Module: Rmega::Nodes::Downloadable

Includes:
Rmega::Net, Options
Included in:
File
Defined in:
lib/rmega/nodes/downloadable.rb

Instance Method Summary collapse

Methods included from Options

included, #options

Methods included from Rmega::Net

#http_get_content, #http_post, #survive

Methods included from Loggable

included, #logger

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 9

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

  @file = ::File.open(path, 'r+b')
  @file.rewind
end

#allocated?(path) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rmega/nodes/downloadable.rb', line 24

def allocated?(path)
  ::File.exists?(path) and ::File.size(path) == filesize
end

#calculate_chunck_mac(data) ⇒ Object 



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# File 'lib/rmega/nodes/downloadable.rb', line 63

def calculate_chunck_mac(data)
  mac_iv = @node_key.ctr_nonce * 2
  return aes_cbc_mac(@node_key.aes_key, data, mac_iv)
end

#decrypt_chunk(start, data) ⇒ Object 



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# File 'lib/rmega/nodes/downloadable.rb', line 58

def decrypt_chunk(start, data)
  iv = @node_key.ctr_nonce + [start/0x1000000000, start/0x10].pack('l>*')
  return aes_ctr_decrypt(@node_key.aes_key, data, iv)
end

#download(path) ⇒ Object 



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# File 'lib/rmega/nodes/downloadable.rb', line 68

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

  progress = Progress.new(filesize, caption: 'Download', filename: self.name)
  pool = Pool.new

  @resumed_download = allocated?(path)
  allocate(path)
  @node_key = NodeKey.load(decrypted_file_key)

  chunk_macs = {}

  each_chunk do |start, size|
    pool.process do
      data = @resumed_download ? read_chunk(start, size) : nil

      if data
        chunk_macs[start] = calculate_chunck_mac(data) if options.file_integrity_check
        progress.increment(size, real: false)
      else
        data = decrypt_chunk(start, download_chunk(start, size))
        chunk_macs[start] = calculate_chunck_mac(data) if options.file_integrity_check
        write_chunk(start, data)
        progress.increment(size)
      end
    end
  end

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

  if options.file_integrity_check
    file_mac = aes_cbc_mac(@node_key.aes_key, chunk_macs.sort.map(&:last).join, "\x0"*16)

    if Utils.compact_to_8_bytes(file_mac) != @node_key.meta_mac
      raise("Checksum failed. File corrupted?")
    end
  end

  return nil
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 47

def download_chunk(start, size)
  stop = start + size - 1
  url = "#{storage_url}/#{start}-#{stop}"

  survive do
    data = http_get_content(url)
    raise("Unexpected data length") if data.size != size
    return data
  end
end

#file_io_synchronize(&block) ⇒ Object 



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

def file_io_synchronize(&block)
  @file_io_mutex ||= Mutex.new
  @file_io_mutex.synchronize(&block)
end

#read_chunk(start, size) ⇒ Object 



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# File 'lib/rmega/nodes/downloadable.rb', line 36

def read_chunk(start, size)
  file_io_synchronize do
    @file.seek(start)
    data = @file.read(size)
    @file.seek(start)
    return (data == "\x0"*size) ? nil : data
  end
end

#write_chunk(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 29

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