Back to index...

	/*
	* Copyright (c) 2017, 2021, 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 jdk.internal.access.SharedSecrets;
	import jdk.internal.loader.BootLoader;
	import jdk.internal.org.objectweb.asm.ClassWriter;
	import jdk.internal.org.objectweb.asm.FieldVisitor;
	import jdk.internal.org.objectweb.asm.MethodVisitor;
	import jdk.internal.vm.annotation.Stable;
	import sun.invoke.util.BytecodeName;

	import java.lang.reflect.Constructor;
	import java.lang.reflect.Field;
	import java.lang.reflect.Modifier;
	import java.security.AccessController;
	import java.security.PrivilegedAction;
	import java.security.ProtectionDomain;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.List;
	import java.util.Objects;
	import java.util.concurrent.ConcurrentHashMap;
	import java.util.function.Function;

	import static java.lang.invoke.LambdaForm.*;
	import static java.lang.invoke.MethodHandleNatives.Constants.REF_getStatic;
	import static java.lang.invoke.MethodHandleNatives.Constants.REF_putStatic;
	import static java.lang.invoke.MethodHandleStatics.*;
	import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
	import static jdk.internal.org.objectweb.asm.Opcodes.*;

	/**
	* Class specialization code.
	* @param <T> top class under which species classes are created.
	* @param <K> key which identifies individual specializations.
	* @param <S> species data type.
	*/
	/non-public/
	abstract class ClassSpecializer<T,K,S extends ClassSpecializer<T,K,S>.SpeciesData> {
	private final Class<T> topClass;
	private final Class<K> keyType;
	private final Class<S> metaType;
	private final MemberName sdAccessor;
	private final String sdFieldName;
	private final List<MemberName> transformMethods;
	private final MethodType baseConstructorType;
	private final S topSpecies;
	private final ConcurrentHashMap<K, Object> cache = new ConcurrentHashMap<>();
	private final Factory factory;
	private @Stable boolean topClassIsSuper;

	/** Return the top type mirror, for type {@code T} */
	public final Class<T> topClass() { return topClass; }

	/** Return the key type mirror, for type {@code K} */
	public final Class<K> keyType() { return keyType; }

	/** Return the species metadata type mirror, for type {@code S} */
	public final Class<S> metaType() { return metaType; }

	/** Report the leading arguments (if any) required by every species factory.
	* Every species factory adds its own field types as additional arguments,
	* but these arguments always come first, in every factory method.
	*/
	protected MethodType baseConstructorType() { return baseConstructorType; }

	/** Return the trivial species for the null sequence of arguments. */
	protected final S topSpecies() { return topSpecies; }

	/** Return the list of transform methods originally given at creation of this specializer. */
	protected final List<MemberName> transformMethods() { return transformMethods; }

	/** Return the factory object used to build and load concrete species code. */
	protected final Factory factory() { return factory; }

	/**
	* Constructor for this class specializer.
	* @param topClass type mirror for T
	* @param keyType type mirror for K
	* @param metaType type mirror for S
	* @param baseConstructorType principal constructor type
	* @param sdAccessor the method used to get the speciesData
	* @param sdFieldName the name of the species data field, inject the speciesData object
	* @param transformMethods optional list of transformMethods
	*/
	protected ClassSpecializer(Class<T> topClass,
	Class<K> keyType,
	Class<S> metaType,
	MethodType baseConstructorType,
	MemberName sdAccessor,
	String sdFieldName,
	List<MemberName> transformMethods) {
	this.topClass = topClass;
	this.keyType = keyType;
	this.metaType = metaType;
	this.sdAccessor = sdAccessor;
	this.transformMethods = List.copyOf(transformMethods);
	this.sdFieldName = sdFieldName;
	this.baseConstructorType = baseConstructorType.changeReturnType(void.class);
	this.factory = makeFactory();
	K tsk = topSpeciesKey();
	S topSpecies = null;
	if (tsk != null && topSpecies == null) {
	// if there is a key, build the top species if needed:
	topSpecies = findSpecies(tsk);
	}
	this.topSpecies = topSpecies;
	}

