Use a stack based XPath evaluator.
This evaluator is capable of processing very, very basic XPath expressions. It does not yet know anything about axes, functions, operators, etc.
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@ -4,92 +4,75 @@ module Oga
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# The Evaluator class is used to evaluate an XPath expression in the
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# The Evaluator class is used to evaluate an XPath expression in the
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# context of a given document.
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# context of a given document.
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#
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#
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class Evaluator < AST::Processor
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class Evaluator
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##
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##
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# @param [Oga::XML::Document|Oga::XML::Node] document
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# @param [Oga::XML::Document|Oga::XML::Node] document
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#
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#
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def initialize(document)
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def initialize(document)
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@document = document
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@document = document
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reset
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end
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end
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def process(node, cursor)
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def reset
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return if node.nil?
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@context = @document.children
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@stack = XML::NodeSet.new
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node = node.to_ast
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on_handler = :"on_#{node.type}"
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if respond_to?(on_handler)
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new_node = send(on_handler, node, cursor)
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else
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new_node = handler_missing(node)
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end
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node = new_node if new_node
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return node
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end
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def process_all(nodes, cursor)
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return nodes.to_a.map do |node|
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process(node, cursor)
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end
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end
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end
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def evaluate(string)
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def evaluate(string)
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ast = Parser.new(string).parse
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ast = Parser.new(string).parse
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cursor = move_cursor(@document)
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return process(ast, cursor)
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process(ast)
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end
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def on_absolute(node, cursor)
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nodes = @stack
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if @document.is_a?(XML::Node)
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cursor = move_cursor(@document.root_node)
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else
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cursor = move_cursor(@document)
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end
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return process_all(node.children, cursor)
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reset
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end
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def on_path(node, cursor)
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test, children = *node
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nodes = process(test, cursor)
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unless nodes.empty?
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nodes = process_all(children, nodes)
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end
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return nodes
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return nodes
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end
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end
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def on_test(node, cursor)
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def process(node)
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ns, name = *node
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handler = "on_#{node.type}"
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nodes = XML::NodeSet.new
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cursor.each do |xml_node|
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if respond_to?(handler)
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send(handler, node)
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end
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end
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def on_path(node)
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test, children = *node
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process(test)
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if children and !@stack.empty?
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swap_context
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process(children)
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end
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end
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def on_test(node)
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ns, name = *node
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@context.each do |xml_node|
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next unless xml_node.is_a?(XML::Element)
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next unless xml_node.is_a?(XML::Element)
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if xml_node.name == name and xml_node.namespace == ns
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if xml_node.name == name and xml_node.namespace == ns
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nodes << xml_node
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@stack << xml_node
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end
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end
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end
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end
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end
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return nodes
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def swap_context
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@context = XML::NodeSet.new
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@stack.each do |xml_node|
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xml_node.children.each do |child|
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@context << child
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end
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end
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end
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def move_cursor(location)
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@stack = XML::NodeSet.new
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if location.is_a?(XML::Document)
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return location.children
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elsif location.is_a?(XML::Node)
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return XML::NodeSet.new([location])
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else
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return location
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end
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end
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end
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end # Evaluator
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end # Evaluator
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end # XPath
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end # XPath
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