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* Copyright (c) 2017, 2023, 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).
*
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*
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package java.lang.runtime;
import java.lang.Enum.EnumDesc;
import java.lang.constant.ClassDesc;
import java.lang.constant.ConstantDescs;
import java.lang.constant.MethodTypeDesc;
import java.lang.invoke.CallSite;
import java.lang.invoke.ConstantCallSite;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.AccessFlag;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.function.BiPredicate;
import java.util.stream.Stream;
import jdk.internal.access.SharedSecrets;
import jdk.internal.classfile.Classfile;
import jdk.internal.classfile.Label;
import jdk.internal.classfile.instruction.SwitchCase;
import jdk.internal.vm.annotation.Stable;
import static java.lang.invoke.MethodHandles.Lookup.ClassOption.NESTMATE;
import static java.lang.invoke.MethodHandles.Lookup.ClassOption.STRONG;
import static java.util.Objects.requireNonNull;
/**
* Bootstrap methods for linking {@code invokedynamic} call sites that implement
* the selection functionality of the {@code switch} statement. The bootstraps
* take additional static arguments corresponding to the {@code case} labels
* of the {@code switch}, implicitly numbered sequentially from {@code [0..N)}.
*
* @since 21
*/
public class SwitchBootstraps {
private SwitchBootstraps() {}
private static final Object SENTINEL = new Object();
private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
private static final MethodHandle NULL_CHECK;
private static final MethodHandle IS_ZERO;
private static final MethodHandle CHECK_INDEX;
private static final MethodHandle MAPPED_ENUM_LOOKUP;
private static final MethodTypeDesc TYPES_SWITCH_DESCRIPTOR =
MethodTypeDesc.ofDescriptor("(Ljava/lang/Object;ILjava/util/function/BiPredicate;Ljava/util/List;)I");
static {
try {
NULL_CHECK = LOOKUP.findStatic(Objects.class, "isNull",
MethodType.methodType(boolean.class, Object.class));
IS_ZERO = LOOKUP.findStatic(SwitchBootstraps.class, "isZero",
MethodType.methodType(boolean.class, int.class));
CHECK_INDEX = LOOKUP.findStatic(Objects.class, "checkIndex",
MethodType.methodType(int.class, int.class, int.class));
MAPPED_ENUM_LOOKUP = LOOKUP.findStatic(SwitchBootstraps.class, "mappedEnumLookup",
MethodType.methodType(int.class, Enum.class, MethodHandles.Lookup.class,
Class.class, EnumDesc[].class, EnumMap.class));
}
catch (ReflectiveOperationException e) {
throw new ExceptionInInitializerError(e);
}
}
/**
* Bootstrap method for linking an {@code invokedynamic} call site that
* implements a {@code switch} on a target of a reference type. The static
* arguments are an array of case labels which must be non-null and of type
* {@code String} or {@code Integer} or {@code Class} or {@code EnumDesc}.
*
* The type of the returned {@code CallSite}'s method handle will have
* a return type of {@code int}. It has two parameters: the first argument
* will be an {@code Object} instance ({@code target}) and the second
* will be {@code int} ({@code restart}).
*
* If the {@code target} is {@code null}, then the method of the call site
* returns {@literal -1}.
*
* If the {@code target} is not {@code null}, then the method of the call site
* returns the index of the first element in the {@code labels} array starting from
* the {@code restart} index matching one of the following conditions:
*
* - the element is of type {@code Class} that is assignable
* from the target's class; or
* - the element is of type {@code String} or {@code Integer} and
* equals to the target.
* - the element is of type {@code EnumDesc}, that describes a constant that is
* equals to the target.
*
*
* If no element in the {@code labels} array matches the target, then
* the method of the call site return the length of the {@code labels} array.
*
* The value of the {@code restart} index must be between {@code 0} (inclusive) and
* the length of the {@code labels} array (inclusive),
* both or an {@link IndexOutOfBoundsException} is thrown.
