Class: Innodb::List::ListCursor

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

Overview

A list iteration cursor used primarily by the Innodb::List #cursor method implicitly. Keeps its own state for iterating through lists efficiently.

Instance Method Summary collapse

Constructor Details

#initialize(list, node = :min, direction = :forward) ⇒ ListCursor

Returns a new instance of ListCursor.



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# File 'lib/innodb/list.rb', line 138

def initialize(list, node=:min, direction=:forward)
  @initial = true
  @list = list
  @direction = direction

  case node
  when :min
    @node = @list.first
  when :max
    @node = @list.last
  else
    @node = node
  end
end

Instance Method Details

#each_node ⇒ Object 



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# File 'lib/innodb/list.rb', line 187

def each_node
  unless block_given?
    return enum_for(:each_node)
  end

  while n = node
    yield n
  end
end

#next_node ⇒ Object

Return the next entry from the current position, and advance the cursor position to the returned entry. If the cursor is currently nil, return the first entry in the list and adjust the cursor position to that entry.



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# File 'lib/innodb/list.rb', line 181

def next_node
  if node = @list.next(@node)
    @node = node
  end
end

#node ⇒ Object 



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# File 'lib/innodb/list.rb', line 153

def node
  if @initial
    @initial = false
    return @node
  end

  case @direction
  when :forward
    next_node
  when :backward
    prev_node
  end
end

#prev_node ⇒ Object

Return the previous entry from the current position, and advance the cursor position to the returned entry. If the cursor is currently nil, return the last entry in the list and adjust the cursor position to that entry.



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# File 'lib/innodb/list.rb', line 171

def prev_node
  if node = @list.prev(@node)
    @node = node
  end
end