Class: Feedzirra::Feed

Inherits:
Object
  • Object
show all
Defined in:
lib/feedzirra/feed.rb

Constant Summary collapse

USER_AGENT = 
"feedzirra http://github.com/pauldix/feedzirra/tree/master"

Class Method Summary collapse

Class Method Details

.add_common_feed_entry_element(element_tag, options = {}) ⇒ Object

Makes all entry types look for the passed in element to parse. This is actually just a call to element (a SAXMachine call) in the class

Parameters

element_tag<String>
options<Hash>

Valid keys are same as with SAXMachine



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# File 'lib/feedzirra/feed.rb', line 60

def self.add_common_feed_entry_element(element_tag, options = {})
  # need to think of a better way to do this. will break for people who want this behavior
  # across their added classes
  feed_classes.map{|k| eval("#{k}Entry") }.each do |klass|
    klass.send(:element, element_tag, options)
  end
end

.add_feed_class(klass) ⇒ Object

Adds a new feed parsing class that will be used for parsing.

Parameters

klass<Constant>

The class/constant that you want to register.

Returns

A updated array of feed parser class names.



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# File 'lib/feedzirra/feed.rb', line 42

def self.add_feed_class(klass) 
  feed_classes.unshift klass
end

.add_feed_to_multi(multi, feed, feed_queue, responses, options) ⇒ Object

An abstraction for adding a feed by a Feed object to the passed Curb::multi stack.

Parameters

multi<Curl::Multi>

The Curl::Multi object that the request should be added too.

feed<Feed>

A feed object that you would like to be fetched.

url_queue<Array>

An array of feed objects that are queued for request.

responses<Hash>

Existing responses that you want the response from the request added to.

feeds<String>

or <Array> A single feed object, or an array of feed objects.

options<Hash>

Valid keys for this argument as as followed:

  • :user_agent - String that overrides the default user agent.

  • :on_success - Block that gets executed after a successful request.

  • :on_failure - Block that gets executed after a failed request.

Returns

The updated Curl::Multi object with the request details added to it’s stack.



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# File 'lib/feedzirra/feed.rb', line 294

def self.add_feed_to_multi(multi, feed, feed_queue, responses, options) 
  easy = Curl::Easy.new(feed.feed_url) do |curl|
    curl.headers["User-Agent"]        = (options[:user_agent] || USER_AGENT)
    curl.headers["If-Modified-Since"] = feed.last_modified.httpdate if feed.last_modified
    curl.headers["If-None-Match"]     = feed.etag if feed.etag
    curl.userpwd = options[:http_authentication].join(':') if options.has_key?(:http_authentication)
    curl.follow_location = true

    curl.max_redirects = options[:max_redirects] if options[:max_redirects]
    curl.timeout = options[:timeout] if options[:timeout]

    curl.on_success do |c|
      begin
        add_feed_to_multi(multi, feed_queue.shift, feed_queue, responses, options) unless feed_queue.empty?
        updated_feed = Feed.parse(c.body_str)
        updated_feed.feed_url = c.last_effective_url
        updated_feed.etag = etag_from_header(c.header_str)
        updated_feed.last_modified = last_modified_from_header(c.header_str)
        feed.update_from_feed(updated_feed)
        responses[feed.feed_url] = feed
        options[:on_success].call(feed) if options.has_key?(:on_success)
      rescue Exception => e
        options[:on_failure].call(feed, c.response_code, c.header_str, c.body_str) if options.has_key?(:on_failure)
      end
    end

    curl.on_failure do |c, err|
      add_feed_to_multi(multi, feed_queue.shift, feed_queue, responses, options) unless feed_queue.empty?
      response_code = c.response_code
      if response_code == 304 # it's not modified. this isn't an error condition
        responses[feed.feed_url] = feed
        options[:on_success].call(feed) if options.has_key?(:on_success)
      else
        responses[feed.url] = c.response_code
        options[:on_failure].call(feed, c.response_code, c.header_str, c.body_str) if options.has_key?(:on_failure)
      end
    end
  end
  multi.add(easy)
end

.add_url_to_multi(multi, url, url_queue, responses, options) ⇒ Object

An abstraction for adding a feed by URL to the passed Curb::multi stack.

Parameters

multi<Curl::Multi>

The Curl::Multi object that the request should be added too.

url<String>

The URL of the feed that you would like to be fetched.

url_queue<Array>

An array of URLs that are queued for request.

responses<Hash>

Existing responses that you want the response from the request added to.

feeds<String> or <Array>

A single feed object, or an array of feed objects.

options<Hash>

Valid keys for this argument as as followed:

  • :user_agent - String that overrides the default user agent.

  • :on_success - Block that gets executed after a successful request.

  • :on_failure - Block that gets executed after a failed request.

Returns

The updated Curl::Multi object with the request details added to it’s stack.



