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 X-Google-Thread: 103376,b5cd7bf26d091c6f X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII Path: g2news2.google.com!news3.google.com!feeder.news-service.com!94.75.214.39.MISMATCH!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: Reading the while standard input into a String Date: Mon, 6 Jun 2011 20:18:16 +0200 Organization: cbb software GmbH Message-ID: <1a84tm53l1wjx.1xdgsbp25vyd5.dlg@40tude.net> References: <1e5e764d-eb7b-4804-8119-b535ddbe5e7e@32g2000vbe.googlegroups.com> Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: 6an/HxOXjVOykPvLkSpw3Q.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit X-Complaints-To: abuse@aioe.org User-Agent: 40tude_Dialog/2.0.15.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: g2news2.google.com comp.lang.ada:20617 Date: 2011-06-06T20:18:16+02:00 List-Id: On Mon, 6 Jun 2011 08:18:44 -0700 (PDT), Maciej Sobczak wrote: > On Jun 6, 10:33�am, Ludovic Brenta wrote: > >> I'd rather process the input one fixed-length chunk at a time > > This is a can of warms - how big should be that chunk? :-) For a compiler it is the maximal length of look ahead / roll-back, normally, less than just one line. The line length can be reasonably limited to say 10_000 characters (usually the language defines the maximal line length). >> Note that reading one character at a time from a stream is quite fast >> since streams normally use the operating system's buffered IO. Adding >> a second layer of buffering inside your program is probably counter- >> productive. > > Or not. System calls are relatively expensive - typically much more > expensive than copying data around. For this reason wisely used > additional buffers can improve performance of I/O operations. The opposite is also possible, unless the OS driver uses user-space buffers. So I would follow Ludovic's advise, especially in the case of a compiler where reading overhead is negligible comparing to other computations per character. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de