	// Utilities for subclass constructors:
	protected static <T> Constructor<T> reflectConstructor(Class<T> defc, Class<?>... ptypes) {
	try {
	return defc.getDeclaredConstructor(ptypes);
	} catch (NoSuchMethodException ex) {
	throw newIAE(defc.getName()+"("+MethodType.methodType(void.class, ptypes)+")", ex);
	}
	}

	protected static Field reflectField(Class<?> defc, String name) {
	try {
	return defc.getDeclaredField(name);
	} catch (NoSuchFieldException ex) {
	throw newIAE(defc.getName()+"."+name, ex);
	}
	}

	private static RuntimeException newIAE(String message, Throwable cause) {
	return new IllegalArgumentException(message, cause);
	}

	private static final Function<Object, Object> CREATE_RESERVATION = new Function<>() {
	@Override
	public Object apply(Object key) {
	return new Object();
	}
	};

	public final S findSpecies(K key) {
	// Note: Species instantiation may throw VirtualMachineError because of
	// code cache overflow. If this happens the species bytecode may be
	// loaded but not linked to its species metadata (with MH's etc).
	// That will cause a throw out of Factory.loadSpecies.
	//
	// In a later attempt to get the same species, the already-loaded
	// class will be present in the system dictionary, causing an
	// error when the species generator tries to reload it.
	// We try to detect this case and link the pre-existing code.
	//
	// Although it would be better to start fresh by loading a new
	// copy, we have to salvage the previously loaded but broken code.
	// (As an alternative, we might spin a new class with a new name,
	// or use the anonymous class mechanism.)
	//
	// In the end, as long as everybody goes through this findSpecies method,
	// it will ensure only one SpeciesData will be set successfully on a
	// concrete class if ever.
	// The concrete class is published via SpeciesData instance
	// returned here only after the class and species data are linked together.
	Object speciesDataOrReservation = cache.computeIfAbsent(key, CREATE_RESERVATION);
	// Separating the creation of a placeholder SpeciesData instance above
	// from the loading and linking a real one below ensures we can never
	// accidentally call computeIfAbsent recursively.
	S speciesData;
	if (speciesDataOrReservation.getClass() == Object.class) {
	synchronized (speciesDataOrReservation) {
	Object existingSpeciesData = cache.get(key);
	if (existingSpeciesData == speciesDataOrReservation) { // won the race
	// create a new SpeciesData...
	speciesData = newSpeciesData(key);
	// load and link it...
	speciesData = factory.loadSpecies(speciesData);
	if (!cache.replace(key, existingSpeciesData, speciesData)) {
	throw newInternalError("Concurrent loadSpecies");
	}
	} else { // lost the race; the retrieved existingSpeciesData is the final
	speciesData = metaType.cast(existingSpeciesData);
	}
	}
	} else {
	speciesData = metaType.cast(speciesDataOrReservation);
	}
	assert(speciesData != null && speciesData.isResolved());
	return speciesData;
	}

	/**
	* Meta-data wrapper for concrete subtypes of the top class.
	* Each concrete subtype corresponds to a given sequence of basic field types (LIJFD).
	* The fields are immutable; their values are fully specified at object construction.
	* Each species supplies an array of getter functions which may be used in lambda forms.
	* A concrete value is always constructed from the full tuple of its field values,
	* accompanied by the required constructor parameters.
	* There may also be transforms which cloning a species instance and
	* either replace a constructor parameter or add one or more new field values.
	* The shortest possible species has zero fields.
	* Subtypes are not interrelated among themselves by subtyping, even though
	* it would appear that a shorter species could serve as a supertype of a
	* longer one which extends it.
	*/
	public abstract class SpeciesData {
	// Bootstrapping requires circular relations Class -> SpeciesData -> Class
	// Therefore, we need non-final links in the chain. Use @Stable fields.
	private final K key;
	private final List<Class<?>> fieldTypes;
	@Stable private Class<? extends T> speciesCode;
	@Stable private List<MethodHandle> factories;
	@Stable private List<MethodHandle> getters;
	@Stable private List<LambdaForm.NamedFunction> nominalGetters;
	@Stable private final MethodHandle[] transformHelpers = new MethodHandle[transformMethods.size()];

	protected SpeciesData(K key) {
	this.key = keyType.cast(Objects.requireNonNull(key));
	List<Class<?>> types = deriveFieldTypes(key);
	this.fieldTypes = List.copyOf(types);
	}

	public final K key() {
	return key;
	}

	protected final List<Class<?>> fieldTypes() {
	return fieldTypes;
	}

	protected final int fieldCount() {
	return fieldTypes.size();
	}

	protected ClassSpecializer<T,K,S> outer() {
	return ClassSpecializer.this;
	}

	protected final boolean isResolved() {
	return speciesCode != null && factories != null && !factories.isEmpty();
	}

