sequence. To output the next number in the sequence, all a user has to do
is write this on a wiki page:
- [[fib ]]
+ \[[!fib]]
-When the page is built, the [[ikiwiki/PreProcessorDirective]] will be
+When the page is built, the [[ikiwiki/directive]] will be
replaced by the next number in the sequence.
Most of ikiwiki's plugins are written in Perl, and it's currently easiest
use warnings;
use strict;
- use IkiWiki 2.00;
+ use IkiWiki 3.00;
Ok, boilerplate is out of the way. Now to add the one function that ikiwiki
expects to find in any module: `import`. The import function is called when
}
This has hooked our plugin into the preprocess hook, which ikiwiki uses to
-expand [[PreprocessorDirectives|ikiwiki/preprocessordirective]]. Notice
+expand preprocessor [[directives|ikiwiki/directive]]. Notice
that "fib" has shown up again. It doesn't actually have to match the module
name this time, but it generally will. This "fib" is telling ikiwiki what
-kind of PreprocessorDirective to handle, namely one that looks like this:
+kind of preprocessor directive to handle, namely one that looks like this:
- [[fib ]]
+ [[!fib ]]
Notice the `\&preprocess`? This is how you pass a reference to a function,
and the `preprocess` function is the one that ikiwiki will call to expand
-the PreprocessorDirective. So, time to write that function:
+the preprocessor directive. So, time to write that function:
sub preprocess {
my %params=@_;
sub fib {
my $num=shift;
- return 0 if $num == 1;
- return 1 if $num == 2;
+ return 0 if $num == 0;
+ return 1 if $num == 1;
return fib($num - 1) + fib($num - 2);
}
sub preprocess {
my %params=@_;
- my $num=$last++;
+ my $num=++$last;
return fib($num);
}
Feel free to try it out with a simple page like this:
- [[fib ]], [[fib ]], [[fib ]], [[fib ]], [[fib ]]
+ [[!fib ]], [[!fib ]], [[!fib ]], [[!fib ]], [[!fib ]]
Looks like it works ok, doesn't it? That creates a page that lists:
- 1, 1, 3, 5, 8
+ 1, 1, 2, 3, 5
But what happens if there are two pages that both use fib? Try it out.
If ikiwiki builds both pages in one pass, the sequence will continue
and the standalone page another. The numbers might even skip over part of
the sequence in some cases.
-Obviously, using a global `$last` veriable was a bad idea. It would
+Obviously, using a global `$last` variable was a bad idea. It would
work ok in a more regular cgi-based wiki, which only outputs one page per
run. But since ikiwiki is a wiki *compiler*, things are a bit more
complicated. It's not very hard to fix, though, if we do want the sequence
sub preprocess {
my %params=@_;
my $page=$params{destpage};
- my $num=$last{$page}++;
+ my $num=++$last{$page};
return fib($num);
}
It would be nice to be able to jump directly to a given point in the
sequence:
- \[[fib seed=20]], [[fib ]], [[fib ]]
+ \[[!fib seed=20]], [[!fib ]], [[!fib ]]
Just insert these lines of code inside `preprocess`, in the appropriate
spot:
if (exists $params{seed}) {
- $last{$page}=$params{seed}-1;
+ $last{$page}=$params{seed};
}
But this highlights another issue with the plugin. The `fib()` function is
but that's not the focus of this tutorial. Instead, let's concentrate on
making the plugin use the existing function safely. A good first step would
be a guard on how high it will go.
-
+
my %last;
sub preprocess {
if (exists $params{seed}) {
$last{$page}=$params{seed}-1;
}
- my $num=$last{$page}++;
+ my $num=++$last{$page};
if ($num > 25) {
error "can only calculate the first 25 numbers in the sequence";
}
so that the user can look at the built page and see what went wrong.
Are we done? Nope, there's still a security hole. Consider what `fib()`
-does for numbers less than 1. Or for any number that's not an integer. In
+does for numbers less than 0. Or for any number that's not an integer. In
either case, it will run forever. Here's one way to fix that:
- if (int($num) != $num || $num < 1) {
+ if (int($num) != $num || $num < 0) {
error "positive integers only, please";
}