bytecode

Basic tool for JVM bytecode generation written in Go

Features

Generate valid bytecode and Java classes
Define classes, methods and global fields
API for creating local variables
Optimized constant pool generation
Automatic locals calculation

TODO

Java 6+ support (missing StackMapTable implementation)
Automatic max stack calculation
Labels support

Example

package main

import (
   "github.com/mikigal/bytecode"
)

func main() {
   code := bytecode.CreateClass("Test", "java/lang/Object")
   code.AddInterface("java/io/Serializable")
   code.SourceFile("Test.java")

   // Add two global fields
   code.AddField(bytecode.Flag_Public | bytecode.Flag_Static | bytecode.Flag_Final, "firstNumber", "I", 5)
   code.AddField(bytecode.Flag_Public | bytecode.Flag_Static | bytecode.Flag_Final, "secondNumber", "I", 10)

   // Create main method
   main := code.AddMainMethod(2)
   localVar := main.AddLocalVar("test") // Define local String var
   main.AddFieldInstruction(bytecode.Getstatic, "java/lang/System", "out", "Ljava/io/PrintStream;")
   main.LoadLocalVar(localVar)
   main.AddInvokeInstruction(bytecode.Invokevirtual, "java/io/PrintStream", "println", "(Ljava/lang/String;)V")
   
   main.AddFieldInstruction(bytecode.Getstatic, "java/lang/System", "out", "Ljava/io/PrintStream;")
   main.AddInvokeInstruction(bytecode.Invokestatic, "Test", "add", "()I")
   main.AddInvokeInstruction(bytecode.Invokevirtual, "java/io/PrintStream", "println", "(I)V")
   main.AddInstruction(bytecode.Return)
   
   // Add second method
   add := code.AddMethod(bytecode.Flag_Private | bytecode.Flag_Static, "add", "()I", 2)
   add.AddFieldInstruction(bytecode.Getstatic, "Test", "firstNumber", "I")
   add.AddFieldInstruction(bytecode.Getstatic, "Test", "secondNumber", "I")
   add.AddInstruction(bytecode.Iadd)
   add.AddInstruction(bytecode.Ireturn)

   writeFile(code.ToBytes())
}

public class Test implements java.io.Serializable
  minor version: 0
  major version: 49
  flags: ACC_PUBLIC
Constant pool:
   #1 = Utf8               Test
   #2 = Class              #1             // Test
   #3 = Utf8               java/lang/Object
   #4 = Class              #3             // java/lang/Object
   #5 = Utf8               java/io/Serializable
   #6 = Class              #5             // java/io/Serializable
   #7 = Utf8               SourceFile
   #8 = Utf8               Test.java
   #9 = Utf8               firstNumber
  #10 = Utf8               I
  #11 = Utf8               ConstantValue
  #12 = Integer            5
  #13 = NameAndType        #9:#10         // firstNumber:I
  #14 = Fieldref           #2.#13         // Test.firstNumber:I
  #15 = Utf8               secondNumber
  #16 = Integer            10
  #17 = NameAndType        #15:#10        // secondNumber:I
  #18 = Fieldref           #2.#17         // Test.secondNumber:I
  #19 = Utf8               main
  #20 = Utf8               ([Ljava/lang/String;)V
  #21 = Utf8               Code
  #22 = Utf8               test
  #23 = String             #22            // test
  #24 = Utf8               java/lang/System
  #25 = Class              #24            // java/lang/System
  #26 = Utf8               out
  #27 = Utf8               Ljava/io/PrintStream;
  #28 = NameAndType        #26:#27        // out:Ljava/io/PrintStream;
  #29 = Fieldref           #25.#28        // java/lang/System.out:Ljava/io/PrintStream;
  #30 = Utf8               java/io/PrintStream
  #31 = Class              #30            // java/io/PrintStream
  #32 = Utf8               println
  #33 = Utf8               (Ljava/lang/String;)V
  #34 = NameAndType        #32:#33        // println:(Ljava/lang/String;)V
  #35 = Methodref          #31.#34        // java/io/PrintStream.println:(Ljava/lang/String;)V
  #36 = Utf8               add
  #37 = Utf8               ()I
  #38 = NameAndType        #36:#37        // add:()I
  #39 = Methodref          #2.#38         // Test.add:()I
  #40 = Utf8               (I)V
  #41 = NameAndType        #32:#40        // println:(I)V
  #42 = Methodref          #31.#41        // java/io/PrintStream.println:(I)V
{
  public static final int firstNumber;
    descriptor: I
    flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: int 5

  public static final int secondNumber;
    descriptor: I
    flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: int 10

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=2, locals=2, args_size=1
         0: ldc           #23                 // String test
         2: astore_1
         3: getstatic     #29                 // Field java/lang/System.out:Ljava/io/PrintStream;
         6: aload_1
         7: invokevirtual #35                 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        10: getstatic     #29                 // Field java/lang/System.out:Ljava/io/PrintStream;
        13: invokestatic  #39                 // Method add:()I
        16: invokevirtual #42                 // Method java/io/PrintStream.println:(I)V
        19: return

  private static int add();
    descriptor: ()I
    flags: ACC_PRIVATE, ACC_STATIC
    Code:
      stack=2, locals=0, args_size=0
         0: getstatic     #14                 // Field firstNumber:I
         3: getstatic     #18                 // Field secondNumber:I
         6: iadd
         7: ireturn
}
SourceFile: "Test.java"

mikigal/bytecode

ErrorLooks like something went wrong!

About

Topics

Resources

Uh oh!

Stars

Watchers

Forks

Releases

Packages 0

Uh oh!

Languages

Error
Looks like something went wrong!

Packages