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comp.lang.ruby

Creating a canonicalized url

Dan Cuddeford

1/24/2008 12:14:00 PM

Hello there guys,

I'm trying to track down an easy way to canonicalize a URL from with
ruby. I've been looking around for this but all I can find are some
procedure hacks sure as # canonicalize the url
if ($url -notmatch "^[a-z]+://") { $url = "http://$url" }

which isn't going to take into account everything according to RFC 2396

* Remove all leading and trailing dots
* Replace consecutive dots with a single dot.
* If the hostname can be parsed as an IP address, it should be
normalized to 4 dot-separated decimal values. The client should handle
any legal IP address encoding, including octal, hex, and fewer than 4
components.
* Lowercase the whole string.


# The sequences "/../" and "/./" in the path should be resolved, by
replacing "/./" with "/", and removing "/../" along with the preceding
path component.
# Runs of consecutive slashes should be replaced with a single slash
character.

So is there a method out there for this?
--
Posted via http://www.ruby-....
9 Answers

Rob Biedenharn

1/24/2008 1:24:00 PM

0


On Jan 24, 2008, at 7:14 AM, Dan Cuddeford wrote:

> Hello there guys,
>
> I'm trying to track down an easy way to canonicalize a URL from with
> ruby. I've been looking around for this but all I can find are some
> procedure hacks sure as # canonicalize the url
> if ($url -notmatch "^[a-z]+://") { $url = "http://$url" }
>
> which isn't going to take into account everything according to RFC
> 2396
>
> * Remove all leading and trailing dots
> * Replace consecutive dots with a single dot.
> * If the hostname can be parsed as an IP address, it should be
> normalized to 4 dot-separated decimal values. The client should handle
> any legal IP address encoding, including octal, hex, and fewer than 4
> components.
> * Lowercase the whole string.
>
>
> # The sequences "/../" and "/./" in the path should be resolved, by
> replacing "/./" with "/", and removing "/../" along with the preceding
> path component.
> # Runs of consecutive slashes should be replaced with a single slash
> character.
>
> So is there a method out there for this?

I'd start looking at URI, in particular, URI#parse.

$ fri URI#parse
------------------------------------------------------------- URI::parse
URI::parse(uri)
------------------------------------------------------------------------
Synopsis
URI::parse(uri_str)

Args
+uri_str+: String with URI.

Description
Creates one of the URI's subclasses instance from the string.

Raises
URI::InvalidURIError

Raised if URI given is not a correct one.

Usage
require 'uri'

uri = URI.parse("http://www.ruby-lang....)
p uri
# => #<URI::HTTP:0x202281be URL:http://www.ruby-lan...
p uri.scheme
# => "http"
p uri.host
# => "www.ruby-lang.org"

As for the "Lowercase the whole string" part, only the domain is
required to be case-insensitive. It is possible for the underlying
web server to ignore case when finding a path, but the URI is not
necessarily a reference to the same resource if the case is altered.

-Rob

Rob Biedenharn http://agileconsult...
Rob@AgileConsultingLLC.com

Jean-François Trân

1/24/2008 2:07:00 PM

0

2008/1/24, Rob Biedenharn <Rob@agileconsultingllc.com>:

> As for the "Lowercase the whole string" part, only the domain is
> required to be case-insensitive. It is possible for the underlying
> web server to ignore case when finding a path, but the URI is not
> necessarily a reference to the same resource if the case is altered.

There's URI#normalize and URI#normalize! to downcase the host
part of the url.

-- Jean-Fran=E7ois.

Dan Cuddeford

1/24/2008 2:12:00 PM

0

Thanks for your help - I'll let you know how I get on

--
Posted via http://www.ruby-....

Dan Cuddeford

1/24/2008 2:23:00 PM

0

So it seems using the two together


require 'uri'

uri = URI.parse("http://www.ruBy-lang.org/...)

can = uri.normalize
p can

p can.host

p can.path


means the path keeps it's case sensitivity but the host is normalized.