	@Override public String toString() {
	return metaType.getSimpleName() + "[" + key.toString() + " => " + (isResolved() ? speciesCode.getSimpleName() : "UNRESOLVED") + "]";
	}

	@Override
	public int hashCode() {
	return key.hashCode();
	}

	@Override
	public boolean equals(Object obj) {
	if (!(obj instanceof ClassSpecializer.SpeciesData)) {
	return false;
	}
	@SuppressWarnings("rawtypes")
	ClassSpecializer.SpeciesData that = (ClassSpecializer.SpeciesData) obj;
	return this.outer() == that.outer() && this.key.equals(that.key);
	}

	/** Throws NPE if this species is not yet resolved. */
	protected final Class<? extends T> speciesCode() {
	return Objects.requireNonNull(speciesCode);
	}

	/**
	* Return a {@link MethodHandle} which can get the indexed field of this species.
	* The return type is the type of the species field it accesses.
	* The argument type is the {@code fieldHolder} class of this species.
	*/
	protected MethodHandle getter(int i) {
	return getters.get(i);
	}

	/**
	* Return a {@link LambdaForm.Name} containing a {@link LambdaForm.NamedFunction} that
	* represents a MH bound to a generic invoker, which in turn forwards to the corresponding
	* getter.
	*/
	protected LambdaForm.NamedFunction getterFunction(int i) {
	LambdaForm.NamedFunction nf = nominalGetters.get(i);
	assert(nf.memberDeclaringClassOrNull() == speciesCode());
	assert(nf.returnType() == BasicType.basicType(fieldTypes.get(i)));
	return nf;
	}

	protected List<LambdaForm.NamedFunction> getterFunctions() {
	return nominalGetters;
	}

	protected List<MethodHandle> getters() {
	return getters;
	}

	protected MethodHandle factory() {
	return factories.get(0);
	}

	protected MethodHandle transformHelper(int whichtm) {
	MethodHandle mh = transformHelpers[whichtm];
	if (mh != null) return mh;
	mh = deriveTransformHelper(transformMethods().get(whichtm), whichtm);
	// Do a little type checking before we start using the MH.
	// (It will be called with invokeBasic, so this is our only chance.)
	final MethodType mt = transformHelperType(whichtm);
	mh = mh.asType(mt);
	return transformHelpers[whichtm] = mh;
	}

	private final MethodType transformHelperType(int whichtm) {
	MemberName tm = transformMethods().get(whichtm);
	ArrayList<Class<?>> args = new ArrayList<>();
	ArrayList<Class<?>> fields = new ArrayList<>();
	Collections.addAll(args, tm.getParameterTypes());
	fields.addAll(fieldTypes());
	List<Class<?>> helperArgs = deriveTransformHelperArguments(tm, whichtm, args, fields);
	return MethodType.methodType(tm.getReturnType(), helperArgs);
	}

	// Hooks for subclasses:

	/**
	* Given a key, derive the list of field types, which all instances of this
	* species must store.
	*/
	protected abstract List<Class<?>> deriveFieldTypes(K key);

	/**
	* Given the index of a method in the transforms list, supply a factory
	* method that takes the arguments of the transform, plus the local fields,
	* and produce a value of the required type.
	* You can override this to return null or throw if there are no transforms.
	* This method exists so that the transforms can be "grown" lazily.
	* This is necessary if the transform adds a field to an instance,
	* which sometimes requires the creation, on the fly, of an extended species.
	* This method is only called once for any particular parameter.
	* The species caches the result in a private array.
	*
	* @param transform the transform being implemented
	* @param whichtm the index of that transform in the original list of transforms
	* @return the method handle which creates a new result from a mix of transform
	* arguments and field values
	*/
	protected abstract MethodHandle deriveTransformHelper(MemberName transform, int whichtm);

