From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=unavailable autolearn_force=no version=3.4.4 X-Received: by 2002:a6b:2209:: with SMTP id i9-v6mr2903542ioi.138.1526048493209; Fri, 11 May 2018 07:21:33 -0700 (PDT) X-Received: by 2002:a9d:24a1:: with SMTP id z30-v6mr274228ota.4.1526048493051; Fri, 11 May 2018 07:21:33 -0700 (PDT) Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!news.uzoreto.com!news.redatomik.org!newsfeed.xs4all.nl!newsfeed9.news.xs4all.nl!85.12.16.69.MISMATCH!peer02.ams1!peer.ams1.xlned.com!news.xlned.com!peer02.am4!peer.am4.highwinds-media.com!peer03.iad!feed-me.highwinds-media.com!news.highwinds-media.com!v8-v6no500300itc.0!news-out.google.com!b185-v6ni655itb.0!nntp.google.com!u74-v6no517933itb.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Fri, 11 May 2018 07:21:32 -0700 (PDT) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=2003:c7:83d7:a522:6d:1703:e2f3:a382; posting-account=rmHyLAoAAADSQmMWJF0a_815Fdd96RDf NNTP-Posting-Host: 2003:c7:83d7:a522:6d:1703:e2f3:a382 References: User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <235d41bc-d7a5-4c66-9dac-640dce5f20c5@googlegroups.com> Subject: Re: AI12-0218: What is the portable representation clause for processing IETF packets on little-endian machines? From: AdaMagica Injection-Date: Fri, 11 May 2018 14:21:33 +0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Received-Bytes: 4321 X-Received-Body-CRC: 544321021 Xref: reader02.eternal-september.org comp.lang.ada:52273 Date: 2018-05-11T07:21:32-07:00 List-Id: Am Donnerstag, 10. Mai 2018 19:45:43 UTC+2 schrieb Dan'l Miller: > The Challenge: > Without the proposed solution in AI12-0218, I challenge anyone to write a= n Ada representation clause that is =E2=80=A2portable=E2=80=A2 to both litt= le-endian and big-endian processors for either of the following IETF packet= formats that must always be in big-endian network byte order: > https://en.wikipedia.org/wiki/IPv4#Packet_structure > https://en.wikipedia.org/wiki/IPv6_packet I'm not sure this is what you are looking for: for IPv4 use record Version at 0 range 0 .. 3; IHL at 0 range 4 .. 7; DSCP at 0 range 8 .. 13; ECN at 0 range 14 .. 15; Total_Length at 0 range 16 .. 31; Identification at 4 range 0 .. 15; Flags at 4 range 16 .. 18; Fragment_Offset at 4 range 19 .. 31; Time_to_Live at 8 range 0 .. 7; Protocol at 8 range 8 .. 15; Header_Checksum at 8 range 16 .. 31; Source_IP_Address at 12 range 0 .. 31; Destination_IP_Address at 16 range 0 .. 31; end record; for IPv4'Bit_Order use System.High_Order_First; Of course you have to byte-swap after a transfer. GNAT reports this upne compilation: reverse bit order in machine scalar of length 32 little-endian range for component "Version" is 28 .. 31 reverse bit order in machine scalar of length 32 little-endian range for component "IHL" is 24 .. 27 reverse bit order in machine scalar of length 32 little-endian range for component "DSCP" is 18 .. 23 reverse bit order in machine scalar of length 32 little-endian range for component "ECN" is 16 .. 17 reverse bit order in machine scalar of length 32 little-endian range for component "Total_Length" is 0 .. 15 reverse bit order in machine scalar of length 32 little-endian range for component "Identification" is 16 .. 31 reverse bit order in machine scalar of length 32 little-endian range for component "Flags" is 13 .. 15 reverse bit order in machine scalar of length 32 little-endian range for component "Fragment_Offset" is 0 .. 12 reverse bit order in machine scalar of length 32 little-endian range for component "Time_to_Live" is 24 .. 31 reverse bit order in machine scalar of length 32 little-endian range for component "Protocol" is 16 .. 23 reverse bit order in machine scalar of length 32 little-endian range for component "Header_Checksum" is 0 .. 15 reverse bit order in machine scalar of length 32 little-endian range for component "Source_IP_Address" is 0 .. 31 reverse bit order in machine scalar of length 32 little-endian range for component "Destination_IP_Address" is 0 .. 31 You might want to look at: https://en.wikibooks.org/wiki/Ada_Programming/Attributes/%27Bit_Order