I think that's it - however,

try it with ruby-lang..org and

/usr/lib/ruby/1.8/uri/generic.rb:195:in `initialize': the scheme http
does not accept registry part: www.ruBy-lang..org (or bad hostname?)
(URI::InvalidURIError)
from /usr/lib/ruby/1.8/uri/http.rb:78:in `initialize'
from /usr/lib/ruby/1.8/uri/common.rb:488:in `new'
from /usr/lib/ruby/1.8/uri/common.rb:488:in `parse'
from canon.rb:3

So I guess it needs a bit or error checking before hand.
--
Posted via http://www.ruby-....

Rob Biedenharn

1/24/2008 4:05:00 PM

0


On Jan 24, 2008, at 9:23 AM, Dan Cuddeford wrote:

> So it seems using the two together
>
>
> require 'uri'
>
> uri = URI.parse("http://www.ruBy-lang.org/...)
>
> can = uri.normalize
> p can
>
> p can.host
>
> p can.path
>
>
> means the path keeps it's case sensitivity but the host is normalized.
>
> I think that's it - however,
>
> try it with ruby-lang..org and
>
> /usr/lib/ruby/1.8/uri/generic.rb:195:in `initialize': the scheme http
> does not accept registry part: www.ruBy-lang..org (or bad hostname?)
> (URI::InvalidURIError)
> from /usr/lib/ruby/1.8/uri/http.rb:78:in `initialize'
> from /usr/lib/ruby/1.8/uri/common.rb:488:in `new'
> from /usr/lib/ruby/1.8/uri/common.rb:488:in `parse'
> from canon.rb:3
>
> So I guess it needs a bit or error checking before hand.

require 'uri'

def canonicalize(uri)
u = uri.kind_of?(URI) ? uri : URI.parse(uri.to_s)
u.normalize!
newpath = u.path
while newpath.gsub!(%r{([^/]+)/\.\./?}) { |match|
$1 == '..' ? match : ''
} do end
newpath = newpath.gsub(%r{/\./}, '/').sub(%r{/\.\z}, '/')
u.path = newpath
u.to_s
end

canonicalize('http://www.Ruby-Lang.ORG/ARSE/done/../../rear/./...)
=> "http://www.ruby-lang.org/rear/...

-Rob

Rob Biedenharn http://agileconsult...
Rob@AgileConsultingLLC.com

Dan Cuddeford

1/24/2008 4:39:00 PM

0

Wow - thanks for the answer mate!
--
Posted via http://www.ruby-....

Jörg W Mittag

1/24/2008 7:23:00 PM

0

Dan Cuddeford wrote:
> Wow - thanks for the answer mate!

There's also the Addressable Gem: <http://Addressable.RubyForg....

It's intended as a standards compliant replacement for the stdlib's
URI library. Take a look into the test directory of that sucker: over
440 Unit Tests (actually, Object Examples) for a frickin' URI parser!
(See: <http://Addressable.RubyForge.Org/sp...) That guy is nuts!
That code's gotta be as rock-solid as it gets.

Oh, and back to the topic at hand: it has a normalize method built in:

begin
require 'rubygems'
gem 'addressable'
rescue LoadError; end
require 'addressable/uri'
uri = Addressable::URI.heuristic_parse('www.Ruby-Lang..ORG/ARSE/done/../../r e a r/./end/.#exit')
uri.normalize!
puts uri.display_uri # => http://www.ruby-lang..org/r%20e%20a%20r...

jwm

Dan Cuddeford

1/25/2008 3:27:00 PM

0

Jörg W Mittag wrote:
> puts uri.display_uri # =>
> http://www.ruby-lang..org/r%20e%20a%20r...
>
> jwm

Nice but shouldn't it go to ruby-lang.org?
--
Posted via http://www.ruby-....

Jörg W Mittag

1/26/2008 12:18:00 AM

0

Dan Cuddeford wrote:
> Jörg W Mittag wrote:
>> puts uri.display_uri # =>
>> http://www.ruby-lang..org/r%20e%20a%20r...
> Nice but shouldn't it go to ruby-lang.org?

I'm not sure. I just scanned RfC3986 and RfC1034 and I'm not even sure
that's a valid URI host part to begin with. *If* it's invalid, then
there's not much a URI normalizer can do, right?

However, I could be wrong. Reading RfCs is not exactly my specialty.

jwm