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| 1 | +package scala.runtime |
| 2 | + |
| 3 | +import java.lang.invoke._ |
| 4 | + |
| 5 | +/** |
| 6 | + * This class is only intended to be called by synthetic `$deserializeLambda$` method that the Scala 2.12 |
| 7 | + * compiler will add to classes hosting lambdas. |
| 8 | + * |
| 9 | + * It is not intended to be consumed directly. |
| 10 | + */ |
| 11 | +object LambdaDeserializer { |
| 12 | + /** |
| 13 | + * Deserialize a lambda by calling `LambdaMetafactory.altMetafactory` to spin up a lambda class |
| 14 | + * and instantiating this class with the captured arguments. |
| 15 | + * |
| 16 | + * A cache may be provided to ensure that subsequent deserialization of the same lambda expression |
| 17 | + * is cheap, it amounts to a reflective call to the constructor of the previously created class. |
| 18 | + * However, deserialization of the same lambda expression is not guaranteed to use the same class, |
| 19 | + * concurrent deserialization of the same lambda expression may spin up more than one class. |
| 20 | + * |
| 21 | + * Assumptions: |
| 22 | + * - No additional marker interfaces are required beyond `{java.io,scala.}Serializable`. These are |
| 23 | + * not stored in `SerializedLambda`, so we can't reconstitute them. |
| 24 | + * - No additional bridge methods are passed to `altMetafactory`. Again, these are not stored. |
| 25 | + * |
| 26 | + * @param lookup The factory for method handles. Must have access to the implementation method, the |
| 27 | + * functional interface class, and `java.io.Serializable` or `scala.Serializable` as |
| 28 | + * required. |
| 29 | + * @param cache A cache used to avoid spinning up a class for each deserialization of a given lambda. May be `null` |
| 30 | + * @param serialized The lambda to deserialize. Note that this is typically created by the `readResolve` |
| 31 | + * member of the anonymous class created by `LambdaMetaFactory`. |
| 32 | + * @return An instance of the functional interface |
| 33 | + */ |
| 34 | + def deserializeLambda(lookup: MethodHandles.Lookup, cache: java.util.Map[String, MethodHandle], serialized: SerializedLambda): AnyRef = { |
| 35 | + def slashDot(name: String) = name.replaceAll("/", ".") |
| 36 | + val loader = lookup.lookupClass().getClassLoader |
| 37 | + val implClass = loader.loadClass(slashDot(serialized.getImplClass)) |
| 38 | + |
| 39 | + def makeCallSite: CallSite = { |
| 40 | + import serialized._ |
| 41 | + def parseDescriptor(s: String) = |
| 42 | + MethodType.fromMethodDescriptorString(s, loader) |
| 43 | + |
| 44 | + val funcInterfaceSignature = parseDescriptor(getFunctionalInterfaceMethodSignature) |
| 45 | + val instantiated = parseDescriptor(getInstantiatedMethodType) |
| 46 | + val functionalInterfaceClass = loader.loadClass(slashDot(getFunctionalInterfaceClass)) |
| 47 | + |
| 48 | + val implMethodSig = parseDescriptor(getImplMethodSignature) |
| 49 | + // Construct the invoked type from the impl method type. This is the type of a factory |
| 50 | + // that will be generated by the meta-factory. It is a method type, with param types |
| 51 | + // coming form the types of the captures, and return type being the functional interface. |
| 52 | + val invokedType: MethodType = { |
| 53 | + // 1. Add receiver for non-static impl methods |
| 54 | + val withReceiver = getImplMethodKind match { |
| 55 | + case MethodHandleInfo.REF_invokeStatic | MethodHandleInfo.REF_newInvokeSpecial => |
| 56 | + implMethodSig |
| 57 | + case _ => |
| 58 | + implMethodSig.insertParameterTypes(0, implClass) |
| 59 | + } |
