Re^2: Sort text by Chapter names

[Anonymous Monk]

Another alternative that I often see used here is to calculate the position and length of each unit within the file as you are scanning through it looking for markers. Put the marker-name, position, and length into an array of hashes, then sort the array by name using a custom sort-function. Retrieve each chapter directly from the original file by seeking to the proper position and reading the calculated number of bytes. (If the length might also be huge, read and write it in chunks not-to-exceed a digestible buffer-size.)

[tybalt89]

For the fun of it ( and also to show you can seek on DATA )

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1215128

use strict;
use warnings;

my %chapters;
my $previous = undef;
my $buffer;
my $max = 4096;

while(<DATA>)
  {
  if( /^Chapter/ )
    {
    $chapters{$_} = $previous = [ tell(DATA) - length, length ];
    }
  elsif( defined $previous )
    {
    $previous->[1] += length;
    }
  }

use Data::Dump 'pp'; print pp \%chapters; print "\n\n";

for ( sort keys %chapters )
  {
  my ($start, $length) = $chapters{$_}->@*;
  seek DATA, $start, 0;
  while( $length > $max )
    {
    read DATA, $buffer, $max;
    print $buffer;
    $length -= $max;
    }
  read DATA, $buffer, $length;
  print $buffer;
  }

__DATA__
Chapter One
There were lots of monkeys here and they ate all the bananas...
lots more text up to hundreds of words.
Chapter Nine
This chapter has probably 1000 words.
Chapter Two
Here is the text in the second chapter...
Chapter Five
Here is the text in the fifth chapter...
every chapter is of differing length, some long some short.

[jimpudar]

This is an elegant solution. I do like it better than mine as it uses only half the disk space!

This thread is a fantastic example of TMTOWTDI.

Best,

Jim