class PEROBS::ObjectBase

Base class for all persistent objects. It provides the functionality common to all classes of persistent objects.

Constants

NATIVE_CLASSES

Attributes

_id[R]
myself[R]
store[R]

Public Class Methods

_finalize(store, id, ruby_object_id) click to toggle source

This method generates the destructor for the objects of this class. It is done this way to prevent the Proc object hanging on to a reference to self which would prevent the object from being collected. This internal method is not intended for users to call.

# File lib/perobs/ObjectBase.rb, line 173
def ObjectBase._finalize(store, id, ruby_object_id)
  proc { store._collect(id, ruby_object_id) }
end
new(p) click to toggle source

New PEROBS objects must always be created by calling # Store.new(). PEROBS users should never call this method or equivalents of derived methods directly. @param p [PEROBS::Handle] PEROBS handle

# File lib/perobs/ObjectBase.rb, line 148
def initialize(p)
  _initialize(p)
end
read(store, id) click to toggle source

Read an raw object with the specified ID from the backing store and instantiate a new object of the specific type.

# File lib/perobs/ObjectBase.rb, line 241
def ObjectBase.read(store, id)
  # Read the object from database.
  db_obj = store.db.get_object(id)

  klass = store.class_map.id_to_class(db_obj['class_id'])
  # Call the constructor of the specified class.
  obj = Object.const_get(klass).allocate
  obj._initialize(Handle.new(store, id))
  obj._deserialize(db_obj['data'])
  obj.restore

  obj
end

Public Instance Methods

==(obj) click to toggle source

Two objects are considered equal if their object IDs are the same.

# File lib/perobs/ObjectBase.rb, line 202
def ==(obj)
  return false unless obj.is_a?(ObjectBase)
  obj && @_id == obj._id
end
_check_assignment_value(val) click to toggle source
# File lib/perobs/ObjectBase.rb, line 221
def _check_assignment_value(val)
  if val.respond_to?(:is_poxreference?)
    # References to other PEROBS::Objects must be handled somewhat
    # special.
    if @store != val.store
      PEROBS.log.fatal 'The referenced object is not part of this store'
    end
  elsif val.is_a?(ObjectBase)
    PEROBS.log.fatal 'A PEROBS::ObjectBase object escaped! ' +
      'Have you used self() instead of myself() to get the reference ' +
      'of the PEROBS object that you are trying to assign here?'
  elsif !NATIVE_CLASSES.include?(val.class)
    PEROBS.log.fatal "Assigning objects of class #{val.class} is not " +
      "supported. Only PEROBS objects or one of the following classes " +
      "are supported: #{NATIVE_CLASSES.join(', ')}"
  end
end
_initialize(p) click to toggle source

This is the real code for initialize. It is called from initialize() but also when we restore objects from the database. In the later case, we don't call the regular constructors. But this code must be exercised on object creation with new() and on restore from DB. param p [PEROBS::Handle] PEROBS handle

# File lib/perobs/ObjectBase.rb, line 157
def _initialize(p)
  @store = p.store
  @_id = p.id
  @store._register_in_memory(self, @_id)
  ObjectSpace.define_finalizer(
    self, ObjectBase._finalize(@store, @_id, object_id))
  @_stash_map = nil
  # Allocate a proxy object for this object. User code should only operate
  # on this proxy, never on self.
  @myself = POXReference.new(@store, @_id)
end
_restore(level) click to toggle source

Restore the object state from the storage back-end. @param level [Integer] the transaction nesting level

# File lib/perobs/ObjectBase.rb, line 257
def _restore(level)
  # Find the most recently stored state of this object. This could be on
  # any previous stash level or in the regular object DB. If the object
  # was created during the transaction, there is no previous state to
  # restore to.
  data = nil
  if @_stash_map
    (level - 1).downto(0) do |lvl|
      break if (data = @_stash_map[lvl])
    end
  end
  if data
    # We have a stashed version that we can restore from.
    _deserialize(data)
  elsif @store.db.include?(@_id)
    # We have no stashed version but can restore from the database.
    db_obj = store.db.get_object(@_id)
    _deserialize(db_obj['data'])
  end
end
_stash(level) click to toggle source

Save the object state for this transaction level to the storage back-end. The object gets a new ID that is stored in @_stash_map to map the stash ID back to the original data.

# File lib/perobs/ObjectBase.rb, line 281
def _stash(level)
  @_stash_map ||= ::Array.new
  # Get a new ID to store this version of the object.
  @_stash_map[level] = _serialize
end
_sync() click to toggle source

Write the object into the backing store database.

# File lib/perobs/ObjectBase.rb, line 208
def _sync
  # Reset the stash map to ensure that it's reset before the next
  # transaction is being started.
  @_stash_map = nil

  db_obj = {
    'class_id' => @store.class_map.class_to_id(self.class.to_s),
    'data' => _serialize
  }
  @store.db.put_object(db_obj, @_id)
end
_transfer(store) click to toggle source

Library internal method to transfer the Object to a new store. @param store [Store] New store

# File lib/perobs/ObjectBase.rb, line 179
def _transfer(store)
  @store = store
  # Remove the previously defined finalizer as it is attached to the old
  # store.
  ObjectSpace.undefine_finalizer(self)
  # Register the object as in-memory object with the new store.
  @store._register_in_memory(self, @_id)
  # Register the finalizer for the new store.
  ObjectSpace.define_finalizer(
    self, ObjectBase._finalize(@store, @_id, object_id))
  @myself = POXReference.new(@store, @_id)
end
restore() click to toggle source

This method can be overloaded by derived classes to do some massaging on the data after it has been restored from the database. This could either be some sanity check or code to migrate the object from one version to another. It is also the right place to initialize non-persistent instance variables as initialize() will only be called when objects are created for the first time.

# File lib/perobs/ObjectBase.rb, line 198
def restore
end