in reply to File::Binary:howto goto a position in file

use Fcntl 'SEEK_SET';

$fb->seek( 10, SEEK_SET );

[download]
seek() takes two parameters - the offset (or POS) and how that offset should be interpreted (or WHENCE). The three WHENCE's are SEEK_SET (absolute position, or relative to file beginning), SEEK_CUR (relative to where I am right now), and SEEK_END (relative to the end of the file). seek might also be useful.
My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

Replies are listed 'Best First'.
Re^2: File::Binary:howto goto a position in file
by jeanluca (Deacon) on Mar 12, 2006 at 13:41 UTC
    Thanks for the explanation. But I still get the same error, here is a small test script (called fio.pl):
    #! /usr/bin/perl

use strict  ;
use File::Binary ;
use Fcntl 'SEEK_SET'; 

my $fb = File::Binary->new("fio.pl");

$fb->seek(10, SEEK_SET ) ;

$fb->close ;

    [download]


    Luca
[reply]
[d/l]
      That's because File::Binary's code is wrong. Specifically, the seek() method is written as so: 
      sub seek {
    my $self = shift;
    my $seek = shift;
    unless ($self->{_is_seekable}) {
        carp "FH is not seekable" if $DEBUG; 
        return 0;
    }

    $self->{_fh}->seek($seek) if defined $seek;
    $self->_init_bits();
    return $self->{_fh}->tell();
}

      [download]

      Which is wrong. The whole module is written rather sloppily, frankly. Which is not surprising, given that the test suite doesn't even have a test for seek().

      Furthermore, the test coverage for the 2874 tests is only 

      ---------------------------- ------ ------ ------ ------ ------ ------
+ ------
File                           stmt   bran   cond    sub    pod   time
+  total
---------------------------- ------ ------ ------ ------ ------ ------
+ ------
blib/lib/File/Binary.pm        79.2   47.6   37.5   87.1   95.0  100.0
+   73.1
Total                          79.2   47.6   37.5   87.1   95.0  100.0
+   73.1
---------------------------- ------ ------ ------ ------ ------ ------
+ ------

      [download]
      If I were you, I would find some other way to do what you're trying to do.
      My criteria for good software:
      1. Does it work?
      2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
[reply]
[d/l]
[select]
        Ok, I thought it was a cool module, like guess_endian.
        Well, for what I need to do right now is only to be able to jump to an other position. Any suggestions what my best alternatives are?

        Thanks for your help!

        Luca
[reply]

In Section Seekers of Perl Wisdom