| /* |
| * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * 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). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.lang.invoke; |
| |
| // Android-changed: Not using Empty. |
| //import sun.invoke.empty.Empty; |
| import static java.lang.invoke.MethodHandleStatics.*; |
| import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP; |
| |
| /** |
| * A {@code CallSite} is a holder for a variable {@link MethodHandle}, |
| * which is called its {@code target}. |
| * An {@code invokedynamic} instruction linked to a {@code CallSite} delegates |
| * all calls to the site's current target. |
| * A {@code CallSite} may be associated with several {@code invokedynamic} |
| * instructions, or it may be "free floating", associated with none. |
| * In any case, it may be invoked through an associated method handle |
| * called its {@linkplain #dynamicInvoker dynamic invoker}. |
| * <p> |
| * {@code CallSite} is an abstract class which does not allow |
| * direct subclassing by users. It has three immediate, |
| * concrete subclasses that may be either instantiated or subclassed. |
| * <ul> |
| * <li>If a mutable target is not required, an {@code invokedynamic} instruction |
| * may be permanently bound by means of a {@linkplain ConstantCallSite constant call site}. |
| * <li>If a mutable target is required which has volatile variable semantics, |
| * because updates to the target must be immediately and reliably witnessed by other threads, |
| * a {@linkplain VolatileCallSite volatile call site} may be used. |
| * <li>Otherwise, if a mutable target is required, |
| * a {@linkplain MutableCallSite mutable call site} may be used. |
| * </ul> |
| * <p> |
| * A non-constant call site may be <em>relinked</em> by changing its target. |
| * The new target must have the same {@linkplain MethodHandle#type() type} |
| * as the previous target. |
| * Thus, though a call site can be relinked to a series of |
| * successive targets, it cannot change its type. |
| * <p> |
| * Here is a sample use of call sites and bootstrap methods which links every |
| * dynamic call site to print its arguments: |
| <blockquote><pre>{@code |
| static void test() throws Throwable { |
| // THE FOLLOWING LINE IS PSEUDOCODE FOR A JVM INSTRUCTION |
| InvokeDynamic[#bootstrapDynamic].baz("baz arg", 2, 3.14); |
| } |
| private static void printArgs(Object... args) { |
| System.out.println(java.util.Arrays.deepToString(args)); |
| } |
| private static final MethodHandle printArgs; |
| static { |
| MethodHandles.Lookup lookup = MethodHandles.lookup(); |
| Class thisClass = lookup.lookupClass(); // (who am I?) |
| printArgs = lookup.findStatic(thisClass, |
| "printArgs", MethodType.methodType(void.class, Object[].class)); |
| } |
| private static CallSite bootstrapDynamic(MethodHandles.Lookup caller, String name, MethodType type) { |
| // ignore caller and name, but match the type: |
| return new ConstantCallSite(printArgs.asType(type)); |
| } |
| }</pre></blockquote> |
| * @author John Rose, JSR 292 EG |
| */ |
| abstract |
| public class CallSite { |
| // Android-changed: not used. |
| // static { MethodHandleImpl.initStatics(); } |
| |
| // The actual payload of this call site: |
| /*package-private*/ |
| MethodHandle target; // Note: This field is known to the JVM. Do not change. |
| |
| /** |
| * Make a blank call site object with the given method type. |
| * An initial target method is supplied which will throw |
| * an {@link IllegalStateException} if called. |
| * <p> |
| * Before this {@code CallSite} object is returned from a bootstrap method, |
| * it is usually provided with a more useful target method, |
| * via a call to {@link CallSite#setTarget(MethodHandle) setTarget}. |
