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Groups > comp.lang.c > #5967

Re: looking at binary files with C

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On 6/12/2011 7:01 PM, Uno wrote:
> On 06/12/2011 03:42 PM, Eric Sosman wrote:
>> On 6/12/2011 4:47 PM, Uno wrote:
>>>
>>> There were a lot of problems with this source that needing ironing out,
>>> and I needed to start to somehwhere.
>>
>> An *excellent* place to start is with a description of what
>> you want the program to do. As it is, you've just thrown a bunch
>> of code at us and expected us to divine your intentions. If the
>> code were not so clearly broken, divination might stand a chance;
>> even then it would be better to state your purpose. With broken
>> code, such a statement is even more important.
>
> It takes me a few posts before I get a syntactical C program to use to
> describe what I'm doing. Without referent source, I can't communicate this.

     If you cannot say what you want your program to do, neither
you nor anyone else can say whether it fulfills your purposes.

>>> When I've got a program that
>>> compiles, I like to have the magic numbers #defined.
>>
>> Your choice, but you're making extra work for yourself. When
>> you're replacing numeric constants with macro names and you come
>> across a 3, should you change it to SHIFTS_PER_DAY or to VERSION?
>> Essentially, you've created a reverse-engineering problem for yourself,
>> giving yourself an extra opportunity to make misteaks.
>
> But you did notice that I have
> #define SIZE2 (UCHAR_MAX+1)
> , and this was the seg fault I couldn't get my head around when I first
> posted.

     No, it had nothing to do with the matter.

> A client paid me

     (!)

> to put a binary file on the net, and I used perl's
> net::ftp without knowing that I had to call the binary method in order
> to upload without *nix eating ascii 13. (Thx a lot c.l.p.misc: for
> nothing.)

     Let me get this straight: You are upset with comp.lang.c for
failing to tell you how to use Perl correctly?  Before we were even
aware you were trying to do anything?

>>> fp = fopen("shoulder.wmv", "rb+");
>>
>> Why the "+", since you never write to the file? And why
>> is there still no check for failure, after others have already
>> pointed out the lack?
>
> The + on all opens because I might want to write to them.

     Foolish.  On some systems, wasteful.

> No check for
> failure because the only one I've got in my head is
> or die "death $@\n"; Is there a K&R2 reference for how to do it?

     After the call and assignment, check whether `fp' is NULL.
If it's not, fopen() succeeded and you're ready to do I/O on
the stream `fp' points to.  If it's NULL, fopen() failed and you
should take alternative action.  Even if the alternative action
amounts to nothing more than "I give up," it will at least be a
predictable response.  Just plowing ahead as if everything were
fine produces unpredictable results: Quite likely a SIGSEGV, but
not necessarily anything that benign.

>>> I needed two different SIZES, one that would be larger than the byte
>>> count of the file to be read and another that was one greater than
>>> UCHAR_MAX.
>>
>> SIZE2 (or equivalent) is necessary, yes. But SIZE seems to
>> serve no useful purpose -- unless, as mentioned above, you have
>> purposes that aren't stated.
>
> Right, so I'm looking for your comment on the dynamic allocation which I
> posted as a reply to keith.

     Since you are collecting payment for the program comp.lang.c
is more or less writing for you, perhaps you should offer the
forum a percentage.  Until then, no more free comments.

-- 
Eric Sosman
esosman@ieee-dot-org.invalid

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Thread

looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 00:06 -0600
  Re: looking at binary files with C Ian Collins <ian-news@hotmail.com> - 2011-06-12 18:41 +1200
    Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 00:58 -0600
  Re: looking at binary files with C Barry Schwarz <schwarz45@yahoo.com> - 2011-06-12 00:05 -0700
    Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 01:41 -0600
      Re: looking at binary files with C "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-06-12 11:44 +0200
      Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-12 10:25 -0600
  Re: looking at binary files with C Ike Naar <ike@sverige.freeshell.org> - 2011-06-12 10:26 +0000
  Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-12 08:23 -0400
    Re: looking at binary files with C Hans Vlems <hvlems@freenet.de> - 2011-06-13 23:48 -0700
    Re: looking at binary files with C Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-23 00:55 -0700
  Re: looking at binary files with C "BartC" <bc@freeuk.com> - 2011-06-12 14:26 +0100
  Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-12 10:24 -0600
    Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 14:47 -0600
      Re: looking at binary files with C "BartC" <bc@freeuk.com> - 2011-06-12 22:23 +0100
        Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-12 14:29 -0700
          Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 16:31 -0600
            Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-12 16:14 -0700
              Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 18:41 -0600
      Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-12 17:42 -0400
        Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 17:01 -0600
          Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-12 16:23 -0700
            Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 17:24 -0600
              Re: looking at binary files with C Ian Collins <ian-news@hotmail.com> - 2011-06-13 11:28 +1200
                Re: looking at binary files with C Geoff <geoff@invalid.invalid> - 2011-06-12 16:52 -0700
              Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-13 08:51 -0700
            Re: looking at binary files with C Seebs <usenet-nospam@seebs.net> - 2011-06-13 14:39 +0000
              Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-13 20:01 -0600
                Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-13 19:24 -0700
                Re: looking at binary files with C Seebs <usenet-nospam@seebs.net> - 2011-06-14 17:02 +0000
                Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-16 01:32 -0600
          Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-13 07:57 -0400
            Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-13 20:23 -0600
              Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-13 23:12 -0400
                Re: looking at binary files with C lovecreatesbeauty <lovecreatesbeauty@gmail.com> - 2011-06-14 01:09 -0700
          Re: looking at binary files with C Oliver Jackson <chexmofo@hotmail.com> - 2011-06-15 20:15 -0700
      Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-12 18:41 -0600
      Re: looking at binary files with C James Waldby <not@valid.invalid> - 2011-06-13 01:16 +0000
        Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 19:48 -0600
        Re: looking at binary files with C "io_x" <a@b.c.invalid> - 2011-06-14 12:19 +0200
          Re: looking at binary files with C lovecreatesbeauty <lovecreatesbeauty@gmail.com> - 2011-06-14 03:58 -0700
            Re: looking at binary files with C "io_x" <a@b.c.invalid> - 2011-06-14 19:07 +0200
              Re: looking at binary files with C "io_x" <a@b.c.invalid> - 2011-06-14 19:46 +0200
              Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-14 16:08 -0600
          Re: looking at binary files with C Ian Collins <ian-news@hotmail.com> - 2011-06-15 08:47 +1200
      Re: looking at binary files with C Hans Vlems <hvlems@freenet.de> - 2011-06-13 23:51 -0700
  Re: looking at binary files with C Michael Press <rubrum@pacbell.net> - 2011-06-15 13:06 -0700
    Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-16 01:38 -0600
      Re: looking at binary files with C Michael Press <rubrum@pacbell.net> - 2011-06-16 00:54 -0700
        Re: looking at binary files with C James Waldby <not@valid.invalid> - 2011-06-16 16:59 +0000
      Re: looking at binary files with C "J. J. Farrell" <jjf@bcs.org.uk> - 2011-06-16 18:32 +0100

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