*
* @param lookup Represents a lookup context with the accessibility
* privileges of the caller. When used with {@code invokedynamic},
* this is stacked automatically by the VM.
* @param invocationName unused
* @param invocationType The invocation type of the {@code CallSite} with two parameters,
* a reference type, an {@code int}, and {@code int} as a return type.
* @param labels case labels - {@code String} and {@code Integer} constants
* and {@code Class} and {@code EnumDesc} instances, in any combination
* @return a {@code CallSite} returning the first matching element as described above
*
* @throws NullPointerException if any argument is {@code null}
* @throws IllegalArgumentException if any element in the labels array is null, if the
* invocation type is not not a method type of first parameter of a reference type,
* second parameter of type {@code int} and with {@code int} as its return type,
* or if {@code labels} contains an element that is not of type {@code String},
* {@code Integer}, {@code Class} or {@code EnumDesc}.
* @jvms 4.4.6 The CONSTANT_NameAndType_info Structure
* @jvms 4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures
*/
public static CallSite typeSwitch(MethodHandles.Lookup lookup,
String invocationName,
MethodType invocationType,
Object... labels) {
if (invocationType.parameterCount() != 2
|| (!invocationType.returnType().equals(int.class))
|| invocationType.parameterType(0).isPrimitive()
|| !invocationType.parameterType(1).equals(int.class))
throw new IllegalArgumentException("Illegal invocation type " + invocationType);
requireNonNull(labels);
labels = labels.clone();
Stream.of(labels).forEach(SwitchBootstraps::verifyLabel);
MethodHandle target = generateInnerClass(lookup, labels);
target = withIndexCheck(target, labels.length);
return new ConstantCallSite(target);
}
private static void verifyLabel(Object label) {
if (label == null) {
throw new IllegalArgumentException("null label found");
}
Class labelClass = label.getClass();
if (labelClass != Class.class &&
labelClass != String.class &&
labelClass != Integer.class &&
labelClass != EnumDesc.class) {
throw new IllegalArgumentException("label with illegal type found: " + label.getClass());
}
}
private static boolean isZero(int value) {
return value == 0;
}
/**
* Bootstrap method for linking an {@code invokedynamic} call site that
* implements a {@code switch} on a target of an enum type. The static
* arguments are used to encode the case labels associated to the switch
* construct, where each label can be encoded in two ways:
*
* - as a {@code String} value, which represents the name of
* the enum constant associated with the label
* - as a {@code Class} value, which represents the enum type
* associated with a type test pattern
*
*
* The returned {@code CallSite}'s method handle will have
* a return type of {@code int} and accepts two parameters: the first argument
* will be an {@code Enum} instance ({@code target}) and the second
* will be {@code int} ({@code restart}).
*
* If the {@code target} is {@code null}, then the method of the call site
* returns {@literal -1}.
*
* If the {@code target} is not {@code null}, then the method of the call site
* returns the index of the first element in the {@code labels} array starting from
* the {@code restart} index matching one of the following conditions:
*
* - the element is of type {@code Class} that is assignable
* from the target's class; or
* - the element is of type {@code String} and equals to the target
* enum constant's {@link Enum#name()}.
*
*
* If no element in the {@code labels} array matches the target, then
* the method of the call site return the length of the {@code labels} array.
*
* The value of the {@code restart} index must be between {@code 0} (inclusive) and
* the length of the {@code labels} array (inclusive),
* both or an {@link IndexOutOfBoundsException} is thrown.
*
* @param lookup Represents a lookup context with the accessibility
* privileges of the caller. When used with {@code invokedynamic},
* this is stacked automatically by the VM.
* @param invocationName unused
* @param invocationType The invocation type of the {@code CallSite} with two parameters,
* an enum type, an {@code int}, and {@code int} as a return type.
