Re: slurped scalar map

If I understand correctly, tie or captures will be useful. Here's an example of the latter:

sub new_accessor {
   my $start    =  $_[0];
   my $end      =  $_[1];
   my $data_ref = \$_[2];  # Avoid making a copy.

   return sub {
      return substr($$data_ref, $start, $end-$start);
   };
}

{
   my $data = ...;

   my $start1 = ...;  # Calculate start from map.
   my $end1   = ...;  # Calculate end   from map.

   my $rec1 = new_accessor($start1, $end1, $data);
   print($rec1->(), "\n");
}
[download]

tie would allow you to do the same, but you'd use
print($rec1, "\n");
instead of
print($rec1->(), "\n");

Untested.

Comment on Re: slurped scalar map Select or Download Code

Replies are listed 'Best First'.
Re^2: slurped scalar map by 0xbeef (Hermit) on Jun 20, 2006 at 15:13 UTC
Thanks, this is spot on for my requirement. ++ Regards, Niel	[reply]
Re^3: slurped scalar map by ikegami (Patriarch) on Jun 20, 2006 at 16:35 UTC
I should have mentioned that `substr` makes a copy when `$rec1->()` is called. That's unavoidable. You can't extract a string from another without making the new string. However, the copy is only done when `$rec1->()` is executed. If that's a problem, you could extract small chunks at a time. For example, only 100 (by default) chars are duplicated at any given time. sub new_callback_accessor { my $start = $_[0]; my $end = $_[1]; my $data_ref = \$_[2]; # Avoid making a copy. return sub { my ($callback, $blk_size) = @_; local *_; $blk_size = 100 unless defined $blk_size; $blk_size = $end-$start unless $blk_size; my $ofs = $start; my $len = $end-$start; while ($len) { $blk_size = $len if $blk_size > $len; $_ = substr($$data_ref, $ofs, $blk_size); $callback->(); $ofs += $len; $len -= $blk_size; } }; } { my $data = ...; my $start1 = ...; # Calculate start from map. my $end1 = ...; # Calculate end from map. my $rec1 = new_callback_accessor($start1, $end1, $data); $rec1->(sub { print }); print("\n"); } [download] Untested.	[reply] [d/l] [select]
Re^3: slurped scalar map by BrowserUk (Patriarch) on Jun 20, 2006 at 18:23 UTC
Be warned. This method uses more space than simply copying the records to an array, Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]