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Class: REXML::XPathParser

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, XMLTokens
Inherits: Object
Defined in: lib/rexml/xpath_parser.rb

Overview

You don't want to use this class. Really. Use XPath, which is a wrapper for this class. Believe me. You don't want to poke around in here. There is strange, dark magic at work in this code. Beware. Go back! Go back while you still can!

Constant Summary

XMLTokens - Included

NAME, NAMECHAR, NAME_CHAR, NAME_START_CHAR, NAME_STR, NCNAME_STR, NMTOKEN, NMTOKENS, REFERENCE

Class Method Summary

Instance Method Summary

Constructor Details

.new ⇒ XPathParser

[ GitHub ] 

  


# File 'lib/rexml/xpath_parser.rb', line 50



def initialize( )
  @parser = REXML::Parsers::XPathParser.new
  @namespaces = nil
  @variables = {}
end


  







Instance Method Details



  

    #[]=(variable_name, value)  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 81



def []=( variable_name, value )
  @variables[ variable_name ] = value
end


  








  

    #compare(a, op, b)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 681



def compare a, op, b
  case op
  when :eq
    a == b
  when :neq
    a != b
  when :lt
    a < b
  when :lteq
    a <= b
  when :gt
    a > b
  when :gteq
    a >= b
  when :and
    a and b
  when :or
    a or b
  else
    false
  end
end


  








  

    #d_o_s(p, ns, r)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 477



def d_o_s( p, ns, r )
  nt = nil
  ns.each_index do |i|
    n = ns[i]
    x = expr( p.dclone, [ n ] )
    nt = n.node_type
    d_o_s( p, n.children, x ) if nt == :element or nt == :document and n.children.size > 0
    r.concat(x) if x.size > 0
  end
end


  








  

    #descendant_or_self(path_stack, nodeset)   (private)
  



  

    

FIXME The next two methods are BAD MOJO! This is my achilles heel.  If anybody thinks of a better way of doing this, be my guest.  This really sucks, but it is a wonder it works at all. ########################################################


  



  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 470



def descendant_or_self( path_stack, nodeset )
  rs = []
  d_o_s( path_stack, nodeset, rs )
  document_order(rs.flatten.compact)
  #rs.flatten.compact
end


  








  

    #document_order(array_of_nodes)   (private)
  



  

    

Reorders an array of nodes so that they are in document order It tries to do this efficiently.



FIXME: I need to get rid of this, but the issue is that most of the XPath interpreter functions as a filter, which means that we lose context going in and out of function calls.  If I knew what the index of the nodes was, I wouldn't have to do this.  Maybe add a document IDX for each node? Problems with mutable documents.  Or, rewrite everything.


  



  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 497



def document_order( array_of_nodes )
  new_arry = []
  array_of_nodes.each { |node|
    node_idx = []
    np = node.node_type == :attribute ? node.element : node
    while np.parent and np.parent.node_type == :element
      node_idx << np.parent.index( np )
      np = np.parent
    end
    new_arry << [ node_idx.reverse, node ]
  }
  new_arry.sort{ |s1, s2| s1[0] <=> s2[0] }.collect{ |s| s[1] }
end


  








  

    #equality_relational_compare(set1, op, set2)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 603



def equality_relational_compare( set1, op, set2 )
  if set1.kind_of? Array and set2.kind_of? Array
    if set1.size == 1 and set2.size == 1
      set1 = set1[0]
      set2 = set2[0]
    elsif set1.size == 0 or set2.size == 0
      nd = set1.size==0 ? set2 : set1
      rv = nd.collect { |il| compare( il, op, nil ) }
      return rv
    else
      res = []
      SyncEnumerator.new( set1, set2 ).each { |i1, i2|
        i1 = norm( i1 )
        i2 = norm( i2 )
        res << compare( i1, op, i2 )
      }
      return res
    end
  end
  # If one is nodeset and other is number, compare number to each item
  # in nodeset s.t. number op number(string(item))
  # If one is nodeset and other is string, compare string to each item
  # in nodeset s.t. string op string(item)
  # If one is nodeset and other is boolean, compare boolean to each item
  # in nodeset s.t. boolean op boolean(item)
  if set1.kind_of? Array or set2.kind_of? Array
    if set1.kind_of? Array
      a = set1
      b = set2
    else
      a = set2
      b = set1
    end

