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VarHandles.java
Vicente Romero authored
Co-authored-by: 
Brian Goetz <brian.goetz@oracle.com>
Reviewed-by: jrose, mcimadamore, darcy, mchung, rriggs, dholmes, forax VarHandles.java 25.38 KiB
/*
* Copyright (c) 2014, 2018, 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 java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import static java.lang.invoke.MethodHandleStatics.UNSAFE;
final class VarHandles {
static VarHandle makeFieldHandle(MemberName f, Class<?> refc, Class<?> type, boolean isWriteAllowedOnFinalFields) {
if (!f.isStatic()) {
long foffset = MethodHandleNatives.objectFieldOffset(f);
if (!type.isPrimitive()) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleReferences.FieldInstanceReadOnly(refc, foffset, type)
: new VarHandleReferences.FieldInstanceReadWrite(refc, foffset, type);
}
else if (type == boolean.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleBooleans.FieldInstanceReadOnly(refc, foffset)
: new VarHandleBooleans.FieldInstanceReadWrite(refc, foffset);
}
else if (type == byte.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleBytes.FieldInstanceReadOnly(refc, foffset)
: new VarHandleBytes.FieldInstanceReadWrite(refc, foffset);
}
else if (type == short.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleShorts.FieldInstanceReadOnly(refc, foffset)
: new VarHandleShorts.FieldInstanceReadWrite(refc, foffset);
}
else if (type == char.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleChars.FieldInstanceReadOnly(refc, foffset)
: new VarHandleChars.FieldInstanceReadWrite(refc, foffset);
}
else if (type == int.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleInts.FieldInstanceReadOnly(refc, foffset)
: new VarHandleInts.FieldInstanceReadWrite(refc, foffset);
}
else if (type == long.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleLongs.FieldInstanceReadOnly(refc, foffset) : new VarHandleLongs.FieldInstanceReadWrite(refc, foffset);
}
else if (type == float.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleFloats.FieldInstanceReadOnly(refc, foffset)
: new VarHandleFloats.FieldInstanceReadWrite(refc, foffset);
}
else if (type == double.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleDoubles.FieldInstanceReadOnly(refc, foffset)
: new VarHandleDoubles.FieldInstanceReadWrite(refc, foffset);
}
else {
throw new UnsupportedOperationException();
}
}
else {
// TODO This is not lazy on first invocation
// and might cause some circular initialization issues
// Replace with something similar to direct method handles
// where a barrier is used then elided after use
if (UNSAFE.shouldBeInitialized(refc))
UNSAFE.ensureClassInitialized(refc);
Object base = MethodHandleNatives.staticFieldBase(f);
long foffset = MethodHandleNatives.staticFieldOffset(f);
if (!type.isPrimitive()) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleReferences.FieldStaticReadOnly(base, foffset, type)
: new VarHandleReferences.FieldStaticReadWrite(base, foffset, type);
}
else if (type == boolean.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleBooleans.FieldStaticReadOnly(base, foffset)
: new VarHandleBooleans.FieldStaticReadWrite(base, foffset);
}
else if (type == byte.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleBytes.FieldStaticReadOnly(base, foffset)
: new VarHandleBytes.FieldStaticReadWrite(base, foffset);
}
else if (type == short.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleShorts.FieldStaticReadOnly(base, foffset)
: new VarHandleShorts.FieldStaticReadWrite(base, foffset);
}
else if (type == char.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleChars.FieldStaticReadOnly(base, foffset)
: new VarHandleChars.FieldStaticReadWrite(base, foffset);
}
else if (type == int.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleInts.FieldStaticReadOnly(base, foffset)