	/**
	* During code generation, this method is called once per transform to determine
	* what is the mix of arguments to hand to the transform-helper. The bytecode
	* which marshals these arguments is open-coded in the species-specific transform.
	* The two lists are of opaque objects, which you shouldn't do anything with besides
	* reordering them into the output list. (They are both mutable, to make editing
	* easier.) The imputed types of the args correspond to the transform's parameter
	* list, while the imputed types of the fields correspond to the species field types.
	* After code generation, this method may be called occasionally by error-checking code.
	*
	* @param transform the transform being implemented
	* @param whichtm the index of that transform in the original list of transforms
	* @param args a list of opaque objects representing the incoming transform arguments
	* @param fields a list of opaque objects representing the field values of the receiver
	* @param <X> the common element type of the various lists
	* @return a new list
	*/
	protected abstract <X> List<X> deriveTransformHelperArguments(MemberName transform, int whichtm,
	List<X> args, List<X> fields);

	/** Given a key, generate the name of the class which implements the species for that key.
	* This algorithm must be stable.
	*
	* @return class name, which by default is {@code outer().topClass().getName() + "$Species_" + deriveTypeString(key)}
	*/
	protected String deriveClassName() {
	return outer().topClass().getName() + "$Species_" + deriveTypeString();
	}

	/**
	* Default implementation collects basic type characters,
	* plus possibly type names, if some types don't correspond
	* to basic types.
	*
	* @return a string suitable for use in a class name
	*/
	protected String deriveTypeString() {
	List<Class<?>> types = fieldTypes();
	StringBuilder buf = new StringBuilder();
	StringBuilder end = new StringBuilder();
	for (Class<?> type : types) {
	BasicType basicType = BasicType.basicType(type);
	if (basicType.basicTypeClass() == type) {
	buf.append(basicType.basicTypeChar());
	} else {
	buf.append('V');
	end.append(classSig(type));
	}
	}
	String typeString;
	if (end.length() > 0) {
	typeString = BytecodeName.toBytecodeName(buf.append("_").append(end).toString());
	} else {
	typeString = buf.toString();
	}
	return LambdaForm.shortenSignature(typeString);
	}

	/**
	* Report what immediate super-class to use for the concrete class of this species.
	* Normally this is {@code topClass}, but if that is an interface, the factory must override.
	* The super-class must provide a constructor which takes the {@code baseConstructorType} arguments, if any.
	* This hook also allows the code generator to use more than one canned supertype for species.
	*
	* @return the super-class of the class to be generated
	*/
	protected Class<? extends T> deriveSuperClass() {
	final Class<T> topc = topClass();
	if (!topClassIsSuper) {
	try {
	final Constructor<T> con = reflectConstructor(topc, baseConstructorType().parameterArray());
	if (!topc.isInterface() && !Modifier.isPrivate(con.getModifiers())) {
	topClassIsSuper = true;
	}
	} catch (Exception\|InternalError ex) {
	// fall through...
	}
	if (!topClassIsSuper) {
	throw newInternalError("must override if the top class cannot serve as a super class");
	}
	}
	return topc;
	}
	}

	protected abstract S newSpeciesData(K key);

	protected K topSpeciesKey() {
	return null; // null means don't report a top species
	}

	/**
	* Code generation support for instances.
	* Subclasses can modify the behavior.
	*/
	public class Factory {
	/**
	* Constructs a factory.
	*/
	Factory() {}

	/**
	* Get a concrete subclass of the top class for a given combination of bound types.
	*
	* @param speciesData the species requiring the class, not yet linked
	* @return a linked version of the same species
	*/
	S loadSpecies(S speciesData) {
	String className = speciesData.deriveClassName();
	assert(className.indexOf('/') < 0) : className;
	Class<?> salvage = null;
	try {
	salvage = BootLoader.loadClassOrNull(className);
	} catch (Error ex) {
	// ignore
	} finally {
	traceSpeciesType(className, salvage);
	}
	final Class<? extends T> speciesCode;
	if (salvage != null) {
	speciesCode = salvage.asSubclass(topClass());
	linkSpeciesDataToCode(speciesData, speciesCode);
	linkCodeToSpeciesData(speciesCode, speciesData, true);
	} else {
	// Not pregenerated, generate the class
	try {
	speciesCode = generateConcreteSpeciesCode(className, speciesData);
	// This operation causes a lot of churn:
	linkSpeciesDataToCode(speciesData, speciesCode);
	// This operation commits the relation, but causes little churn:
	linkCodeToSpeciesData(speciesCode, speciesData, false);
	} catch (Error ex) {
	// We can get here if there is a race condition loading a class.
	// Or maybe we are out of resources. Back out of the CHM.get and retry.
	throw ex;
	}
	}

	if (!speciesData.isResolved()) {
	throw newInternalError("bad species class linkage for " + className + ": " + speciesData);
	}
	assert(speciesData == loadSpeciesDataFromCode(speciesCode));
	return speciesData;
	}

