Class: Minjs::Compressor

Inherits:
Object
  • Object
show all
Includes:
Exp, Func, Literal, Program, Statement
Defined in:
lib/minjs/compressor.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Program

#source_element, #source_elements

Methods included from Func

#formal_parameter_list, #func_body, #func_declaration, #func_exp

Methods included from Exp

#additive_exp, #arguments, #array_literal, #assignment_exp, #bitwise_and_exp, #bitwise_or_exp, #bitwise_xor_exp, #call_exp, #cond_exp, #equality_exp, #exp, #identifier, #left_hand_side_exp, #logical_and_exp, #logical_or_exp, #member_exp, #multiplicative_exp, #new_exp, #object_literal, #postfix_exp, #primary_exp, #property_name, #property_name_and_value_list, #property_set_parameter_list, #relational_exp, #shift_exp, #unary_exp

Methods included from Statement

#block, #break_statement, #case_block, #continue_statement, #debugger_statement, #do_while_statement, #empty_statement, #exp_statement, #for_statement, #if_statement, #initialiser, #iteration_statement, #labelled_statement, #return_statement, #semicolon, #statement, #statement_list, #switch_statement, #throw_statement, #try_catch, #try_finally, #try_statement, #var_decl, #var_decl_list, #var_statement, #while_statement, #with_statement

Methods included from Literal

#boolean_literal, #literal, #null_literal

Constructor Details

#initialize(options = {}) ⇒ Compressor

Returns a new instance of Compressor.



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# File 'lib/minjs/compressor.rb', line 23

def initialize(options = {})
  @logger = options[:logger]
  if !@logger
    @logger = Logger.new(STDERR)
    @logger.level = (options[:debug_level] || Logger::WARN)
    @logger.formatter = proc{|severity, datetime, progname, message|
      "#{message}\n"
    }
  end
end

Instance Attribute Details

#prog ⇒ Object (readonly)

Returns the value of attribute prog.



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# File 'lib/minjs/compressor.rb', line 21

def prog
  @prog
end

Instance Method Details

#assignment_after_var(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 766

def assignment_after_var(node = @prog)
  def rewrite_var(var_st, name, initializer)
    var_st.normalization
    i = 0
    var_st.vars.each do |_name, _initializer|
      if _name == name and _initializer.nil?
        var_st.vars[i] = [name, initializer]
        var_st.normalization
        return true
      end
      i += 1
    end
    false
  end

  retry_flag = true
  while retry_flag
    retry_flag = false
    node.traverse(nil) {|st, parent|
      if st.kind_of? ECMA262::StVar and parent.kind_of? ECMA262::SourceElements
        catch(:break){
          idx = parent.index(st) + 1
          while true
            st2 = parent[idx]
            if st2.kind_of? ECMA262::StEmpty or (st2.kind_of? ECMA262::StFunc and st2.decl?)
              idx +=1
              next
            elsif st2.kind_of? ECMA262::StExp and st2.exp.kind_of? ECMA262::ExpAssign
              if rewrite_var(st, st2.exp.val, st2.exp.val2)
                parent.replace(st2, ECMA262::StEmpty.new())
                retry_flag = true
              else
                throw :break
              end
              idx += 1
              next
            elsif st2.kind_of? ECMA262::StFor and st2.exp1.kind_of? ECMA262::ExpAssign
              if rewrite_var(st, st2.exp1.val, st2.exp1.val2)
                st2.replace(st2.exp1, nil)
                retry_flag = true
              else
                throw :break
              end
              throw  :break
            elsif st2.kind_of? ECMA262::StExp and st2.exp.kind_of? ECMA262::ExpComma
              exp_parent = st2
              exp = st2.exp

              while exp.val.kind_of? ECMA262::ExpComma
                exp_parent = exp
                exp = exp.val
              end

              if exp.val.kind_of? ECMA262::ExpAssign
                if rewrite_var(st, exp.val.val, exp.val.val2)
                  exp_parent.replace(exp, exp.val2)
                  retry_flag = true
                else
                  throw :break
                end
              else
                throw :break
              end
            else
              throw :break
            end
          end
        }
      end
    }
  end
  self
end

