// Copyright 2013 Bill Campbell, Swami Iyer and Bahar Akbal-Delibas
import jminusminus.CLEmitter;
import static jminusminus.CLConstants.*;
import java.util.ArrayList;
/**
* This class programatically generates the class file for the
* following Java application using CLEmitter:
*
* This application computes the factorial of a number recursively.
*
* public class Factorial
* {
* public int compute( int n )
* {
* if ( n <= 1 ) {
* return n;
* }
* else {
* return ( n * compute( n - 1 ) );
* }
* }
*
* public static void main( String[] args )
* {
* try {
* Factorial f = new Factorial();
* int n = Int.parseInt( args[ 0 ] );
* System.out.println( "Factorial( " + n + " ) = " +
* f.compute( n ) );
* }
* catch ( NumberFormatException nfe ) {
* System.err.println( "Invalid number " + args[ 0 ] );
* }
* }
* }
*/
public class GenFactorial {
public static void main(String[] args) {
CLEmitter e = new CLEmitter(true);
ArrayList<String> accessFlags = new ArrayList<String>();
// Add Factorial class
accessFlags.add("public");
e.addClass(accessFlags, "Factorial", "java/lang/Object", null, true);
// Add the implicit no-arg constructor Factorial() to
// Factorial
accessFlags.clear();
accessFlags.add("public");
e.addMethod(accessFlags, "<init>", "()V", null, true);
e.addNoArgInstruction(ALOAD_0);
e.addMemberAccessInstruction(INVOKESPECIAL, "java/lang/Object",
"<init>", "()V");
e.addNoArgInstruction(RETURN);
// Add compute() method to Factorial
accessFlags.clear();
accessFlags.add("public");
e.addMethod(accessFlags, "compute", "(I)I", null, true);
e.addNoArgInstruction(ILOAD_1);
e.addNoArgInstruction(ICONST_1);
e.addBranchInstruction(IF_ICMPGT, "falseLabel");
e.addNoArgInstruction(ILOAD_1);
e.addNoArgInstruction(IRETURN);
e.addLabel("falseLabel");
e.addNoArgInstruction(ILOAD_1);
e.addNoArgInstruction(ALOAD_0);
e.addNoArgInstruction(ILOAD_1);
e.addNoArgInstruction(ICONST_1);
e.addNoArgInstruction(ISUB);
e.addMemberAccessInstruction(INVOKEVIRTUAL, "Factorial", "compute",
"(I)I");
e.addNoArgInstruction(IMUL);
e.addNoArgInstruction(IRETURN);
// Add main() method to Factorial
accessFlags.clear();
accessFlags.add("public");
accessFlags.add("static");
e.addMethod(accessFlags, "main", "([Ljava/lang/String;)V", null, true);
e.addExceptionHandler("tryStart", "tryEnd", "catch",
"java/lang/NumberFormatException");
e.addLabel("tryStart");
e.addReferenceInstruction(NEW, "Factorial");
e.addNoArgInstruction(DUP);
e.addMemberAccessInstruction(INVOKESPECIAL, "Factorial", "<init>",
"()V");
e.addNoArgInstruction(ASTORE_1);
e.addNoArgInstruction(ALOAD_0);
e.addNoArgInstruction(ICONST_0);
e.addNoArgInstruction(AALOAD);
e.addMemberAccessInstruction(INVOKESTATIC, "java/lang/Integer",
"parseInt", "(Ljava/lang/String;)I");
e.addNoArgInstruction(ISTORE_2);
e.addMemberAccessInstruction(GETSTATIC, "java/lang/System", "out",
"Ljava/io/PrintStream;");
e.addReferenceInstruction(NEW, "java/lang/StringBuffer");
e.addNoArgInstruction(DUP);
e.addMemberAccessInstruction(INVOKESPECIAL, "java/lang/StringBuffer",
"<init>", "()V");
e.addLDCInstruction("Factorial(");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
e.addNoArgInstruction(ILOAD_2);
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"append", "(I)Ljava/lang/StringBuffer;");
e.addLDCInstruction(") = ");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
e.addNoArgInstruction(ALOAD_1);
e.addNoArgInstruction(ILOAD_2);
e.addMemberAccessInstruction(INVOKEVIRTUAL, "Factorial", "compute",
"(I)I");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"append", "(I)Ljava/lang/StringBuffer;");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"toString", "()Ljava/lang/String;");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/io/PrintStream",
"println", "(Ljava/lang/String;)V");
e.addLabel("tryEnd");
e.addBranchInstruction(GOTO, "done");
e.addLabel("catch");
e.addNoArgInstruction(ASTORE_1);
e.addMemberAccessInstruction(GETSTATIC, "java/lang/System", "err",
"Ljava/io/PrintStream;");
e.addReferenceInstruction(NEW, "java/lang/StringBuffer");
e.addNoArgInstruction(DUP);
e.addMemberAccessInstruction(INVOKESPECIAL, "java/lang/StringBuffer",
"<init>", "()V");
e.addLDCInstruction("Invalid number ");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
e.addNoArgInstruction(ALOAD_0);
e.addNoArgInstruction(ICONST_0);
e.addNoArgInstruction(AALOAD);
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"append", "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/lang/StringBuffer",
"toString", "()Ljava/lang/String;");
e.addMemberAccessInstruction(INVOKEVIRTUAL, "java/io/PrintStream",
"println", "(Ljava/lang/String;)V");
e.addLabel("done");
e.addNoArgInstruction(RETURN);
// Write Factorial.class to file system
e.write();
}
}