Re: Working with files on different operating systems

From	"Morten W. Petersen" <morphex@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Working with files on different operating systems
Date	2015-10-09 22:01 +0200
Organization	Aioe.org NNTP Server
Message-ID	<mv96e1$m7b$1@speranza.aioe.org> (permalink)
References	(2 earlier) <87twq0jqo5.fsf@bsb.me.uk> <mv8uba$g6p$1@dont-email.me> <mv92di$vs$1@dont-email.me> <mv935c$eoe$1@speranza.aioe.org> <mv95s1$f0e$1@dont-email.me>

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On 09.10.2015 21:53, James Kuyper wrote:
> On 10/09/2015 03:05 PM, Morten W. Petersen wrote:
>> On 09.10.2015 20:54, James Kuyper wrote:
>>> On 10/09/2015 01:48 PM, Les Cargill wrote:
>>>> Ben Bacarisse wrote:
>>> ...
>>>>> To the OP: there's no obvious reason for you to know the input size
>>>>> before you parse it.  Are you storing it whole for some purpose that has
>>>>> eluded me?  If so, you will have to avoid knowing the size if you want
>>>>> to handle the widest range in input sources.
>>>>>
>>>>
>>>> He wants to know how big a buffer to allocate. That is not unreasonable.
>>>
>>> He wants to read the entire file into a single buffer. Depending upon
>>> context, that might be unreasonable. Many programs can do their intended
>>> job by reading in only one character at a time, or one line at a time,
>>> or one record at a time. When that's the case, reading in the entire
>>> file before processing it can lead to unnecessary complications, like
>>> this one.
>>
>> Well you can read answers other places in this thread posted well
>> before you posted this one and see what we're actually discussing.
>
> I did. I didn't see anything that gave enough information about the
> intended purpose of this code to determine whether or not reading the
> entire file in at one time was a good idea. You posted the first message
> you that said anything about the purpose of this program at 03:09 today,
> 4 minutes after the message I'm responding to.

To me it looked like you and Ben responded well after different
approaches and reasoning behind those approaches were mentioned.

Message ID <mv8r8o$ru8$1@speranza.aioe.org> for example has the
local time here of 18:51, while in your message with ID
<87zizrj2ky.fsf@bsb.me.uk> local time 20:53 you say that it is
unreasonable to know how big of a buffer to allocate.

>  From that explanation, I strongly suspect that the best approach would
> be to do a buffered read of a single character at a time using fgetc(),
> and to push that character through a parsing engine that recognizes the
> syntax of the files you're reading, and builds structures in memory to
> represent their contents. Depending upon that syntax, you might need a
> limited amount of look-ahead, but you shouldn't need to have the ability
> to look at the entire input file at one time.

There are reasons for different approaches, fgetc is one, while there
may be benefits of others as well.

-Morten

Thread

Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 05:11 +0200
  Re: Working with files on different operating systems Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-10-08 22:12 -0600
  Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 00:18 -0500
    Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 11:13 +0100
      Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 18:05 +0200
        Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 12:49 -0500
        Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-09 17:32 -0400
        Re: Working with files on different operating systems Ian Collins <ian-news@hotmail.com> - 2015-10-10 12:37 +1300
      Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 12:48 -0500
        Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 19:53 +0100
          Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:09 +0200
            Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 20:28 +0100
              Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:40 +0200
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 15:59 -0400
                Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 22:07 +0200
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 16:24 -0400
                Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-10 03:08 +0200
                Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 21:50 +0100
        Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 14:54 -0400
          Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:05 +0200
            Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:47 +0200
            Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 15:53 -0400
              Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 22:01 +0200
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 16:05 -0400
          Re: Working with files on different operating systems glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-10 01:16 +0000
            Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-10 03:46 +0200
            Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-10 08:08 -0400
          Re: Working with files on different operating systems raltbos@xs4all.nl (Richard Bos) - 2015-10-10 17:02 +0000
        Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-09 15:53 -0400
    Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 18:00 +0200
      Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 12:59 -0500
        Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 12:37 -0700
          Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 17:36 -0500
            Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 16:52 -0700
              Re: Working with files on different operating systems raltbos@xs4all.nl (Richard Bos) - 2015-10-14 11:27 +0000
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-14 11:27 -0400
                Re: Working with files on different operating systems Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-14 16:46 +0000
                Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-14 10:18 -0700
              Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-14 23:06 -0500
    Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 09:16 -0700
      Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 17:43 -0500
        Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 16:57 -0700
          Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-09 22:41 -0700
    Re: Working with files on different operating systems David Thompson <dave.thompson2@verizon.net> - 2015-10-31 06:50 -0400
  Re: Working with files on different operating systems Siri Cruz <chine.bleu@yahoo.com> - 2015-10-08 23:25 -0700
    Re: Working with files on different operating systems Geoff <geoff@invalid.invalid> - 2015-10-10 10:35 -0700
  Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-09 08:42 -0400
    Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 18:51 +0200
      Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-15 18:09 -0700
        Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-17 04:01 +0200
          Re: Working with files on different operating systems Ian Collins <ian-news@hotmail.com> - 2015-10-17 15:55 +1300
            Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-16 20:09 -0700
              Re: Working with files on different operating systems Ian Collins <ian-news@hotmail.com> - 2015-10-17 16:36 +1300
            Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-17 05:10 +0200
        Re: Working with files on different operating systems supercat@casperkitty.com - 2015-10-31 12:05 -0700
          Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-31 12:42 -0700
            Re: Working with files on different operating systems supercat@casperkitty.com - 2015-10-31 13:40 -0700
          Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-31 19:55 +0000
            Re: Working with files on different operating systems supercat@casperkitty.com - 2015-10-31 13:43 -0700
              Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-31 21:38 +0000

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