#block_to_statement(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 298

def block_to_statement(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StBlock and !parent.kind_of?(ECMA262::StTry) and !parent.kind_of?(ECMA262::StIf)
        if st.to_statement?
          parent.replace(st, st.to_statement)
        end
    end
  }
  if_block_to_statement
end

#c2i(c) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 108

def c2i(c)
  c = c.ord
  if c >= 0x30 and c <= 0x39
    c = c - 0x30
  elsif c >= 0x61 and c <= 0x7a
    c = c - 0x61 + 10
  elsif c >= 0x41 and c <= 0x5a
    c = c - 0x41 + 10 + 26
  elsif c == 0x5f
    c = 62
  elsif c == 0x24
    c = 63
  end
end

#compress(data, options = {}) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 52

def compress(data, options = {})
  @logger.info '* parse'
  parse(data)

  if options[:only_parse]
    return
  end

  algo = [
    :reorder_function_decl,
    :simple_replacement,
    :reorder_var,
    :assignment_after_var,
    :grouping_statement,
    :reduce_if,
    :block_to_statement,
    :if_to_cond,
    :optimize_if_return,
    :compress_var,
    :reduce_exp,
    :grouping_statement,
    :block_to_statement,
    :if_to_cond,
    :optimize_if_return2,
    :remove_paren,
  ]
  algo.each do |a|
    if (options.empty? || options[:all] || options[a]) && !options[("no_" + a.to_s).to_sym]
      @logger.info "* #{a}"
      __send__(a, @prog)
    end
  end

  @heading_comments.reverse.each do |c|
    @prog.source_elements.source_elements.unshift(c)
  end
  self
end

#compress_var(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 472

def compress_var(node = @prog)
  #compress_var_sub(@prog, :longer => true)
  compress_var_sub
end

#compress_var_sub(node = @prog, options = {}) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 477

def compress_var_sub(node = @prog, options = {})
  #
  #traverse all statemtns and expression
  #
  scopes = []
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StFunc
      _context = st.context
      _parent = parent
      _st = st
      scopes.push([st, parent, _parent, _context, _st])
    end
  }
  scopes.reverse!
  scopes.each {|st, parent, _parent, _context, _st|
    var_sym = :a
    if _parent and _context and _st
      #
      # collect and counting all variables under this function/catch
      # collect and counting all var-variables under this function/catch
      #
      all_vars = {}
      var_vars = {}
      var_vars_list = []
      outer_vars = {}
      nesting_vars = {}
      nesting_vars_list = []

      _st.traverse(_parent) {|st2|
        #
        # In this function,
        #
        # 1. outer_vars:
        #    Variables which locate out of this function(or global variable)
        #    Them name cannot be renamed
        # 2. nesting_vars:
        #    Variables which locate in the function of this function.
        #    Them name cannot be renamed
        # 3. var_vars:
        #    Variables which have same scope in this function.
        #    Them name can be renamed under the following conditions
        #
        #   a. If the new name is not used, the name can be renamed to it.
        #   b. If the new name belongs to var_vars, the name cannot be renamed.
        #   c. If the new name belongs to outer_vars the name cannot be renamed.
        #   d. If the new name belongs to nesting_vars, the name can be rename
        #      to it after rename nesting_vars's name to another name.
        #
        if st2.kind_of? ECMA262::IdentifierName
          var_name = st2.val.to_sym
          st2_env = st2.binding_env
          all_vars[var_name] ||= 0
          all_vars[var_name] += 1
          if st2_env == nil #global
            outer_vars[var_name] ||= 0
            outer_vars[var_name] += 1
          elsif st2_env == @global_context.var_env #global
            outer_vars[var_name] ||= 0
            outer_vars[var_name] += 1
          elsif st2_env == st.context.var_env
            var_vars[var_name] ||= 0
            var_vars[var_name] += 1
            var_vars_list.push(st2)
          else
            e = st2.binding_env
            while e
              e = e.outer
              if e == st.context.var_env
                nesting_vars[var_name] ||= 0
                nesting_vars[var_name] += 1
                nesting_vars_list.push(st2)
                break
              end
              if e.nil?
                outer_vars[var_name] ||= 0
                outer_vars[var_name] += 1
                break
              end
            end
          end
        end
      }
      unless var_vars[:eval]
        eval_flag = false
        _st.traverse(_parent) {|st2|
          if st2.kind_of? ECMA262::ExpCall and st2.name.to_js({}) == "eval"
            eval_flag = true
            break
          end
        }
        if eval_flag
          next
        end
      end
      #
      # sort var_vars
      #
      var_vars_array = var_vars.sort {|(k1,v1), (k2,v2)| v2 <=> v1}
      #
      # create renaming table
      #
      rename_table = {}
      var_vars_array.each {|name, count|
        if name.nil?
          next #bug?
        end
        while outer_vars[var_sym] or var_vars[var_sym]
          var_sym = next_sym(var_sym)
        end
        #rename nesting_vars
        if nesting_vars[var_sym]
          nesting_vars_list.each do |x|
            raise 'error' if x.binding_env(:var).nil?
            raise 'error' if x.binding_env(:lex).nil?
          end