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# File 'lib/feedzirra/feed.rb', line 230

def self.add_url_to_multi(multi, url, url_queue, responses, options)
  easy = Curl::Easy.new(url) do |curl|
    curl.headers["User-Agent"]        = (options[:user_agent] || USER_AGENT)
    curl.headers["If-Modified-Since"] = options[:if_modified_since].httpdate if options.has_key?(:if_modified_since)
    curl.headers["If-None-Match"]     = options[:if_none_match] if options.has_key?(:if_none_match)
    curl.headers["Accept-encoding"]   = 'gzip, deflate' if options.has_key?(:compress)
    curl.follow_location = true
    curl.userpwd = options[:http_authentication].join(':') if options.has_key?(:http_authentication)

    curl.max_redirects = options[:max_redirects] if options[:max_redirects]
    curl.timeout = options[:timeout] if options[:timeout]
    
    curl.on_success do |c|
      add_url_to_multi(multi, url_queue.shift, url_queue, responses, options) unless url_queue.empty?
      xml = decode_content(c)
      klass = determine_feed_parser_for_xml(xml)
      
      if klass
        begin
          feed = klass.parse(xml)
          feed.feed_url = c.last_effective_url
          feed.etag = etag_from_header(c.header_str)
          feed.last_modified = last_modified_from_header(c.header_str)
          responses[url] = feed
          options[:on_success].call(url, feed) if options.has_key?(:on_success)
        rescue Exception => e
          options[:on_failure].call(url, c.response_code, c.header_str, c.body_str) if options.has_key?(:on_failure)
        end
      else
        # puts "Error determining parser for #{url} - #{c.last_effective_url}"
        if options.has_key?(:on_failure)
            options[:on_failure].call(url, c.response_code, c.header_str, c.body_str)
        else
            # this will unfortunately fail the whole 'multi', so it's not really useable
            url_message = url
            url_message += "- #{c.last_effective_url}" unless url == c.last_effective_url
            raise NoParserAvailable.new("No valid parser for #{url_message}")
        end
      end
    end
    
    curl.on_failure do |c, err|
      add_url_to_multi(multi, url_queue.shift, url_queue, responses, options) unless url_queue.empty?
      responses[url] = c.response_code
      options[:on_failure].call(url, c.response_code, c.header_str, c.body_str) if options.has_key?(:on_failure)
    end
  end
  multi.add(easy)
end

.decode_content(c) ⇒ Object

Decodes the XML document if it was compressed.

Parameters

curl_request<Curl::Easy>

The Curl::Easy response object from the request.

Returns

A decoded string of XML.



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# File 'lib/feedzirra/feed.rb', line 147

def self.decode_content(c)
  if c.header_str.match(/Content-Encoding: gzip/)
    begin
      gz =  Zlib::GzipReader.new(StringIO.new(c.body_str))
      xml = gz.read
      gz.close
    rescue Zlib::GzipFile::Error 
      # Maybe this is not gzipped?
      xml = c.body_str
    end
  elsif c.header_str.match(/Content-Encoding: deflate/)
    xml = Zlib::Inflate.inflate(c.body_str)
  else
    xml = c.body_str
  end

  # if we retrieved a web page, rather than RSS, look for a linked RSS feed
  if c.header_str.match(/Content-Type: text\/html/)
    html = c.body_str
    # parse the web page for the URL of an embedded RSS feed
    parsed_page = WebPage.parse(html)

    if !parsed_page.nil? && !parsed_page.feed_url.nil?
        
        # If the extracted URL is relative to the web page URL, create an absolute
        # URL we can use
        unless parsed_page.feed_url =~ /:\/\//
            # parse the URL of the web page that was retrieved
            uri = URI.parse(c.last_effective_url)
            # reconstruct a feed URL
            parsed_page.feed_url = uri.scheme + '://' + uri.host + parsed_page.feed_url
        end

        # re-use the same curl instance that generated this response, so that
        # any calling context can pick up on things like last_effective_url from it
        c.url = parsed_page.feed_url
        c.perform
    end
    xml = c.body_str
  end

  xml
end

.determine_feed_parser_for_xml(xml) ⇒ Object

Determines the correct parser class to use for parsing the feed.

Parameters

xml<String>

The XML that you would like determine the parser for.

Returns

The class name of the parser that can handle the XML.



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# File 'lib/feedzirra/feed.rb', line 31

def self.determine_feed_parser_for_xml(xml)
  start_of_doc = xml.slice(0, 2000)
  feed_classes.detect {|klass| klass.able_to_parse?(start_of_doc)}
end

.etag_from_header(header) ⇒ Object

Determines the etag from the request headers.

Parameters

header<String>

Raw request header returned from the request

Returns

A string of the etag or nil if it cannot be found in the headers.



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# File 'lib/feedzirra/feed.rb', line 341

def self.etag_from_header(header)
  header =~ /.*ETag:\s(.*)\r/
  $1
end

.feed_classes ⇒ Object

Provides a list of registered feed parsing classes.

Returns

A array of class names.



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# File 'lib/feedzirra/feed.rb', line 50

def self.feed_classes
  @feed_classes ||= [Feedzirra::Parser::RSS, Feedzirra::Parser::AtomFeedBurner, Feedzirra::Parser::Atom]
end

.fetch_and_parse(urls, options = {}) ⇒ Object

Fetches and returns the parsed XML for each URL provided.