    case b
    when true, false
      return a.collect {|v| compare( Functions::boolean(v), op, b ) }
    when Numeric
      return a.collect {|v| compare( Functions::number(v), op, b )}
    when /^\d(\.\d)?$/
      b = Functions::number( b )
      return a.collect {|v| compare( Functions::number(v), op, b )}
    else
      b = Functions::string( b )
      return a.collect { |v| compare( Functions::string(v), op, b ) }
    end
  else
    # If neither is nodeset,
    #   If op is = or !=
    #     If either boolean, convert to boolean
    #     If either number, convert to number
    #     Else, convert to string
    #   Else
    #     Convert both to numbers and compare
    s1 = set1.to_s
    s2 = set2.to_s
    if s1 == 'true' or s1 == 'false' or s2 == 'true' or s2 == 'false'
      set1 = Functions::boolean( set1 )
      set2 = Functions::boolean( set2 )
    else
      if op == :eq or op == :neq
        if s1 =~ /^\d(\.\d)?$/ or s2 =~ /^\d(\.\d)?$/
          set1 = Functions::number( s1 )
          set2 = Functions::number( s2 )
        else
          set1 = Functions::string( set1 )
          set2 = Functions::string( set2 )
        end
      else
        set1 = Functions::number( set1 )
        set2 = Functions::number( set2 )
      end
    end
    return compare( set1, op, set2 )
  end
  return false
end


  








  

    #expr(path_stack, nodeset, context = nil)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 153



def expr( path_stack, nodeset, context=nil )
  node_types = ELEMENTS
  return nodeset if path_stack.length == 0 || nodeset.length == 0
  while path_stack.length > 0
    if nodeset.length == 0
      path_stack.clear
      return []
    end
    case (op = path_stack.shift)
    when :document
      nodeset = [ nodeset[0].root_node ]

    when :qname
      prefix = path_stack.shift
      name = path_stack.shift
      nodeset.delete_if do |node|
        # FIXME: This DOUBLES the time XPath searches take
        ns = get_namespace( node, prefix )
        if node.node_type == :element
          if node.name == name
          end
        end
        !(node.node_type == :element and
          node.name == name and
          node.namespace == ns )
      end
      node_types = ELEMENTS

    when :any
      nodeset.delete_if { |node| !node_types.include?(node.node_type) }

    when :self
      # This space left intentionally blank

    when :processing_instruction
      target = path_stack.shift
      nodeset.delete_if do |node|
        (node.node_type != :processing_instruction) or
        ( target!='' and ( node.target != target ) )
      end

    when :text
      nodeset.delete_if { |node| node.node_type != :text }

    when :comment
      nodeset.delete_if { |node| node.node_type != :comment }

    when :node
      # This space left intentionally blank
      node_types = ALL

    when :child
      new_nodeset = []
      nt = nil
      nodeset.each do |node|
        nt = node.node_type
        new_nodeset += node.children if nt == :element or nt == :document
      end
      nodeset = new_nodeset
      node_types = ELEMENTS

    when :literal
      return path_stack.shift

    when :attribute
      new_nodeset = []
      case path_stack.shift
      when :qname
        prefix = path_stack.shift
        name = path_stack.shift
        for element in nodeset
          if element.node_type == :element
            attrib = element.attribute( name, get_namespace(element, prefix) )
            new_nodeset << attrib if attrib
          end
        end
      when :any
        for element in nodeset
          if element.node_type == :element
            new_nodeset += element.attributes.to_a
          end
        end
      end
      nodeset = new_nodeset

    when :parent
      nodeset = nodeset.collect{|n| n.parent}.compact
      #nodeset = expr(path_stack.dclone, nodeset.collect{|n| n.parent}.compact)
      node_types = ELEMENTS

    when :ancestor
      new_nodeset = []
      nodeset.each do |node|
        while node.parent
          node = node.parent
          new_nodeset << node unless new_nodeset.include? node
        end
      end
      nodeset = new_nodeset
      node_types = ELEMENTS

    when :ancestor_or_self
      new_nodeset = []
      nodeset.each do |node|
        if node.node_type == :element
          new_nodeset << node
          while ( node.parent )
            node = node.parent
            new_nodeset << node unless new_nodeset.include? node
          end
        end
      end
      nodeset = new_nodeset
      node_types = ELEMENTS