| 60 | + // 2. Remove lambda parameters, leaving only captures. Note: the receiver may be a lambda parameter, |
| 61 | + // such as in `Function<Object, String> s = Object::toString` |
| 62 | + val lambdaArity = funcInterfaceSignature.parameterCount() |
| 63 | + val from = withReceiver.parameterCount() - lambdaArity |
| 64 | + val to = withReceiver.parameterCount() |
| 65 | + |
| 66 | + // 3. Drop the lambda return type and replace with the functional interface. |
| 67 | + withReceiver.dropParameterTypes(from, to).changeReturnType(functionalInterfaceClass) |
| 68 | + } |
| 69 | + |
| 70 | + // Lookup the implementation method |
| 71 | + val implMethod: MethodHandle = try { |
| 72 | + findMember(lookup, getImplMethodKind, implClass, getImplMethodName, implMethodSig) |
| 73 | + } catch { |
| 74 | + case e: ReflectiveOperationException => throw new IllegalArgumentException("Illegal lambda deserialization", e) |
| 75 | + } |
| 76 | + |
| 77 | + val flags: Int = LambdaMetafactory.FLAG_SERIALIZABLE | LambdaMetafactory.FLAG_MARKERS |
| 78 | + val isScalaFunction = functionalInterfaceClass.getName.startsWith("scala.Function") |
| 79 | + val markerInterface: Class[_] = loader.loadClass(if (isScalaFunction) ScalaSerializable else JavaIOSerializable) |
| 80 | + |
| 81 | + LambdaMetafactory.altMetafactory( |
| 82 | + lookup, getFunctionalInterfaceMethodName, invokedType, |
| 83 | + |
| 84 | + /* samMethodType = */ funcInterfaceSignature, |
| 85 | + /* implMethod = */ implMethod, |
| 86 | + /* instantiatedMethodType = */ instantiated, |
| 87 | + /* flags = */ flags.asInstanceOf[AnyRef], |
| 88 | + /* markerInterfaceCount = */ 1.asInstanceOf[AnyRef], |
| 89 | + /* markerInterfaces[0] = */ markerInterface, |
| 90 | + /* bridgeCount = */ 0.asInstanceOf[AnyRef] |
| 91 | + ) |
| 92 | + } |
| 93 | + |
| 94 | + val key = serialized.getImplMethodName + " : " + serialized.getImplMethodSignature |
| 95 | + val factory: MethodHandle = if (cache == null) { |
| 96 | + makeCallSite.getTarget |
| 97 | + } else cache.get(key) match { |
| 98 | + case null => |
| 99 | + val callSite = makeCallSite |
| 100 | + val temp = callSite.getTarget |
| 101 | + cache.put(key, temp) |
| 102 | + temp |
| 103 | + case target => target |
| 104 | + } |
| 105 | + |
| 106 | + val captures = Array.tabulate(serialized.getCapturedArgCount)(n => serialized.getCapturedArg(n)) |
| 107 | + factory.invokeWithArguments(captures: _*) |
| 108 | + } |
| 109 | + |
| 110 | + private val ScalaSerializable = "scala.Serializable" |
| 111 | + |
| 112 | + private val JavaIOSerializable = { |
| 113 | + // We could actually omit this marker interface as LambdaMetaFactory will add it if |
| 114 | + // the FLAG_SERIALIZABLE is set and of the provided markers extend it. But the code |
| 115 | + // is cleaner if we uniformly add a single marker, so I'm leaving it in place. |
| 116 | + "java.io.Serializable" |
| 117 | + } |
| 118 | + |
| 119 | + private def findMember(lookup: MethodHandles.Lookup, kind: Int, owner: Class[_], |
| 120 | + name: String, signature: MethodType): MethodHandle = { |
| 121 | + kind match { |
| 122 | + case MethodHandleInfo.REF_invokeStatic => |
| 123 | + lookup.findStatic(owner, name, signature) |
| 124 | + case MethodHandleInfo.REF_newInvokeSpecial => |
| 125 | + lookup.findConstructor(owner, signature) |
| 126 | + case MethodHandleInfo.REF_invokeVirtual | MethodHandleInfo.REF_invokeInterface => |
| 127 | + lookup.findVirtual(owner, name, signature) |
| 128 | + case MethodHandleInfo.REF_invokeSpecial => |
| 129 | + lookup.findSpecial(owner, name, signature, owner) |
| 130 | + } |
| 131 | + } |
| 132 | +} |
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