* @param labels case labels - {@code String} constants and {@code Class} instances,
* in any combination
* @return a {@code CallSite} returning the first matching element as described above
*
* @throws NullPointerException if any argument is {@code null}
* @throws IllegalArgumentException if any element in the labels array is null, if the
* invocation type is not a method type whose first parameter type is an enum type,
* second parameter of type {@code int} and whose return type is {@code int},
* or if {@code labels} contains an element that is not of type {@code String} or
* {@code Class} of the target enum type.
* @jvms 4.4.6 The CONSTANT_NameAndType_info Structure
* @jvms 4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures
*/
public static CallSite enumSwitch(MethodHandles.Lookup lookup,
String invocationName,
MethodType invocationType,
Object... labels) {
if (invocationType.parameterCount() != 2
|| (!invocationType.returnType().equals(int.class))
|| invocationType.parameterType(0).isPrimitive()
|| !invocationType.parameterType(0).isEnum()
|| !invocationType.parameterType(1).equals(int.class))
throw new IllegalArgumentException("Illegal invocation type " + invocationType);
requireNonNull(labels);
labels = labels.clone();
Class enumClass = invocationType.parameterType(0);
labels = Stream.of(labels).map(l -> convertEnumConstants(lookup, enumClass, l)).toArray();
MethodHandle target;
boolean constantsOnly = Stream.of(labels).allMatch(l -> enumClass.isAssignableFrom(EnumDesc.class));
if (labels.length > 0 && constantsOnly) {
//If all labels are enum constants, construct an optimized handle for repeat index 0:
//if (selector == null) return -1
//else if (idx == 0) return mappingArray[selector.ordinal()]; //mapping array created lazily
//else return "typeSwitch(labels)"
MethodHandle body =
MethodHandles.guardWithTest(MethodHandles.dropArguments(NULL_CHECK, 0, int.class),
MethodHandles.dropArguments(MethodHandles.constant(int.class, -1), 0, int.class, Object.class),
MethodHandles.guardWithTest(MethodHandles.dropArguments(IS_ZERO, 1, Object.class),
generateInnerClass(lookup, labels),
MethodHandles.insertArguments(MAPPED_ENUM_LOOKUP, 1, lookup, enumClass, labels, new EnumMap())));
target = MethodHandles.permuteArguments(body, MethodType.methodType(int.class, Object.class, int.class), 1, 0);
} else {
target = generateInnerClass(lookup, labels);
}
target = target.asType(invocationType);
target = withIndexCheck(target, labels.length);
return new ConstantCallSite(target);
}
private static > Object convertEnumConstants(MethodHandles.Lookup lookup, Class enumClassTemplate, Object label) {
if (label == null) {
throw new IllegalArgumentException("null label found");
}
Class labelClass = label.getClass();
if (labelClass == Class.class) {
if (label != enumClassTemplate) {
throw new IllegalArgumentException("the Class label: " + label +
", expected the provided enum class: " + enumClassTemplate);
}
return label;
} else if (labelClass == String.class) {
return EnumDesc.of(enumClassTemplate.describeConstable().orElseThrow(), (String) label);
} else {
throw new IllegalArgumentException("label with illegal type found: " + labelClass +
", expected label of type either String or Class");
}
}
private static > int mappedEnumLookup(T value, MethodHandles.Lookup lookup, Class enumClass, EnumDesc[] labels, EnumMap enumMap) {