	/**
	* Generate a concrete subclass of the top class for a given combination of bound types.
	*
	* A concrete species subclass roughly matches the following schema:
	*
	* <pre>
	* class Species_[[types]] extends [[T]] {
	* final [[S]] speciesData() { return ... }
	* static [[T]] make([[fields]]) { return ... }
	* [[fields]]
	* final [[T]] transform([[args]]) { return ... }
	* }
	* </pre>
	*
	* The {@code [[types]]} signature is precisely the key for the species.
	*
	* The {@code [[fields]]} section consists of one field definition per character in
	* the type signature, adhering to the naming schema described in the definition of
	* {@link #chooseFieldName}.
	*
	* For example, a concrete species for two references and one integral bound value
	* has a shape like the following:
	*
	* <pre>
	* class TopClass {
	* ...
	* private static final class Species_LLI extends TopClass {
	* final Object argL0;
	* final Object argL1;
	* final int argI2;
	* private Species_LLI(CT ctarg, ..., Object argL0, Object argL1, int argI2) {
	* super(ctarg, ...);
	* this.argL0 = argL0;
	* this.argL1 = argL1;
	* this.argI2 = argI2;
	* }
	* final SpeciesData speciesData() { return BMH_SPECIES; }
	* @Stable static SpeciesData BMH_SPECIES; // injected afterwards
	* static TopClass make(CT ctarg, ..., Object argL0, Object argL1, int argI2) {
	* return new Species_LLI(ctarg, ..., argL0, argL1, argI2);
	* }
	* final TopClass copyWith(CT ctarg, ...) {
	* return new Species_LLI(ctarg, ..., argL0, argL1, argI2);
	* }
	* // two transforms, for the sake of illustration:
	* final TopClass copyWithExtendL(CT ctarg, ..., Object narg) {
	* return BMH_SPECIES.transform(L_TYPE).invokeBasic(ctarg, ..., argL0, argL1, argI2, narg);
	* }
	* final TopClass copyWithExtendI(CT ctarg, ..., int narg) {
	* return BMH_SPECIES.transform(I_TYPE).invokeBasic(ctarg, ..., argL0, argL1, argI2, narg);
	* }
	* }
	* }
	* </pre>
	*
	* @param className of the species
	* @param speciesData what species we are generating
	* @return the generated concrete TopClass class
	*/
	@SuppressWarnings("removal")
	Class<? extends T> generateConcreteSpeciesCode(String className, ClassSpecializer<T,K,S>.SpeciesData speciesData) {
	byte[] classFile = generateConcreteSpeciesCodeFile(className, speciesData);

	// load class
	InvokerBytecodeGenerator.maybeDump(classBCName(className), classFile);
	ClassLoader cl = topClass.getClassLoader();
	ProtectionDomain pd = null;
	if (cl != null) {
	pd = AccessController.doPrivileged(
	new PrivilegedAction<>() {
	@Override
	public ProtectionDomain run() {
	return topClass().getProtectionDomain();
	}
	});
	}
	Class<?> speciesCode = SharedSecrets.getJavaLangAccess()
	.defineClass(cl, className, classFile, pd, "_ClassSpecializer_generateConcreteSpeciesCode");
	return speciesCode.asSubclass(topClass());
	}

	// These are named like constants because there is only one per specialization scheme:
	private final String SPECIES_DATA = classBCName(metaType);
	private final String SPECIES_DATA_SIG = classSig(SPECIES_DATA);
	private final String SPECIES_DATA_NAME = sdAccessor.getName();
	private final int SPECIES_DATA_MODS = sdAccessor.getModifiers();
	private final List<String> TRANSFORM_NAMES; // derived from transformMethods
	private final List<MethodType> TRANSFORM_TYPES;
	private final List<Integer> TRANSFORM_MODS;
	{
	// Tear apart transformMethods to get the names, types, and modifiers.
	List<String> tns = new ArrayList<>();
	List<MethodType> tts = new ArrayList<>();
	List<Integer> tms = new ArrayList<>();
	for (int i = 0; i < transformMethods.size(); i++) {
	MemberName tm = transformMethods.get(i);
	tns.add(tm.getName());
	final MethodType tt = tm.getMethodType();
	tts.add(tt);
	tms.add(tm.getModifiers());
	}
	TRANSFORM_NAMES = List.of(tns.toArray(new String[0]));
	TRANSFORM_TYPES = List.of(tts.toArray(new MethodType[0]));
	TRANSFORM_MODS = List.of(tms.toArray(new Integer[0]));
	}
	private static final int ACC_PPP = ACC_PUBLIC \| ACC_PRIVATE \| ACC_PROTECTED;

