Ok, I'll answer the easy question first. The problem with having too much data doesn't really happen here. The user of the converter is allowed to set a maximum amount of time for each step to run. If it exceeds that time, the converter jumps out of the conversion loop and dumps anything that needs to be saved to a Perl file. When the user clicks "next", it's loaded into memory again. It doesn't auto-reload, but it should be perfect at saving and resuming, as long as it's within the same time period.
Now, for the howto. Your existing code will need to be separated and transfered into 3 different types of routines for this to work. I'll explain the basic format of the indriver here, as well as explain the Init routine.
This might seem really complicated. It probably is, compared to most of the programming I do. But it's fairly easy to understand if you understand the following points:
- There's 3 main parts of the file: The setup part, which determines what parts of the conversion you can do and what code is executed when; the initial/finish routines, which are generally simple and similar to other routines of the same type; and the conversion routines.
- The save/resume work in progress is very generic. For saving, you just need a list of what variables to store and what they're named. For saving, you just call the resume routine and it does the rest.
- Use localized variables and filehandles all the time. This works wonders to prevent unexpected results of variables that weren't intended to be global.
I recommend taking my Eblah input driver (or if you want a fictional board format, I can provide that input driver) to start with and using the basic framework, especially the Init/Finish routines. If you know what you are doing, you can write a second converter in less than 10 hours, as I did with the Eblah one.
For the input driver, here's the basic form:
package indriver;
# strict + warnings is good
use strict;
use warnings;
our %CONFIG = (
'BOARD_TYPE', 'the board type it converts (e.g. phpBB 2)',
'NAME', 'name of the converter',
'VERSION', 'Alpha'
);
# What I can convert
our @CONVERT = qw(Boards Categories Messages Members);
our %SUBROUTINES = (
'Boards', 'BoardConvert',
'Categories', 'CatConvert',
'Messages', 'MessageConvert',
'Members', 'MemberConvert'
);
our %INITSUBROUTINES = (
'Boards', 'BoardConvertInit',
'Categories', 'CatConvertInit',
'Messages', 'MessageConvertInit',
'Members', 'MemberConvertInit'
);
our %FINISHSUBROUTINES = (
'Messages', 'MessageConvertFinish'
);
Using warnings and strict is optional, but recommended.
SetupThe %CONFIG hash does nothing at the moment, but it's good to have in there for when it might be used.
Now, the @CONVERT array is important. It specifies what items the converter can convert. So far, there's four that are supported by YaBB's output driver: Boards, Categories, Messages, and Members. The converter uses the @CONVERT arrays of the input and output driver to find out what to convert.
Each item in the @CONVERT array is matched up to a subroutine using the %SUBROUTINES, %INITSUBROUTINES, and %FINISHSUBROUTINES hashes. You can call the subroutines that match up anything you want.
We'll start with the easy subroutines, which are the init/finish ones.
The input driver's init routine for each step has a very important step: telling how many steps to run the loop for. It also sets up package globals needed throughout the conversion process, like matching what board goes to what category, or what topics are sticky.
Here's the BoardConvertInit routine from my Eblah indriver
sub BoardConvertInit {
my $fh; # Use a localized variable for a filehandle to prevent problems.
open($fh, "<$convertdir/Boards/bdindex.db") || die "Can't open $convertdir/Boards/bdindex.db: $!";
@boardlist = <$fh>;
close($fh);
$maxsteps = scalar @boardlist;
open($fh, "<$convertdir/Boards/bdscats.db") || die "Can't open $convertdir/Boards/bdscat.db: $!";
@catlist = <$fh>;
close($fh);
return 1;
}
The first interesting thing is the $fh variable. It's used exactly the same as a filehandle. I consistently use $fh when I need an anonymous filehandle.
Second, I use "die". Die outputs HTML, but you don't need to worry about the templating area, which is handled in the converter. Same goes for "warn", which is also considered a fatal error.
I open up the board index file and count up the boards present. Since there's one board per line, I capture the whole list in the global @boardlist. I use it in forced scalar context to count up the maxsteps.
Something important is that maxsteps is actually the number of steps, plus one! It works this way due to how I made the for loop. It usually works out perfectly since you often count the lines in the file.
A change from the Beta 1.0 and Beta 1.1 versions is that you should return the number of steps. All you have to do is return it instead of store it in $maxsteps.
Resuming work in progressIf you run out of time, you can resume work in progress like this:
if($_[0] eq 'resumeworkinprogress') {&ResumeWorkInProgess();}
else {
# The rest of the init code goes here
}
That's it. You just need to make sure you're saving work in the corresponding Finish routine. You'll notice that sometimes I don't save/resume in the input driver. That's due to the fact that I only need to open 1 or 2 files, and there's no real problem with counting it again.
I'm running out of characters in this post, so I'll continue typing in my next post.
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YaBB Universal Converter [Beta 4] (Read 160,416 times)