| * @throws NullPointerException if the proposed type is null |
| */ |
| /*package-private*/ |
| CallSite(MethodType type) { |
| // Android-changed: No cache for these. |
| // Instead create uninitializedCallSite target here using method handle transformations |
| // to create a method handle that has the expected method type but throws an |
| // IllegalStateException. |
| // target = makeUninitializedCallSite(type); |
| this.target = MethodHandles.throwException(type.returnType(), IllegalStateException.class); |
| this.target = MethodHandles.insertArguments( |
| this.target, 0, new IllegalStateException("uninitialized call site")); |
| if (type.parameterCount() > 0) { |
| this.target = MethodHandles.dropArguments(this.target, 0, type.ptypes()); |
| } |
| |
| // Android-changed: Using initializer method for GET_TARGET instead of static initializer. |
| initializeGetTarget(); |
| } |
| |
| /** |
| * Make a call site object equipped with an initial target method handle. |
| * @param target the method handle which will be the initial target of the call site |
| * @throws NullPointerException if the proposed target is null |
| */ |
| /*package-private*/ |
| CallSite(MethodHandle target) { |
| target.type(); // null check |
| this.target = target; |
| |
| // Android-changed: Using initializer method for GET_TARGET instead of static initializer. |
| initializeGetTarget(); |
| } |
| |
| /** |
| * Make a call site object equipped with an initial target method handle. |
| * @param targetType the desired type of the call site |
| * @param createTargetHook a hook which will bind the call site to the target method handle |
| * @throws WrongMethodTypeException if the hook cannot be invoked on the required arguments, |
| * or if the target returned by the hook is not of the given {@code targetType} |
| * @throws NullPointerException if the hook returns a null value |
| * @throws ClassCastException if the hook returns something other than a {@code MethodHandle} |
| * @throws Throwable anything else thrown by the hook function |
| */ |
| /*package-private*/ |
| CallSite(MethodType targetType, MethodHandle createTargetHook) throws Throwable { |
| this(targetType); |
| ConstantCallSite selfCCS = (ConstantCallSite) this; |
| MethodHandle boundTarget = (MethodHandle) createTargetHook.invokeWithArguments(selfCCS); |
| checkTargetChange(this.target, boundTarget); |
| this.target = boundTarget; |
| |
| // Android-changed: Using initializer method for GET_TARGET instead of static initializer. |
| initializeGetTarget(); |
| } |
| |
| /** |
| * Returns the type of this call site's target. |
| * Although targets may change, any call site's type is permanent, and can never change to an unequal type. |
| * The {@code setTarget} method enforces this invariant by refusing any new target that does |
| * not have the previous target's type. |
| * @return the type of the current target, which is also the type of any future target |
| */ |
| public MethodType type() { |
| // warning: do not call getTarget here, because CCS.getTarget can throw IllegalStateException |
| return target.type(); |
| } |
| |
| /** |
| * Returns the target method of the call site, according to the |
| * behavior defined by this call site's specific class. |
| * The immediate subclasses of {@code CallSite} document the |
| * class-specific behaviors of this method. |
| * |
| * @return the current linkage state of the call site, its target method handle |
| * @see ConstantCallSite |
| * @see VolatileCallSite |
| * @see #setTarget |
| * @see ConstantCallSite#getTarget |
| * @see MutableCallSite#getTarget |
| * @see VolatileCallSite#getTarget |
| */ |
| public abstract MethodHandle getTarget(); |
| |
| /** |
| * Updates the target method of this call site, according to the |
