Method: PEROBS::SpaceManager#get_space

Defined in:
lib/perobs/SpaceManager.rb

#get_space(length) ⇒ Object 



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# File 'lib/perobs/SpaceManager.rb', line 117

def get_space(length)
  # We use a simple exact fit strategy. All attempts to use a more
  # elaborate scheme were actually less efficient. Non-exact matches
  # generate new spaces for the remainder and fragment the blob file with
  # lots of unusable small spaces. Most applications seem to have
  # clustered their blob sizes around a number of popular sizes. So exact
  # match is very efficient to implement and results in the highest
  # probability that a space will be reused soon.
  list_entry_addr = @index.get(length)

  if list_entry_addr
    blob = @list.retrieve_blob(list_entry_addr)
    space_address, next_entry_addr = blob.unpack('QQ')
    @list.delete_blob(list_entry_addr)

    if next_entry_addr > 0
      # Update the index entry for the length to point to the
      # following space list entry.
      @index.insert(length, next_entry_addr)
    else
      # The space list for this length is empty. Remove the entry
      # from the index.
      @index.remove(length)
    end
    @recycled_spaces += 1

    # We return the length to remain compatible with the old SpaceTree
    # API.
    return [ space_address, length ]
  end

  @failed_requests += 1
  nil
end