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require 'psych/handler'
module Psych
###
# This class builds an in-memory parse tree tree that represents a YAML
# document.
#
# See Psych::Handler for documentation on the event methods used in this
# class.
class TreeBuilder < Psych::Handler
def initialize
@stack = []
@last = nil
end
def root
@stack.first
end
%w{
Sequence
Mapping
}.each do |node|
class_eval %{
def start_#{node.downcase}(anchor, tag, implicit, style)
n = Nodes::#{node}.new(anchor, tag, implicit, style)
@last.children << n
push n
end
def end_#{node.downcase}
pop
end
}
end
def start_document version, tag_directives, implicit
n = Nodes::Document.new(version, tag_directives, implicit)
@last.children << n
push n
end
def end_document implicit_end
@last.implicit_end = implicit_end
pop
end
def start_stream encoding
push Nodes::Stream.new(encoding)
end
def scalar value, anchor, tag, plain, quoted, style
@last.children << Nodes::Scalar.new(value,anchor,tag,plain,quoted,style)
end
def alias anchor
@last.children << Nodes::Alias.new(anchor)
end
private
def push value
@stack.push value
@last = value
end
def pop
@stack.pop
@last = @stack.last
end
end
end
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