Parameters

urls<String> or <Array>

A single feed URL, or an array of feed URLs.

options<Hash>

Valid keys for this argument as as followed:

  • :user_agent - String that overrides the default user agent.

  • :if_modified_since - Time object representing when the feed was last updated.

  • :if_none_match - String, an etag for the request that was stored previously.

  • :on_success - Block that gets executed after a successful request.

  • :on_failure - Block that gets executed after a failed request.

Returns

A Feed object if a single URL is passed.

A Hash if multiple URL’s are passed. The key will be the URL, and the value the Feed object.



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# File 'lib/feedzirra/feed.rb', line 126

def self.fetch_and_parse(urls, options = {})
  url_queue = [*urls]
  multi = Curl::Multi.new
  responses = {}
  
  # I broke these down so I would only try to do 30 simultaneously because
  # I was getting weird errors when doing a lot. As one finishes it pops another off the queue.
  url_queue.slice!(0, 30).each do |url|
    add_url_to_multi(multi, url, url_queue, responses, options)
  end
 
  multi.perform
  return urls.is_a?(String) ? responses.values.first : responses
end

.fetch_raw(urls, options = {}) ⇒ Object

Fetches and returns the raw XML for each URL provided.

Parameters

urls<String> or <Array>

A single feed URL, or an array of feed URLs.

options<Hash>

Valid keys for this argument as as followed: :user_agent - String that overrides the default user agent. :if_modified_since - Time object representing when the feed was last updated. :if_none_match - String that’s normally an etag for the request that was stored previously. :on_success - Block that gets executed after a successful request. :on_failure - Block that gets executed after a failed request.

Returns

A String of XML if a single URL is passed.

A Hash if multiple URL’s are passed. The key will be the URL, and the value the XML.



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# File 'lib/feedzirra/feed.rb', line 82

def self.fetch_raw(urls, options = {})
  url_queue = [*urls]
  multi = Curl::Multi.new
  responses = {}
  url_queue.each do |url|
    easy = Curl::Easy.new(url) do |curl|
      curl.headers["User-Agent"]        = (options[:user_agent] || USER_AGENT)
      curl.headers["If-Modified-Since"] = options[:if_modified_since].httpdate if options.has_key?(:if_modified_since)
      curl.headers["If-None-Match"]     = options[:if_none_match] if options.has_key?(:if_none_match)
      curl.headers["Accept-encoding"]   = 'gzip, deflate' if options.has_key?(:compress)
      curl.follow_location = true
      curl.userpwd = options[:http_authentication].join(':') if options.has_key?(:http_authentication)
      
      curl.max_redirects = options[:max_redirects] if options[:max_redirects]
      curl.timeout = options[:timeout] if options[:timeout]

      curl.on_success do |c|
        responses[url] = decode_content(c)
      end
      curl.on_failure do |c, err|
        responses[url] = c.response_code
      end
    end
    multi.add(easy)
  end

  multi.perform
  urls.is_a?(String) ? responses.values.first : responses
end

.last_modified_from_header(header) ⇒ Object

Determines the last modified date from the request headers.

Parameters

header<String>

Raw request header returned from the request

Returns

A Time object of the last modified date or nil if it cannot be found in the headers.



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# File 'lib/feedzirra/feed.rb', line 352

def self.last_modified_from_header(header)
  header =~ /.*Last-Modified:\s(.*)\r/
  Time.parse($1) if $1
end

.parse(xml) ⇒ Object

Takes a raw XML feed and attempts to parse it. If no parser is available a Feedzirra::NoParserAvailable exception is raised.

Parameters

xml<String>

The XML that you would like parsed.

Returns

An instance of the determined feed type. By default a Feedzirra::Atom, Feedzirra::AtomFeedBurner, Feedzirra::RDF, or Feedzirra::RSS object.

Raises

Feedzirra::NoParserAvailable : If no valid parser classes could be found for the feed.



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# File 'lib/feedzirra/feed.rb', line 17

def self.parse(xml)
  if parser = determine_feed_parser_for_xml(xml)
    parser.parse(xml)
  else
    raise NoParserAvailable.new("No valid parser for XML.")
  end
end

.update(feeds, options = {}) ⇒ Object

Updates each feed for each Feed object provided.

Parameters

feeds<Feed> or <Array>

A single feed object, or an array of feed objects.

options<Hash>

Valid keys for this argument as as followed:

  • :user_agent - String that overrides the default user agent.

  • :on_success - Block that gets executed after a successful request.

  • :on_failure - Block that gets executed after a failed request.

Returns

A updated Feed object if a single URL is passed.

A Hash if multiple Feeds are passed. The key will be the URL, and the value the updated Feed object.



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# File 'lib/feedzirra/feed.rb', line 203

def self.update(feeds, options = {})
  feed_queue = [*feeds]
  multi = Curl::Multi.new
  responses = {}
  
  feed_queue.slice!(0, 30).each do |feed|
    add_feed_to_multi(multi, feed, feed_queue, responses, options)
  end

  multi.perform
  responses.size == 1 ? responses.values.first : responses.values
end