1+ import java .lang .reflect .{Method , Modifier }
2+
3+ import Implicits ._
4+ import org .objectweb .asm .Opcodes ._
5+ import org .objectweb .asm .Type ._
6+ import org .objectweb .asm ._
7+
8+ import scala .collection .mutable .ArrayBuffer
9+
10+ case class MethodContainer (methodName : String , methodDesc : String , interface : String , signature : String )
11+ class ClassModifier (visitor : ClassVisitor , byteCodeVersion : Int = V1_6 ) extends ClassVisitor (ASM5 , visitor) {
12+
13+ var methodsToOverride : List [MethodContainer ] = Nil
14+ var className : String = _
15+ type MethodDesc = (String , String )
16+ var implementedMethods = ArrayBuffer [MethodDesc ]()
17+
18+ override def visit (version : Int , access : Int , name : String , signature : String , superName : String , interfaces : Array [String ]) = {
19+ val isClass = (access & ACC_INTERFACE ) == 0
20+ if (isClass) {
21+ val defaultMethods = for {
22+ interface <- interfaces
23+ cl = interface.getInternalClass
24+ m @ DefaultMethod () <- cl.getMethods
25+ } yield MethodContainer (m.getName, Type .getMethodDescriptor(m), interface, signature)
26+ println(s " Default methods: ${defaultMethods.mkString(" ," " )
27+ methodsToOverride = defaultMethods.toList
28+ className = name
29+ }
30+ super .visit(byteCodeVersion, access, name, signature, superName, interfaces)
31+ }
32+
33+ // gotta keep track of overriden default methods
34+ override def visitMethod (access : Int , name : String , desc : String , signature : String , exceptions : Array [String ]): MethodVisitor = {
35+ implementedMethods += name -> desc
36+ new InterfaceToHelperRewriter (super .visitMethod(access, name, desc, signature, exceptions))
37+ }
38+
39+ override def visitEnd () = {
40+ def createProxy (l : MethodContainer ) = l match {
41+ case MethodContainer (name, desc, interface, signature) if ! implementedMethods.contains(name -> desc) =>
42+ val tmp = super .visitMethod(ACC_PUBLIC , name, desc, signature, null )
43+ tmp.visitVarInsn(ALOAD , 0 )
44+ Type .getArgumentTypes(desc).zipWithIndex.foreach{
45+ case (PrimitiveLoad (instruction), i) => tmp.visitVarInsn(instruction, i + 1 )
46+ case (_, i) => tmp.visitVarInsn(ALOAD , i + 1 )
47+ }
48+ tmp.visitMethodInsn(INVOKESTATIC , interface + " helper" false )
49+ Type .getReturnType(desc) match {
50+ case ReturnIns (ins) => tmp.visitInsn(ins)
51+ case otherwise : Type => tmp.visitInsn(ARETURN )
52+ }
53+ tmp.visitMaxs(0 , 0 )
54+ tmp.visitEnd()
55+ case _ => // noop
56+ }
57+ methodsToOverride.foreach{ createProxy }
58+ super .visitEnd()
59+ }
60+ }
61+
62+ class InterfaceToHelperRewriter (mv : MethodVisitor ) extends MethodVisitor (Opcodes .ASM5 , mv) {
63+ override def visitMethodInsn (opcode : Int , owner : String , name : String , desc : String , isInterface : Boolean ) = opcode match {
64+ case INVOKESPECIAL if isInterface =>
65+ super .visitMethodInsn(INVOKESTATIC , owner + " helper" false )
66+ case INVOKESTATIC if isInterface =>
67+ super .visitMethodInsn(INVOKESTATIC , owner + " helper" + " $static" false )
68+ case _ =>
69+ super .visitMethodInsn(opcode, owner, name, desc, isInterface)
70+ }
71+ }
72+
73+ object DefaultMethod {
74+ def unapply (m : Method ) = ! Modifier .isAbstract(m.getModifiers)
75+ }
76+
77+ object InstructorExtractor {
78+ val (loadMap, returnMap) = {
79+ val types = List (INT_TYPE , LONG_TYPE , FLOAT_TYPE , DOUBLE_TYPE , VOID_TYPE )
80+ val loads = List (ILOAD , LLOAD , FLOAD , DLOAD , - 1 ) // omg a null
81+ val rets = List (IRETURN , LRETURN , FRETURN , DRETURN , RETURN )
82+ val mkMap = types.zip(_ : List [Int ]).toMap
83+ mkMap(loads) -> mkMap(rets)
84+ }
85+ }
86+
87+ class InstructorExtractor (m : Map [Type , Int ]) {
88+ def unapply (f : Type ) = m.get(f)
89+ }
90+ object PrimitiveLoad extends InstructorExtractor (InstructorExtractor .loadMap)
91+ object ReturnIns extends InstructorExtractor (InstructorExtractor .returnMap)
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