Chasm - Java assembler and disassembler using S-expressions

Chasm can disassemble *.class files and *.jar files and output assembly in s-expression form. Furthermore the main use case is to read s-expression assembly files and output *.class or *.jar files. The s-expression syntax is both easy to parse and easy to generate. Chasm uses the de-facto standard library ow2 ASM for bytecode generation. Since Chasm is only a minimal syntax on top of ASM it is easy to keep it up to date with the current bytecode standard.

(class 53 (final public super) chasm/Main null java/lang/Object ()
 (source "Main.java" null)
 (inner-class chasm/Server$Command chasm/Server Command (abstract interface public static))
 (inner-class java/lang/invoke/MethodHandles$Lookup java/lang/invoke/MethodHandles Lookup (final public static))
 (method (public static) main "([Ljava/lang/String;)V" null (java/io/IOException)
  (code
   (label L0)
   (line 13 L0)
   (invokedynamic run "()Lchasm/Server$Command;"
    (H invokestatic java/lang/invoke/LambdaMetafactory metafactory
     "(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;" false)
    ((T "(Ljava/nio/file/Path;[Ljava/lang/String;Ljava/io/PrintStream;)V")
     (H invokestatic chasm/Main run
      "(Ljava/nio/file/Path;[Ljava/lang/String;Ljava/io/PrintStream;)V" false)
     (T "(Ljava/nio/file/Path;[Ljava/lang/String;Ljava/io/PrintStream;)V")))
   (aload 0)
   (invokestatic chasm/Server main "(Lchasm/Server$Command;[Ljava/lang/String;)V")
   (label L1)
   (line 14 L1)
   (return)
   (label L2)
   (local args "[Ljava/lang/String;" null L0 L2 0)
   (maxs 2 1)))
...

See example.chasm for the full example.

Quick start

1. Build with gradle or use the precompiled binary in dist (reproducible build).

2. Disassemble class/jar file to chasm with chasm example.{class|jar} example.chasm

3. Assemble chasm to class/jar file with chasm example.chasm example.{class|jar}

Binary version

The 'dist' directory contains a precompiled version which includes a copy of ASM.

License

MIT (c) 2018 Daniel Mendler

ASM: a very small and fast Java bytecode manipulation framework Copyright (c) 2000-2011 INRIA, France Telecom All rights reserved.

Related projects

• ObjectWeb ASM

• jdk asmtools

• Lilac

  • Does perfect roundtrip like chasm

  • Overall more complex and more complex syntax

  • Not based on ObjectWeb ASM

• Krakatau

  • Written in Python

  • Includes a decompiler

• Jasmin

• Whiley Jasm

• Jamaica

• BCEL