    when :predicate
      new_nodeset = []
      subcontext = { :size => nodeset.size }
      pred = path_stack.shift
      nodeset.each_with_index { |node, index|
        subcontext[ :node ] = node
        subcontext[ :index ] = index+1
        pc = pred.dclone
        result = expr( pc, [node], subcontext )
        result = result[0] if result.kind_of? Array and result.length == 1
        if result.kind_of? Numeric
          new_nodeset << node if result == (index+1)
        elsif result.instance_of? Array
          if result.size > 0 and result.inject(false) {|k,s| s or k}
            new_nodeset << node if result.size > 0
          end
        else
          new_nodeset << node if result
        end
      }
      nodeset = new_nodeset
=begin
      predicate = path_stack.shift
      ns = nodeset.clone
      result = expr( predicate, ns )
      if result.kind_of? Array
        nodeset = result.zip(ns).collect{|m,n| n if m}.compact
      else
        nodeset = result ? nodeset : []
      end
=end

    when :descendant_or_self
      rv = descendant_or_self( path_stack, nodeset )
      path_stack.clear
      nodeset = rv
      node_types = ELEMENTS

    when :descendant
      results = []
      nt = nil
      nodeset.each do |node|
        nt = node.node_type
        results += expr( path_stack.dclone.unshift( :descendant_or_self ),
          node.children ) if nt == :element or nt == :document
      end
      nodeset = results
      node_types = ELEMENTS

    when :following_sibling
      results = []
      nodeset.each do |node|
        next if node.parent.nil?
        all_siblings = node.parent.children
        current_index = all_siblings.index( node )
        following_siblings = all_siblings[ current_index+1 .. -1 ]
        results += expr( path_stack.dclone, following_siblings )
      end
      nodeset = results

    when :preceding_sibling
      results = []
      nodeset.each do |node|
        next if node.parent.nil?
        all_siblings = node.parent.children
        current_index = all_siblings.index( node )
        preceding_siblings = all_siblings[ 0, current_index ].reverse
        results += preceding_siblings
      end
      nodeset = results
      node_types = ELEMENTS

    when :preceding
      new_nodeset = []
      nodeset.each do |node|
        new_nodeset += preceding( node )
      end
      nodeset = new_nodeset
      node_types = ELEMENTS

    when :following
      new_nodeset = []
      nodeset.each do |node|
        new_nodeset += following( node )
      end
      nodeset = new_nodeset
      node_types = ELEMENTS

    when :namespace
      new_nodeset = []
      prefix = path_stack.shift
      nodeset.each do |node|
        if (node.node_type == :element or node.node_type == :attribute)
          if @namespaces
            namespaces = @namespaces
          elsif (node.node_type == :element)
            namespaces = node.namespaces
          else
            namespaces = node.element.namesapces
          end
          if (node.namespace == namespaces[prefix])
            new_nodeset << node
          end
        end
      end
      nodeset = new_nodeset

    when :variable
      var_name = path_stack.shift
      return @variables[ var_name ]

    # :and, :or, :eq, :neq, :lt, :lteq, :gt, :gteq
    # TODO: Special case for :or and :and -- not evaluate the right
    # operand if the left alone determines result (i.e. is true for
    # :or and false for :and).
    when :eq, :neq, :lt, :lteq, :gt, :gteq, :or
      left = expr( path_stack.shift, nodeset.dup, context )
      right = expr( path_stack.shift, nodeset.dup, context )
      res = equality_relational_compare( left, op, right )
      return res

    when :and
      left = expr( path_stack.shift, nodeset.dup, context )
      return [] unless left
      if left.respond_to?(:inject) and !left.inject(false) {|a,b| a | b}
        return []
      end
      right = expr( path_stack.shift, nodeset.dup, context )
      res = equality_relational_compare( left, op, right )
      return res

    when :div
      left = Functions::number(expr(path_stack.shift, nodeset, context)).to_f
      right = Functions::number(expr(path_stack.shift, nodeset, context)).to_f
      return (left / right)

    when :mod
      left = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      right = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      return (left % right)

    when :mult
      left = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      right = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      return (left * right)

    when :plus
      left = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      right = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      return (left + right)

    when :minus
      left = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      right = Functions::number(expr(path_stack.shift, nodeset, context )).to_f
      return (left - right)

    when :union
      left = expr( path_stack.shift, nodeset, context )
      right = expr( path_stack.shift, nodeset, context )
      return (left | right)

    when :neg
      res = expr( path_stack, nodeset, context )
      return -(res.to_f)

    when :not
    when :function
      func_name = path_stack.shift.tr('-','_')
      arguments = path_stack.shift
      subcontext = context ? nil : { :size => nodeset.size }

      res = []
      cont = context
      nodeset.each_with_index { |n, i|
        if subcontext
          subcontext[:node]  = n
          subcontext[:index] = i
          cont = subcontext
        end
        arg_clone = arguments.dclone
        args = arg_clone.collect { |arg|
          expr( arg, [n], cont )
        }
        Functions.context = cont
        res << Functions.send( func_name, *args )
      }
      return res

    end
  end # while
  return nodeset
end


  








  

    #first(path_stack, node)  
  



  

    

Performs a depth-first (document order) XPath search, and returns the first match.  This is the fastest, lightest way to return a single result.



