any redirects
 that may have been followed).

 Our interpretations of the nsIRequestObserver status codes:
   NS_BINDING_SUCCEEDED:   link is valid
   NS_BINDING_FAILED:      link is invalid (gave an error)
   NS_BINDING_ABORTED:     timed out, or cancelled

 @param aObserver
        The object to notify when the link is verified.  We will
        call aObserver.OnStartRequest followed immediately by
        aObserver.OnStopRequest.  It is recommended that the caller use
        OnStopRequest to act on the link's status.  The underlying request
        will not be cancelled until after OnStopRequest has been called.
 @param aContext
        A closure that will be passed back to the nsIRequestObserver
        methods.
void asyncCheck(in nsIRequestObserver aObserver, in nsISupports aContext) 
 Initializes the URI checker.  After this method is called, it is valid
 to further configure the URI checker by calling its nsIRequest methods.
 This method creates the channel that will be used to verify the URI.
 In the case of the HTTP protocol, only a HEAD request will be issued.

 @param aURI
        The URI to be checked.
void init(in nsIURI aURI)