whilenode.java

一个JAVA编写的简单编译器

package ast.statement;

public class WhileNode extends StatementNode {
  private ast.booleanExpr.JSubBooleanNode expr = null;
  private ast.IJSubNode statement;
  public String toString (String prefix) {
    return prefix + "while";
  }
  public WhileNode (ast.booleanExpr.JSubBooleanNode expr, ast.IJSubNode statement){
    this.expr = expr;
    this.statement = statement;
  }

  public void dump(String prefix) {
    System.out.println ("if");
    expr.dump (prefix + "  ");
    if (statement != null)
      statement.dump (prefix + "  ");
  }

  public void codegen () {
    int labelStart = codegen.WriteCode.getLabel ();
    int labelEnd = codegen.WriteCode.getLabel ();
      

    codegen.WriteCode.genLabel (labelStart);
    expr.codegen (labelEnd, false);
    if (statement != null) {
      statement.codegen ();
      codegen.WriteCode.genGoto (labelStart);
    }
    codegen.WriteCode.genLabel (labelEnd);
  }  
  public int getDepth () {
    int nExprDepth = expr == null? 0: expr.getDepth ();
    int nstatementDepth = statement == null? 0: statement.getDepth ();
    return java.lang.Math.max (nExprDepth, nstatementDepth);
  }

  public String getXMLType () {
    return "while";
  }
  public void genXML (java.io.PrintStream p, String prefix) {
    p.println (prefix + "<whilestatement>");
    expr.genXML (p, prefix + "  ");
    if (statement != null)
      statement.genXML (p, prefix + "  ");
    p.println (prefix + "</whilestatement>");
  }
}