1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/lang/invoke/CallSite.java Sat Aug 09 11:11:13 2014 +0200
1.3 @@ -0,0 +1,347 @@
1.4 +/*
1.5 + * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation. Oracle designates this
1.11 + * particular file as subject to the "Classpath" exception as provided
1.12 + * by Oracle in the LICENSE file that accompanied this code.
1.13 + *
1.14 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 + * version 2 for more details (a copy is included in the LICENSE file that
1.18 + * accompanied this code).
1.19 + *
1.20 + * You should have received a copy of the GNU General Public License version
1.21 + * 2 along with this work; if not, write to the Free Software Foundation,
1.22 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 + *
1.24 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 + * or visit www.oracle.com if you need additional information or have any
1.26 + * questions.
1.27 + */
1.28 +
1.29 +package java.lang.invoke;
1.30 +
1.31 +import sun.invoke.empty.Empty;
1.32 +import static java.lang.invoke.MethodHandleStatics.*;
1.33 +import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
1.34 +
1.35 +/**
1.36 + * A {@code CallSite} is a holder for a variable {@link MethodHandle},
1.37 + * which is called its {@code target}.
1.38 + * An {@code invokedynamic} instruction linked to a {@code CallSite} delegates
1.39 + * all calls to the site's current target.
1.40 + * A {@code CallSite} may be associated with several {@code invokedynamic}
1.41 + * instructions, or it may be "free floating", associated with none.
1.42 + * In any case, it may be invoked through an associated method handle
1.43 + * called its {@linkplain #dynamicInvoker dynamic invoker}.
1.44 + * <p>
1.45 + * {@code CallSite} is an abstract class which does not allow
1.46 + * direct subclassing by users. It has three immediate,
1.47 + * concrete subclasses that may be either instantiated or subclassed.
1.48 + * <ul>
1.49 + * <li>If a mutable target is not required, an {@code invokedynamic} instruction
1.50 + * may be permanently bound by means of a {@linkplain ConstantCallSite constant call site}.
1.51 + * <li>If a mutable target is required which has volatile variable semantics,
1.52 + * because updates to the target must be immediately and reliably witnessed by other threads,
1.53 + * a {@linkplain VolatileCallSite volatile call site} may be used.
1.54 + * <li>Otherwise, if a mutable target is required,
1.55 + * a {@linkplain MutableCallSite mutable call site} may be used.
1.56 + * </ul>
1.57 + * <p>
1.58 + * A non-constant call site may be <em>relinked</em> by changing its target.
1.59 + * The new target must have the same {@linkplain MethodHandle#type() type}
1.60 + * as the previous target.
1.61 + * Thus, though a call site can be relinked to a series of
1.62 + * successive targets, it cannot change its type.
1.63 + * <p>
1.64 + * Here is a sample use of call sites and bootstrap methods which links every
1.65 + * dynamic call site to print its arguments:
1.66 +<blockquote><pre>{@code
1.67 +static void test() throws Throwable {
1.68 + // THE FOLLOWING LINE IS PSEUDOCODE FOR A JVM INSTRUCTION
1.69 + InvokeDynamic[#bootstrapDynamic].baz("baz arg", 2, 3.14);
1.70 +}
1.71 +private static void printArgs(Object... args) {
1.72 + System.out.println(java.util.Arrays.deepToString(args));
1.73 +}
1.74 +private static final MethodHandle printArgs;
1.75 +static {
1.76 + MethodHandles.Lookup lookup = MethodHandles.lookup();
1.77 + Class thisClass = lookup.lookupClass(); // (who am I?)
1.78 + printArgs = lookup.findStatic(thisClass,
1.79 + "printArgs", MethodType.methodType(void.class, Object[].class));
1.80 +}
1.81 +private static CallSite bootstrapDynamic(MethodHandles.Lookup caller, String name, MethodType type) {
1.82 + // ignore caller and name, but match the type:
1.83 + return new ConstantCallSite(printArgs.asType(type));
1.84 +}
1.85 +}</pre></blockquote>
1.86 + * @author John Rose, JSR 292 EG
1.87 + */
1.88 +abstract
1.89 +public class CallSite {
1.90 + static { MethodHandleImpl.initStatics(); }
1.91 +
1.92 + // The actual payload of this call site:
1.93 + /*package-private*/
1.94 + MethodHandle target; // Note: This field is known to the JVM. Do not change.
