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Ulm's Oberon Library:
IPv4NameSystems

NAME

SYNOPSIS

CONST errors = 6;
CONST colonExpected = 0;
CONST portExpected = 1;
CONST invalidPortNumber = 2;
CONST hostnameExpected = 3;
CONST unableToFindPort = 4;
CONST tooManyIndirections = 5;
TYPE ErrorCode = SHORTINT; (* colonExpected.. *)
TYPE ErrorEvent = POINTER TO ErrorEventRec;
TYPE ErrorEventRec =
   RECORD
      (Events.EventRec)
      errorcode: ErrorCode;
      source: ARRAY 128 OF CHAR;
   END;
VAR error: Events.EventType;
VAR errormsg: ARRAY errors OF Events.Message;



PROCEDURE Import(ipaddr: IPv4Addresses.SocketAddress;
                 VAR root: Names.Node;
                 errors: RelatedEvents.Object) : BOOLEAN;
PROCEDURE ImportFrom(source: ARRAY OF CHAR;
                     VAR root: Names.Node;
                     errors: RelatedEvents.Object) : BOOLEAN;



PROCEDURE Convert(source: ARRAY OF CHAR;
                  VAR address: Networks.Address;
                  errors: RelatedEvents.Object) : BOOLEAN;

DESCRIPTION

Import allows the direct specification of an IPv4 address whereas ImportFrom accepts a specification which can be either

• a fully qualified host name for which A records can be found, followed by a colon and a port number, or
• an IPv4 address in the dotted decimal notation, followed by a colon and a port number, or
• a domain name for which a TXT record can be found that provides an ``ons'' attribute according to RFC 1464. In this case, ImportFrom works recursively with the attribute value found. At maximum three indirections are accepted.

Convert converts a specification as described above for ImportFrom to be converted into a network address that can be passed on to NamesBootService.

DIAGNOSTICS

colonExpected

A colon was expected but not found in the specification.

portExpected

A port number was expected but not found in the specification.

invalidPortNumber

The port number was out of range.

hostnameExpected

The specification was empty.

unableToFindPort

Just a domain name was given in the specification and a TXT record could not be obtained.

tooManyIndirections

The upper limit of three indirections for TXT record references was exceeded.

In addition, error events can be expected by the underlying modules. This includes mainly events from DNSResolvers and of InetTCP. All error events are related to the errors parameters.

SEE ALSO

NamesBootService

service that provides the address of the root object at a known location.

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