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| 1 | +/* | |
| 2 | + * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package java.lang.invoke; | |
| 27 | + | |
| 28 | +import sun.invoke.empty.Empty; | |
| 29 | +import sun.misc.Unsafe; | |
| 30 | +import static java.lang.invoke.MethodHandleStatics.*; | |
| 31 | +import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP; | |
| 32 | + | |
| 33 | +/** | |
| 34 | + * A {@code CallSite} is a holder for a variable {@link MethodHandle}, | |
| 35 | + * which is called its {@code target}. | |
| 36 | + * An {@code invokedynamic} instruction linked to a {@code CallSite} delegates | |
| 37 | + * all calls to the site's current target. | |
| 38 | + * A {@code CallSite} may be associated with several {@code invokedynamic} | |
| 39 | + * instructions, or it may be "free floating", associated with none. | |
| 40 | + * In any case, it may be invoked through an associated method handle | |
| 41 | + * called its {@linkplain #dynamicInvoker dynamic invoker}. | |
| 42 | + * <p> | |
| 43 | + * {@code CallSite} is an abstract class which does not allow | |
| 44 | + * direct subclassing by users. It has three immediate, | |
| 45 | + * concrete subclasses that may be either instantiated or subclassed. | |
| 46 | + * <ul> | |
| 47 | + * <li>If a mutable target is not required, an {@code invokedynamic} instruction | |
| 48 | + * may be permanently bound by means of a {@linkplain ConstantCallSite constant call site}. | |
| 49 | + * <li>If a mutable target is required which has volatile variable semantics, | |
| 50 | + * because updates to the target must be immediately and reliably witnessed by other threads, | |
| 51 | + * a {@linkplain VolatileCallSite volatile call site} may be used. | |
| 52 | + * <li>Otherwise, if a mutable target is required, | |
| 53 | + * a {@linkplain MutableCallSite mutable call site} may be used. | |
| 54 | + * </ul> | |
| 55 | + * <p> | |
| 56 | + * A non-constant call site may be <em>relinked</em> by changing its target. | |
| 57 | + * The new target must have the same {@linkplain MethodHandle#type() type} | |
| 58 | + * as the previous target. | |
| 59 | + * Thus, though a call site can be relinked to a series of | |
| 60 | + * successive targets, it cannot change its type. | |
| 61 | + * <p> | |
| 62 | + * Here is a sample use of call sites and bootstrap methods which links every | |
| 63 | + * dynamic call site to print its arguments: | |
| 64 | +<blockquote><pre><!-- see indy-demo/src/PrintArgsDemo.java --> | |
| 65 | +static void test() throws Throwable { | |
| 66 | + // THE FOLLOWING LINE IS PSEUDOCODE FOR A JVM INSTRUCTION | |
| 67 | + InvokeDynamic[#bootstrapDynamic].baz("baz arg", 2, 3.14); | |
| 68 | +} | |
| 69 | +private static void printArgs(Object... args) { | |
| 70 | + System.out.println(java.util.Arrays.deepToString(args)); | |
| 71 | +} | |
| 72 | +private static final MethodHandle printArgs; | |
| 73 | +static { | |
| 74 | + MethodHandles.Lookup lookup = MethodHandles.lookup(); | |
| 75 | + Class thisClass = lookup.lookupClass(); // (who am I?) | |
| 76 | + printArgs = lookup.findStatic(thisClass, | |
| 77 | + "printArgs", MethodType.methodType(void.class, Object[].class)); | |
| 78 | +} | |
| 79 | +private static CallSite bootstrapDynamic(MethodHandles.Lookup caller, String name, MethodType type) { | |
| 80 | + // ignore caller and name, but match the type: | |
| 81 | + return new ConstantCallSite(printArgs.asType(type)); | |
| 82 | +} | |
| 83 | +</pre></blockquote> | |
| 84 | + * @author John Rose, JSR 292 EG | |
| 85 | + */ | |
| 86 | +abstract | |
| 87 | +public class CallSite { | |
| 88 | + static { MethodHandleImpl.initStatics(); } | |
| 89 | + | |
| 90 | + // Fields used only by the JVM. Do not use or change. | |
| 91 | + private MemberName vmmethod; // supplied by the JVM (ref. to calling method) | |
| 92 | + private int vmindex; // supplied by the JVM (BCI within calling method) | |
| 93 | + | |
| 94 | + // The actual payload of this call site: | |
