From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: encode-time vs decode-time Date: Mon, 26 Aug 2019 14:35:34 -0700 Organization: UCLA Computer Science Department Message-ID: <66c63314-c859-6772-f22f-3f3257991bf1@cs.ucla.edu> References: <502b23f8-58ed-38ff-ae50-fae391129a10@cs.ucla.edu> <87v9viuivo.fsf@mouse.gnus.org> <83blx2cr2o.fsf@gnu.org> <8336iecfvr.fsf@gnu.org> <68d24d6a-d427-baef-27e9-ea1cbbd64c18@cs.ucla.edu> <87sgqd9plt.fsf@mouse.gnus.org> <89271843-6d47-8315-ed9a-540657298985@cs.ucla.edu> <87v9uvmsfa.fsf@mouse.gnus.org> <83af2f70-480b-6e5f-06a5-876224e2b715@cs.ucla.edu> <88b57699-fbdb-bd43-6627-f7491b834955@cs.ucla.edu> <87tvaag54l.fsf@alphapapa.net> <23355b15-fdb2-4f17-8203-82a493ddd3fd@cs.ucla.edu> <87imqkgpk5.fsf@alphapapa.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="247992"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 Cc: emacs-devel@gnu.org To: Adam Porter Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 26 23:36:16 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1i2Met-0012PQ-H4 for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 23:36:15 +0200 Original-Received: from localhost ([::1]:57868 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2Mes-0005fg-1U for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 17:36:14 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:39467) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2MeI-0005fY-Ip for emacs-devel@gnu.org; Mon, 26 Aug 2019 17:35:39 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i2MeH-0004nD-Gn for emacs-devel@gnu.org; Mon, 26 Aug 2019 17:35:38 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:44236) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i2MeH-0004lc-BA for emacs-devel@gnu.org; Mon, 26 Aug 2019 17:35:37 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 0D2091600CE; Mon, 26 Aug 2019 14:35:36 -0700 (PDT) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id VJ-JCIFl84fJ; Mon, 26 Aug 2019 14:35:35 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 4FBE91600E6; Mon, 26 Aug 2019 14:35:35 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id pn8jmqnu2r3A; Mon, 26 Aug 2019 14:35:35 -0700 (PDT) Original-Received: from [192.168.1.9] (cpe-23-242-74-103.socal.res.rr.com [23.242.74.103]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 1B5B11600CE; Mon, 26 Aug 2019 14:35:35 -0700 (PDT) In-Reply-To: <87imqkgpk5.fsf@alphapapa.net> Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 131.179.128.68 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:239592 Archived-At: Adam Porter wrote: > I'm curious, is Emacs fast enough or consistent enough to make use of > high-resolution timestamps anyway? I guessed that, with GC pauses, > etc., it wouldn't be a suitable platform for such calculations in > real-time. Although I guess if the timestamps were from outside Emacs, > one could operate on them anyway. You're right that calling (current-time) from Elisp won't give you nanosecond accuracy; on my platform, just calling that function takes a few hundred nanoseconds so some error is inherent. You're also right that Emacs isn't suitable for hard real-time applications. As you mention, a common use for Emacs timestamps is to process times generated outside Emacs itself, e.g., file timestamps. On typical POSIXish platforms, file timestamps have nanosecond resolution and range from -2**63 to 2**63 seconds after the epoch, and Emacs can handle all of these timestamps though a few functions like decode-time will probably fail due to limitations of the underlying C libraries.