ifnode.java

一个JAVA编写的简单编译器

package ast.statement;

public class IfNode extends ast.statement.StatementNode {
  private ast.booleanExpr.JSubBooleanNode expr = null;
  private ast.IJSubNode trueStatement;
  private ast.IJSubNode falseStatement;
  public String toString (String prefix) {
    return prefix + "if";
  }
  public IfNode (ast.booleanExpr.JSubBooleanNode expr, ast.IJSubNode s1, ast.IJSubNode s2) {
    this.expr = expr;
    trueStatement = s1;
    falseStatement = s2;
  }
  public void dump(String prefix) {
    System.out.println ("if");
    expr.dump (prefix + "  ");
    if (trueStatement != null)
      trueStatement.dump (prefix + "  ");
    if (falseStatement != null)
      falseStatement.dump (prefix + "  ");
  }

  public void codegen () {
    int label = codegen.WriteCode.getLabel ();
    int labelEqual = 0;
    if (falseStatement != null)
      labelEqual = codegen.WriteCode.getLabel ();
      
    expr.codegen (label, false);
    if (trueStatement != null)
      trueStatement.codegen ();
    if (falseStatement != null) {
      codegen.WriteCode.genGoto (labelEqual);
      codegen.WriteCode.genLabel (label);
      falseStatement.codegen ();
      codegen.WriteCode.genLabel (labelEqual);
    } else
      codegen.WriteCode.genLabel (label);
  }  

  public int getDepth () {
    int nExprDepth = expr == null? 0: expr.getDepth ();
    int ntrueStatementDepth = trueStatement == null? 0: trueStatement.getDepth ();
    int nfalseStatementDepth = falseStatement == null? 0: falseStatement.getDepth ();
    return java.lang.Math.max (nExprDepth, java.lang.Math.max(ntrueStatementDepth, nfalseStatementDepth));
  }

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