--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/lang/invoke/CallSite.java Wed Mar 23 23:02:31 2011 -0700
@@ -0,0 +1,323 @@
+/*
+ * Copyright (c) 2008, 2011, 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;
+
+import sun.invoke.empty.Empty;
+import sun.misc.Unsafe;
+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><!-- see indy-demo/src/PrintArgsDemo.java -->
+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 {
+ static { MethodHandleImpl.initStatics(); }
+
+ // Fields used only by the JVM. Do not use or change.
+ private MemberName vmmethod; // supplied by the JVM (ref. to calling method)
+ private int vmindex; // supplied by the JVM (BCI within calling method)
+
+ // The actual payload of this call site:
+ /*package-private*/
+ MethodHandle target;
+
+ /**
+ * 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) {
+ target = type.invokers().uninitializedCallSite();
+ }
+
+ /**
+ * Make a blank call site object, possibly 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;
+ }
+
+ /**
+ * 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() {
+ return target.type();
+ }
+
+ /** Called from JVM (or low-level Java code) after the BSM returns the newly created CallSite.
+ * The parameters are JVM-specific.
+ */
+ void initializeFromJVM(String name,
+ MethodType type,
+ MemberName callerMethod,
+ int callerBCI) {
+ if (this.vmmethod != null) {
+ // FIXME
+ throw new BootstrapMethodError("call site has already been linked to an invokedynamic instruction");
+ }
+ if (!this.type().equals(type)) {
+ throw wrongTargetType(target, type);
+ }
+ this.vmindex = callerBCI;
+ this.vmmethod = callerMethod;
+ }
+
+ /**
+ * 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>
+ * 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() {
+ MethodHandle getTarget = MethodHandleImpl.bindReceiver(GET_TARGET, this);
+ MethodHandle invoker = MethodHandles.exactInvoker(this.type());
+ return MethodHandles.foldArguments(invoker, getTarget);
+ }
+
+ private static final MethodHandle GET_TARGET;
+ static {
+ try {
+ GET_TARGET = IMPL_LOOKUP.
+ findVirtual(CallSite.class, "getTarget", MethodType.methodType(MethodHandle.class));
+ } catch (ReflectiveOperationException ignore) {
+ throw new InternalError();
+ }
+ }
+
+ /** 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 Unsafe unsafe = Unsafe.getUnsafe();
+ 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) {
+ target = newTarget;
+ }
+ /*package-private*/
+ MethodHandle getTargetVolatile() {
+ return (MethodHandle) unsafe.getObjectVolatile(this, TARGET_OFFSET);
+ }
+ /*package-private*/
+ void setTargetVolatile(MethodHandle newTarget) {
+ unsafe.putObjectVolatile(this, TARGET_OFFSET, newTarget);
+ }
+
+ // 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:
+ MemberName callerMethod, int callerBCI) {
+ Class<?> callerClass = callerMethod.getDeclaringClass();
+ Object caller = IMPL_LOOKUP.in(callerClass);
+ CallSite site;
+ try {
+ Object binding;
+ info = maybeReBox(info);
+ if (info == null) {
+ binding = bootstrapMethod.invokeGeneric(caller, name, type);
+ } else if (!info.getClass().isArray()) {
+ binding = bootstrapMethod.invokeGeneric(caller, name, type, info);
+ } else {
+ Object[] argv = (Object[]) info;
+ maybeReBoxElements(argv);
+ if (3 + argv.length > 255)
+ throw new BootstrapMethodError("too many bootstrap method arguments");
+ MethodType bsmType = bootstrapMethod.type();
+ if (bsmType.parameterCount() == 4 && bsmType.parameterType(3) == Object[].class)
+ binding = bootstrapMethod.invokeGeneric(caller, name, type, argv);
+ else
+ binding = MethodHandles.spreadInvoker(bsmType, 3)
+ .invokeGeneric(bootstrapMethod, caller, name, 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");
+ }
+ assert(site.getTarget() != null);
+ assert(site.getTarget().type().equals(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]);
+ }
+ }
+}