I wrote this mainly because someone asked how to do this in PHP. Turns out there is nothing in like the venerable URI module in all of PHP-dom (how pathetic is that for a language as web-centric as it?).
First, I tried writing this with mostly string functions, but that was too painful, so I switched to doing it using regexes, even though they’re piss-poorly supported. After a while, my eyes glazed over, so I resorted to writing and debugging the code in Perl first, and then compiling it down to machine code PHP.
I thought I’d post this byproduct here for posterity, in case someone needs it in some circumstance.
Tests included, but I’m pretty sure they’re not extensive enough to be 100% confident in the code. Proceed at your discretion.
sub abs_url {
my ( $relative, $base ) = @_;
return $relative if $relative =~ m{ \A http:// }ix;
my ( $host, $hostrelative_abs ) = $base =~ m{
\A
http:// # skip scheme
([^/]*) # capture hostname
/* # skip front slashes
(.*?) # capture everything that follows, but
[^/]* # leave out the optional final non-directory component
\z
}ix;
$hostrelative_abs = '' if $relative =~ m!^/!;
my $abs_url = join '/', $host, $hostrelative_abs, $relative;
# replace '//' or '/./' with '/'
1 while $abs_url =~ s{ / \.? (?=/|\z) }{}x;
# remove '/foo/..' (but be careful to skip '/../..')
1 while $abs_url =~ s{ / (?!\.\.) [^/]+ / \.\. (?=/|\z) }{}x;
return "http://$abs_url";
}
use Test::More;
my @test = qw(
/foo/bar.gif http://www.example.com/baz/quux/ http://www.exam
+ple.com/foo/bar.gif
foo/bar.gif http://www.example.com/baz/quux/ http://www.exam
+ple.com/baz/quux/foo/bar.gif
../../bar.gif http://www.example.com/baz/quux/ http://www.exam
+ple.com/bar.gif
foo/bar.gif http://www.example.com/baz/quux http://www.exam
+ple.com/baz/foo/bar.gif
../foo/bar.gif http://www.example.com/baz/quux http://www.exam
+ple.com/foo/bar.gif
../../foo/bar.gif http://www.example.com/baz/quux/qux http://www.exam
+ple.com/foo/bar.gif
);
plan tests => @test / 3;
do { is abs_url( $test[0], $test[1] ), $test[2]; splice @test, 0, 3 }
+while @test;