Class: Packr::Base62

Inherits:
Encoder show all
Defined in:
lib/packr/base62.rb

Constant Summary collapse

WORDS = 
/\b[\da-zA-Z]\b|\w{2,}/
ENCODE10 = 
"String"
ENCODE36 = 
"function(c){return c.toString(36)}"
ENCODE62 = 
"function(c){return(c<62?'':e(parseInt(c/62)))+((c=c%62)>35?String.fromCharCode(c+29):c.toString(36))}"
UNPACK = 
lambda do |p,a,c,k,e,r|
  "eval(function(p,a,c,k,e,r){e=#{e};if('0'.replace(0,e)==0){while(c--)r[e(c)]=k[c];" +
      "k=[function(e){return r[e]||e}];e=function(){return'#{r}'};c=1};while(c--)if(k[c])p=p." +
      "replace(new RegExp('\\\\b'+e(c)+'\\\\b','g'),k[c]);return p}('#{p}',#{a},#{c},'#{k}'.split('|'),0,{}))"
end

Instance Method Summary collapse

Methods inherited from Encoder

#initialize

Constructor Details

This class inherits a constructor from Packr::Encoder

Instance Method Details

#encode(script) ⇒ Object 



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# File 'lib/packr/base62.rb', line 16

def encode(script)
  words = search(script)
  words.sort!

  encoded = Collection.new # a dictionary of base62 -> base10
  words.size.times { |i| encoded.put(Packr.encode62(i), i) }

  replacement = lambda { |word| words.get(word).replacement }

  index = 0
  words.each do |word, key|
    if encoded.has?(word)
      word.index = encoded.get(word)
      def word.to_s; ""; end
    else
      index += 1 while words.has?(Packr.encode62(index))
      word.index = index
      index += 1
      if word.count == 1
        def word.to_s; ""; end
      end
    end
    word.replacement = Packr.encode62(word.index)
    if word.replacement.length == word.to_s.length
      def word.to_s; ""; end
    end
  end

  # sort by encoding
  words.sort! { |word1, word2| word1.index - word2.index }

  # trim unencoded words
  words = words.slice(0, get_key_words(words).split("|").length)

  script = script.gsub(get_pattern(words), &replacement)

  # build the packed script

  p = escape(script)
  a = "[]"
  c = get_count(words)
  k = get_key_words(words)
  e = get_encoder(words)
  d = get_decoder(words)

  # the whole thing
  UNPACK.call(p,a,c,k,e,d)
end

#escape(script) ⇒ Object 



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# File 'lib/packr/base62.rb', line 71

def escape(script)
  # Single quotes wrap the final string so escape them.
  # Also, escape new lines (required by conditional comments).
  script.gsub(/([\\'])/) { |match| "\\#{$1}" }.gsub(/[\r\n]+/, "\\n")
end

#get_count(words) ⇒ Object 



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# File 'lib/packr/base62.rb', line 77

def get_count(words)
  size = words.size
  size.zero? ? 1 : size
end

#get_decoder(words) ⇒ Object 



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# File 'lib/packr/base62.rb', line 82

def get_decoder(words)
  # returns a pattern used for fast decoding of the packed script
  trim = RegexpGroup.new.
    put("(\\d)(\\|\\d)+\\|(\\d)", "\\1-\\3").
    put("([a-z])(\\|[a-z])+\\|([a-z])", "\\1-\\3").
    put("([A-Z])(\\|[A-Z])+\\|([A-Z])", "\\1-\\3").
    put("\\|", "")

  pattern = trim.exec(words.map { |word, key|
    word.to_s.empty? ? "" : word.replacement
  }[0...62].join("|"))

  return "^$" if pattern.empty?

  pattern = "[#{pattern}]"

  size = words.size
  if size > 62
    pattern = "(#{pattern}|"
    c = Packr.encode62(size)[0].chr
    if c > "9"
      pattern += "[\\\\d"
      if c >= "a"
        pattern += "a"
        if c >= "z"
          pattern += "-z"
          if c >= "A"
            pattern += "A"
            pattern += "-#{c}" if c > "A"
          end
        elsif c == "b"
          pattern += "-#{c}"
        end
      end
      pattern += "]"
    elsif c == "9"
      pattern += "\\\\d"
    elsif c == "2"
      pattern += "[12]"
    elsif c == "1"
      pattern += "1"
    else
      pattern += "[1-#{c}]"
    end

    pattern += "\\\\w)"
  end
  pattern
end

#get_encoder(words) ⇒ Object 



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# File 'lib/packr/base62.rb', line 132

def get_encoder(words)
  c = words.size
  self.class.const_get("ENCODE#{c > 10 ? (c > 36 ? 62 : 36) : 10}")
end

#get_key_words(words) ⇒ Object 



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# File 'lib/packr/base62.rb', line 137

def get_key_words(words)
  words.map { |word, key| word.to_s }.join("|").gsub(/\|+$/, "")
end

#get_pattern(words) ⇒ Object 



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# File 'lib/packr/base62.rb', line 141

def get_pattern(words)
  words = words.map { |word, key| word.to_s }.join("|").gsub(/\|{2,}/, "|").gsub(/^\|+|\|+$/, "")
  words = "\\x0" if words == ""
  string = "\\b(#{words})\\b"
  %r{#{string}}
end

#search(script) ⇒ Object 



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# File 'lib/packr/base62.rb', line 65

def search(script)
  words = Words.new
  script.scan(WORDS).each { |word| words.add(word) }
  words
end