Class: PPTX::OPC::PackageStreamer

Inherits:
Object
  • Object
show all
Defined in:
lib/pptx/opc/package_streamer.rb

Instance Method Summary collapse

Constructor Details

#initialize(package, ignore_part_exceptions = false) ⇒ PackageStreamer

Use ignore_part_exceptions to ignore exceptions while marshalling or streaming a part. Useful to ignore missing files on S3.



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# File 'lib/pptx/opc/package_streamer.rb', line 6

def initialize(package, ignore_part_exceptions=false)
  @package = package
  @ignore_part_exceptions = ignore_part_exceptions
end

Instance Method Details

#each(&block) ⇒ Object

This method uses parts of zipline to implement streaming.

This is how Zipline usually works:

  • Rails calls response_body.each

  • response_body is Zipline::ZipGenerator, it creates a Zipline::FakeStream with the block given to each

  • The FakeStream is used as output for ZipLine::OutputStream (which inherits from Zip::OutputStream)

  • ZipGenerator goes through files and calls write_file on the OutputStream for each file

  • OutputStream writes the data as String to FakeStream via the << method

  • FakeStream yields the String to the block given by Rails

This method uses Zipline’s FakeStream and OutputStream, but writes the entries to the zip file on it’s own, so we can write data for a file in multiple steps and don’t have to rely on Zipline’s crazy logic (e.g. on what can be streamed and what not - only IO and StringIO). Basically, this replaces ZipGenerator.



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# File 'lib/pptx/opc/package_streamer.rb', line 27

def each(&block)
  fake_stream = Zipline::FakeStream.new(&block)
  Zipline::OutputStream.open(fake_stream) do |zip|
    @package.parts.each do |name, part|
      begin
        if part.respond_to?(:stream) && part.respond_to?(:size)
          zip.put_next_entry name, part.size
          part.stream zip
        else
          data = @package.marshal_part(name)
          zip.put_next_entry name, data.size
          zip << data
        end
      rescue => e
        raise e unless @ignore_part_exceptions
      end
    end
  end
end