: new VarHandleInts.FieldStaticReadWrite(base, foffset);
}
else if (type == long.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleLongs.FieldStaticReadOnly(base, foffset)
: new VarHandleLongs.FieldStaticReadWrite(base, foffset);
}
else if (type == float.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields
? new VarHandleFloats.FieldStaticReadOnly(base, foffset)
: new VarHandleFloats.FieldStaticReadWrite(base, foffset);
}
else if (type == double.class) {
return f.isFinal() && !isWriteAllowedOnFinalFields ? new VarHandleDoubles.FieldStaticReadOnly(base, foffset)
: new VarHandleDoubles.FieldStaticReadWrite(base, foffset);
}
else {
throw new UnsupportedOperationException();
}
}
}
// Required by instance field handles
static Field getFieldFromReceiverAndOffset(Class<?> receiverType,
long offset,
Class<?> fieldType) {
for (Field f : receiverType.getDeclaredFields()) {
if (Modifier.isStatic(f.getModifiers())) continue;
if (offset == UNSAFE.objectFieldOffset(f)) {
assert f.getType() == fieldType;
return f;
}
}
throw new InternalError("Field not found at offset");
}
// Required by instance static field handles
static Field getStaticFieldFromBaseAndOffset(Object base,
long offset,
Class<?> fieldType) {
// @@@ This is a little fragile assuming the base is the class
Class<?> receiverType = (Class<?>) base;
for (Field f : receiverType.getDeclaredFields()) {
if (!Modifier.isStatic(f.getModifiers())) continue;
if (offset == UNSAFE.staticFieldOffset(f)) {
assert f.getType() == fieldType;
return f;
}
}
throw new InternalError("Static field not found at offset");
}
static VarHandle makeArrayElementHandle(Class<?> arrayClass) {
if (!arrayClass.isArray())
throw new IllegalArgumentException("not an array: " + arrayClass);
Class<?> componentType = arrayClass.getComponentType();
int aoffset = UNSAFE.arrayBaseOffset(arrayClass);
int ascale = UNSAFE.arrayIndexScale(arrayClass);
int ashift = 31 - Integer.numberOfLeadingZeros(ascale);
if (!componentType.isPrimitive()) {
return new VarHandleReferences.Array(aoffset, ashift, arrayClass);
}
else if (componentType == boolean.class) {
return new VarHandleBooleans.Array(aoffset, ashift);
}
else if (componentType == byte.class) {
return new VarHandleBytes.Array(aoffset, ashift);
}
else if (componentType == short.class) {
return new VarHandleShorts.Array(aoffset, ashift);
}
else if (componentType == char.class) {
return new VarHandleChars.Array(aoffset, ashift);
}
else if (componentType == int.class) {
return new VarHandleInts.Array(aoffset, ashift);
}
else if (componentType == long.class) { return new VarHandleLongs.Array(aoffset, ashift);
}
else if (componentType == float.class) {
return new VarHandleFloats.Array(aoffset, ashift);
}
else if (componentType == double.class) {
return new VarHandleDoubles.Array(aoffset, ashift);
}
else {
throw new UnsupportedOperationException();
}
}
static VarHandle byteArrayViewHandle(Class<?> viewArrayClass,
boolean be) {
if (!viewArrayClass.isArray())
throw new IllegalArgumentException("not an array: " + viewArrayClass);
Class<?> viewComponentType = viewArrayClass.getComponentType();
if (viewComponentType == long.class) {
return new VarHandleByteArrayAsLongs.ArrayHandle(be);
}
else if (viewComponentType == int.class) {
return new VarHandleByteArrayAsInts.ArrayHandle(be);
}
else if (viewComponentType == short.class) {
return new VarHandleByteArrayAsShorts.ArrayHandle(be);
}
else if (viewComponentType == char.class) {
return new VarHandleByteArrayAsChars.ArrayHandle(be);
}
else if (viewComponentType == double.class) {
return new VarHandleByteArrayAsDoubles.ArrayHandle(be);
}
else if (viewComponentType == float.class) {
return new VarHandleByteArrayAsFloats.ArrayHandle(be);
}
throw new UnsupportedOperationException();
}
static VarHandle makeByteBufferViewHandle(Class<?> viewArrayClass,
