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*
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* 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
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*
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package jdk.nashorn.internal.runtime.linker;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.Arrays;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.NamedOperation;
import jdk.dynalink.Operation;
import jdk.dynalink.StandardOperation;
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.Guards;
/**
* Links {@link BoundCallable} objects. Passes through to linker services for linking a callable (for either
* StandardOperation.CALL or .NEW, and modifies the returned invocation to deal with the receiver and argument binding.
*/
final class BoundCallableLinker implements TypeBasedGuardingDynamicLinker {
@Override
public boolean canLinkType(final Class<?> type) {
return type == BoundCallable.class;
}
@Override
public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {
final Object objBoundCallable = linkRequest.getReceiver();
if(!(objBoundCallable instanceof BoundCallable)) {
return null;
}
final CallSiteDescriptor descriptor = linkRequest.getCallSiteDescriptor();
final Operation operation = NamedOperation.getBaseOperation(descriptor.getOperation());
// We need to distinguish NEW from CALL because CALL sites have parameter list of the form
// "callee, this, args", while NEW sites have "callee, args" -- they lack the "this" parameter.
final boolean isCall;
if (operation == StandardOperation.NEW) {
isCall = false;
} else if (operation == StandardOperation.CALL) {
isCall = true;
} else {
// Only CALL and NEW are supported.
return null;
}
final BoundCallable boundCallable = (BoundCallable)objBoundCallable;
final Object callable = boundCallable.getCallable();
final Object boundThis = boundCallable.getBoundThis();
// We need to ask the linker services for a delegate invocation on the target callable.
// Replace arguments (boundCallable[, this], args) => (callable[, boundThis], boundArgs, args) when delegating
final Object[] args = linkRequest.getArguments();
final Object[] boundArgs = boundCallable.getBoundArgs();
final int argsLen = args.length;
final int boundArgsLen = boundArgs.length;
final Object[] newArgs = new Object[argsLen + boundArgsLen];
newArgs[0] = callable;
final int firstArgIndex;
if (isCall) {
newArgs[1] = boundThis;
firstArgIndex = 2;
} else {
firstArgIndex = 1;
}
System.arraycopy(boundArgs, 0, newArgs, firstArgIndex, boundArgsLen);
System.arraycopy(args, firstArgIndex, newArgs, firstArgIndex + boundArgsLen, argsLen - firstArgIndex);
// Use R(T0, T1, T2, ...) => R(callable.class, boundThis.class, boundArg0.class, ..., boundArgn.class, T2, ...)
// call site type when delegating to underlying linker (for NEW, there's no this).
final MethodType type = descriptor.getMethodType();
// Use R(T0, ...) => R(callable.class, ...)
MethodType newMethodType = descriptor.getMethodType().changeParameterType(0, callable.getClass());
if (isCall) {
// R(callable.class, T1, ...) => R(callable.class, boundThis.class, ...)
newMethodType = newMethodType.changeParameterType(1, boundThis == null? Object.class : boundThis.getClass());
}
// R(callable.class[, boundThis.class], T2, ...) => R(callable.class[, boundThis.class], boundArg0.class, ..., boundArgn.class, T2, ...)
for(int i = boundArgs.length; i-- > 0;) {
newMethodType = newMethodType.insertParameterTypes(firstArgIndex, boundArgs[i] == null ? Object.class : boundArgs[i].getClass());
}
final CallSiteDescriptor newDescriptor = descriptor.changeMethodType(newMethodType);
// Delegate to target's linker
final GuardedInvocation inv = linkerServices.getGuardedInvocation(linkRequest.replaceArguments(newDescriptor, newArgs));
if(inv == null) {
return null;
}
// Bind (callable[, boundThis], boundArgs) to the delegate handle
final MethodHandle boundHandle = MethodHandles.insertArguments(inv.getInvocation(), 0,
Arrays.copyOf(newArgs, firstArgIndex + boundArgs.length));
final Class<?> p0Type = type.parameterType(0);
final MethodHandle droppingHandle;
if (isCall) {
// Ignore incoming boundCallable and this
droppingHandle = MethodHandles.dropArguments(boundHandle, 0, p0Type, type.parameterType(1));
} else {
// Ignore incoming boundCallable
droppingHandle = MethodHandles.dropArguments(boundHandle, 0, p0Type);
}
// Identity guard on boundCallable object
final MethodHandle newGuard = Guards.getIdentityGuard(boundCallable);
return inv.replaceMethods(droppingHandle, newGuard.asType(newGuard.type().changeParameterType(0, p0Type)));
}
}