From: transfire@...
Date: 2006-08-04T02:05:10+09:00
Subject: remote require

I know there are other solutions to this out there. Just wanted to
share my work/play at it. I was trying to make it reletvely secure
without being too much a pain to use. This is was I arrived at.

Usage looks like this:

  remote_source 'fruitapp',
'http://roll.rubyforge.org/source/fruitapp/lib/fruitapp/1.0.0/'
  remote_dependency '9de3cd6daece5f07aa3ddb0319a21415', 'tryme.rb'

  require 'fruitapp/tryme.rb'

The MD5 checksum of course is there to help ensure you get what you
expect. Of course that's the most time consuming part becasue you have
to keep those upto date with new versions.

Anyway, just thought I'd share it just in case it interested anyone.
Here's the code:


# --- remote_require.rb

require 'open-uri'
require 'digest/md5'
require 'fileutils'

REMOTE_CACHE = File.expand_path( '~/.lib/site_ruby/1.8/' )
FileUtils.mkdir_p REMOTE_CACHE unless File.directory? REMOTE_CACHE
$:.unshift REMOTE_CACHE

$current_source = nil
$current_source_stack = []
$remote_source = nil
$remote_dependency = {}

module Kernel

  class ChecksumError < LoadError ; end

  def remote_source( ref, uri )
    $remote_source = { :ref=>ref.chomp('/'), :uri=>uri.chomp('/') }
  end

  def remote_dependency( md5sum, file )
    raise "dependency without source" unless $remote_source
    $remote_dependency[ File.join( $remote_source[:ref], file ) ] = {
      :ref => $remote_source[:ref],
      :file => file,
      :uri  => $remote_source[:uri],
      :md5  => md5sum
    }
  end

  req = method(:require)

  define_method :require do |fname|
    if r = $remote_dependency[fname]
      $current_source_stack << $current_source
      $current_source = r
    end
    begin
      req.call fname
    rescue LoadError => e
      # Bit of a shortcoming here since it's not very efficient to
      # be searching an remote location for multiple matches.
      # .so suffix must be specified explicity on the remote end.
      fname = fname + '.rb' unless fname =~ /\.rb$/ or fname =~ /\.so$/
      raise e unless $current_source
      s = $current_source
      url = fname.sub( /^#{s[:ref]}/, s[:uri] )
      $stderr << "remote require -- " + url if $DEBUG
      rf = URI.parse( url ).read
      if r
        unless Digest::MD5.new( rf ).hexdigest == s[:md5]  # TODO
checksum
          raise ChecksumError.new(e)
        end
      end
      newfile = File.join( REMOTE_CACHE, fname )
      newdir = File.dirname( newfile )
      FileUtils.mkdir_p newdir
      File.open( newfile, 'w+' ) do |f|
        f << rf
      end
      retry
    ensure
      $current_source = $current_source_stack.pop if r
    end
  end

end