boolean be) {
if (!viewArrayClass.isArray())
throw new IllegalArgumentException("not an array: " + viewArrayClass);
Class<?> viewComponentType = viewArrayClass.getComponentType();
if (viewComponentType == long.class) {
return new VarHandleByteArrayAsLongs.ByteBufferHandle(be);
}
else if (viewComponentType == int.class) {
return new VarHandleByteArrayAsInts.ByteBufferHandle(be);
}
else if (viewComponentType == short.class) {
return new VarHandleByteArrayAsShorts.ByteBufferHandle(be);
}
else if (viewComponentType == char.class) {
return new VarHandleByteArrayAsChars.ByteBufferHandle(be);
}
else if (viewComponentType == double.class) {
return new VarHandleByteArrayAsDoubles.ByteBufferHandle(be);
}
else if (viewComponentType == float.class) {
return new VarHandleByteArrayAsFloats.ByteBufferHandle(be);
}
throw new UnsupportedOperationException();
}
// /**
// * A helper program to generate the VarHandleGuards class with a set of
// * static guard methods each of which corresponds to a particular shape and
// * performs a type check of the symbolic type descriptor with the VarHandle
// * type descriptor before linking/invoking to the underlying operation as
// * characterized by the operation member name on the VarForm of the
// * VarHandle.
// * <p>
// * The generated class essentially encapsulates pre-compiled LambdaForms,
// * one for each method, for the most set of common method signatures.
// * This reduces static initialization costs, footprint costs, and circular
// * dependencies that may arise if a class is generated per LambdaForm.
// * <p>
// * A maximum of L*T*S methods will be generated where L is the number of
// * access modes kinds (or unique operation signatures) and T is the number
// * of variable types and S is the number of shapes (such as instance field,
// * static field, or array access).
// * If there are 4 unique operation signatures, 5 basic types (Object, int,
// * long, float, double), and 3 shapes then a maximum of 60 methods will be
// * generated. However, the number is likely to be less since there
// * be duplicate signatures.
// * <p>
// * Each method is annotated with @LambdaForm.Compiled to inform the runtime
// * that such methods should be treated as if a method of a class that is the
// * result of compiling a LambdaForm. Annotation of such methods is
// * important for correct evaluation of certain assertions and method return
// * type profiling in HotSpot.
// */
// public static class GuardMethodGenerator {
//
// static final String GUARD_METHOD_SIG_TEMPLATE = "<RETURN> <NAME>_<SIGNATURE>(<PARAMS>)";
//
// static final String GUARD_METHOD_TEMPLATE =
// "@ForceInline\n" +
// "@LambdaForm.Compiled\n" +
// "final static <METHOD> throws Throwable {\n" +
// " if (handle.vform.methodType_table[ad.type] == ad.symbolicMethodType) {\n" +
// " <RESULT_ERASED>MethodHandle.linkToStatic(<LINK_TO_STATIC_ARGS>);<RETURN_ERASED>\n" +
// " }\n" +
// " else {\n" +
// " MethodHandle mh = handle.getMethodHandle(ad.mode);\n" +
// " <RETURN>mh.asType(ad.symbolicMethodTypeInvoker).invokeBasic(<LINK_TO_INVOKER_ARGS>);\n" +
// " }\n" +
// "}";
//
// static final String GUARD_METHOD_TEMPLATE_V =
// "@ForceInline\n" +
// "@LambdaForm.Compiled\n" +
// "final static <METHOD> throws Throwable {\n" +
// " if (handle.vform.methodType_table[ad.type] == ad.symbolicMethodType) {\n" +
// " MethodHandle.linkToStatic(<LINK_TO_STATIC_ARGS>);\n" +
// " }\n" +
// " else if (handle.vform.getMethodType_V(ad.type) == ad.symbolicMethodType) {\n" +
// " MethodHandle.linkToStatic(<LINK_TO_STATIC_ARGS>);\n" +
// " }\n" +
// " else {\n" +
// " MethodHandle mh = handle.getMethodHandle(ad.mode);\n" +
// " mh.asType(ad.symbolicMethodTypeInvoker).invokeBasic(<LINK_TO_INVOKER_ARGS>);\n" +
// " }\n" +
// "}";
//
// // A template for deriving the operations
