#!/usr/bin/env perl

# This program is part of Percona Toolkit: http://www.percona.com/software/
# See "COPYRIGHT, LICENSE, AND WARRANTY" at the end of this file for legal
# notices and disclaimers.

use strict;
use warnings FATAL => 'all';
use English qw(-no_match_vars);
use constant MKDEBUG => $ENV{MKDEBUG};

my $file = shift @ARGV || '-';
my $fh;
if ( $file eq '-' ) {
   $fh = *STDIN;
}
else {
   open $fh, "<", $file or die "Cannot open $file: $OS_ERROR";
}

my @line_patterns;
my %last_match;
my %printf_for;

while ( my $line = <$fh> ) {
   MKDEBUG && print "read: $line\n";
   my $matched = 0;
   foreach my $pat ( @line_patterns ) {
      MKDEBUG && print "trying to match: $pat\n";
      if ( my @vals = $line =~ m/$pat/ ) {
         MKDEBUG && print "matches\n";
         $matched = 1;
         my @last_vals = @{ $last_match{$pat} };
         my @offset_vals;
         for my $i ( 0..$#vals ) {
            $offset_vals[$i] = $vals[$i] - $last_vals[$i];
         }
         $last_match{$pat} = \@vals;
         printf $printf_for{$pat}, @offset_vals;
         last;
      }
   }
   if ( !$matched ) {
      my $new_pat = $line;
      $new_pat    =~ s/\d+/(\\d+)/g;
      my @vals    = $line =~ m/$new_pat/;
      MKDEBUG && print "new pattern: $new_pat: @vals\n";
      push @line_patterns, $new_pat;
      (my $printf_pat = $line ) =~ s/\d+/%d/g;
      $printf_for{$new_pat} = $printf_pat;
      $last_match{$new_pat} = \@vals;
      print $line;
   }
}

close $fh or warn "Cannot close $file: $OS_ERROR";
exit;

=pod

=head1 NAME

pt-rel - Relativize values to previous matching lines.

=head1 SYNOPSIS

Usage: pt-rel [FILES]

pt-rel matches lines and subtracts the value of the previous line's values
from the current line's values.  The lines must be text with numeric values
that repeat, varying only the values.

=head1 DESCRIPTION

For example, if the text is this:

  Mutex spin waits 0, rounds 99584819933, OS waits 437663963
  RW-shared spins 834337527, OS waits 20258150; RW-excl spins 1769749834
  Mutex spin waits 0, rounds 99591465498, OS waits 437698122
  RW-shared spins 834352175, OS waits 20259032; RW-excl spins 1769762980

Then the output will be:

  Mutex spin waits 0, rounds 99584819933, OS waits 437663963
  RW-shared spins 834337527, OS waits 20258150; RW-excl spins 1769749834
  Mutex spin waits 0, rounds 6645565, OS waits 34159
  RW-shared spins 14648, OS waits 882; RW-excl spins 13146

The first values (line 1) for "Mutex spin waits", "rounds", and "OS waits"
were subtracted from the second values (line 3); the same happened for values
from lines 2 and 4.

=head1 OPTIONS

This tool does not have any command-line options.

=head1 ENVIRONMENT

The environment variable C<PTDEBUG> enables verbose debugging output to STDERR.
To enable debugging and capture all output to a file, run the tool like:

   PTDEBUG=1 pt-rel ... > FILE 2>&1

Be careful: debugging output is voluminous and can generate several megabytes
of output.

=head1 SYSTEM REQUIREMENTS

This tool requires Perl v5.8 or newer.

=head1 BUGS

For a list of known bugs, see L<http://www.percona.com/bugs/pt-rel>.

Please report bugs at L<https://bugs.launchpad.net/percona-toolkit>.
Include the following information in your bug report:

=over

=item * Complete command-line used to run the tool

=item * Tool L<"--version">

=item * MySQL version of all servers involved

=item * Output from the tool including STDERR

=item * Input files (log/dump/config files, etc.)

=back

If possible, include debugging output by running the tool with C<PTDEBUG>;
see L<"ENVIRONMENT">.

=head1 DOWNLOADING

Visit L<http://www.percona.com/software/percona-toolkit/> to download the
latest release of Percona Toolkit.  Or, get the latest release from the
command line:

   wget percona.com/get/percona-toolkit.tar.gz

   wget percona.com/get/percona-toolkit.rpm

   wget percona.com/get/percona-toolkit.deb

You can also get individual tools from the latest release:

   wget percona.com/get/TOOL

Replace C<TOOL> with the name of any tool.

=head1 AUTHORS

Baron Schwartz

=head1 ABOUT PERCONA TOOLKIT

This tool is part of Percona Toolkit, a collection of advanced command-line
tools developed by Percona for MySQL support and consulting.  Percona Toolkit
was forked from two projects in June, 2011: Maatkit and Aspersa.  Those
projects were created by Baron Schwartz and developed primarily by him and
Daniel Nichter, both of whom are employed by Percona.  Visit
L<http://www.percona.com/software/> for more software developed by Percona.

=head1 COPYRIGHT, LICENSE, AND WARRANTY

This program is copyright 2010 Baron Schwartz, 2011 Percona Inc.
Feedback and improvements are welcome.

THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar
systems, you can issue `man perlgpl' or `man perlartistic' to read these
licenses.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA  02111-1307  USA.

=head1 VERSION

Percona Toolkit v1.0.0 released 2011-08-01

=cut