| 95 | + /*package-private*/ | |
| 96 | + MethodHandle target; | |
| 97 | + | |
| 98 | + /** | |
| 99 | + * Make a blank call site object with the given method type. | |
| 100 | + * An initial target method is supplied which will throw | |
| 101 | + * an {@link IllegalStateException} if called. | |
| 102 | + * <p> | |
| 103 | + * Before this {@code CallSite} object is returned from a bootstrap method, | |
| 104 | + * it is usually provided with a more useful target method, | |
| 105 | + * via a call to {@link CallSite#setTarget(MethodHandle) setTarget}. | |
| 106 | + * @throws NullPointerException if the proposed type is null | |
| 107 | + */ | |
| 108 | + /*package-private*/ | |
| 109 | + CallSite(MethodType type) { | |
| 110 | + target = type.invokers().uninitializedCallSite(); | |
| 111 | + } | |
| 112 | + | |
| 113 | + /** | |
| 114 | + * Make a call site object equipped with an initial target method handle. | |
| 115 | + * @param target the method handle which will be the initial target of the call site | |
| 116 | + * @throws NullPointerException if the proposed target is null | |
| 117 | + */ | |
| 118 | + /*package-private*/ | |
| 119 | + CallSite(MethodHandle target) { | |
| 120 | + target.type(); // null check | |
| 121 | + this.target = target; | |
| 122 | + } | |
| 123 | + | |
| 124 | + /** | |
| 125 | + * Make a call site object equipped with an initial target method handle. | |
| 126 | + * @param targetType the desired type of the call site | |
| 127 | + * @param createTargetHook a hook which will bind the call site to the target method handle | |
| 128 | + * @throws WrongMethodTypeException if the hook cannot be invoked on the required arguments, | |
| 129 | + * or if the target returned by the hook is not of the given {@code targetType} | |
| 130 | + * @throws NullPointerException if the hook returns a null value | |
| 131 | + * @throws ClassCastException if the hook returns something other than a {@code MethodHandle} | |
| 132 | + * @throws Throwable anything else thrown by the the hook function | |
| 133 | + */ | |
| 134 | + /*package-private*/ | |
| 135 | + CallSite(MethodType targetType, MethodHandle createTargetHook) throws Throwable { | |
| 136 | + this(targetType); | |
| 137 | + ConstantCallSite selfCCS = (ConstantCallSite) this; | |
| 138 | + MethodHandle boundTarget = (MethodHandle) createTargetHook.invokeWithArguments(selfCCS); | |
| 139 | + checkTargetChange(this.target, boundTarget); | |
| 140 | + this.target = boundTarget; | |
| 141 | + } | |
| 142 | + | |
| 143 | + /** | |
| 144 | + * Returns the type of this call site's target. | |
| 145 | + * Although targets may change, any call site's type is permanent, and can never change to an unequal type. | |
| 146 | + * The {@code setTarget} method enforces this invariant by refusing any new target that does | |
| 147 | + * not have the previous target's type. | |
| 148 | + * @return the type of the current target, which is also the type of any future target | |
| 149 | + */ | |
| 150 | + public MethodType type() { | |
| 151 | + // warning: do not call getTarget here, because CCS.getTarget can throw IllegalStateException | |
| 152 | + return target.type(); | |
| 153 | + } | |
| 154 | + | |
| 155 | + /** Called from JVM (or low-level Java code) after the BSM returns the newly created CallSite. | |
| 156 | + * The parameters are JVM-specific. | |
| 157 | + */ | |
| 158 | + void initializeFromJVM(String name, | |
| 159 | + MethodType type, | |
| 160 | + MemberName callerMethod, | |
| 161 | + int callerBCI) { | |
| 162 | + if (this.vmmethod != null) { | |
| 163 | + // FIXME | |
| 164 | + throw new BootstrapMethodError("call site has already been linked to an invokedynamic instruction"); | |
| 165 | + } | |
| 166 | + if (!this.type().equals(type)) { | |
| 167 | + throw wrongTargetType(target, type); | |
| 168 | + } | |
| 169 | + this.vmindex = callerBCI; | |
| 170 | + this.vmmethod = callerMethod; | |
| 171 | + } | |
