Class: Packr::Shrinker

Inherits:
Object
  • Object
show all
Defined in:
lib/packr/shrinker.rb

Constant Summary collapse

ENCODED_DATA = 
/~\^(\d+)\^~/
PREFIX = 
'@'
SHRUNK = 
/\@\d+\b/

Instance Method Summary collapse

Instance Method Details

#decode_data(script) ⇒ Object 



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# File 'lib/packr/shrinker.rb', line 8

def decode_data(script)
  # put strings and regular expressions back
  script.gsub(ENCODED_DATA) { |match| @strings[$1.to_i] }
end

#encode_data(script) ⇒ Object 



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# File 'lib/packr/shrinker.rb', line 13

def encode_data(script)
  # encode strings and regular expressions
  @strings = [] # encoded strings and regular expressions
  DATA.exec(script, lambda { |match, *args|
    operator, regexp = args[0].to_s, args[1].to_s
    replacement = "~^#{@strings.length}^~"
    unless regexp.empty?
      replacement = operator + replacement
      match = regexp
    end
    @strings << match
    replacement
  })
end

#shrink(script, protected_names = []) ⇒ Object 



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# File 'lib/packr/shrinker.rb', line 28

def shrink(script, protected_names = [])
  script = encode_data(script)
  protected_names ||= []
  protected_names = protected_names.map { |s| s.to_s }
  
  # identify blocks, particularly identify function blocks (which define scope)
  __block         = /((catch|do|if|while|with|function)\b[^~{};]*(\(\s*[^{};]*\s*\))\s*)?(\{[^{}]*\})/
  __brackets      = /\{[^{}]*\}|\[[^\[\]]*\]|\([^\(\)]*\)|~[^~]+~/
  __encoded_block = /~#?(\d+)~/
  __identifier    = /[a-zA-Z_$][\w\$]*/
  __scoped        = /~#(\d+)~/
  __var           = /\bvar\b/
  __vars          = /\bvar\s+[\w$]+[^;#]*|\bfunction\s+[\w$]+/
  __var_tidy      = /\b(var|function)\b|\sin\s+[^;]+/
  __var_equal     = /\s*=[^,;]*/
  
  blocks = [] # store program blocks (anything between braces {})
  total = 0
  # decoder for program blocks
  decode_blocks = lambda do |script, encoded|
    script = script.gsub(encoded) { |match| blocks[$1.to_i] } while script =~ encoded
    script
  end
  
  # encoder for program blocks
  encode_blocks = lambda do |match|
    prefix, block_type, args, block = $1 || "", $2, $3, $4
    if block_type == 'function'
      # decode the function block (THIS IS THE IMPORTANT BIT)
      # We are retrieving all sub-blocks and will re-parse them in light
      # of newly shrunk variables
      block = args + decode_blocks.call(block, __scoped)
      prefix = prefix.gsub(__brackets, "")
      
      # create the list of variable and argument names
      args = args[1...-1]
      
      if args != '_no_shrink_'
        vars = block.scan(__vars).join(";").gsub(__var, ";var")
        vars = vars.gsub(__brackets, "") while vars =~ __brackets
        vars = vars.gsub(__var_tidy, "").gsub(__var_equal, "")
      end
      block = decode_blocks.call(block, __encoded_block)
      
      # process each identifier
      if args != '_no_shrink_'
        count, short_id = 0, nil
        ids = [args, vars].join(",").scan(__identifier)
        processed = {}
        ids.each do |id|
          if !processed['#' + id] and !protected_names.include?(id)
            processed['#' + id] = true
            id = id.gsub(/([\/()\[\]{}|*+-.,^$?\\])/) { |m| "\\#{$1}" }
            # encode variable names
            count += 1 while block =~ Regexp.new("#{PREFIX}#{count}\\b")
            reg = Regexp.new("([^\\w$.])#{id}([^\\w$:])")
            block = block.gsub(reg, "\\1#{PREFIX}#{count}\\2") while block =~ reg
            reg = Regexp.new("([^{,\\w$.])#{id}:")
            block = block.gsub(reg, "\\1#{PREFIX}#{count}:")
            count += 1
          end
        end
        total = [total, count].max
      end
      replacement = "#{prefix}~#{blocks.length}~"
      blocks << block
    else
      replacement = "~##{blocks.length}~"
      blocks << (prefix + block)
    end
    replacement
  end
  
  # encode blocks, as we encode we replace variable and argument names
  script = script.gsub(__block, &encode_blocks) while script =~ __block
  
  # put the blocks back
  script = decode_blocks.call(script, __encoded_block)
  
  short_id, count = nil, 0
  shrunk = Encoder.new(SHRUNK, lambda { |object|
    # find the next free short name
    begin
      short_id = Packr.encode52(count)
      count += 1
    end while script =~ Regexp.new("[^\\w$.]#{short_id}[^\\w$:]")
    short_id
  })
  script = shrunk.encode(script)
  
  decode_data(script)
end