1.95 +
1.96 + /**
1.97 + * Make a blank call site object with the given method type.
1.98 + * An initial target method is supplied which will throw
1.99 + * an {@link IllegalStateException} if called.
1.100 + * <p>
1.101 + * Before this {@code CallSite} object is returned from a bootstrap method,
1.102 + * it is usually provided with a more useful target method,
1.103 + * via a call to {@link CallSite#setTarget(MethodHandle) setTarget}.
1.104 + * @throws NullPointerException if the proposed type is null
1.105 + */
1.106 + /*package-private*/
1.107 + CallSite(MethodType type) {
1.108 + target = type.invokers().uninitializedCallSite();
1.109 + }
1.110 +
1.111 + /**
1.112 + * Make a call site object equipped with an initial target method handle.
1.113 + * @param target the method handle which will be the initial target of the call site
1.114 + * @throws NullPointerException if the proposed target is null
1.115 + */
1.116 + /*package-private*/
1.117 + CallSite(MethodHandle target) {
1.118 + target.type(); // null check
1.119 + this.target = target;
1.120 + }
1.121 +
1.122 + /**
1.123 + * Make a call site object equipped with an initial target method handle.
1.124 + * @param targetType the desired type of the call site
1.125 + * @param createTargetHook a hook which will bind the call site to the target method handle
1.126 + * @throws WrongMethodTypeException if the hook cannot be invoked on the required arguments,
1.127 + * or if the target returned by the hook is not of the given {@code targetType}
1.128 + * @throws NullPointerException if the hook returns a null value
1.129 + * @throws ClassCastException if the hook returns something other than a {@code MethodHandle}
1.130 + * @throws Throwable anything else thrown by the hook function
1.131 + */
1.132 + /*package-private*/
1.133 + CallSite(MethodType targetType, MethodHandle createTargetHook) throws Throwable {
1.134 + this(targetType);
1.135 + ConstantCallSite selfCCS = (ConstantCallSite) this;
1.136 + MethodHandle boundTarget = (MethodHandle) createTargetHook.invokeWithArguments(selfCCS);
1.137 + checkTargetChange(this.target, boundTarget);
1.138 + this.target = boundTarget;
1.139 + }
1.140 +
1.141 + /**
1.142 + * Returns the type of this call site's target.
1.143 + * Although targets may change, any call site's type is permanent, and can never change to an unequal type.
1.144 + * The {@code setTarget} method enforces this invariant by refusing any new target that does
1.145 + * not have the previous target's type.
1.146 + * @return the type of the current target, which is also the type of any future target
1.147 + */
1.148 + public MethodType type() {
1.149 + // warning: do not call getTarget here, because CCS.getTarget can throw IllegalStateException
1.150 + return target.type();
1.151 + }
1.152 +
1.153 + /**
1.154 + * Returns the target method of the call site, according to the
1.155 + * behavior defined by this call site's specific class.
1.156 + * The immediate subclasses of {@code CallSite} document the
1.157 + * class-specific behaviors of this method.
1.158 + *
1.159 + * @return the current linkage state of the call site, its target method handle
1.160 + * @see ConstantCallSite
1.161 + * @see VolatileCallSite
1.162 + * @see #setTarget
1.163 + * @see ConstantCallSite#getTarget
1.164 + * @see MutableCallSite#getTarget
1.165 + * @see VolatileCallSite#getTarget
1.166 + */
1.167 + public abstract MethodHandle getTarget();
1.168 +
1.169 + /**
1.170 + * Updates the target method of this call site, according to the
1.171 + * behavior defined by this call site's specific class.
1.172 + * The immediate subclasses of {@code CallSite} document the
1.173 + * class-specific behaviors of this method.
1.174 + * <p>
1.175 + * The type of the new target must be {@linkplain MethodType#equals equal to}
1.176 + * the type of the old target.