          var_sym2 = "abc#{var_sym.to_s}".to_sym
          while all_vars[var_sym2]
            var_sym2 = next_sym(var_sym2)
          end
          rl = {}
          nesting_vars_list.each do |x|
            if x.val.to_sym == var_sym
              _var_env = x.binding_env(:var)
              _lex_env = x.binding_env(:lex)
              rl[_var_env] = true
              rl[_lex_env] = true
            end
          end
          rl.keys.each do |_env|
            if _env && _env.record.binding[var_sym]
              _env.record.binding[var_sym2] = _env.record.binding[var_sym]
              _env.record.binding.delete var_sym
            end
          end

          nesting_vars_list.each do |x|
            if x.val.to_sym == var_sym
              x.instance_eval{
                @val = var_sym2
              }
            end
            raise 'error' if x.binding_env(:var).nil?
            raise 'error' if x.binding_env(:lex).nil?
          end
        end
        rename_table[name] = var_sym
        var_sym = next_sym(var_sym)
      }
      var_vars_list.each {|st2|
        raise 'error' if st2.binding_env(:var).nil?
        raise 'error' if st2.binding_env(:lex).nil?
      }

      rename_table.each do |name, new_name|
        if name != new_name
          if st.context.var_env.record.binding[name]
            st.context.var_env.record.binding[new_name] = st.context.var_env.record.binding[name]
            st.context.var_env.record.binding.delete(name)
          end
          if st.context.lex_env.record.binding[name]
            st.context.lex_env.record.binding[new_name] = st.context.lex_env.record.binding[name]
            st.context.lex_env.record.binding.delete(name)
          end
        end
      end

      var_vars_list.each {|st2|
        st2.instance_eval{
          @val = rename_table[@val]
        }
        raise 'error' if st2.binding_env(:var).nil?
        raise 'error' if st2.binding_env(:lex).nil?
      }
    end
  }
  self
end

#debug ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 34

def debug
  puts @prog.to_js()
end

#grouping_statement(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 163

def grouping_statement(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StatementList
      st.grouping
    end
  }
  remove_paren
  self
end

#i2c(c) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 122

def i2c(c)
  if c < 10
    c = "%c" % (0x30 + c)
  elsif c < 10 + 26
    c = "%c" % (0x61 + c - 10)
  elsif c < 10 + 26 + 26
    c = "%c" % (0x41 + c - 10 -  26)
  elsif c < 63
    c = "_"
  elsif c < 64
    c = "$"
  end
end

#if_block_to_statement(node = @prog) ⇒ Object

To determine removing “if block” is available or not is difficult. For example, next codes block must not be removed, because “else” cluase combined to second “if” statement.

if(a){ //<= this block must not be removed
  while(true)
    if(b){
      ;
    }
}
else{
 ;
}



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# File 'lib/minjs/compressor.rb', line 324

def if_block_to_statement(node = @prog)
  # The "else" cluase's block can be removed always
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StIf
      if st.else_st and st.else_st.kind_of? ECMA262::StBlock
        st.else_st.remove_empty_statement
      end

      if st.else_st and st.else_st.kind_of? ECMA262::StBlock and st.else_st.to_statement?
        st.replace(st.else_st, st.else_st.to_statement)
      end
    end
  }
  node.traverse(nil) {|st0, parent|
    st = st0.deep_dup
    if st.kind_of? ECMA262::StIf
      if st.then_st and st.then_st.kind_of? ECMA262::StBlock
        st.then_st.remove_empty_statement
      end

      if st.then_st and st.then_st.kind_of? ECMA262::StBlock and st.then_st.to_statement?
        st.replace(st.then_st, st.then_st.to_statement)
      end