// // could be supported by annotating VarHandle directly with the
// // operation kind and shape
// interface VarHandleTemplate {
// Object get();
//
// void set(Object value);
//// boolean compareAndSet(Object actualValue, Object expectedValue);
//
// Object compareAndExchange(Object actualValue, Object expectedValue);
//
// Object getAndUpdate(Object value);
// }
//
// static class HandleType {
// final Class<?> receiver;
// final Class<?>[] intermediates;
// final Class<?> value;
//
// HandleType(Class<?> receiver, Class<?> value, Class<?>... intermediates) {
// this.receiver = receiver;
// this.intermediates = intermediates;
// this.value = value;
// }
// }
//
// /**
// * @param args parameters
// */
// public static void main(String[] args) {
// System.out.println("package java.lang.invoke;");
// System.out.println();
// System.out.println("import jdk.internal.vm.annotation.ForceInline;");
// System.out.println();
// System.out.println("// This class is auto-generated by " +
// GuardMethodGenerator.class.getName() +
// ". Do not edit.");
// System.out.println("final class VarHandleGuards {");
//
// System.out.println();
//
// // Declare the stream of shapes
// Stream<HandleType> hts = Stream.of(
// // Object->Object
// new HandleType(Object.class, Object.class),
// // Object->int
// new HandleType(Object.class, int.class),
// // Object->long
// new HandleType(Object.class, long.class),
// // Object->float
// new HandleType(Object.class, float.class),
// // Object->double
// new HandleType(Object.class, double.class),
//
// // <static>->Object
// new HandleType(null, Object.class),
// // <static>->int
// new HandleType(null, int.class),
// // <static>->long
// new HandleType(null, long.class),
// // <static>->float
// new HandleType(null, float.class),
// // <static>->double
// new HandleType(null, double.class),
//
// // Array[int]->Object
// new HandleType(Object.class, Object.class, int.class),
// // Array[int]->int
// new HandleType(Object.class, int.class, int.class),
// // Array[int]->long
// new HandleType(Object.class, long.class, int.class),
// // Array[int]->float
// new HandleType(Object.class, float.class, int.class),
// // Array[int]->double
// new HandleType(Object.class, double.class, int.class),
//
// // Array[long]->int// new HandleType(Object.class, int.class, long.class),
// // Array[long]->long
// new HandleType(Object.class, long.class, long.class)
// );
//
// hts.flatMap(ht -> Stream.of(VarHandleTemplate.class.getMethods()).
// map(m -> generateMethodType(m, ht.receiver, ht.value, ht.intermediates))).
// distinct().
// map(mt -> generateMethod(mt)).
// forEach(s -> {
// System.out.println(s);
// System.out.println();
// });
//
// System.out.println("}");
// }
//
// static MethodType generateMethodType(Method m, Class<?> receiver, Class<?> value, Class<?>... intermediates) {
// Class<?> returnType = m.getReturnType() == Object.class
// ? value : m.getReturnType();
//
// List<Class<?>> params = new ArrayList<>();
// if (receiver != null)
// params.add(receiver);
// for (int i = 0; i < intermediates.length; i++) {
// params.add(intermediates[i]);
// }
// for (Parameter p : m.getParameters()) {
// params.add(value);
// }
// return MethodType.methodType(returnType, params);
// }
//
// static String generateMethod(MethodType mt) {
// Class<?> returnType = mt.returnType();
//
// LinkedHashMap<String, Class<?>> params = new LinkedHashMap<>();
// params.put("handle", VarHandle.class);
// for (int i = 0; i < mt.parameterCount(); i++) {
// params.put("arg" + i, mt.parameterType(i));
// }
// params.put("ad", VarHandle.AccessDescriptor.class);
//
// // Generate method signature line
// String RETURN = className(returnType);
// String NAME = "guard";
// String SIGNATURE = getSignature(mt);
// String PARAMS = params.entrySet().stream().