if (enumMap.map == null) {
T[] constants = SharedSecrets.getJavaLangAccess().getEnumConstantsShared(enumClass);
int[] map = new int[constants.length];
int ordinal = 0;
for (T constant : constants) {
map[ordinal] = labels.length;
for (int i = 0; i < labels.length; i++) {
if (Objects.equals(labels[i].constantName(), constant.name())) {
map[ordinal] = i;
break;
}
}
ordinal++;
}
}
return enumMap.map[value.ordinal()];
}
private static MethodHandle withIndexCheck(MethodHandle target, int labelsCount) {
MethodHandle checkIndex = MethodHandles.insertArguments(CHECK_INDEX, 1, labelsCount + 1);
return MethodHandles.filterArguments(target, 1, checkIndex);
}
private static final class ResolvedEnumLabels implements BiPredicate {
private final MethodHandles.Lookup lookup;
private final EnumDesc[] enumDescs;
@Stable
private Object[] resolvedEnum;
public ResolvedEnumLabels(MethodHandles.Lookup lookup, EnumDesc[] enumDescs) {
this.lookup = lookup;
this.enumDescs = enumDescs;
this.resolvedEnum = new Object[enumDescs.length];
}
@Override
public boolean test(Integer labelIndex, Object value) {
Object result = resolvedEnum[labelIndex];
if (result == null) {
try {
if (!(value instanceof Enum enumValue)) {
return false;
}
EnumDesc label = enumDescs[labelIndex];
Class clazz = label.constantType().resolveConstantDesc(lookup);
if (enumValue.getDeclaringClass() != clazz) {
return false;
}
result = label.resolveConstantDesc(lookup);
} catch (IllegalArgumentException | ReflectiveOperationException ex) {
result = SENTINEL;
}
resolvedEnum[labelIndex] = result;
}
return result == value;
}
}
private static final class EnumMap {
@Stable
public int[] map;
}
/*
* Construct test chains for labels inside switch, to handle switch repeats:
* switch (idx) {
* case 0 -> if (selector matches label[0]) return 0;
* case 1 -> if (selector matches label[1]) return 1;
* ...
* }
*/
@SuppressWarnings("removal")
private static MethodHandle generateInnerClass(MethodHandles.Lookup caller, Object[] labels) {
List> enumDescs = new ArrayList<>();
List> extraClassLabels = new ArrayList<>();
byte[] classBytes = Classfile.of().build(ClassDesc.of(typeSwitchClassName(caller.lookupClass())), clb -> {
clb.withFlags(AccessFlag.FINAL, AccessFlag.SUPER, AccessFlag.SYNTHETIC)
.withMethodBody("typeSwitch",
TYPES_SWITCH_DESCRIPTOR,
Classfile.ACC_FINAL | Classfile.ACC_PUBLIC | Classfile.ACC_STATIC,
cb -> {
cb.aload(0);
Label nonNullLabel = cb.newLabel();
cb.if_nonnull(nonNullLabel);
cb.iconst_m1();
cb.ireturn();
cb.labelBinding(nonNullLabel);
if (labels.length == 0) {
cb.constantInstruction(0)
.ireturn();
return ;
}
cb.iload(1);
Label dflt = cb.newLabel();
record Element(Label target, Label next, Object caseLabel) {}
List cases = new ArrayList<>();
List switchCases = new ArrayList<>();
Object lastLabel = null;
for (int idx = labels.length - 1; idx >= 0; idx--) {
Object currentLabel = labels[idx];
Label target = cb.newLabel();
Label next;
if (lastLabel == null) {
next = dflt;
} else if (lastLabel.equals(currentLabel)) {
next = cases.getLast().next();
} else {
next = cases.getLast().target();
}
lastLabel = currentLabel;
cases.add(new Element(target, next, currentLabel));
switchCases.add(SwitchCase.of(idx, target));
}
cases = cases.reversed();
switchCases = switchCases.reversed();
cb.tableswitch(0, labels.length - 1, dflt, switchCases);
