974 * @throws NullPointerException if {@code arrayType} is a null reference
975 * @throws IllegalArgumentException if {@code arrayType} is not an array type
976 * or {@code arrayType} is not assignable to this method handle's trailing parameter type,
977 * or {@code arrayLength} is not a legal array size,
978 * or the resulting method handle's type would have
979 * <a href="MethodHandle.html#maxarity">too many parameters</a>
980 * @throws WrongMethodTypeException if the implied {@code asType} call fails
981 * @see #asSpreader
982 * @see #asVarargsCollector
983 */
984 public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
985 asCollectorChecks(arrayType, arrayLength);
986 int collectArgPos = type().parameterCount()-1;
987 MethodHandle target = this;
988 if (arrayType != type().parameterType(collectArgPos))
989 target = convertArguments(type().changeParameterType(collectArgPos, arrayType));
990 MethodHandle collector = MethodHandleImpl.varargsArray(arrayType, arrayLength);
991 return MethodHandles.collectArguments(target, collectArgPos, collector);
992 }
993
994 // private API: return true if last param exactly matches arrayType
995 private boolean asCollectorChecks(Class<?> arrayType, int arrayLength) {
996 spreadArrayChecks(arrayType, arrayLength);
997 int nargs = type().parameterCount();
998 if (nargs != 0) {
999 Class<?> lastParam = type().parameterType(nargs-1);
1000 if (lastParam == arrayType) return true;
1001 if (lastParam.isAssignableFrom(arrayType)) return false;
1002 }
1003 throw newIllegalArgumentException("array type not assignable to trailing argument", this, arrayType);
1004 }
1005
1006 /**
1007 * Makes a <em>variable arity</em> adapter which is able to accept
1008 * any number of trailing positional arguments and collect them
1009 * into an array argument.
1010 * <p>
1011 * The type and behavior of the adapter will be the same as
1012 * the type and behavior of the target, except that certain
1013 * {@code invoke} and {@code asType} requests can lead to
1014 * trailing positional arguments being collected into target's
1015 * trailing parameter.
1137 * pre-collected arrays of any length. Users should be aware of the
1138 * special role of the final argument, and of the effect of a
1139 * type match on that final argument, which determines whether
1140 * or not a single trailing argument is interpreted as a whole
1141 * array or a single element of an array to be collected.
1142 * Note that the dynamic type of the trailing argument has no
1143 * effect on this decision, only a comparison between the symbolic
1144 * type descriptor of the call site and the type descriptor of the method handle.)
1145 *
1146 * @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
1147 * @return a new method handle which can collect any number of trailing arguments
1148 * into an array, before calling the original method handle
1149 * @throws NullPointerException if {@code arrayType} is a null reference
1150 * @throws IllegalArgumentException if {@code arrayType} is not an array type
1151 * or {@code arrayType} is not assignable to this method handle's trailing parameter type
1152 * @see #asCollector
1153 * @see #isVarargsCollector
1154 * @see #asFixedArity
1155 */
1156 public MethodHandle asVarargsCollector(Class<?> arrayType) {
1157 Class<?> arrayElement = arrayType.getComponentType();
1158 boolean lastMatch = asCollectorChecks(arrayType, 0);
1159 if (isVarargsCollector() && lastMatch)
1160 return this;
1161 return MethodHandleImpl.makeVarargsCollector(this, arrayType);
1162 }
1163
1164 /**
1165 * Determines if this method handle
1166 * supports {@linkplain #asVarargsCollector variable arity} calls.
1167 * Such method handles arise from the following sources:
1168 * <ul>
1169 * <li>a call to {@linkplain #asVarargsCollector asVarargsCollector}
1170 * <li>a call to a {@linkplain java.lang.invoke.MethodHandles.Lookup lookup method}
1171 * which resolves to a variable arity Java method or constructor
1172 * <li>an {@code ldc} instruction of a {@code CONSTANT_MethodHandle}
1173 * which resolves to a variable arity Java method or constructor
1174 * </ul>
1175 * @return true if this method handle accepts more than one arity of plain, inexact {@code invoke} calls
1176 * @see #asVarargsCollector
1177 * @see #asFixedArity
1294 }
1295
1296 //// Implementation methods.
1297 //// Sub-classes can override these default implementations.
1298 //// All these methods assume arguments are already validated.
