emit.java

我开发的一个用java语言实现的编译器,内含词法分析器,语法分析器,而且可以实现中间代码生成.用到了SLR算法和LR(1)算法

      out.println();

      symbols_time = System.currentTimeMillis() - start_time;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Emit code for the non-public class holding the actual action code. 
   * @param out        stream to produce output on.
   * @param start_prod the start production of the grammar.
   */
  protected static void emit_action_code(PrintWriter out, production start_prod)
    throws internal_error
    {
      production prod;

      long start_time = System.currentTimeMillis();

      /* class header */
      out.println();
      out.println(
       "/** Cup generated class to encapsulate user supplied action code.*/"
      );  
      out.println("class " +  pre("actions") + " {");

      /* user supplied code */
      if (action_code != null)
	{
	  out.println();
          out.println(action_code);
	}

      /* field for parser object */
      out.println("  private final "+parser_class_name+" parser;");

      /* constructor */
      out.println();
      out.println("  /** Constructor */");
      out.println("  " + pre("actions") + "("+parser_class_name+" parser) {");
      out.println("    this.parser = parser;");
      out.println("  }");

      /* action method head */
      out.println();
      out.println("  /** Method with the actual generated action code. */");
      out.println("  public final java_cup.runtime.Symbol " + 
		     pre("do_action") + "(");
      out.println("    int                        " + pre("act_num,"));
      out.println("    java_cup.runtime.lr_parser " + pre("parser,"));
      out.println("    java.util.Stack            " + pre("stack,"));
      out.println("    int                        " + pre("top)"));
      out.println("    throws java.lang.Exception");
      out.println("    {");

      /* declaration of result symbol */
      /* New declaration!! now return Symbol
	 6/13/96 frankf */
      out.println("      /* Symbol object for return from actions */");
      out.println("      java_cup.runtime.Symbol " + pre("result") + ";");
      out.println();

      /* switch top */
      out.println("      /* select the action based on the action number */");
      out.println("      switch (" + pre("act_num") + ")");
      out.println("        {");

      /* emit action code for each production as a separate case */
      for (Enumeration p = production.all(); p.hasMoreElements(); )
	{
	  prod = (production)p.nextElement();

	  /* case label */
          out.println("          /*. . . . . . . . . . . . . . . . . . . .*/");
          out.println("          case " + prod.index() + ": // " + 
					  prod.to_simple_string());

	  /* give them their own block to work in */
	  out.println("            {");

	  /* create the result symbol */
	  /*make the variable RESULT which will point to the new Symbol (see below)
	    and be changed by action code
	    6/13/96 frankf */
	  out.println("              " +  prod.lhs().the_symbol().stack_type() +
		      " RESULT = null;");

	  /* Add code to propagate RESULT assignments that occur in
	   * action code embedded in a production (ie, non-rightmost
	   * action code). 24-Mar-1998 CSA
	   */
	  for (int i=0; i<prod.rhs_length(); i++) {
	    // only interested in non-terminal symbols.
	    if (!(prod.rhs(i) instanceof symbol_part)) continue;
	    symbol s = ((symbol_part)prod.rhs(i)).the_symbol();
	    if (!(s instanceof non_terminal)) continue;
	    // skip this non-terminal unless it corresponds to
	    // an embedded action production.
	    if (((non_terminal)s).is_embedded_action == false) continue;
	    // OK, it fits.  Make a conditional assignment to RESULT.
	    int index = prod.rhs_length() - i - 1; // last rhs is on top.
	    out.println("              " + "// propagate RESULT from " +
			s.name());
	    out.println("              " + "if ( " +
	      "((java_cup.runtime.Symbol) " + emit.pre("stack") + ".elementAt("
              + emit.pre("top") + "-" + index + ")).value != null )");
	    out.println("                " + "RESULT = " +
	      "(" + prod.lhs().the_symbol().stack_type() + ") " +
	      "((java_cup.runtime.Symbol) " + emit.pre("stack") + ".elementAt("
              + emit.pre("top") + "-" + index + ")).value;");
	  }

        /* if there is an action string, emit it */
          if (prod.action() != null && prod.action().code_string() != null &&
              !prod.action().equals(""))
            out.println(prod.action().code_string());

	  /* here we have the left and right values being propagated.  
		must make this a command line option.
	     frankf 6/18/96 */

