Module: Rmega::Nodes::Downloadable

Included in:
File
Defined in:
lib/rmega/nodes/downloadable.rb

Instance Method Summary collapse

Instance Method Details

#allocate(path) ⇒ Object

Creates the local file allocating filesize-n bytes (of /dev/zero) for it. Opens the local file to start writing from the beginning of it.



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# File 'lib/rmega/nodes/downloadable.rb', line 10

def allocate(path)
  `dd if=/dev/zero of="#{path}" bs=1 count=0 seek=#{filesize} > /dev/null 2>&1`
  raise "Unable to create file #{path}" if ::File.size(path) != filesize

  ::File.open(path, 'r+b').tap { |f| f.rewind }
end

#decrypt_chunk(start, encrypted_buffer) ⇒ Object 



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# File 'lib/rmega/nodes/downloadable.rb', line 31

def decrypt_chunk(start, encrypted_buffer)
  k = decrypted_file_key
  nonce = [k[4], k[5], (start/0x1000000000) >> 0, (start/0x10) >> 0]
  decrypt_key = [k[0] ^ k[4], k[1] ^ k[5], k[2] ^ k[6], k[3] ^ k[7]]
  Crypto::AesCtr.decrypt(decrypt_key, nonce, encrypted_buffer)[:data]
end

#download(path) ⇒ Object 



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# File 'lib/rmega/nodes/downloadable.rb', line 38

def download(path)
  path = ::File.expand_path(path)
  path = Dir.exists?(path) ? ::File.join(path, name) : path

  logger.info "Download #{name} (#{filesize} bytes) => #{path}"

  pool = Pool.new
  write_mutex = Mutex.new
  file = allocate(path)

  progress = Progress.new(total: filesize, caption: 'Download')

  Utils.chunks(filesize).each do |start, size|
    pool.defer do
      encrypted_buffer = download_chunk(start, size)

      write_mutex.synchronize do
        clean_buffer = decrypt_chunk(start, encrypted_buffer)
        progress.increment(size)
        write_chunk(file, start, clean_buffer)
      end
    end
  end

  # waits for the last running threads to finish
  pool.wait_done

  file.flush
ensure
  file.close rescue nil
end

#download_chunk(start, size) ⇒ Object

Downloads a part of the remote file, starting from the start-n byte and ending after size-n bytes.



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# File 'lib/rmega/nodes/downloadable.rb', line 19

def download_chunk(start, size)
  stop = start + size - 1
  url = "#{storage_url}/#{start}-#{stop}"
  HTTPClient.new.get_content(url)
end

#write_chunk(file, start, buffer) ⇒ Object

Writes a buffer in the local file, starting from the start-n byte.



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# File 'lib/rmega/nodes/downloadable.rb', line 26

def write_chunk(file, start, buffer)
  file.seek(start)
  file.write(buffer)
end