Class: Innodb::List

Inherits:
Object
  • Object
show all
Defined in:
lib/innodb/list.rb

Direct Known Subclasses

History, Inode, UndoPage, Xdes

Defined Under Namespace

Classes: BaseNode, History, Inode, ListCursor, Node, UndoPage, Xdes

Constant Summary collapse

ADDRESS_SIZE =

An “address”, which consists of a page number and byte offset within the page. This points to the list “node” pointers (prev and next) of the node, not necessarily the node object.

4 + 2
NODE_SIZE =

A list node consists of two addresses: the “previous” node address, and the “next” node address.

2 * ADDRESS_SIZE
BASE_NODE_SIZE =

A list base node consists of a list length followed by two addresses: the “first” node address, and the “last” node address.

4 + (2 * ADDRESS_SIZE)

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(space, base) ⇒ List

Returns a new instance of List.



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# File 'lib/innodb/list.rb', line 71

def initialize(space, base)
  @space = space
  @base = base
end

Instance Attribute Details

#base ⇒ Object (readonly)

Returns the value of attribute base.



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# File 'lib/innodb/list.rb', line 69

def base
  @base
end

#space ⇒ Object (readonly)

Returns the value of attribute space.



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# File 'lib/innodb/list.rb', line 68

def space
  @space
end

Class Method Details

.get_address(cursor) ⇒ Object

Read a node address from a cursor. Return nil if the address is an end or “NULL” pointer (the page number is UINT32_MAX), or the address if valid.



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# File 'lib/innodb/list.rb', line 30

def self.get_address(cursor)
  page = cursor.name("page") { Innodb::Page.maybe_undefined(cursor.read_uint32) }
  offset = cursor.name("offset") { cursor.read_uint16 }

  Innodb::Page::Address.new(page: page, offset: offset) if page
end

.get_base_node(cursor) ⇒ Object

Read a base node, consisting of a list length followed by two addresses (:first and :last) from a cursor. Either address may be nil. An empty list has a :length of 0 and :first and :last are nil. A list with only a single item will have a :length of 1 and :first and :last will point to the same address.



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# File 'lib/innodb/list.rb', line 60

def self.get_base_node(cursor)
  BaseNode.new(
    length: cursor.name("length") { cursor.read_uint32 },
    first: cursor.name("first") { get_address(cursor) },
    last: cursor.name("last") { get_address(cursor) }
  )
end

.get_node(cursor) ⇒ Object

Read a node, consisting of two consecutive addresses (:prev and :next) from a cursor. Either address may be nil, indicating the end of the linked list.



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# File 'lib/innodb/list.rb', line 44

def self.get_node(cursor)
  Node.new(
    prev: cursor.name("prev") { get_address(cursor) },
    next: cursor.name("next") { get_address(cursor) }
  )
end

Instance Method Details

#each(&block) ⇒ Object

Iterate through all nodes in the list.



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# File 'lib/innodb/list.rb', line 134

def each(&block)
  return enum_for(:each) unless block_given?

  list_cursor.each_node(&block)
end

#empty? ⇒ Boolean

Is the list currently empty?

Returns:

  • (Boolean) 


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# File 'lib/innodb/list.rb', line 104

def empty?
  length.zero?
end

#first ⇒ Object

Return the first object in the list using the list base node “first” address pointer.



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# File 'lib/innodb/list.rb', line 110

def first
  object_from_address(@base.first)
end

#include?(item) ⇒ Boolean

Return whether the given item is present in the list. This depends on the item and the items in the list implementing some sufficient == method. This is implemented rather inefficiently by constructing an array and leaning on Array#include? to do the real work.

Returns:

  • (Boolean) 


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# File 'lib/innodb/list.rb', line 129

def include?(item)
  each.to_a.include?(item)
end

#last ⇒ Object

Return the first object in the list using the list base node “last” address pointer.



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# File 'lib/innodb/list.rb', line 116

def last
  object_from_address(@base.last)
end

#length ⇒ Object

Return the number of items in the list.



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# File 'lib/innodb/list.rb', line 99

def length
  @base.length
end

#list_cursor(node = :min, direction = :forward) ⇒ Object

Return a list cursor for the list.



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# File 'lib/innodb/list.rb', line 121

def list_cursor(node = :min, direction = :forward)
  ListCursor.new(self, node, direction)
end

#next(object) ⇒ Object

Return the object pointed to by the “next” address pointer of the provided object.



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# File 'lib/innodb/list.rb', line 92

def next(object)
  raise "Class #{object.class} does not respond to next_address" unless object.respond_to?(:next_address)

  object_from_address(object.next_address)
end

#object_from_address(_address) ⇒ Object

Abstract #object_from_address method which must be implemented by sub-classes in order to return a useful object given an object address.



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# File 'lib/innodb/list.rb', line 78

def object_from_address(_address)
  raise "#{self.class} must implement object_from_address"
end

#prev(object) ⇒ Object

Return the object pointed to by the “previous” address pointer of the provided object.



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# File 'lib/innodb/list.rb', line 84

def prev(object)
  raise "Class #{object.class} does not respond to prev_address" unless object.respond_to?(:prev_address)

  object_from_address(object.prev_address)
end