         /* Create the code that assigns the left and right values of
            the new Symbol that the production is reducing to */
	  if (emit.lr_values()) {	    
	    int loffset;
	    String leftstring, rightstring;
	    int roffset = 0;
	    rightstring = "((java_cup.runtime.Symbol)" + emit.pre("stack") + ".elementAt(" + 
	      emit.pre("top") + "-" + roffset + ")).right";	  
	    if (prod.rhs_length() == 0) 
	      leftstring = rightstring;
	    else {
	      loffset = prod.rhs_length() - 1;
	      leftstring = "((java_cup.runtime.Symbol)" + emit.pre("stack") + ".elementAt(" + 
		emit.pre("top") + "-" + loffset + ")).left";	  
	    }
	    out.println("              " + pre("result") + " = new java_cup.runtime.Symbol(" + 
			prod.lhs().the_symbol().index() + "/*" +
			prod.lhs().the_symbol().name() + "*/" + 
			", " + leftstring + ", " + rightstring + ", RESULT);");
	  } else {
	    out.println("              " + pre("result") + " = new java_cup.runtime.Symbol(" + 
			prod.lhs().the_symbol().index() + "/*" +
			prod.lhs().the_symbol().name() + "*/" + 
			", RESULT);");
	  }
	  
	  /* end of their block */
	  out.println("            }");

	  /* if this was the start production, do action for accept */
	  if (prod == start_prod)
	    {
	      out.println("          /* ACCEPT */");
	      out.println("          " + pre("parser") + ".done_parsing();");
	    }

	  /* code to return lhs symbol */
	  out.println("          return " + pre("result") + ";");
	  out.println();
	}

      /* end of switch */
      out.println("          /* . . . . . .*/");
      out.println("          default:");
      out.println("            throw new Exception(");
      out.println("               \"Invalid action number found in " +
				  "internal parse table\");");
      out.println();
      out.println("        }");

      /* end of method */
      out.println("    }");

      /* end of class */
      out.println("}");
      out.println();

      action_code_time = System.currentTimeMillis() - start_time;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Emit the production table. 
   * @param out stream to produce output on.
   */
  protected static void emit_production_table(PrintWriter out)
    {
      production all_prods[];
      production prod;

      long start_time = System.currentTimeMillis();

      /* collect up the productions in order */
      all_prods = new production[production.number()];
      for (Enumeration p = production.all(); p.hasMoreElements(); )
	{
	  prod = (production)p.nextElement();
	  all_prods[prod.index()] = prod;
	}

      // make short[][]
      short[][] prod_table = new short[production.number()][2];
      for (int i = 0; i<production.number(); i++)
	{
	  prod = all_prods[i];
	  // { lhs symbol , rhs size }
	  prod_table[i][0] = (short) prod.lhs().the_symbol().index();
	  prod_table[i][1] = (short) prod.rhs_length();
	}
      /* do the top of the table */
      out.println();
      out.println("  /** Production table. */");
      out.println("  protected static final short _production_table[][] = ");
      out.print  ("    unpackFromStrings(");
      do_table_as_string(out, prod_table);
      out.println(");");

      /* do the public accessor method */
      out.println();
      out.println("  /** Access to production table. */");
      out.println("  public short[][] production_table() " + 
						 "{return _production_table;}");

      production_table_time = System.currentTimeMillis() - start_time;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Emit the action table. 
   * @param out             stream to produce output on.
   * @param act_tab         the internal representation of the action table.
   * @param compact_reduces do we use the most frequent reduce as default?
   */
  protected static void do_action_table(
    PrintWriter        out, 
    parse_action_table act_tab,
    boolean            compact_reduces)
    throws internal_error
    {
      parse_action_row row;
      parse_action     act;
      int              red;

      long start_time = System.currentTimeMillis();

      /* collect values for the action table */
      short[][] action_table = new short[act_tab.num_states()][];
      /* do each state (row) of the action table */
      for (int i = 0; i < act_tab.num_states(); i++)
	{
	  /* get the row */
	  row = act_tab.under_state[i];

	  /* determine the default for the row */
	  if (compact_reduces)
	    row.compute_default();
	  else
	    row.default_reduce = -1;

	  /* make temporary table for the row. */
	  short[] temp_table = new short[2*row.size()];
	  int nentries = 0;

	  /* do each column */
	  for (int j = 0; j < row.size(); j++)
	    {
	      /* extract the action from the table */
	      act = row.under_term[j];

	      /* skip error entries these are all defaulted out */
	      if (act.kind() != parse_action.ERROR)
		{
		  /* first put in the symbol index, then the actual entry */

		  /* shifts get positive entries of state number + 1 */
		  if (act.kind() == parse_action.SHIFT)
		    {
		      /* make entry */
		      temp_table[nentries++] = (short) j;
		      temp_table[nentries++] = (short)
			(((shift_action)act).shift_to().index() + 1);
		    }

		  /* reduce actions get negated entries of production# + 1 */
		  else if (act.kind() == parse_action.REDUCE)
		    {
		      /* if its the default entry let it get defaulted out */
		      red = ((reduce_action)act).reduce_with().index();
		      if (red != row.default_reduce) {
			/* make entry */
			temp_table[nentries++] = (short) j;
			temp_table[nentries++] = (short) (-(red+1));
		      }
		    } else if (act.kind() == parse_action.NONASSOC)
		      {
			/* do nothing, since we just want a syntax error */
		      }
		  /* shouldn't be anything else */
		  else
		    throw new internal_error("Unrecognized action code " +