63 lines
1.9 KiB
Ruby
63 lines
1.9 KiB
Ruby
class Propane
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class Grammar
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attr_reader :classname
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attr_reader :drop_tokens
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attr_reader :modulename
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attr_reader :rule_sets
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attr_reader :tokens
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def initialize(input)
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@tokens = []
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@drop_tokens = []
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@rule_sets = {}
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input = input.gsub("\r\n", "\n")
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parse_grammar(input)
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end
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private
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def parse_grammar(input)
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line_number = 1
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while !input.empty?
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if sliced = input.slice!(/\A\s+/)
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# Skip white space.
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elsif sliced = input.slice!(/\A#.*\n/)
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# Skip comment lines.
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elsif sliced = input.slice!(/\Amodule\s+(\S+)\n/)
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@modulename = $1
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elsif sliced = input.slice!(/\Aclass\s+(\S+)\n/)
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@classname = $1
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elsif sliced = input.slice!(/\Atoken\s+(\S+)(?:\s+(\S+))?\n/)
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name, pattern = $1, $2
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if pattern.nil?
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pattern = name
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end
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unless name =~ /^[a-zA-Z_][a-zA-Z_0-9]*$/
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raise Error.new("Invalid token name #{name}")
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end
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@tokens << Token.new(name, pattern, @tokens.size, line_number)
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elsif sliced = input.slice!(/\Adrop\s+(\S+)\n/)
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pattern = $1
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@drop_tokens << Token.new(nil, pattern, nil, line_number)
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elsif sliced = input.slice!(/\A(\S+)\s*:\s*\[(.*?)\] <<\n(.*?)^>>\n/m)
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rule_name, components, code = $1, $2, $3
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components = components.strip.split(/\s+/)
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@rule_sets[rule_name] ||= RuleSet.new(rule_name, @rule_sets.size)
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rule = Rule.new(rule_name, components, code, line_number)
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@rule_sets[rule_name].add_rule(rule)
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else
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if input.size > 25
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input = input.slice(0..20) + "..."
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end
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raise Error.new("Unexpected grammar input at line #{line_number}: #{input.chomp}")
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end
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line_number += sliced.count("\n")
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end
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end
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end
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end
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