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theuserbl

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Date of registration: Dec 20th 2008

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Friday, February 15th 2013, 12:28am

Class-File generation from a Jabaco-program

Only a test by myself for fun.

Jabaco Source

 
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Public Sub main(ByJava args() As String)
  System.out.println("This is a little Jabaco-program")
  System.out.println("Counting to 10:")
  Dim i As Integer
  For i = 1 to 10
    System.out.println("Number " & i)
  Next i
  System.out.println("End")

End Sub


You can create such a program inside an Jabaco-program:

Jabaco Source

 
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Import com#sun#xml#internal#ws#org#objectweb#asm#ClassWriter
Import com#sun#xml#internal#ws#org#objectweb#asm#FieldVisitor
Import com#sun#xml#internal#ws#org#objectweb#asm#MethodVisitor
Import com#sun#xml#internal#ws#org#objectweb#asm#AnnotationVisitor
Import com#sun#xml#internal#ws#org#objectweb#asm#Label

Implements com#sun#xml#internal#ws#org#objectweb#asm#Opcodes

Public Sub main(ByJava args() As String)
   Dim myArgs() As String
   myArgs = args
   ' [Your Source]

   Dim fos As New java#io#FileOutputStream(New java#io#File(HomeDir() & System.getProperty("file.separator") & "Program.class"))
   fos.write(dump())
  
   
End Sub

Public Function dump() AS Byte()
  Dim cw As New ClassWriter(0)
  Dim fv As FieldVisitor
  Dim mv As MethodVisitor
  Dim av0 As AnnotationVisitor

  Dim z() As String

  cw.visit(V1_6, ACC_PUBLIC + ACC_SUPER, "Program", Nothing, "java/lang/Object", z)
  
  mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", Nothing, z)
  mv.visitCode()
  mv.visitVarInsn(ALOAD, 0)
  mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V")
  mv.visitInsn(RETURN)
  mv.visitMaxs(1, 1)
  mv.visitEnd()
 
  mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "main", "([Ljava/lang/String;)V", Nothing, z)
  mv.visitCode()
  mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;")
  mv.visitLdcInsn("This is a little Jabaco-program")
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V")
  mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;")
  mv.visitLdcInsn("Counting to 10:")
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V")
  mv.visitInsn(ICONST_1)
  mv.visitVarInsn(ISTORE, 1)
  Dim l0 As New com#sun#xml#internal#ws#org#objectweb#asm#Label
  mv.visitLabel(l0)
  Dim o1(0) As Object
  o1(0) = Opcodes.INTEGER
  Dim o2() AS Object
  mv.visitFrame(Opcodes.F_APPEND,1, o1, 0, o2)
  mv.visitVarInsn(ILOAD, 1)
  mv.visitIntInsn(BIPUSH, 10)
  Dim l1 As New com#sun#xml#internal#ws#org#objectweb#asm#Label
  mv.visitJumpInsn(IF_ICMPGT, l1)
  mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;")
  mv.visitTypeInsn(Opcodes.NEW, "java/lang/StringBuilder")
  mv.visitInsn(DUP)
  mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V")
  mv.visitLdcInsn("Number ")
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;")
  mv.visitVarInsn(ILOAD, 1)
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;")
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;")
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V")
  mv.visitIincInsn(1, 1)
  mv.visitJumpInsn(Opcodes.GOTO, l0)
  mv.visitLabel(l1)
  mv.visitFrame(Opcodes.F_CHOP,1, o2, 0, o2)
  mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;")
  mv.visitLdcInsn("End")
  mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V")
  mv.visitInsn(RETURN)
  mv.visitMaxs(3, 2)
  mv.visitEnd()

  cw.visitEnd()

  dump = cw.toByteArray()

End Function


If you start the second program, it creates in your home-directory a file called "Program.class". And if you start this program, it do the same like if you would start the first program.

Only a test by myself, if it is possible to create something like this in Jabaco.

Greatings
theuserbl

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