// map(e -> className(e.getValue()) + " " + e.getKey()).
// collect(joining(", "));
// String METHOD = GUARD_METHOD_SIG_TEMPLATE.
// replace("<RETURN>", RETURN).
// replace("<NAME>", NAME).
// replace("<SIGNATURE>", SIGNATURE).
// replace("<PARAMS>", PARAMS);
//
// // Generate method
// params.remove("ad");
//
// List<String> LINK_TO_STATIC_ARGS = params.keySet().stream().
// collect(toList());
// LINK_TO_STATIC_ARGS.add("handle.vform.getMemberName(ad.mode)");
// List<String> LINK_TO_STATIC_ARGS_V = params.keySet().stream().
// collect(toList());
// LINK_TO_STATIC_ARGS_V.add("handle.vform.getMemberName_V(ad.mode)");
//
// List<String> LINK_TO_INVOKER_ARGS = params.keySet().stream().
// collect(toList());
//
// RETURN = returnType == void.class// ? ""
// : returnType == Object.class
// ? "return "
// : "return (" + returnType.getName() + ") ";
//
// String RESULT_ERASED = returnType == void.class
// ? ""
// : returnType != Object.class
// ? "return (" + returnType.getName() + ") "
// : "Object r = ";
//
// String RETURN_ERASED = returnType != Object.class
// ? ""
// : " return ad.returnType.cast(r);";
//
// String template = returnType == void.class
// ? GUARD_METHOD_TEMPLATE_V
// : GUARD_METHOD_TEMPLATE;
// return template.
// replace("<METHOD>", METHOD).
// replace("<NAME>", NAME).
// replaceAll("<RETURN>", RETURN).
// replace("<RESULT_ERASED>", RESULT_ERASED).
// replace("<RETURN_ERASED>", RETURN_ERASED).
// replaceAll("<LINK_TO_STATIC_ARGS>", LINK_TO_STATIC_ARGS.stream().
// collect(joining(", "))).
// replaceAll("<LINK_TO_STATIC_ARGS_V>", LINK_TO_STATIC_ARGS_V.stream().
// collect(joining(", "))).
// replace("<LINK_TO_INVOKER_ARGS>", LINK_TO_INVOKER_ARGS.stream().
// collect(joining(", ")))
// ;
// }
//
// static String className(Class<?> c) {
// String n = c.getName();
// if (n.startsWith("java.lang.")) {
// n = n.replace("java.lang.", "");
// if (n.startsWith("invoke.")) {
// n = n.replace("invoke.", "");
// }
// }
// return n.replace('$', '.');
// }
//
// static String getSignature(MethodType m) {
// StringBuilder sb = new StringBuilder(m.parameterCount() + 1);
//
// for (int i = 0; i < m.parameterCount(); i++) {
// Class<?> pt = m.parameterType(i);
// sb.append(getCharType(pt));
// }
//
// sb.append('_').append(getCharType(m.returnType()));
//
// return sb.toString();
// }
//
// static char getCharType(Class<?> pt) {
// if (pt == void.class) {
// return 'V';
// }
// else if (!pt.isPrimitive()) {
// return 'L';
// }
// else if (pt == boolean.class) {
// return 'Z';
// }
// else if (pt == int.class) {
// return 'I';
// }// else if (pt == long.class) {
// return 'J';
// }
// else if (pt == float.class) {
// return 'F';
// }
// else if (pt == double.class) {
// return 'D';
// }
// else {
// throw new IllegalStateException(pt.getName());
// }
// }
// }
}