Class: EventMachine::FileStreamer

Inherits:
Object
  • Object
show all
Includes:
Deferrable
Defined in:
lib/em/streamer.rb

Overview

Streams a file over a given connection. Streaming begins once the object is instantiated. Typically FileStreamer instances are not reused.

Streaming uses buffering for files larger than 16K and uses so-called fast file reader (a C++ extension) if available (it is part of eventmachine gem itself).

Examples:


module FileSender
  def post_init
    streamer = EventMachine::FileStreamer.new(self, '/tmp/bigfile.tar')
    streamer.callback{
      # file was sent successfully
      close_connection_after_writing
    }
  end
end

Author:

  • Francis Cianfrocca

Constant Summary

MappingThreshold =

Use mapped streamer for files bigger than 16k

16384
BackpressureLevel =

Wait until next tick to send more data when 50k is still in the outgoing buffer

50000
ChunkSize =

Send 16k chunks at a time

16384

Constants included from Deferrable

Deferrable::Pool

Instance Method Summary collapse

Methods included from Deferrable

#callback, #cancel_callback, #cancel_errback, #cancel_timeout, #errback, #fail, future, #set_deferred_status, #succeed, #timeout

Constructor Details

#initialize(connection, filename, args = {}) ⇒ FileStreamer

Returns a new instance of FileStreamer

Parameters:

  • connection (EventMachine::Connection)
  • filename (String)

    File path

  • args (Hash) (defaults to: {})

    a customizable set of options

Options Hash (args):

  • :http_chunks (Boolean) — default: false

    Use HTTP 1.1 style chunked-encoding semantics.



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# File 'lib/em/streamer.rb', line 36

def initialize connection, filename, args = {}
  @connection = connection
  @http_chunks = args[:http_chunks]

  if File.exist?(filename)
    @size = File.size(filename)
    if @size <= MappingThreshold
      stream_without_mapping filename
    else
      stream_with_mapping filename
    end
  else
    fail "file not found"
  end
end

Instance Method Details

#stream_one_chunkObject

Used internally to stream one chunk at a time over multiple reactor ticks



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# File 'lib/em/streamer.rb', line 77

def stream_one_chunk
  loop {
    if @position < @size
      if @connection.get_outbound_data_size > BackpressureLevel
        EventMachine::next_tick {stream_one_chunk}
        break
      else
        len = @size - @position
        len = ChunkSize if (len > ChunkSize)

        @connection.send_data( "#{len.to_s(16)}\r\n" ) if @http_chunks
        @connection.send_data( @mapping.get_chunk( @position, len ))
        @connection.send_data("\r\n") if @http_chunks

        @position += len
      end
    else
      @connection.send_data "0\r\n\r\n" if @http_chunks
      @mapping.close
      succeed
      break
    end
  }
end