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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package jdk.nashorn.internal.runtime.linker;
import static jdk.dynalink.StandardNamespace.METHOD;
import static jdk.dynalink.StandardOperation.GET;
import static jdk.nashorn.internal.runtime.linker.JavaAdapterBytecodeGenerator.SUPER_PREFIX;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.Operation;
import jdk.dynalink.beans.BeansLinker;
import jdk.dynalink.linker.GuardedInvocation;
import jdk.dynalink.linker.LinkRequest;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
import jdk.dynalink.linker.support.Lookup;
import jdk.nashorn.internal.runtime.ScriptRuntime;
/**
* A linker for instances of {@code JavaSuperAdapter}. Only links {@code getMethod} calls, by forwarding them to the
* bean linker for the adapter class and prepending {@code super$} to method names.
*
*/
final class JavaSuperAdapterLinker implements TypeBasedGuardingDynamicLinker {
private static final MethodHandle ADD_PREFIX_TO_METHOD_NAME;
private static final MethodHandle BIND_DYNAMIC_METHOD;
private static final MethodHandle GET_ADAPTER;
private static final MethodHandle IS_ADAPTER_OF_CLASS;
static {
final Lookup lookup = new Lookup(MethodHandles.lookup());
ADD_PREFIX_TO_METHOD_NAME = lookup.findOwnStatic("addPrefixToMethodName", Object.class, Object.class);
BIND_DYNAMIC_METHOD = lookup.findOwnStatic("bindDynamicMethod", Object.class, Object.class, Object.class);
GET_ADAPTER = lookup.findVirtual(JavaSuperAdapter.class, "getAdapter", MethodType.methodType(Object.class));
IS_ADAPTER_OF_CLASS = lookup.findOwnStatic("isAdapterOfClass", boolean.class, Class.class, Object.class);
}
private static final Operation GET_METHOD = GET.withNamespace(METHOD);
private final BeansLinker beansLinker;
JavaSuperAdapterLinker(final BeansLinker beansLinker) {
this.beansLinker = beansLinker;
}
@Override
public boolean canLinkType(final Class<?> type) {
return type == JavaSuperAdapter.class;
}
@Override
public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)
throws Exception {
final Object objSuperAdapter = linkRequest.getReceiver();
if(!(objSuperAdapter instanceof JavaSuperAdapter)) {
return null;
}
final CallSiteDescriptor descriptor = linkRequest.getCallSiteDescriptor();
if(!NashornCallSiteDescriptor.contains(descriptor, GET, METHOD)) {
// We only handle GET:METHOD
return null;
}
final Object adapter = ((JavaSuperAdapter)objSuperAdapter).getAdapter();
// Replace argument (javaSuperAdapter, ...) => (adapter, ...) when delegating to BeansLinker
final Object[] args = linkRequest.getArguments();
args[0] = adapter;
// Use R(T0, ...) => R(adapter.class, ...) call site type when delegating to BeansLinker.
final MethodType type = descriptor.getMethodType();
final Class<?> adapterClass = adapter.getClass();
final String name = NashornCallSiteDescriptor.getOperand(descriptor);
final Operation newOp = name == null ? GET_METHOD : GET_METHOD.named(SUPER_PREFIX + name);
final CallSiteDescriptor newDescriptor = new CallSiteDescriptor(
NashornCallSiteDescriptor.getLookupInternal(descriptor), newOp,
type.changeParameterType(0, adapterClass));
// Delegate to BeansLinker
final GuardedInvocation guardedInv = NashornBeansLinker.getGuardedInvocation(
beansLinker, linkRequest.replaceArguments(newDescriptor, args),
linkerServices);
// Even for non-existent methods, Bootstrap's BeansLinker will link a
// noSuchMember handler.
assert guardedInv != null;
final MethodHandle guard = IS_ADAPTER_OF_CLASS.bindTo(adapterClass);
final MethodHandle invocation = guardedInv.getInvocation();
final MethodType invType = invocation.type();
// For invocation typed R(T0, ...) create a dynamic method binder of type Object(R, T0)
final MethodHandle typedBinder = BIND_DYNAMIC_METHOD.asType(MethodType.methodType(Object.class,
invType.returnType(), invType.parameterType(0)));
// For invocation typed R(T0, T1, ...) create a dynamic method binder of type Object(R, T0, T1, ...)
final MethodHandle droppingBinder = MethodHandles.dropArguments(typedBinder, 2,
invType.parameterList().subList(1, invType.parameterCount()));
// Finally, fold the invocation into the binder to produce a method handle that will bind every returned
// DynamicMethod object from StandardOperation.GET_METHOD calls to the actual receiver
// Object(R(T0, T1, ...), T0, T1, ...)
final MethodHandle bindingInvocation = MethodHandles.foldArguments(droppingBinder, invocation);
final MethodHandle typedGetAdapter = asFilterType(GET_ADAPTER, 0, invType, type);
final MethodHandle adaptedInvocation;
if(name != null) {
adaptedInvocation = MethodHandles.filterArguments(bindingInvocation, 0, typedGetAdapter);
} else {
// Add a filter that'll prepend "super$" to each name passed to the variable-name StandardOperation.GET_METHOD.
final MethodHandle typedAddPrefix = asFilterType(ADD_PREFIX_TO_METHOD_NAME, 1, invType, type);
adaptedInvocation = MethodHandles.filterArguments(bindingInvocation, 0, typedGetAdapter, typedAddPrefix);
}
return guardedInv.replaceMethods(adaptedInvocation, guard).asType(descriptor);
}
/**
* Adapts the type of a method handle used as a filter in a position from a source method type to a target method type.
* @param filter the filter method handle
* @param pos the position in the argument list that it's filtering
* @param targetType the target method type for filtering
* @param sourceType the source method type for filtering
* @return a type adapted filter
*/
private static MethodHandle asFilterType(final MethodHandle filter, final int pos, final MethodType targetType, final MethodType sourceType) {
return filter.asType(MethodType.methodType(targetType.parameterType(pos), sourceType.parameterType(pos)));
}
@SuppressWarnings("unused")
private static Object addPrefixToMethodName(final Object name) {
return SUPER_PREFIX.concat(String.valueOf(name));
}
/**
* Used to transform the return value of getMethod; transform a {@code DynamicMethod} into a
* {@code BoundDynamicMethod} while also accounting for the possibility of a non-existent method.
* @param dynamicMethod the dynamic method to bind
* @param boundThis the adapter underlying a super adapter, to which the dynamic method is bound.
* @return a dynamic method bound to the adapter instance.
*/
@SuppressWarnings("unused")
private static Object bindDynamicMethod(final Object dynamicMethod, final Object boundThis) {
return dynamicMethod == ScriptRuntime.UNDEFINED ? ScriptRuntime.UNDEFINED : Bootstrap.bindCallable(dynamicMethod, boundThis, null);
}
/**
* Used as the guard of linkages, as the receiver is not guaranteed to be a JavaSuperAdapter.
* @param clazz the class the receiver's adapter is tested against.
* @param obj receiver
* @return true if the receiver is a super adapter, and its underlying adapter is of the specified class
*/
@SuppressWarnings("unused")
private static boolean isAdapterOfClass(final Class<?> clazz, final Object obj) {
return obj instanceof JavaSuperAdapter && clazz == (((JavaSuperAdapter)obj).getAdapter()).getClass();
}
}