	/non-public/
	byte[] generateConcreteSpeciesCodeFile(String className0, ClassSpecializer<T,K,S>.SpeciesData speciesData) {
	final String className = classBCName(className0);
	final String superClassName = classBCName(speciesData.deriveSuperClass());

	final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);
	final int NOT_ACC_PUBLIC = 0; // not ACC_PUBLIC
	cw.visit(V1_6, NOT_ACC_PUBLIC + ACC_FINAL + ACC_SUPER, className, null, superClassName, null);

	final String sourceFile = className.substring(className.lastIndexOf('.')+1);
	cw.visitSource(sourceFile, null);

	// emit static types and BMH_SPECIES fields
	FieldVisitor fw = cw.visitField(NOT_ACC_PUBLIC + ACC_STATIC, sdFieldName, SPECIES_DATA_SIG, null, null);
	fw.visitAnnotation(STABLE_SIG, true);
	fw.visitEnd();

	// handy holder for dealing with groups of typed values (ctor arguments and fields)
	class Var {
	final int index;
	final String name;
	final Class<?> type;
	final String desc;
	final BasicType basicType;
	final int slotIndex;
	Var(int index, int slotIndex) {
	this.index = index;
	this.slotIndex = slotIndex;
	name = null; type = null; desc = null;
	basicType = BasicType.V_TYPE;
	}
	Var(String name, Class<?> type, Var prev) {
	int slotIndex = prev.nextSlotIndex();
	int index = prev.nextIndex();
	if (name == null) name = "x";
	if (name.endsWith("#"))
	name = name.substring(0, name.length()-1) + index;
	assert(!type.equals(void.class));
	String desc = classSig(type);
	BasicType basicType = BasicType.basicType(type);
	this.index = index;
	this.name = name;
	this.type = type;
	this.desc = desc;
	this.basicType = basicType;
	this.slotIndex = slotIndex;
	}
	Var lastOf(List<Var> vars) {
	int n = vars.size();
	return (n == 0 ? this : vars.get(n-1));
	}
	<X> List<Var> fromTypes(List<X> types) {
	Var prev = this;
	ArrayList<Var> result = new ArrayList<>(types.size());
	int i = 0;
	for (X x : types) {
	String vn = name;
	Class<?> vt;
	if (x instanceof Class) {
	vt = (Class<?>) x;
	// make the names friendlier if debugging
	assert((vn = vn + "_" + (i++)) != null);
	} else {
	@SuppressWarnings("unchecked")
	Var v = (Var) x;
	vn = v.name;
	vt = v.type;
	}
	prev = new Var(vn, vt, prev);
	result.add(prev);
	}
	return result;
	}

	int slotSize() { return basicType.basicTypeSlots(); }
	int nextIndex() { return index + (slotSize() == 0 ? 0 : 1); }
	int nextSlotIndex() { return slotIndex >= 0 ? slotIndex + slotSize() : slotIndex; }
	boolean isInHeap() { return slotIndex < 0; }
	void emitVarInstruction(int asmop, MethodVisitor mv) {
	if (asmop == ALOAD)
	asmop = typeLoadOp(basicType.basicTypeChar());
	else
	throw new AssertionError("bad op="+asmop+" for desc="+desc);
	mv.visitVarInsn(asmop, slotIndex);
	}
	public void emitFieldInsn(int asmop, MethodVisitor mv) {
	mv.visitFieldInsn(asmop, className, name, desc);
	}
	}

	final Var NO_THIS = new Var(0, 0),
	AFTER_THIS = new Var(0, 1),
	IN_HEAP = new Var(0, -1);

