Re: Ugly variable-length record handling

I've had to put up with that sort of loop lots of times -- yes, it has a klugy feel to it, but it still seems easier, simpler, clearer, etc, than alternatives, so I just live with it.

Other things can be done in general to streamline your code a little bit -- fewer variables, fewer lines of code, less open/close overhead on the temp file:

open( DAT, '<', 'export.dat' )
    or die "Open for read failed on export.dat: $!";
my $tmp;  # file handle

while ( <DAT> ) {
    next unless ( /\S/ );
    if ( /^1/ ) {
        if ( defined( $tmp )) {
            output_data( $tmp );
        }
        open( $tmp, '+>', 'export.tmp' )  # open read/write, truncate 
+first
            or die "Open failed for export.tmp: $!";
    }
    print $tmp $_;
}
output_data( $tmp );

sub output_data
{
    my $fh = shift;
    seek( $fh, 0, 0 );  # rewind to start of file
    # do stuff with export.tmp contents...
    close $fh;
}
[download]

Comment on Re: Ugly variable-length record handling Download Code

Replies are listed 'Best First'.
Re^2: Ugly variable-length record handling by Melly (Chaplain) on Jan 04, 2007 at 09:58 UTC
Thanks all - some nice variations... but I'll probably stick with the original (IIABDFI) - that said, here's a 'nicer' version I came up with (which uses a two-element array, plus a push and a shift), but I suspect that the niceness comes at the expense of readability... use strict; open(DAT, "export.dat")\|\|die "Cannot open export.dat for read:$!\n"; my @temp_lines; push @temp_lines, scalar <DAT>; my $closed = 1; while($temp_lines[0] !~ /^<EOF>$/){ open(TEMP, ">temp.dat") if $closed; $closed = 0; push @temp_lines, (eof DAT) ? '<EOF>' : (scalar <DAT>) ; print TEMP shift @temp_lines; if($temp_lines[0] =~ /^(1\|<EOF>)/){ close TEMP; &output_data(); $closed = 1; } } close DAT; sub output_data{ print "in output_data\n"; open(TEST, 'temp.dat')\|\|die "cannot open temp in sub:$!\n"; while(<TEST>){ chomp; print "$_\n" if $_ =~ /\S/; } print "end of output_data\n"; } [download] `map{$a=1-$_/10;map{$d=$a;$e=$b=$_/20-2;map{($d,$e)=(2$d$e+$a,$e2 -$d2+$b);$c=$d2+$e2>4?$d=8:_}1..50;print$c}0..59;print$/}0..20` [download] Tom Melly, pm@tomandlu.co.uk	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^2: Ugly variable-length record handling
by Melly (Chaplain) on Jan 04, 2007 at 09:58 UTC

Thanks all - some nice variations... but I'll probably stick with the original (IIABDFI) - that said, here's a 'nicer' version I came up with (which uses a two-element array, plus a push and a shift), but I suspect that the niceness comes at the expense of readability...

use strict;

open(DAT, "export.dat")||die "Cannot open export.dat for read:$!\n";

my @temp_lines;
push @temp_lines, scalar <DAT>;
my $closed = 1;

while($temp_lines[0] !~ /^<EOF>$/){
  open(TEMP, ">temp.dat") if $closed;
  $closed = 0;
  push @temp_lines, (eof DAT) ? '<EOF>' : (scalar <DAT>) ;

  print TEMP shift @temp_lines;

  if($temp_lines[0] =~ /^(1|<EOF>)/){
    close TEMP;
    &output_data();
    $closed = 1;
  }
}
close DAT;

sub output_data{
  print "in output_data\n";
  open(TEST, 'temp.dat')||die "cannot open temp in sub:$!\n";
  while(<TEST>){
    chomp;
    print "$_\n" if $_ =~ /\S/;
  }
  print "end of output_data\n";
}
[download]

map{$a=1-$_/10;map{$d=$a;$e=$b=$_/20-2;map{($d,$e)=(2*$d*$e+$a,$e**2
-$d**2+$b);$c=$d**2+$e**2>4?$d=8:_}1..50;print$c}0..59;print$/}0..20
[download]

Tom Melly, pm@tomandlu.co.uk

[reply]
[d/l]
[select]