| 172 | + | |
| 173 | + /** | |
| 174 | + * Returns the target method of the call site, according to the | |
| 175 | + * behavior defined by this call site's specific class. | |
| 176 | + * The immediate subclasses of {@code CallSite} document the | |
| 177 | + * class-specific behaviors of this method. | |
| 178 | + * | |
| 179 | + * @return the current linkage state of the call site, its target method handle | |
| 180 | + * @see ConstantCallSite | |
| 181 | + * @see VolatileCallSite | |
| 182 | + * @see #setTarget | |
| 183 | + * @see ConstantCallSite#getTarget | |
| 184 | + * @see MutableCallSite#getTarget | |
| 185 | + * @see VolatileCallSite#getTarget | |
| 186 | + */ | |
| 187 | + public abstract MethodHandle getTarget(); | |
| 188 | + | |
| 189 | + /** | |
| 190 | + * Updates the target method of this call site, according to the | |
| 191 | + * behavior defined by this call site's specific class. | |
| 192 | + * The immediate subclasses of {@code CallSite} document the | |
| 193 | + * class-specific behaviors of this method. | |
| 194 | + * <p> | |
| 195 | + * The type of the new target must be {@linkplain MethodType#equals equal to} | |
| 196 | + * the type of the old target. | |
| 197 | + * | |
| 198 | + * @param newTarget the new target | |
| 199 | + * @throws NullPointerException if the proposed new target is null | |
| 200 | + * @throws WrongMethodTypeException if the proposed new target | |
| 201 | + * has a method type that differs from the previous target | |
| 202 | + * @see CallSite#getTarget | |
| 203 | + * @see ConstantCallSite#setTarget | |
| 204 | + * @see MutableCallSite#setTarget | |
| 205 | + * @see VolatileCallSite#setTarget | |
| 206 | + */ | |
| 207 | + public abstract void setTarget(MethodHandle newTarget); | |
| 208 | + | |
| 209 | + void checkTargetChange(MethodHandle oldTarget, MethodHandle newTarget) { | |
| 210 | + MethodType oldType = oldTarget.type(); | |
| 211 | + MethodType newType = newTarget.type(); // null check! | |
| 212 | + if (!newType.equals(oldType)) | |
| 213 | + throw wrongTargetType(newTarget, oldType); | |
| 214 | + } | |
| 215 | + | |
| 216 | + private static WrongMethodTypeException wrongTargetType(MethodHandle target, MethodType type) { | |
| 217 | + return new WrongMethodTypeException(String.valueOf(target)+" should be of type "+type); | |
| 218 | + } | |
| 219 | + | |
| 220 | + /** | |
| 221 | + * Produces a method handle equivalent to an invokedynamic instruction | |
| 222 | + * which has been linked to this call site. | |
| 223 | + * <p> | |
| 224 | + * This method is equivalent to the following code: | |
| 225 | + * <blockquote><pre> | |
| 226 | + * MethodHandle getTarget, invoker, result; | |
| 227 | + * getTarget = MethodHandles.publicLookup().bind(this, "getTarget", MethodType.methodType(MethodHandle.class)); | |
| 228 | + * invoker = MethodHandles.exactInvoker(this.type()); | |
| 229 | + * result = MethodHandles.foldArguments(invoker, getTarget) | |
| 230 | + * </pre></blockquote> | |
| 231 | + * | |
| 232 | + * @return a method handle which always invokes this call site's current target | |
| 233 | + */ | |
| 234 | + public abstract MethodHandle dynamicInvoker(); | |
| 235 | + | |
| 236 | + /*non-public*/ MethodHandle makeDynamicInvoker() { | |
| 237 | + MethodHandle getTarget = MethodHandleImpl.bindReceiver(GET_TARGET, this); | |
| 238 | + MethodHandle invoker = MethodHandles.exactInvoker(this.type()); | |
| 239 | + return MethodHandles.foldArguments(invoker, getTarget); | |
| 240 | + } | |
| 241 | + | |
| 242 | + private static final MethodHandle GET_TARGET; | |
| 243 | + static { | |
| 244 | + try { | |
| 245 | + GET_TARGET = IMPL_LOOKUP. | |
| 246 | + findVirtual(CallSite.class, "getTarget", MethodType.methodType(MethodHandle.class)); | |
| 247 | + } catch (ReflectiveOperationException ignore) { | |
| 248 | + throw new InternalError(); | |
| 249 | + } | |
| 250 | + } | |
| 251 | + | |
| 252 | + /** This guy is rolled into the default target if a MethodType is supplied to the constructor. */ | |