1299
1300 // Other transforms to do: convert, explicitCast, permute, drop, filter, fold, GWT, catch
1301
1302 /*non-public*/
1303 MethodHandle setVarargs(MemberName member) throws IllegalAccessException {
1304 if (!member.isVarargs()) return this;
1305 int argc = type().parameterCount();
1306 if (argc != 0) {
1307 Class<?> arrayType = type().parameterType(argc-1);
1308 if (arrayType.isArray()) {
1309 return MethodHandleImpl.makeVarargsCollector(this, arrayType);
1310 }
1311 }
1312 throw member.makeAccessException("cannot make variable arity", null);
1313 }
1314 /*non-public*/
1315 MethodHandle viewAsType(MethodType newType) {
1316 // No actual conversions, just a new view of the same method.
1317 return MethodHandleImpl.makePairwiseConvert(this, newType, 0);
1318 }
1319
1320 // Decoding
1321
1322 /*non-public*/
1323 LambdaForm internalForm() {
1324 return form;
1325 }
1326
1327 /*non-public*/
1328 MemberName internalMemberName() {
1329 return null; // DMH returns DMH.member
1330 }
1331
1332 /*non-public*/
1333 Class<?> internalCallerClass() {
1452 private static final LambdaForm.NamedFunction NF_reinvokerTarget;
1453 static {
1454 try {
1455 NF_reinvokerTarget = new LambdaForm.NamedFunction(MethodHandle.class
1456 .getDeclaredMethod("reinvokerTarget"));
1457 } catch (ReflectiveOperationException ex) {
1458 throw newInternalError(ex);
1459 }
1460 }
1461
1462 /**
1463 * Replace the old lambda form of this method handle with a new one.
1464 * The new one must be functionally equivalent to the old one.
1465 * Threads may continue running the old form indefinitely,
1466 * but it is likely that the new one will be preferred for new executions.
1467 * Use with discretion.
1468 */
1469 /*non-public*/
1470 void updateForm(LambdaForm newForm) {
1471 if (form == newForm) return;
1472 // ISSUE: Should we have a memory fence here?
1473 UNSAFE.putObject(this, FORM_OFFSET, newForm);
1474 this.form.prepare(); // as in MethodHandle.<init>
1475 }
1476
1477 private static final long FORM_OFFSET;
1478 static {
1479 try {
1480 FORM_OFFSET = UNSAFE.objectFieldOffset(MethodHandle.class.getDeclaredField("form"));
1481 } catch (ReflectiveOperationException ex) {
1482 throw newInternalError(ex);
1483 }
1484 }
1485 }
|
974 * @throws NullPointerException if {@code arrayType} is a null reference
975 * @throws IllegalArgumentException if {@code arrayType} is not an array type
976 * or {@code arrayType} is not assignable to this method handle's trailing parameter type,
977 * or {@code arrayLength} is not a legal array size,
978 * or the resulting method handle's type would have
979 * <a href="MethodHandle.html#maxarity">too many parameters</a>
980 * @throws WrongMethodTypeException if the implied {@code asType} call fails
981 * @see #asSpreader
982 * @see #asVarargsCollector
983 */
984 public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
985 asCollectorChecks(arrayType, arrayLength);
986 int collectArgPos = type().parameterCount()-1;
987 MethodHandle target = this;
988 if (arrayType != type().parameterType(collectArgPos))
989 target = convertArguments(type().changeParameterType(collectArgPos, arrayType));
990 MethodHandle collector = MethodHandleImpl.varargsArray(arrayType, arrayLength);
991 return MethodHandles.collectArguments(target, collectArgPos, collector);
992 }
993
994 /**
995 * See if {@code asCollector} can be validly called with the given arguments.
996 * Return false if the last parameter is not an exact match to arrayType.
997 */
998 /*non-public*/ boolean asCollectorChecks(Class<?> arrayType, int arrayLength) {
999 spreadArrayChecks(arrayType, arrayLength);
1000 int nargs = type().parameterCount();
1001 if (nargs != 0) {
1002 Class<?> lastParam = type().parameterType(nargs-1);
1003 if (lastParam == arrayType) return true;
1004 if (lastParam.isAssignableFrom(arrayType)) return false;
1005 }
1006 throw newIllegalArgumentException("array type not assignable to trailing argument", this, arrayType);
1007 }
1008
1009 /**
1010 * Makes a <em>variable arity</em> adapter which is able to accept
1011 * any number of trailing positional arguments and collect them
1012 * into an array argument.
1013 * <p>
1014 * The type and behavior of the adapter will be the same as
1015 * the type and behavior of the target, except that certain
1016 * {@code invoke} and {@code asType} requests can lead to
1017 * trailing positional arguments being collected into target's
1018 * trailing parameter.
1140 * pre-collected arrays of any length. Users should be aware of the
1141 * special role of the final argument, and of the effect of a
1142 * type match on that final argument, which determines whether
1143 * or not a single trailing argument is interpreted as a whole
1144 * array or a single element of an array to be collected.
