Koffee: Java bytecode assembler as a Kotlin DSL

Koffee

A Kotlin DSL wrapping ObjectWeb's ASM bytecode manipulation library. (In particular, asm-tree .)

Limitations

Since the DSL is in Kotlin, there are a few reserved words that get in our way. In order to get around this, we provide properties with the literal name and use backtick-escaping, and the preferred approach of a leading underscore before the reserved name.

• Since 'interface' is a globally reserved keyword in Kotlin, the access flag interface can be referenced using interface` or _interface
• Since 'super' is a globally reserved keyword in Kotlin, the access flag super can be referenced using super` or _super
• Since 'return' is a globally reserved keyword in Kotlin, the instruction return can be referenced using return` or _return

Example

val helloWorld: ClassNode = assembleClass(public, "com/example/HelloWorld") {
    name = "com/example/HelloWorld"

    method(public + static, "main", type(Array<String>::class)) {
        getstatic(System::class, "out", PrintStream::class)
        ldc("Hello, world!")
        invokevirtual(PrintStream::class, void, String::class)
        _return
    }
}

Goals

• Koffee is designed to be used in projects that already make use of ASM, so we don't need to abstract too far away.
• Despite this, Koffee should aim to make the use of ASM easier - High-level abstractions are acceptable if they are common. (e.g. 'load int constant' can be made uniform)