	// figure out the field types
	final List<Class<?>> fieldTypes = speciesData.fieldTypes();
	final List<Var> fields = new ArrayList<>(fieldTypes.size());
	{
	Var nextF = IN_HEAP;
	for (Class<?> ft : fieldTypes) {
	String fn = chooseFieldName(ft, nextF.nextIndex());
	nextF = new Var(fn, ft, nextF);
	fields.add(nextF);
	}
	}

	// emit bound argument fields
	for (Var field : fields) {
	cw.visitField(ACC_FINAL, field.name, field.desc, null, null).visitEnd();
	}

	MethodVisitor mv;

	// emit implementation of speciesData()
	mv = cw.visitMethod((SPECIES_DATA_MODS & ACC_PPP) + ACC_FINAL,
	SPECIES_DATA_NAME, "()" + SPECIES_DATA_SIG, null, null);
	mv.visitCode();
	mv.visitFieldInsn(GETSTATIC, className, sdFieldName, SPECIES_DATA_SIG);
	mv.visitInsn(ARETURN);
	mv.visitMaxs(0, 0);
	mv.visitEnd();

	// figure out the constructor arguments
	MethodType superCtorType = ClassSpecializer.this.baseConstructorType();
	MethodType thisCtorType = superCtorType.appendParameterTypes(fieldTypes);

	// emit constructor
	{
	mv = cw.visitMethod(ACC_PRIVATE,
	"<init>", methodSig(thisCtorType), null, null);
	mv.visitCode();
	mv.visitVarInsn(ALOAD, 0); // this

	final List<Var> ctorArgs = AFTER_THIS.fromTypes(superCtorType.parameterList());
	for (Var ca : ctorArgs) {
	ca.emitVarInstruction(ALOAD, mv);
	}

	// super(ca...)
	mv.visitMethodInsn(INVOKESPECIAL, superClassName,
	"<init>", methodSig(superCtorType), false);

	// store down fields
	Var lastFV = AFTER_THIS.lastOf(ctorArgs);
	for (Var f : fields) {
	// this.argL1 = argL1
	mv.visitVarInsn(ALOAD, 0); // this
	lastFV = new Var(f.name, f.type, lastFV);
	lastFV.emitVarInstruction(ALOAD, mv);
	f.emitFieldInsn(PUTFIELD, mv);
	}

	mv.visitInsn(RETURN);
	mv.visitMaxs(0, 0);
	mv.visitEnd();
	}

	// emit make() ...factory method wrapping constructor
	{
	MethodType ftryType = thisCtorType.changeReturnType(topClass());
	mv = cw.visitMethod(NOT_ACC_PUBLIC + ACC_STATIC,
	"make", methodSig(ftryType), null, null);
	mv.visitCode();
	// make instance
	mv.visitTypeInsn(NEW, className);
	mv.visitInsn(DUP);
	// load factory method arguments: ctarg... and arg...
	for (Var v : NO_THIS.fromTypes(ftryType.parameterList())) {
	v.emitVarInstruction(ALOAD, mv);
	}

	// finally, invoke the constructor and return
	mv.visitMethodInsn(INVOKESPECIAL, className,
	"<init>", methodSig(thisCtorType), false);
	mv.visitInsn(ARETURN);
	mv.visitMaxs(0, 0);
	mv.visitEnd();
	}

	// For each transform, emit the customized override of the transform method.
	// This method mixes together some incoming arguments (from the transform's
	// static type signature) with the field types themselves, and passes
	// the resulting mish-mosh of values to a method handle produced by
	// the species itself. (Typically this method handle is the factory
	// method of this species or a related one.)
	for (int whichtm = 0; whichtm < TRANSFORM_NAMES.size(); whichtm++) {
	final String TNAME = TRANSFORM_NAMES.get(whichtm);
	final MethodType TTYPE = TRANSFORM_TYPES.get(whichtm);
	final int TMODS = TRANSFORM_MODS.get(whichtm);
	mv = cw.visitMethod((TMODS & ACC_PPP) \| ACC_FINAL,
	TNAME, TTYPE.toMethodDescriptorString(), null, E_THROWABLE);
	mv.visitCode();
	// return a call to the corresponding "transform helper", something like this:
	// MY_SPECIES.transformHelper(whichtm).invokeBasic(ctarg, ..., argL0, ..., xarg)
	mv.visitFieldInsn(GETSTATIC, className,
	sdFieldName, SPECIES_DATA_SIG);
	emitIntConstant(whichtm, mv);
	mv.visitMethodInsn(INVOKEVIRTUAL, SPECIES_DATA,
	"transformHelper", "(I)" + MH_SIG, false);

