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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 | } | ||