Class: Btree::Node

Inherits:
Object
  • Object
show all
Defined in:
lib/btree/node.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(degree) ⇒ Node

Returns a new instance of Node.



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# File 'lib/btree/node.rb', line 3

def initialize(degree)
  @degree = degree
  @keys = []
  @children = []
  @leaf = true
end

Instance Attribute Details

#leaf ⇒ Object

Returns the value of attribute leaf.



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# File 'lib/btree/node.rb', line 2

def leaf
  @leaf
end

Instance Method Details

#add_child(node) ⇒ Object 



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# File 'lib/btree/node.rb', line 23

def add_child(node)
  @children << node
end

#children ⇒ Object 



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# File 'lib/btree/node.rb', line 27

def children
  @children.dup.freeze
end

#dump(level = 0) ⇒ Object 



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# File 'lib/btree/node.rb', line 10

def dump(level = 0)
  @keys.each_with_index do |key, idx|
    if @children[idx]
       @children[idx].dump(level + 1)
    end
    puts "#{level}: #{key.first}: full? #{full?} leaf? #{leaf?}"
  end
  (@children[@keys.size..-1] || []).each do |c|
    c.dump(level+1)
  end
  nil
end

#full? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/btree/node.rb', line 39

def full?
  size >= 2 * @degree - 1
end

#insert(key, value) ⇒ Object 



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# File 'lib/btree/node.rb', line 66

def insert(key, value)
  i = size - 1
  #puts "INSERTING #{key} INTO NODE: #{self.inspect}"
  if leaf?
    raise "Duplicate key" if @keys.any?{|(k,v)| k == key }  #OPTIMIZE: This is inefficient
    while i >= 0 && @keys[i] && key < @keys[i].first
      @keys[i+1] = @keys[i]
      i -= 1
    end
    @keys[i+1] = [key, value]
  else
    while i >= 0 && @keys[i] &&  key < @keys[i].first
      i -= 1
    end
    #puts "   -- INSERT KEY INDEX #{i}"
    if @children[i+1] && @children[i+1].full?
      split(i+1)
      if key > @keys[i+1].first
        i += 1
      end
    end
    @children[i+1].insert(key, value)
  end
end

#keys ⇒ Object 



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# File 'lib/btree/node.rb', line 31

def keys
  @keys.map(&:first).freeze
end

#leaf? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/btree/node.rb', line 43

def leaf?
  @leaf
end

#size ⇒ Object 



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# File 'lib/btree/node.rb', line 47

def size
  @keys.size
end

#split(child_idx) ⇒ Object 



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# File 'lib/btree/node.rb', line 91

def split(child_idx)
  raise "Invalid child index #{child_idx} in split, num_children = #{@children.size}" if child_idx < 0 || child_idx >= @children.size
  #puts "SPLIT1: #{self.inspect}"
  splitee = @children[child_idx]
  y = Btree::Node.new(@degree)
  z = Btree::Node.new(@degree)
  z.leaf = splitee.leaf
  (@degree-1).times do |j|
    z._keys[j] = splitee._keys[j+@degree]
    y._keys[j] = splitee._keys[j]
  end
  if !splitee.leaf?
    @degree.times do |j|
      z._children[j] = splitee._children[j+@degree]
      y._children[j] = splitee._children[j]
    end
  end
  mid_val = splitee._keys[@degree-1]
  #puts "SPLIT2: #{self.inspect}"
  (@keys.size).downto(child_idx) do |j|
    @children[j+1] = @children[j]
  end

  @children[child_idx+1] = z
  @children[child_idx] = y
  
  #puts "SPLIT3: #{self.inspect}"

  (@keys.size - 1).downto(child_idx) do |j|
    @keys[j+1] = @keys[j]
  end

  #puts "SPLIT4: #{self.inspect}"

  @keys[child_idx] = mid_val
  #puts "SPLIT5: #{self.inspect}"
end

#value_of(key) ⇒ Object 



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# File 'lib/btree/node.rb', line 51

def value_of(key)
  i = 1
  while i <= size && key > @keys[i-1].first
    i += 1
  end

  if i <= size && key == @keys[i-1].first
    return @keys[i-1].last
  elsif leaf?
    return nil
  else
    return @children[i-1].value_of(key)
  end
end

#values ⇒ Object 



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# File 'lib/btree/node.rb', line 35

def values
  @keys.map(&:last).freeze
end