| * behavior defined by this call site's specific class. |
| * The immediate subclasses of {@code CallSite} document the |
| * class-specific behaviors of this method. |
| * <p> |
| * The type of the new target must be {@linkplain MethodType#equals equal to} |
| * the type of the old target. |
| * |
| * @param newTarget the new target |
| * @throws NullPointerException if the proposed new target is null |
| * @throws WrongMethodTypeException if the proposed new target |
| * has a method type that differs from the previous target |
| * @see CallSite#getTarget |
| * @see ConstantCallSite#setTarget |
| * @see MutableCallSite#setTarget |
| * @see VolatileCallSite#setTarget |
| */ |
| public abstract void setTarget(MethodHandle newTarget); |
| |
| void checkTargetChange(MethodHandle oldTarget, MethodHandle newTarget) { |
| MethodType oldType = oldTarget.type(); |
| MethodType newType = newTarget.type(); // null check! |
| if (!newType.equals(oldType)) |
| throw wrongTargetType(newTarget, oldType); |
| } |
| |
| private static WrongMethodTypeException wrongTargetType(MethodHandle target, MethodType type) { |
| return new WrongMethodTypeException(String.valueOf(target)+" should be of type "+type); |
| } |
| |
| /** |
| * Produces a method handle equivalent to an invokedynamic instruction |
| * which has been linked to this call site. |
| * <p> |
| * This method is equivalent to the following code: |
| * <blockquote><pre>{@code |
| * MethodHandle getTarget, invoker, result; |
| * getTarget = MethodHandles.publicLookup().bind(this, "getTarget", MethodType.methodType(MethodHandle.class)); |
| * invoker = MethodHandles.exactInvoker(this.type()); |
| * result = MethodHandles.foldArguments(invoker, getTarget) |
| * }</pre></blockquote> |
| * |
| * @return a method handle which always invokes this call site's current target |
| */ |
| public abstract MethodHandle dynamicInvoker(); |
| |
| /*non-public*/ MethodHandle makeDynamicInvoker() { |
| // Android-changed: Use bindTo() rather than bindArgumentL() (not implemented). |
| MethodHandle getTarget = GET_TARGET.bindTo(this); |
| MethodHandle invoker = MethodHandles.exactInvoker(this.type()); |
| return MethodHandles.foldArguments(invoker, getTarget); |
| } |
| |
| // Android-changed: no longer final. GET_TARGET assigned in initializeGetTarget(). |
| private static MethodHandle GET_TARGET = null; |
| |
| private void initializeGetTarget() { |
| // Android-changed: moved from static initializer for GET_TARGET. |
| // This avoids issues with running early. Called from constructors. |
| // CallSite creation is not performance critical. |
| synchronized (CallSite.class) { |
| if (GET_TARGET == null) { |
| try { |
| GET_TARGET = IMPL_LOOKUP. |
| findVirtual(CallSite.class, "getTarget", |
| MethodType.methodType(MethodHandle.class)); |
| } catch (ReflectiveOperationException e) { |
| throw new InternalError(e); |
| } |
| } |
| } |
| } |
| |
| // Android-changed: not used. |
| // /** This guy is rolled into the default target if a MethodType is supplied to the constructor. */ |
| // /*package-private*/ |
| // static Empty uninitializedCallSite() { |
| // throw new IllegalStateException("uninitialized call site"); |
| // } |
| |
| // unsafe stuff: |
| private static final long TARGET_OFFSET; |
| static { |
| try { |
| TARGET_OFFSET = UNSAFE.objectFieldOffset(CallSite.class.getDeclaredField("target")); |
| } catch (Exception ex) { throw new Error(ex); } |
| } |
| |
| /*package-private*/ |
| void setTargetNormal(MethodHandle newTarget) { |
| // Android-changed: Set value directly. |
| // MethodHandleNatives.setCallSiteTargetNormal(this, newTarget); |
| target = newTarget; |
| } |
| /*package-private*/ |
| MethodHandle getTargetVolatile() { |
