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80 lines
1.9 KiB
80 lines
1.9 KiB
require "strscan"
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Packet = Struct.new(:version, :type_id, :content) do
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include Enumerable
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def self.parse(ss)
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version = ss.scan(/.{3}/).to_i(2)
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type_id = ss.scan(/.{3}/).to_i(2)
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case type_id
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when 4 # literal value
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value = ss.scan(/(1.{4})*(0.{4})/).chars
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.each_slice(5).flat_map { _1[1..4] }.join
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.to_i(2)
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Literal.new(version, type_id, value)
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else # operator
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sub_packets = case
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when ss.scan(/0(.{15})/)
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length = ss.captures[0].to_i(2)
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sub_packet = ss.scan(/.{#{length}}/)
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sss = StringScanner.new(sub_packet)
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sub_packets = []
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until sss.eos?
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sub_packets << parse(sss)
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end
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sub_packets
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when ss.scan(/1(.{11})/)
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n = ss.captures[0].to_i(2)
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n.times.map { parse(ss) }
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else
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fail
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end
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Operator.new(version, type_id, sub_packets)
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end
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end
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def each
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return enum_for(__method__) unless block_given?
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yield self
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end
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end
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class Literal < Packet
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def value = content
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end
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class Operator < Packet
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def each(&block)
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super
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content.each do |sub_packet|
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sub_packet.each(&block)
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end
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end
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def value
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values = content.map(&:value)
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case type_id
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when 0 then values.sum
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when 1 then values.inject(:*)
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when 2 then values.min
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when 3 then values.max
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when 4 then fail
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when 5 then values.inject(:>) ? 1 : 0
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when 6 then values.inject(:<) ? 1 : 0
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when 7 then values.inject(:==) ? 1 : 0
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else fail
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end
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end
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end
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message = ARGF.read.chomp.chars.map { _1.to_i(16).to_s(2).rjust(4, ?0) }.join
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ss = StringScanner.new(message)
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packet = Packet.parse(ss)
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p packet.sum(&:version)
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p packet.value
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