1145 * Note that the dynamic type of the trailing argument has no
1146 * effect on this decision, only a comparison between the symbolic
1147 * type descriptor of the call site and the type descriptor of the method handle.)
1148 *
1149 * @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
1150 * @return a new method handle which can collect any number of trailing arguments
1151 * into an array, before calling the original method handle
1152 * @throws NullPointerException if {@code arrayType} is a null reference
1153 * @throws IllegalArgumentException if {@code arrayType} is not an array type
1154 * or {@code arrayType} is not assignable to this method handle's trailing parameter type
1155 * @see #asCollector
1156 * @see #isVarargsCollector
1157 * @see #asFixedArity
1158 */
1159 public MethodHandle asVarargsCollector(Class<?> arrayType) {
1160 arrayType.getClass(); // explicit NPE
1161 boolean lastMatch = asCollectorChecks(arrayType, 0);
1162 if (isVarargsCollector() && lastMatch)
1163 return this;
1164 return MethodHandleImpl.makeVarargsCollector(this, arrayType);
1165 }
1166
1167 /**
1168 * Determines if this method handle
1169 * supports {@linkplain #asVarargsCollector variable arity} calls.
1170 * Such method handles arise from the following sources:
1171 * <ul>
1172 * <li>a call to {@linkplain #asVarargsCollector asVarargsCollector}
1173 * <li>a call to a {@linkplain java.lang.invoke.MethodHandles.Lookup lookup method}
1174 * which resolves to a variable arity Java method or constructor
1175 * <li>an {@code ldc} instruction of a {@code CONSTANT_MethodHandle}
1176 * which resolves to a variable arity Java method or constructor
1177 * </ul>
1178 * @return true if this method handle accepts more than one arity of plain, inexact {@code invoke} calls
1179 * @see #asVarargsCollector
1180 * @see #asFixedArity
1297 }
1298
1299 //// Implementation methods.
1300 //// Sub-classes can override these default implementations.
1301 //// All these methods assume arguments are already validated.
1302
1303 // Other transforms to do: convert, explicitCast, permute, drop, filter, fold, GWT, catch
1304
1305 /*non-public*/
1306 MethodHandle setVarargs(MemberName member) throws IllegalAccessException {
1307 if (!member.isVarargs()) return this;
1308 int argc = type().parameterCount();
1309 if (argc != 0) {
1310 Class<?> arrayType = type().parameterType(argc-1);
1311 if (arrayType.isArray()) {
1312 return MethodHandleImpl.makeVarargsCollector(this, arrayType);
1313 }
1314 }
1315 throw member.makeAccessException("cannot make variable arity", null);
1316 }
1317
1318 /*non-public*/
1319 MethodHandle viewAsType(MethodType newType) {
1320 // No actual conversions, just a new view of the same method.
1321 return MethodHandleImpl.makePairwiseConvert(this, newType, 0);
1322 }
1323
1324 // Decoding
1325
1326 /*non-public*/
1327 LambdaForm internalForm() {
1328 return form;
1329 }
1330
1331 /*non-public*/
1332 MemberName internalMemberName() {
1333 return null; // DMH returns DMH.member
1334 }
1335
1336 /*non-public*/
1337 Class<?> internalCallerClass() {
1456 private static final LambdaForm.NamedFunction NF_reinvokerTarget;
1457 static {
1458 try {
1459 NF_reinvokerTarget = new LambdaForm.NamedFunction(MethodHandle.class
1460 .getDeclaredMethod("reinvokerTarget"));
1461 } catch (ReflectiveOperationException ex) {
1462 throw newInternalError(ex);
1463 }
1464 }
1465
1466 /**
1467 * Replace the old lambda form of this method handle with a new one.
1468 * The new one must be functionally equivalent to the old one.
1469 * Threads may continue running the old form indefinitely,
1470 * but it is likely that the new one will be preferred for new executions.
1471 * Use with discretion.
1472 */
1473 /*non-public*/
1474 void updateForm(LambdaForm newForm) {
1475 if (form == newForm) return;
1476 assert(this instanceof DirectMethodHandle && this.internalMemberName().isStatic());
1477 // ISSUE: Should we have a memory fence here?
1478 UNSAFE.putObject(this, FORM_OFFSET, newForm);
1479 this.form.prepare(); // as in MethodHandle.<init>
1480 }
1481
1482 private static final long FORM_OFFSET;
1483 static {
1484 try {
1485 FORM_OFFSET = UNSAFE.objectFieldOffset(MethodHandle.class.getDeclaredField("form"));
1486 } catch (ReflectiveOperationException ex) {
1487 throw newInternalError(ex);
1488 }
1489 }
1490 }
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