| return (MethodHandle) UNSAFE.getObjectVolatile(this, TARGET_OFFSET); |
| } |
| /*package-private*/ |
| void setTargetVolatile(MethodHandle newTarget) { |
| // Android-changed: Set value directly. |
| // MethodHandleNatives.setCallSiteTargetVolatile(this, newTarget); |
| UNSAFE.putObjectVolatile(this, TARGET_OFFSET, newTarget); |
| } |
| |
| // Android-changed: not used. |
| // this implements the upcall from the JVM, MethodHandleNatives.makeDynamicCallSite: |
| // static CallSite makeSite(MethodHandle bootstrapMethod, |
| // // Callee information: |
| // String name, MethodType type, |
| // // Extra arguments for BSM, if any: |
| // Object info, |
| // // Caller information: |
| // Class<?> callerClass) { |
| // MethodHandles.Lookup caller = IMPL_LOOKUP.in(callerClass); |
| // CallSite site; |
| // try { |
| // Object binding; |
| // info = maybeReBox(info); |
| // if (info == null) { |
| // binding = bootstrapMethod.invoke(caller, name, type); |
| // } else if (!info.getClass().isArray()) { |
| // binding = bootstrapMethod.invoke(caller, name, type, info); |
| // } else { |
| // Object[] argv = (Object[]) info; |
| // maybeReBoxElements(argv); |
| // switch (argv.length) { |
| // case 0: |
| // binding = bootstrapMethod.invoke(caller, name, type); |
| // break; |
| // case 1: |
| // binding = bootstrapMethod.invoke(caller, name, type, |
| // argv[0]); |
| // break; |
| // case 2: |
| // binding = bootstrapMethod.invoke(caller, name, type, |
| // argv[0], argv[1]); |
| // break; |
| // case 3: |
| // binding = bootstrapMethod.invoke(caller, name, type, |
| // argv[0], argv[1], argv[2]); |
| // break; |
| // case 4: |
| // binding = bootstrapMethod.invoke(caller, name, type, |
| // argv[0], argv[1], argv[2], argv[3]); |
| // break; |
| // case 5: |
| // binding = bootstrapMethod.invoke(caller, name, type, |
| // argv[0], argv[1], argv[2], argv[3], argv[4]); |
| // break; |
| // case 6: |
| // binding = bootstrapMethod.invoke(caller, name, type, |
| // argv[0], argv[1], argv[2], argv[3], argv[4], argv[5]); |
| // break; |
| // default: |
| // final int NON_SPREAD_ARG_COUNT = 3; // (caller, name, type) |
| // if (NON_SPREAD_ARG_COUNT + argv.length > MethodType.MAX_MH_ARITY) |
| // throw new BootstrapMethodError("too many bootstrap method arguments"); |
| // MethodType bsmType = bootstrapMethod.type(); |
| // MethodType invocationType = MethodType.genericMethodType(NON_SPREAD_ARG_COUNT + argv.length); |
| // MethodHandle typedBSM = bootstrapMethod.asType(invocationType); |
| // MethodHandle spreader = invocationType.invokers().spreadInvoker(NON_SPREAD_ARG_COUNT); |
| // binding = spreader.invokeExact(typedBSM, (Object)caller, (Object)name, (Object)type, argv); |
| // } |
| // } |
| // //System.out.println("BSM for "+name+type+" => "+binding); |
| // if (binding instanceof CallSite) { |
| // site = (CallSite) binding; |
| // } else { |
| // throw new ClassCastException("bootstrap method failed to produce a CallSite"); |
| // } |
| // if (!site.getTarget().type().equals(type)) |
| // throw wrongTargetType(site.getTarget(), type); |
| // } catch (Throwable ex) { |
| // BootstrapMethodError bex; |
| // if (ex instanceof BootstrapMethodError) |
| // bex = (BootstrapMethodError) ex; |
| // else |
| // bex = new BootstrapMethodError("call site initialization exception", ex); |
| // throw bex; |
| // } |
| // return site; |
| // } |
| |
| // private static Object maybeReBox(Object x) { |
| // if (x instanceof Integer) { |
| // int xi = (int) x; |
| // if (xi == (byte) xi) |
| // x = xi; // must rebox; see JLS 5.1.7 |
| // } |
| // return x; |
| // } |
| // private static void maybeReBoxElements(Object[] xa) { |
| // for (int i = 0; i < xa.length; i++) { |
| // xa[i] = maybeReBox(xa[i]); |
| // } |
| // } |
| } |