for (int idx = 0; idx < cases.size(); idx++) {
Element element = cases.get(idx);
Label next = element.next();
cb.labelBinding(element.target());
if (element.caseLabel() instanceof Class classLabel) {
Optional classLabelConstableOpt = classLabel.describeConstable();
if (classLabelConstableOpt.isPresent()) {
cb.aload(0);
cb.instanceof_(classLabelConstableOpt.orElseThrow());
cb.ifeq(next);
} else {
cb.aload(3);
cb.constantInstruction(extraClassLabels.size());
cb.invokeinterface(ConstantDescs.CD_List,
"get",
MethodTypeDesc.of(ConstantDescs.CD_Object,
ConstantDescs.CD_int));
cb.checkcast(ConstantDescs.CD_Class);
cb.aload(0);
cb.invokevirtual(ConstantDescs.CD_Class,
"isInstance",
MethodTypeDesc.of(ConstantDescs.CD_boolean,
ConstantDescs.CD_Object));
cb.ifeq(next);
extraClassLabels.add(classLabel);
}
} else if (element.caseLabel() instanceof EnumDesc enumLabel) {
int enumIdx = enumDescs.size();
enumDescs.add(enumLabel);
cb.aload(2);
cb.constantInstruction(enumIdx);
cb.invokestatic(ConstantDescs.CD_Integer,
"valueOf",
MethodTypeDesc.of(ConstantDescs.CD_Integer,
ConstantDescs.CD_int));
cb.aload(0);
cb.invokeinterface(BiPredicate.class.describeConstable().orElseThrow(),
"test",
MethodTypeDesc.of(ConstantDescs.CD_boolean,
ConstantDescs.CD_Object,
ConstantDescs.CD_Object));
cb.ifeq(next);
} else if (element.caseLabel() instanceof String stringLabel) {
cb.ldc(stringLabel);
cb.aload(0);
cb.invokevirtual(ConstantDescs.CD_Object,
"equals",
MethodTypeDesc.of(ConstantDescs.CD_boolean,
ConstantDescs.CD_Object));
cb.ifeq(next);
} else if (element.caseLabel() instanceof Integer integerLabel) {
Label compare = cb.newLabel();
Label notNumber = cb.newLabel();
cb.aload(0);
cb.instanceof_(ConstantDescs.CD_Number);
cb.ifeq(notNumber);
cb.aload(0);
cb.checkcast(ConstantDescs.CD_Number);
cb.invokevirtual(ConstantDescs.CD_Number,
"intValue",
MethodTypeDesc.of(ConstantDescs.CD_int));
cb.goto_(compare);
cb.labelBinding(notNumber);
cb.aload(0);
cb.instanceof_(ConstantDescs.CD_Character);
cb.ifeq(next);
cb.aload(0);
cb.checkcast(ConstantDescs.CD_Character);
cb.invokevirtual(ConstantDescs.CD_Character,
"charValue",
MethodTypeDesc.of(ConstantDescs.CD_char));
cb.labelBinding(compare);
cb.ldc(integerLabel);
cb.if_icmpne(next);
} else {
throw new InternalError("Unsupported label type: " +
element.caseLabel().getClass());
}
cb.constantInstruction(idx);
cb.ireturn();
}
cb.labelBinding(dflt);
cb.constantInstruction(cases.size());
cb.ireturn();
});
});
try {
// this class is linked at the indy callsite; so define a hidden nestmate
MethodHandles.Lookup lookup;
lookup = caller.defineHiddenClass(classBytes, true, NESTMATE, STRONG);
MethodHandle typeSwitch = lookup.findStatic(lookup.lookupClass(),
"typeSwitch",
MethodType.methodType(int.class,
Object.class,
int.class,
BiPredicate.class,
List.class));
return MethodHandles.insertArguments(typeSwitch, 2, new ResolvedEnumLabels(caller, enumDescs.toArray(EnumDesc[]::new)),
List.copyOf(extraClassLabels));
} catch (Throwable t) {
throw new IllegalArgumentException(t);
}
}
//based on src/java.base/share/classes/java/lang/invoke/InnerClassLambdaMetafactory.java:
private static String typeSwitchClassName(Class targetClass) {
String name = targetClass.getName();
if (targetClass.isHidden()) {
// use the original class name
name = name.replace('/', '_');
}
return name + "$$TypeSwitch";
}
}