      _lex = Minjs::Lex.new(st.to_js)
      _context = ECMA262::Context.new
      _if = if_statement(_lex, _context)
      if _if == st #
        parent.replace(st0, st)
      end
    end
  }
  self
end

#if_to_cond(node = @prog) ⇒ Object

if(a)b;else c;

>

a?b:c

if(a)b

>

a&&b;



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# File 'lib/minjs/compressor.rb', line 368

def if_to_cond(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StIf
      if st.to_exp?
        t = ECMA262::StExp.new(st.to_exp({}))
        remove_paren(t)
        if t.to_js.length <= st.to_js.length
          parent.replace(st, t)
        end
      end
    end
  }
  if_to_return(node)
  self
end

#if_to_return(node = @prog) ⇒ Object

if(a)return b;else return c;

> return a?b:c;



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# File 'lib/minjs/compressor.rb', line 387

def if_to_return(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StIf
      if st.to_return?
        t = st.to_return
        remove_paren(t)
        if t.to_js.length <= st.to_js.length
          parent.replace(st, t)
        end
      end
    end
  }
  self
end

#next_sym(s) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 107

def next_sym(s)
  def c2i(c)
    c = c.ord
    if c >= 0x30 and c <= 0x39
      c = c - 0x30
    elsif c >= 0x61 and c <= 0x7a
      c = c - 0x61 + 10
    elsif c >= 0x41 and c <= 0x5a
      c = c - 0x41 + 10 + 26
    elsif c == 0x5f
      c = 62
    elsif c == 0x24
      c = 63
    end
  end
  def i2c(c)
    if c < 10
      c = "%c" % (0x30 + c)
    elsif c < 10 + 26
      c = "%c" % (0x61 + c - 10)
    elsif c < 10 + 26 + 26
      c = "%c" % (0x41 + c - 10 -  26)
    elsif c < 63
      c = "_"
    elsif c < 64
      c = "$"
    end
  end

  v = 0
  s.to_s.split("").each do |x|
    v *= 64
    v += c2i(x)
  end

  while true
    v += 1
    ret = []
    vv = v
    while vv > 0
      ret.unshift(i2c(vv % 64))
      vv /= 64
    end
    ret = ret.join("")
    if ECMA262::IdentifierName.reserved?(ret.to_sym)
      ;
    elsif ret.to_s.match(/^\d/)
      ;
    else
      break
    end
  end
  ret.to_sym

end

#optimize_if_return(node = @prog) ⇒ Object

if(a)return b; return c;

> if(a)return b;else return c;

> return a?b:c;



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# File 'lib/minjs/compressor.rb', line 409

def optimize_if_return(node = @prog)
  retry_flag = true
  while retry_flag
    retry_flag = false
    node.traverse(nil) {|st0, parent0|
      if st0.kind_of? ECMA262::StIf and parent0.kind_of? ECMA262::StatementList
        i = parent0.index(st0)
        break if i.nil?
        parent = parent0.deep_dup
        st = parent[i]
        #
        if parent[i+1].nil? and !parent.kind_of?(ECMA262::SourceElements)
          next
        end
        if parent[i+1].nil? or parent[i+1].to_return?
          s = st
          while s.kind_of? ECMA262::StIf and s.else_st and s.then_st.to_return?
            s = s.else_st
          end
          if s and s.kind_of? ECMA262::StIf and s.then_st.to_return?
            if parent[i+1]
              s.replace(s.else_st, parent[i+1])
              parent.replace(parent[i+1], ECMA262::StEmpty.new)
            else
              s.replace(s.else_st, ECMA262::StReturn.new(ECMA262::ExpVoid.new(ECMA262::ECMA262Numeric.new(0))))
            end
            if_to_cond(parent)
            if parent.to_js(:no_debug => true).length <= parent0.to_js(:no_debug => true).length
              parent0.replace(st0, st)
              if parent[i+1]
                parent0.replace(parent0[i+1], ECMA262::StEmpty.new)
              end
              retry_flag = true
              node = parent0
            end
          end
        end
      end
    }
  end
  self
end