| 253 | + /*package-private*/ | |
| 254 | + static Empty uninitializedCallSite() { | |
| 255 | + throw new IllegalStateException("uninitialized call site"); | |
| 256 | + } | |
| 257 | + | |
| 258 | + // unsafe stuff: | |
| 259 | + private static final Unsafe unsafe = Unsafe.getUnsafe(); | |
| 260 | + private static final long TARGET_OFFSET; | |
| 261 | + | |
| 262 | + static { | |
| 263 | + try { | |
| 264 | + TARGET_OFFSET = unsafe.objectFieldOffset(CallSite.class.getDeclaredField("target")); | |
| 265 | + } catch (Exception ex) { throw new Error(ex); } | |
| 266 | + } | |
| 267 | + | |
| 268 | + /*package-private*/ | |
| 269 | + void setTargetNormal(MethodHandle newTarget) { | |
| 270 | + target = newTarget; | |
| 271 | + } | |
| 272 | + /*package-private*/ | |
| 273 | + MethodHandle getTargetVolatile() { | |
| 274 | + return (MethodHandle) unsafe.getObjectVolatile(this, TARGET_OFFSET); | |
| 275 | + } | |
| 276 | + /*package-private*/ | |
| 277 | + void setTargetVolatile(MethodHandle newTarget) { | |
| 278 | + unsafe.putObjectVolatile(this, TARGET_OFFSET, newTarget); | |
| 279 | + } | |
| 280 | + | |
| 281 | + // this implements the upcall from the JVM, MethodHandleNatives.makeDynamicCallSite: | |
| 282 | + static CallSite makeSite(MethodHandle bootstrapMethod, | |
| 283 | + // Callee information: | |
| 284 | + String name, MethodType type, | |
| 285 | + // Extra arguments for BSM, if any: | |
| 286 | + Object info, | |
| 287 | + // Caller information: | |
| 288 | + MemberName callerMethod, int callerBCI) { | |
| 289 | + Class<?> callerClass = callerMethod.getDeclaringClass(); | |
| 290 | + Object caller = IMPL_LOOKUP.in(callerClass); | |
| 291 | + CallSite site; | |
| 292 | + try { | |
| 293 | + Object binding; | |
| 294 | + info = maybeReBox(info); | |
| 295 | + if (info == null) { | |
| 296 | + binding = bootstrapMethod.invoke(caller, name, type); | |
| 297 | + } else if (!info.getClass().isArray()) { | |
| 298 | + binding = bootstrapMethod.invoke(caller, name, type, info); | |
| 299 | + } else { | |
| 300 | + Object[] argv = (Object[]) info; | |
| 301 | + maybeReBoxElements(argv); | |
| 302 | + if (3 + argv.length > 255) | |
| 303 | + throw new BootstrapMethodError("too many bootstrap method arguments"); | |
| 304 | + MethodType bsmType = bootstrapMethod.type(); | |
| 305 | + if (bsmType.parameterCount() == 4 && bsmType.parameterType(3) == Object[].class) | |
| 306 | + binding = bootstrapMethod.invoke(caller, name, type, argv); | |
| 307 | + else | |
| 308 | + binding = MethodHandles.spreadInvoker(bsmType, 3) | |
| 309 | + .invoke(bootstrapMethod, caller, name, type, argv); | |
| 310 | + } | |
| 311 | + //System.out.println("BSM for "+name+type+" => "+binding); | |
| 312 | + if (binding instanceof CallSite) { | |
| 313 | + site = (CallSite) binding; | |
| 314 | + } else { | |
| 315 | + throw new ClassCastException("bootstrap method failed to produce a CallSite"); | |
| 316 | + } | |
| 317 | + if (!site.getTarget().type().equals(type)) | |
| 318 | + throw new WrongMethodTypeException("wrong type: "+site.getTarget()); | |
| 319 | + } catch (Throwable ex) { | |
| 320 | + BootstrapMethodError bex; | |
| 321 | + if (ex instanceof BootstrapMethodError) | |
| 322 | + bex = (BootstrapMethodError) ex; | |
| 323 | + else | |
| 324 | + bex = new BootstrapMethodError("call site initialization exception", ex); | |
| 325 | + throw bex; | |
| 326 | + } | |
| 327 | + return site; | |
| 328 | + } | |
| 329 | + | |
| 330 | + private static Object maybeReBox(Object x) { | |
| 331 | + if (x instanceof Integer) { | |
| 332 | + int xi = (int) x; | |
| 333 | + if (xi == (byte) xi) | |
| 334 | + x = xi; // must rebox; see JLS 5.1.7 | |
| 335 | + } | |
| 336 | + return x; | |
| 337 | + } | |
| 338 | + private static void maybeReBoxElements(Object[] xa) { | |
| 339 | + for (int i = 0; i < xa.length; i++) { | |
| 340 | + xa[i] = maybeReBox(xa[i]); | |
| 341 | + } | |
| 342 | + } | |
| 343 | +} | |