Simple fragment caching in sinatra

readme.txt

Simple fragment caching helper for Sinatra
Bryan Thompson - bryan@radiowebservices.com - twitter.com/bryanthompson

Helper structure can probably be simplified, but I'm leaving space 
for future improvements like memcache and other settings that I 
might be overlooking right now

Actual caching scheme strongly inspired by merb and rails caching
methods.

Usage:

* drop cache_helper in a lib/ dir and require it
* set CACHE_ROOT 

<% cache "name_of_cache", :max_age => 60 do %>
  ... Stuff you want cached ...
<% end %>

For now, .cache files are dumped right into a tmp directory.  
defined as CACHE_ROOT.  I set mine in my site.rb file as
CACHE_ROOT = File.dirname(__FILE__)

cache_helper.rb

require 'sinatra/base'

class CacheHelper
  module Sinatra
    module Helpers      
      def cache(name, options = {}, &block)
        if cache = read_fragment(name, options)
          @_out_buf << cache
        else
          pos = @_out_buf.length
          tmp = block.call
          write_fragment(name, tmp[pos..-1], options)
        end        
      end
      
      def read_fragment(name, options = {})
        cache_file = "#{CACHE_ROOT}/tmp/#{name}.cache"
        now = Time.now
        if File.file?(cache_file)
          if options[:max_age]
            (current_age = (now - File.mtime(cache_file)).to_i / 60)
            puts "Fragment for '#{name}' is #{current_age} minutes old."
            return false if (current_age > options[:max_age])
          end
          return File.read(cache_file)
        end
        false
      end
      
      def write_fragment(name, buf, options = {})
        cache_file = "#{SINATRA_ROOT}/tmp/#{name}.cache"
        f = File.new(cache_file, "w+")
        f.write(buf)
        f.close
        puts "Fragment written for '#{name}'"
        buf
      end
    end
    
    def self.registered(app)
      app.helpers CacheHelper::Sinatra::Helpers
    end    
  end
end

Sinatra.register CacheHelper::Sinatra 

Thanks for inspiration. Couldn't make it working with Haml, but I made my own cache helper (specially for Haml) - https://gist.github.com/3742161