Protocol Families, Service Flavors
A protocol family ($ARPA, $XNS, etc) implies a name/address space. A flavor ($SunYP, $DNS, etc) identifies a directory service for the space.
Addresses and Names
Addresses and names are represented by ropes in protocol-family-specific syntax.
An address comprises two components: a host part (identifying a host) and a port part (identifying a communications endpoint on a host). An address rope can always be parsed unambiguously into its host and port parts. There are unspecified host and port addresses, as well as a broadcast host address, in each protocol family.
In general a name may denote a host, a port, or a host-port pair. The interpretation of a name (as host, port, or pair) may depend on context. NIL is a valid name for the unspecified host or port. The protocol-family-independent ROPE broadcastHostName, below, denotes the unspecified port on the broadcast host in every protocol family.
An address ROPE can always be used where a name ROPE is expected.
Components: TYPE ~ { host, port, hostAndPort };
broadcastHostName: ROPE;
Client Lookups
In all cases a (protocol) family is specified. Lookups are done in one or more services registered as serving the specified family. If a service flavor is specified, that registered service (and no other) is used; if the service flavor is defaulted, all services registered for the family are tried in the order specified at registration (see Registration, below). This may take a long time in the (unusual) case that there are many service flavors registered for the same family.
Addresses from Names
AddressFromName:
PROC [family:
ATOM, name:
ROPE, portHint:
ROPE ¬
NIL, components: Components ¬ hostAndPort, serviceFlavor:
ATOM ¬
NIL]
RETURNS [addr:
ROPE, responderFlavor:
ATOM];
Look up given name in the name space associated with given (protocol) family.
Return an address rope containing the requested components (with unspecified for the non-requested components.
The meaning of portHint is family-specific; it will usually name a default port to use if the name lookup doesn't specify a port and the requested components include port.
! Error[$notFound ...]
! Error[$noService, ...]
! Error[$serviceError, ... ]
Names from Addresses
NameFromAddress:
PROC [family:
ATOM, addr:
ROPE, components: Components ¬ hostAndPort, serviceFlavor:
ATOM ¬
NIL]
RETURNS [name:
ROPE, responderFlavor:
ATOM];
Try to map given address rope to a name in the name space associated with the given (protocol) family.
Return name including requested components.
! Error[$notFound ...]
! Error[$noService, ...]
! Error[$notImplemented, ...]
! Error[$serviceError, ... ]
Enumerating Registered Families
EachFamilyProc: TYPE ~ PROC [family: ATOM] RETURNS [continue: BOOL];
EnumerateFamilies:
PROC [eachFamily: EachFamilyProc];
Enumerate the families for which there is at least one registered service flavor.
Registration, Implementation details ...
Register:
PROC [family:
ATOM, proc: RegistrationCallbackProc];
Used to register and unregister name service instances.
AddressFromNameProc:
TYPE ~
PROC [r: Registration, name:
ROPE, portHint:
ROPE, components: Components]
RETURNS [addr:
ROPE];
Implements the AddressFromName operation.
NameFromAddressProc:
TYPE ~
PROC [r: Registration, addr:
ROPE, components: Components]
RETURNS [name:
ROPE];
Implements the NameFromAddress operation.
DestroyProc:
TYPE ~
PROC [r: Registration];
Called just before deleting a registration (in EnumerateRegistrations) e.g. to clean up caches.
Registration: TYPE ~ REF RegistrationObject;
RegistrationObject:
TYPE ~
RECORD [
family: ATOM,
flavor: ATOM,
addressFromName: AddressFromNameProc,
nameFromAddress: NameFromAddressProc ¬ NIL,
destroy: DestroyProc ¬ NIL,
clientData: REF ¬ NIL,
packageData: REF ¬ NIL -- opaque to flavor implementors
];
RegistrationAction:
TYPE ~ {
continue, -- continue enumeration
abort, -- abort enumeration
insert, -- insert new registration before old one
replace, -- replace old registration with new one (call its DestroyProc)
delete -- delete old registration (call its DestroyProc)
};
RegistrationCallbackProc:
TYPE ~
PROC [oldRegistration: Registration]
RETURNS [action: RegistrationAction, newRegistration: Registration];
Callback for Register.