#optimize_if_return2(node = @prog) ⇒ Object

if(a)return b;else c;

>

if(a)return b;c;



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# File 'lib/minjs/compressor.rb', line 457

def optimize_if_return2(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StIf and st.else_st and parent.kind_of? ECMA262::StatementList
      st.remove_empty_statement
      if (st.then_st.kind_of? ECMA262::StBlock and st.then_st[-1].kind_of? ECMA262::StReturn) or
         st.then_st.kind_of? ECMA262::StReturn
        idx = parent.index(st)
        parent[idx+1..0] = st.else_st
        st.replace(st.else_st, nil)
      end
    end
  }
  self
end

#parse(data) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 91

def parse(data)
  @lex = Minjs::Lex.new(data, :logger => @logger)
  @global_context = ECMA262::Context.new
  @heading_comments = []
  @lex.eval_lit{
    while a = @lex.ws_lit
      @heading_comments.push(a)
    end
    nil
  }
  @prog = source_elements(@lex, @global_context)

  remove_empty_statement
  self
end

#reduce_exp(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 656

def reduce_exp(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::Exp
      st.reduce(parent)
    end
  }
  self
end

#reduce_if(node = @prog) ⇒ Object

reduce_if



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# File 'lib/minjs/compressor.rb', line 715

def reduce_if(node = @prog)
  retry_flag = true
  while(retry_flag)
    retry_flag = false
    node.traverse(nil) {|st, parent|
      if st.kind_of? ECMA262::StIf
        # if(a)
        #   if(b) ...;
        # if(a && b) ...;
        #
        if st.else_st.nil? and
          st.then_st.kind_of? ECMA262::StIf and st.then_st.else_st.nil?
          st.replace(st.cond, ECMA262::ExpLogicalAnd.new(st.cond, st.then_st.cond))
          st.replace(st.then_st, st.then_st.then_st)
        end
        #if(a);
        # => a
        #if(a){}
        # => a
        if st.then_st.empty? and st.else_st.nil?
          parent.replace(st, ECMA262::StExp.new(st.cond))
          retry_flag = true
        end
        #if(a)z;else;
        #if(a)z;else{}
        # => {if(a)z;}
        if st.else_st and st.else_st.empty?
          st.replace(st.else_st, nil)
          parent.replace(st, ECMA262::StBlock.new([st]))
          retry_flag = true
        end

        #if(a);else z;
        #=>if(!a)z;
        #if(a){}else z;
        #=>if(!a)z;
        if st.then_st.empty? and st.else_st
          st.replace(st.cond, ECMA262::ExpLogicalNot.new(st.cond));
          else_st = st.else_st
          st.replace(st.else_st, nil)
          st.replace(st.then_st, else_st)
          parent.replace(st, ECMA262::StBlock.new([st]))
          retry_flag = true
        end
      end
    }
    block_to_statement if retry_flag
  end
  self
end

#remove_block_in_block(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 280

def remove_block_in_block(node = @prog)
  while true
    _retry = false
    node.traverse(nil) {|st, parent|
      if parent.kind_of? ECMA262::StatementList and st.kind_of? ECMA262::StBlock
        idx = parent.index(st)
        parent.statement_list[idx..idx] = st.statement_list.statement_list
        _retry = true
        break
      elsif st.kind_of? ECMA262::StBlock
        ;
      end
    }
    break if !_retry
  end
  self
end

#remove_empty_statement(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 43

def remove_empty_statement(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StatementList
      st.remove_empty_statement
    end
  }
  self
end

#remove_paren(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 270

def remove_paren(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.respond_to? :remove_paren
      st.remove_paren
      st.add_paren
    end
  }
  self
end

#reorder_function_decl(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 173

def reorder_function_decl(node = @prog)
  flist = []
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::StFunc and parent.kind_of? ECMA262::StatementList and st.decl?
      if parent.index(st)
        flist.push([st, parent])
      end
    end
  }
  flist.reverse.each do |st, parent|
    parent.remove(st)
    parent.statement_list.unshift(st)
  end
  self
end

