
    <<ArpaImpl.mesa>>
        <<Demers, August 26, 1987 4:18:43 pm PDT>>
        <<>>
    DIRECTORY
        Arpa USING [Address, Net, netMasks, nullAddress],
        ArpaExtras USING [AddressAnd, broadcastAddress, MaskNot],
        ArpaTranslation USING [GetNet, GetSubnetMask],
        CommDriver USING [GetNetworkChain, Network]
        ;

    ArpaImpl: CEDAR PROGRAM
        IMPORTS ArpaExtras, ArpaTranslation, CommDriver
        EXPORTS Arpa, ArpaExtras
        ~ {

        Address: TYPE ~ Arpa.Address;
        Class: TYPE ~ Arpa.Net;

        broadcastAddress: Address ~ ArpaExtras.broadcastAddress;
        nullAddress: Address ~ Arpa.nullAddress;

        NetClassInner: PROC [address: Address] RETURNS [Class] ~ INLINE {
            RETURN[SELECT address.a FROM < 080H => a, < 0C0H => b, ENDCASE => c] };

        NetType, NetClass: PUBLIC PROC [address: Address] RETURNS [Class] ~ {
            RETURN[NetClassInner[address]] };

        NetMask: PUBLIC PROC [address: Address] RETURNS [Address] ~ {
            RETURN[SELECT address.a FROM
                < 080H => Arpa.netMasks[a],
                < 0C0H => Arpa.netMasks[b],
                ENDCASE => Arpa.netMasks[c]
                ];
            };

        NetNumber: PUBLIC PROC [address: Address] RETURNS [Address] ~ {
            RETURN[SELECT address.a FROM
                < 080H => ArpaExtras.AddressAnd[address, Arpa.netMasks[a]],
                < 0C0H => ArpaExtras.AddressAnd[address, Arpa.netMasks[b]],
                ENDCASE => ArpaExtras.AddressAnd[address, Arpa.netMasks[c]]
                ];
            };

        SubnetAndHostNumber: PUBLIC PROC [address: Address] RETURNS [Address] ~ {
            RETURN[
                ArpaExtras.AddressAnd[address, ArpaExtras.MaskNot[NetMask[address]]]
                ];
            };

        NetAndSubnetMask: PUBLIC PROC [address: Address] RETURNS [Address]
            ~ {
            net: Address _ NetNumber[address];
            FOR n: CommDriver.Network _ CommDriver.GetNetworkChain[], n.next WHILE n # NIL DO
                IF n.arpa.host = nullAddress THEN LOOP; -- avoid NIL fault in GetNet below
                IF ArpaTranslation.GetNet[n] = net
                    THEN RETURN [ArpaTranslation.GetSubnetMask[n]];
                ENDLOOP;
            RETURN [NetMask[address]];
            };

        IsMyAddress: PUBLIC PROC [address: Address] RETURNS [BOOL]
            ~ {
            IF address # Arpa.nullAddress THEN {
                FOR n: CommDriver.Network _ CommDriver.GetNetworkChain[], n.next WHILE n # NIL DO
                    IF n.arpa.host = address THEN RETURN [TRUE];
                    ENDLOOP;
                };
            RETURN [FALSE];
            };

        MyAddress: PUBLIC PROC RETURNS [Address _ nullAddress] ~ {
            FOR n: CommDriver.Network _ CommDriver.GetNetworkChain[], n.next WHILE n # NIL DO
                IF n.arpa.host # nullAddress THEN RETURN [n.arpa.host];
                ENDLOOP;
            };

        MyAddresses: PUBLIC PROC RETURNS [addresses: LIST OF Address] ~ {
            GetOne: PROC [n: CommDriver.Network] RETURNS [list: LIST OF Address] ~ {
                IF n = NIL THEN RETURN [NIL];
                list _ GetOne[n.next];
                IF n.arpa.host # nullAddress THEN list _ CONS[n.arpa.host, list];
                };
            RETURN[GetOne[CommDriver.GetNetworkChain[]]];
            };

        }...