Class: Sqreen::Trie

Inherits:
Struct
  • Object
show all
Defined in:
lib/sqreen/trie.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ Trie

Returns a new instance of Trie.



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# File 'lib/sqreen/trie.rb', line 15

def initialize(*args)
  super
  self.family ||= Socket::AF_INET
  self.num_active_nodes = 0
  @max_num_bits = family == Socket::AF_INET ? 32 : 128
end

Instance Attribute Details

#family ⇒ Object

Returns the value of attribute family

Returns:

  • (Object) —

    the current value of family



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# File 'lib/sqreen/trie.rb', line 12

def family
  @family
end

#head ⇒ Object

Returns the value of attribute head

Returns:

  • (Object) —

    the current value of head



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# File 'lib/sqreen/trie.rb', line 12

def head
  @head
end

#max_num_bits ⇒ Object (readonly)

Returns the value of attribute max_num_bits.



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# File 'lib/sqreen/trie.rb', line 13

def max_num_bits
  @max_num_bits
end

#num_active_nodes ⇒ Object

Returns the value of attribute num_active_nodes

Returns:

  • (Object) —

    the current value of num_active_nodes



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# File 'lib/sqreen/trie.rb', line 12

def num_active_nodes
  @num_active_nodes
end

Instance Method Details

#insert(arg_prefix) ⇒ Object 



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# File 'lib/sqreen/trie.rb', line 22

def insert(arg_prefix)
  raise 'family mismatch' if arg_prefix.family != family

  if head.nil?
    node = Node.new(
        arg_prefix.bitlen, # bit
        arg_prefix,
        nil, nil, nil, #l , r, parent
    )
    self.head = node
    self.num_active_nodes += 1
    return node
  end

  arg_addr = arg_prefix.address
  arg_bitlen = arg_prefix.bitlen
  xcur = self.head

  # descend until we find the end of the tree or go past the
  # bitlen of the prefix we're adding
  while xcur.bit < arg_bitlen || xcur.empty?
    if bit_set?(arg_addr, xcur.bit)
      break if xcur.r.nil?
      xcur = xcur.r
    else
      break if xcur.l.nil?
      xcur = xcur.l
    end
  end

  trie_addr = xcur.prefix.address

  # find first bit that differs between addr and trie_addr
  cmp_bit_end = [arg_bitlen, xcur.bit].min # after last to be compared

  differ_bit = (0...cmp_bit_end).find do |i|
    bit_set?(arg_addr, i) ^ bit_set?(trie_addr, i)
  end
  differ_bit = cmp_bit_end if differ_bit.nil?

  # go up till we find the parent before the bits differ
  xparent = xcur.parent
  while !xparent.nil? && xparent.bit >= differ_bit
    xcur = xparent
    xparent = xcur.parent
  end

  # case 1: replace current node's prefix
  if differ_bit == arg_bitlen && xcur.bit == arg_bitlen
    xcur.prefix = arg_prefix
    return xcur
  end

  xnew = Node.new(arg_prefix.bitlen, arg_prefix, nil, nil, nil)
  self.num_active_nodes += 1

  # case 2: append below found node
  if xcur.bit == differ_bit
    xnew.parent = xcur
    if bit_set?(arg_addr, xcur.bit)
      xcur.r = xnew
    else
      xcur.l = xnew
    end

    return xnew
  end

  # case 3: take place of found node
  if arg_bitlen == differ_bit
    if bit_set?(trie_addr, arg_bitlen)
      xnew.r = xcur
    else
      xnew.l = xcur
    end

    xnew.parent = xcur.parent

    if xcur.parent.nil?
      self.head = xnew
    elsif xcur.parent.r.equal?(xcur)
      xcur.parent.r = xnew
    else
      xcur.parent.l = xnew
    end

    xcur.parent = xnew

    return xnew
  end

  # case 4: need to add intermediate node to be parent of the
  #         both xnew and xcur

  # last arg is the parent of the new node
  xglue = Node.new(differ_bit, nil, nil, nil, xcur.parent)
  self.num_active_nodes += 1

  if bit_set?(arg_addr, differ_bit)
    xglue.r = xnew
    xglue.l = xcur
  else
    xglue.r = xcur
    xglue.l = xnew
  end

  xnew.parent = xglue

  if xcur.parent.nil?
    self.head = xglue
  elsif xcur.equal?(xcur.parent.r)
    xcur.parent.r = xglue
  else
    xcur.parent.l = xglue
  end

  xcur.parent = xglue

  xnew
end

#search_best(addr, family) ⇒ Object 



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# File 'lib/sqreen/trie.rb', line 172

def search_best(addr, family)
  nodes = search_common(addr, family)
  for i in (nodes.size - 1).downto(0)
    xcur = nodes[i]
    return node_to_ip_addr(xcur) if xcur.prefix.matches?(addr, family)
  end

  nil
end

#search_matching(addr, family) ⇒ Object 



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# File 'lib/sqreen/trie.rb', line 182

def search_matching(addr, family)
  nodes = search_common(addr, family)
  nodes.select { |xcur| xcur.prefix.matches?(addr, family) }
       .map { |xcur| node_to_ip_addr(xcur) }
       .reverse
end

#to_dot(header = true) ⇒ Object

generate pdf with ‘dot -Tpdf <input> > foo.pdf`



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# File 'lib/sqreen/trie.rb', line 144

def to_dot(header = true)
  res = ''
  res = "graph trie {\n" if header

  next_name = 'a'
  obj_label_map = Hash.new do |h, k|
    h[k] = next_name
    next_name = next_name.next
    h[k]
  end

  head.walk(max_num_bits, true) do |node|
    node_name = obj_label_map[node.object_id]

    if node.empty?
      label = "<glue at bit #{node.bit}>"
    else
      ip_addr = IPAddr.new(node.prefix.address, node.prefix.family)
      label = ip_addr.to_s + '/' + node.prefix.bitlen.to_s
    end
    res += "#{node_name} [label=\"#{label}\"]\n"
    res += "#{node_name} -- #{obj_label_map[node.l.object_id]} [label=\"l\"]\n" if node.l
    res += "#{node_name} -- #{obj_label_map[node.r.object_id]} [label=\"r\"]\n" if node.r
  end
  res += "}\n" if header
  res
end