1.177 + *
1.178 + * @param newTarget the new target
1.179 + * @throws NullPointerException if the proposed new target is null
1.180 + * @throws WrongMethodTypeException if the proposed new target
1.181 + * has a method type that differs from the previous target
1.182 + * @see CallSite#getTarget
1.183 + * @see ConstantCallSite#setTarget
1.184 + * @see MutableCallSite#setTarget
1.185 + * @see VolatileCallSite#setTarget
1.186 + */
1.187 + public abstract void setTarget(MethodHandle newTarget);
1.188 +
1.189 + void checkTargetChange(MethodHandle oldTarget, MethodHandle newTarget) {
1.190 + MethodType oldType = oldTarget.type();
1.191 + MethodType newType = newTarget.type(); // null check!
1.192 + if (!newType.equals(oldType))
1.193 + throw wrongTargetType(newTarget, oldType);
1.194 + }
1.195 +
1.196 + private static WrongMethodTypeException wrongTargetType(MethodHandle target, MethodType type) {
1.197 + return new WrongMethodTypeException(String.valueOf(target)+" should be of type "+type);
1.198 + }
1.199 +
1.200 + /**
1.201 + * Produces a method handle equivalent to an invokedynamic instruction
1.202 + * which has been linked to this call site.
1.203 + * <p>
1.204 + * This method is equivalent to the following code:
1.205 + * <blockquote><pre>{@code
1.206 + * MethodHandle getTarget, invoker, result;
1.207 + * getTarget = MethodHandles.publicLookup().bind(this, "getTarget", MethodType.methodType(MethodHandle.class));
1.208 + * invoker = MethodHandles.exactInvoker(this.type());
1.209 + * result = MethodHandles.foldArguments(invoker, getTarget)
1.210 + * }</pre></blockquote>
1.211 + *
1.212 + * @return a method handle which always invokes this call site's current target
1.213 + */
1.214 + public abstract MethodHandle dynamicInvoker();
1.215 +
1.216 + /*non-public*/ MethodHandle makeDynamicInvoker() {
1.217 + MethodHandle getTarget = GET_TARGET.bindReceiver(this);
1.218 + MethodHandle invoker = MethodHandles.exactInvoker(this.type());
1.219 + return MethodHandles.foldArguments(invoker, getTarget);
1.220 + }
1.221 +
1.222 + private static final MethodHandle GET_TARGET;
1.223 + static {
1.224 + try {
1.225 + GET_TARGET = IMPL_LOOKUP.
1.226 + findVirtual(CallSite.class, "getTarget", MethodType.methodType(MethodHandle.class));
1.227 + } catch (ReflectiveOperationException e) {
1.228 + throw newInternalError(e);
1.229 + }
1.230 + }
1.231 +
1.232 + /** This guy is rolled into the default target if a MethodType is supplied to the constructor. */
1.233 + /*package-private*/
1.234 + static Empty uninitializedCallSite() {
1.235 + throw new IllegalStateException("uninitialized call site");
1.236 + }
1.237 +
1.238 + // unsafe stuff:
1.239 + private static final long TARGET_OFFSET;
1.240 + static {
1.241 + try {
1.242 + TARGET_OFFSET = UNSAFE.objectFieldOffset(CallSite.class.getDeclaredField("target"));
1.243 + } catch (Exception ex) { throw new Error(ex); }
1.244 + }
1.245 +
1.246 + /*package-private*/
1.247 + void setTargetNormal(MethodHandle newTarget) {
1.248 + MethodHandleNatives.setCallSiteTargetNormal(this, newTarget);
1.249 + }
1.250 + /*package-private*/
1.251 + MethodHandle getTargetVolatile() {
1.252 + return (MethodHandle) UNSAFE.getObjectVolatile(this, TARGET_OFFSET);
1.253 + }
1.254 + /*package-private*/
1.255 + void setTargetVolatile(MethodHandle newTarget) {
1.256 + MethodHandleNatives.setCallSiteTargetVolatile(this, newTarget);
1.257 + }
1.258 +
1.259 + // this implements the upcall from the JVM, MethodHandleNatives.makeDynamicCallSite:
