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=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: CRC in Ada? Date: Thu, 14 Nov 2013 21:09:00 +0100 Organization: cbb software GmbH Message-ID: References: <1997Mar2.220652@nova.wright.edu> <96f19631-cbfa-416c-bca5-c7f67977f65d@googlegroups.com> Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: yj4Mse0EzG3G3C55Dl6uWQ.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: 40tude_Dialog/2.0.15.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:17677 Date: 2013-11-14T21:09:00+01:00 List-Id: On Thu, 14 Nov 2013 09:39:54 -0800 (PST), david wrote: > On Sunday, March 2, 1997 3:00:00 AM UTC-5, Dr. John B. Matthews wrote: >> Hi! Can anyone point me to 16-bit CRC code in Ada? I've checked the >> PAL and several other archives without luck. Any help appreciated. >From simple components: http://www.dmitry-kazakov.de/ada/components.htm function Fletcher_16 ( Data : Stream_Element_Array; Last : Stream_Element_Offset ) return Stream_Element_Array is Sum_1 : Unsigned_16 := 16#FF#; Sum_2 : Unsigned_16 := 16#FF#; Index : Stream_Element_Offset := Data'First; begin for Major in 1..(Last - Data'First + 1) / 21 loop for Index in Major * 21 - 20..Major * 21 loop Sum_1 := Sum_1 + Unsigned_16 (Data (Index)); Sum_2 := Sum_2 + Sum_1; end loop; Sum_1 := (Sum_1 and 16#FF#) + Sum_1 / 2**8; Sum_2 := (Sum_2 and 16#FF#) + Sum_2 / 2**8; end loop; Sum_1 := (Sum_1 and 16#FF#) + Sum_1 / 2**8; Sum_2 := (Sum_2 and 16#FF#) + Sum_2 / 2**8; return ( 1 => Stream_Element (Sum_1 and 16#FF#), 2 => Stream_Element (Sum_2 and 16#FF#) ); end Fletcher_16; -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de