FIXME: This method is incomplete!


  



  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 90



def first( path_stack, node )
  return nil if path.size == 0

  case path[0]
  when :document
    # do nothing
    return first( path[1..-1], node )
  when :child
    for c in node.children
      r = first( path[1..-1], c )
      return r if r
    end
  when :qname
    name = path[2]
    if node.name == name
      return node if path.size == 3
      return first( path[3..-1], node )
    else
      return nil
    end
  when :descendant_or_self
    r = first( path[1..-1], node )
    return r if r
    for c in node.children
      r = first( path, c )
      return r if r
    end
  when :node
    return first( path[1..-1], node )
  when :any
    return first( path[1..-1], node )
  end
  return nil
end


  








  

    #following(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 561



def following( node )
  acc = []
  p = next_sibling_node( node )
  while p
    acc << p
    p = following_node_of( p )
  end
  acc
end


  








  

    #following_node_of(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 571



def following_node_of( node )
  if node.kind_of? Element and node.children.size > 0
    return node.children[0]
  end
  return next_sibling_node(node)
end


  








  

    #get_first(path, nodeset)  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 71



def get_first path, nodeset
  path_stack = @parser.parse( path )
  first( path_stack, nodeset )
end


  








  

    #get_namespace(node, prefix)   (private)
  



  

    

Returns a String namespace for a node, given a prefix The rules are:



1. Use the supplied namespace mapping first.
2. If no mapping was supplied, use the context node to look up the namespace


  



  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 139



def get_namespace( node, prefix )
  if @namespaces
    return @namespaces[prefix] || ''
  else
    return node.namespace( prefix ) if node.node_type == :element
    return ''
  end
end


  








  

    #match(path_stack, nodeset)  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 126



def match( path_stack, nodeset )
  r = expr( path_stack, nodeset )
  r
end


  








  

    #namespaces=(namespaces = {})  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 56



def namespaces=( namespaces={} )
  Functions::namespace_context = namespaces
  @namespaces = namespaces
end


  








  

    #next_sibling_node(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 578



def next_sibling_node(node)
  psn = node.next_sibling_node
  while psn.nil?
    if node.parent.nil? or node.parent.class == Document
      return nil
    end
    node = node.parent
    psn = node.next_sibling_node
  end
  return psn
end


  








  

    #norm(b)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 590



def norm b
  case b
  when true, false
    return b
  when 'true', 'false'
    return Functions::boolean( b )
  when /^\d(\.\d)?$/
    return Functions::number( b )
  else
    return Functions::string( b )
  end
end


  








  

    #parse(path, nodeset)  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 66



def parse path, nodeset
  path_stack = @parser.parse( path )
  match( path_stack, nodeset )
end


  








  

    #preceding(node)   (private)
  



  

    

Builds a nodeset of all of the preceding nodes of the supplied node, in reverse document order


preceding



includes every element in the document that precedes this node,





except for ancestors


  



  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 525



def preceding( node )
  ancestors = []
  p = node.parent
  while p
    ancestors << p
    p = p.parent
  end

  acc = []
  p = preceding_node_of( node )
  while p
    if ancestors.include? p
      ancestors.delete(p)
    else
      acc << p
    end
    p = preceding_node_of( p )
  end
  acc
end


  








  

    #preceding_node_of(node)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 546



def preceding_node_of( node )
  psn = node.previous_sibling_node
  if psn.nil?
    if node.parent.nil? or node.parent.class == Document
      return nil
    end
    return node.parent
    #psn = preceding_node_of( node.parent )
  end
  while psn and psn.kind_of? Element and psn.children.size > 0
    psn = psn.children[-1]
  end
  psn
end


  








  

    #predicate(path, nodeset)  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 76



def predicate path, nodeset
  path_stack = @parser.parse( path )
  expr( path_stack, nodeset )
end


  








  

    #recurse(nodeset, &block)   (private)
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 512



def recurse( nodeset, &block )
  for node in nodeset
    yield node
    recurse( node, &block ) if node.node_type == :element
  end
end


  








  

    #variables=(vars = {})  
  

  [ GitHub ]


  

  


# File 'lib/rexml/xpath_parser.rb', line 61



def variables=( vars={} )
  Functions::variables = vars
  @variables = vars
end