1.260 + static CallSite makeSite(MethodHandle bootstrapMethod,
1.261 + // Callee information:
1.262 + String name, MethodType type,
1.263 + // Extra arguments for BSM, if any:
1.264 + Object info,
1.265 + // Caller information:
1.266 + Class<?> callerClass) {
1.267 + MethodHandles.Lookup caller = IMPL_LOOKUP.in(callerClass);
1.268 + CallSite site;
1.269 + try {
1.270 + Object binding;
1.271 + info = maybeReBox(info);
1.272 + if (info == null) {
1.273 + binding = bootstrapMethod.invoke(caller, name, type);
1.274 + } else if (!info.getClass().isArray()) {
1.275 + binding = bootstrapMethod.invoke(caller, name, type, info);
1.276 + } else {
1.277 + Object[] argv = (Object[]) info;
1.278 + maybeReBoxElements(argv);
1.279 + switch (argv.length) {
1.280 + case 0:
1.281 + binding = bootstrapMethod.invoke(caller, name, type);
1.282 + break;
1.283 + case 1:
1.284 + binding = bootstrapMethod.invoke(caller, name, type,
1.285 + argv[0]);
1.286 + break;
1.287 + case 2:
1.288 + binding = bootstrapMethod.invoke(caller, name, type,
1.289 + argv[0], argv[1]);
1.290 + break;
1.291 + case 3:
1.292 + binding = bootstrapMethod.invoke(caller, name, type,
1.293 + argv[0], argv[1], argv[2]);
1.294 + break;
1.295 + case 4:
1.296 + binding = bootstrapMethod.invoke(caller, name, type,
1.297 + argv[0], argv[1], argv[2], argv[3]);
1.298 + break;
1.299 + case 5:
1.300 + binding = bootstrapMethod.invoke(caller, name, type,
1.301 + argv[0], argv[1], argv[2], argv[3], argv[4]);
1.302 + break;
1.303 + case 6:
1.304 + binding = bootstrapMethod.invoke(caller, name, type,
1.305 + argv[0], argv[1], argv[2], argv[3], argv[4], argv[5]);
1.306 + break;
1.307 + default:
1.308 + final int NON_SPREAD_ARG_COUNT = 3; // (caller, name, type)
1.309 + if (NON_SPREAD_ARG_COUNT + argv.length > MethodType.MAX_MH_ARITY)
1.310 + throw new BootstrapMethodError("too many bootstrap method arguments");
1.311 + MethodType bsmType = bootstrapMethod.type();
1.312 + MethodType invocationType = MethodType.genericMethodType(NON_SPREAD_ARG_COUNT + argv.length);
1.313 + MethodHandle typedBSM = bootstrapMethod.asType(invocationType);
1.314 + MethodHandle spreader = invocationType.invokers().spreadInvoker(NON_SPREAD_ARG_COUNT);
1.315 + binding = spreader.invokeExact(typedBSM, (Object)caller, (Object)name, (Object)type, argv);
1.316 + }
1.317 + }
1.318 + //System.out.println("BSM for "+name+type+" => "+binding);
1.319 + if (binding instanceof CallSite) {
1.320 + site = (CallSite) binding;
1.321 + } else {
1.322 + throw new ClassCastException("bootstrap method failed to produce a CallSite");
1.323 + }
1.324 + if (!site.getTarget().type().equals(type))
1.325 + throw new WrongMethodTypeException("wrong type: "+site.getTarget());
1.326 + } catch (Throwable ex) {
1.327 + BootstrapMethodError bex;
1.328 + if (ex instanceof BootstrapMethodError)
1.329 + bex = (BootstrapMethodError) ex;
1.330 + else
1.331 + bex = new BootstrapMethodError("call site initialization exception", ex);
1.332 + throw bex;
1.333 + }
1.334 + return site;
1.335 + }
1.336 +
1.337 + private static Object maybeReBox(Object x) {
1.338 + if (x instanceof Integer) {
1.339 + int xi = (int) x;
1.340 + if (xi == (byte) xi)
1.341 + x = xi; // must rebox; see JLS 5.1.7
1.342 + }
1.343 + return x;
1.344 + }
1.345 + private static void maybeReBoxElements(Object[] xa) {
1.346 + for (int i = 0; i < xa.length; i++) {
1.347 + xa[i] = maybeReBox(xa[i]);
1.348 + }
1.349 + }
1.350 +}