The Access Manager
At this point most of the design issues have been addressed and the
Library it is now possible to use the Library to exchange information
between the application an the Internet. The Library provides a set of
functions that can be used to request a URI either on a remote server or
on the local file system. The access method binds the URL with a
specific protocol module as described in section
Access Methods and the stream chains defines the
data flow for incoming and outgoing data.
Searching a URL
MORE
Receiving an Entity
MORE
Sending an Entity
MORE
Return Codes from the Access manager
The access manager has a standard set of return codes that the
application can use for diagnostics. They should only be used as
indications of the result as a more detailed description of any error
situation is registered in the error handler. The set of codes are:
HT_LOADED
- A generic success code that indicates that the request has been
fulfilled
HT_NO_DATA
- Partly a success code, but no document has been retrieved and a
client application is encouraged to maintain the previous document view
as the current view. A
HT_NO_DATA code might be the result
when a telnet session is started etc.
HT_ERROR
- An error has occured and the request could not be fulfilled
HT_RETRY
- The remote server is temporarily unavailable and no more requests
should be issued to the server before the calendar time indicated in
HTRequest->retry_after field. No action is taken by the
Library to automatically retry the request, this is uniquely for the
application to decide.
HT_WOULD_BLOCK
- An I/O operation would block and the request must pause. As the
request is not yet terminated, the operation will continue at a later
time when the blocking situation has ceased to exist.
Context Swapping
In a multithreaded environment it is necessary to keep track of the context of each simultanous
requests issued to the Library as the response might return in another order than the one they were
issued. The Library allows such a context registration in the HTRequest object by providing the registration mechanism
of a call back function and a pointer to an arbitrary data object to be passed to that call back
function.
Henrik Frystyk, libwww@w3.org,
@(#) $Id: Access.html,v 1.13 1997/02/16 18:41:41 frystyk Exp $