#reorder_var(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 189

def reorder_var(node = @prog)
  node.traverse(nil) {|st, parent|
    if st.kind_of? ECMA262::Prog
      vars = nil
      context = st.context
      #
      # collect all of var variable in this function
      #
      var_vars = {}
      context.var_env.record.binding.each do|k, v|
        if v and v[:_parameter_list].nil? and !v[:value].kind_of?(ECMA262::StFunc)
          var_vars[k] = true
        end
      end
      #
      # traverse block and convert var statement to assignment expression
      # if variable has initializer
      #
      st.traverse(parent){|st2, parent2|
        if st2.kind_of? ECMA262::StVar and st2.context.var_env == context.var_env
          exp = nil
          st2.vars.each do |name, initializer|
            if initializer
              if exp.nil?
                exp = ECMA262::ExpAssign.new(name, initializer)
              else
                exp = ECMA262::ExpComma.new(exp, ECMA262::ExpAssign.new(name, initializer))
              end
            end
          end
          if exp
            parent2.replace(st2, ECMA262::StExp.new(exp))
          else
            parent2.replace(st2, ECMA262::StEmpty.new())
          end
        elsif st2.kind_of? ECMA262::StForVar and st2.context.var_env == context.var_env
          parent2.replace(st2, st2.to_st_for)
        elsif st2.kind_of? ECMA262::StForInVar and st2.context.var_env == context.var_env
          parent2.replace(st2, st2.to_st_for_in)
        end
      }
      if var_vars.length > 0
        elems = st.source_elements.source_elements
        v = ECMA262::StVar.new(
          context,
          var_vars.collect do |k, v|
            [ECMA262::IdentifierName.new(context, k)]
          end
        )

        idx = 0
        elems.each do |e|
          next if e.kind_of? ECMA262::StFunc and e.decl?
          found = false
          if e.kind_of? ECMA262::StFunc and e.decl?
            ;
          else
            e.traverse(nil){|ee, pp|
              if ee.kind_of? ECMA262::IdentifierName and var_vars[ee.val.to_sym]
                found = true
                break
              end
            }
          end
          break if found
          idx += 1
        end

        if idx == 0
          elems.unshift(v)
        else
          elems[idx..0] = v
        end
        st.source_elements.remove_empty_statement
      end
    end
    self
  }
  self
end

#rewrite_var(var_st, name, initializer) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 767

def rewrite_var(var_st, name, initializer)
  var_st.normalization
  i = 0
  var_st.vars.each do |_name, _initializer|
    if _name == name and _initializer.nil?
      var_st.vars[i] = [name, initializer]
      var_st.normalization
      return true
    end
    i += 1
  end
  false
end

#simple_replacement(node = @prog) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 665

def simple_replacement(node = @prog)
  retry_flag = false
  node.traverse(nil) {|st, parent|
    #
    #true => !0
    #false => !1
    #
    if st.kind_of? ECMA262::Boolean
      if st.true?
        parent.replace(st, ECMA262::ExpParen.new(ECMA262::ExpLogicalNot.new(ECMA262::ECMA262Numeric.new(0))))
      else
        parent.replace(st, ECMA262::ExpParen.new(ECMA262::ExpLogicalNot.new(ECMA262::ECMA262Numeric.new(1))))
      end
    #
    #if(true){<then>}else{<else>} => then
    #
    elsif st.kind_of? ECMA262::StIf
      if st.cond.respond_to? :to_ecma262_boolean
        if st.cond.to_ecma262_boolean
          parent.replace(st, st.then_st)
        elsif st.else_st
          parent.replace(st, st.else_st)
        else
          parent.replace(st, ECMA262::StEmpty.new())
        end
      end
    #
    # while(true) => for(;;)
    # while(false) => remove
    #
    elsif st.kind_of? ECMA262::StWhile and st.exp.respond_to? :to_ecma262_boolean
      if st.exp.to_ecma262_boolean
        parent.replace(st, ECMA262::StFor.new(nil,nil,nil, st.statement))
      else
        parent.replace(st, ECMA262::StEmpty.new)
      end
    #
    # new A() => (new A)
    #
    elsif st.kind_of? ECMA262::ExpNew and st.args and st.args.length == 0
      st.replace(st.args, nil)
      parent.add_paren.remove_paren
    end
  }
  self
end

#to_js(options = {}) ⇒ Object 



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# File 'lib/minjs/compressor.rb', line 38

def to_js(options = {})
  remove_empty_statement
  @prog.to_js(options).sub(/;;\Z/, ";")
end