Query String Parser In Ruby

Here is a RubyLanguage version of the QueryStringParserTranslations. (See also CommentingChallengeResponsePartTwo).

There are some minor interface changes in the Ruby version. The public methods are parse_stream(input_stream) and parse_string(string) with the obvious semantics. Since we don't require the use of a stream, we can toss out the initialization. It also means the parser object can be reused to parse multiple strings or streams.

This code was written from scratch, rather than trying to translate either the Java or Python versions. I did use the unit tests from CommentingChallengeResponse. With the exception of one of the degenerate cases, this parser passes all the unit tests found there. The one exception is that I chose to parse "name%=value" as {'name' => 'value'} rather than {'namealue' => ''} in the testDegenerate_MissingHexDigitsBeforeValue test.

-- JimWeirich

---

Here is the code.

  class QueryStringParser
    def parse_stream(input)
      lines = input.readlines.collect { |line| line.chomp } 
      parse_string(lines.join('&'))
    end

    def parse_string(string)
      hash = Hash.new
      string.split('&').each { |pair|
key, value = pair.split('=', 2)
hash[normalize(key)] = normalize(value)
      }
      hash
    end

    private

    def normalize(str)
      return "" if str.nil?
      str = replace_pluses_with_spaces(str)
      return replace_hex_encodings(str)
    end

    def replace_pluses_with_spaces(str)
      str.gsub(/\+/, ' ')
    end

    def replace_hex_encodings(str)
      str.gsub(/%(.{0,2})/) { |hex|
digits = $1
if digits =~ /[0-9A-Fa-f]{2}/
  digits.hex.chr
else
  ''
end
      }
    end
  end

---

Jim,

What do the ||| characters mean? e.g. |hex| |line| |pair|

-- SteveHowell

Ruby syntax for parameters to a block.

{ |a, b| self.doSomethingWith(a, b) }

would be not-quite-equivalent-but-pretty-close to Python's

lambda a, b: self.doSomethingWith(a, b)

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CategoryRuby