	List<Var> targs = AFTER_THIS.fromTypes(TTYPE.parameterList());
	List<Var> tfields = new ArrayList<>(fields);
	// mix them up and load them for the transform helper:
	List<Var> helperArgs = speciesData.deriveTransformHelperArguments(transformMethods.get(whichtm), whichtm, targs, tfields);
	List<Class<?>> helperTypes = new ArrayList<>(helperArgs.size());
	for (Var ha : helperArgs) {
	helperTypes.add(ha.basicType.basicTypeClass());
	if (ha.isInHeap()) {
	assert(tfields.contains(ha));
	mv.visitVarInsn(ALOAD, 0);
	ha.emitFieldInsn(GETFIELD, mv);
	} else {
	assert(targs.contains(ha));
	ha.emitVarInstruction(ALOAD, mv);
	}
	}

	// jump into the helper (which is probably a factory method)
	final Class<?> rtype = TTYPE.returnType();
	final BasicType rbt = BasicType.basicType(rtype);
	MethodType invokeBasicType = MethodType.methodType(rbt.basicTypeClass(), helperTypes);
	mv.visitMethodInsn(INVOKEVIRTUAL, MH,
	"invokeBasic", methodSig(invokeBasicType), false);
	if (rbt == BasicType.L_TYPE) {
	mv.visitTypeInsn(CHECKCAST, classBCName(rtype));
	mv.visitInsn(ARETURN);
	} else {
	throw newInternalError("NYI: transform of type "+rtype);
	}
	mv.visitMaxs(0, 0);
	mv.visitEnd();
	}

	cw.visitEnd();

	return cw.toByteArray();
	}

	private int typeLoadOp(char t) {
	return switch (t) {
	case 'L' -> ALOAD;
	case 'I' -> ILOAD;
	case 'J' -> LLOAD;
	case 'F' -> FLOAD;
	case 'D' -> DLOAD;
	default -> throw newInternalError("unrecognized type " + t);
	};
	}

	private void emitIntConstant(int con, MethodVisitor mv) {
	if (ICONST_M1 - ICONST_0 <= con && con <= ICONST_5 - ICONST_0)
	mv.visitInsn(ICONST_0 + con);
	else if (con == (byte) con)
	mv.visitIntInsn(BIPUSH, con);
	else if (con == (short) con)
	mv.visitIntInsn(SIPUSH, con);
	else {
	mv.visitLdcInsn(con);
	}

	}

	//
	// Getter MH generation.
	//

	private MethodHandle findGetter(Class<?> speciesCode, List<Class<?>> types, int index) {
	Class<?> fieldType = types.get(index);
	String fieldName = chooseFieldName(fieldType, index);
	try {
	return IMPL_LOOKUP.findGetter(speciesCode, fieldName, fieldType);
	} catch (NoSuchFieldException \| IllegalAccessException e) {
	throw newInternalError(e);
	}
	}

	private List<MethodHandle> findGetters(Class<?> speciesCode, List<Class<?>> types) {
	MethodHandle[] mhs = new MethodHandle[types.size()];
	for (int i = 0; i < mhs.length; ++i) {
	mhs[i] = findGetter(speciesCode, types, i);
	assert(mhs[i].internalMemberName().getDeclaringClass() == speciesCode);
	}
	return List.of(mhs);
	}

	private List<MethodHandle> findFactories(Class<? extends T> speciesCode, List<Class<?>> types) {
	MethodHandle[] mhs = new MethodHandle[1];
	mhs[0] = findFactory(speciesCode, types);
	return List.of(mhs);
	}

	List<LambdaForm.NamedFunction> makeNominalGetters(List<Class<?>> types, List<MethodHandle> getters) {
	LambdaForm.NamedFunction[] nfs = new LambdaForm.NamedFunction[types.size()];
	for (int i = 0; i < nfs.length; ++i) {
	nfs[i] = new LambdaForm.NamedFunction(getters.get(i));
	}
	return List.of(nfs);
	}

	//
	// Auxiliary methods.
	//

	protected void linkSpeciesDataToCode(ClassSpecializer<T,K,S>.SpeciesData speciesData, Class<? extends T> speciesCode) {
	speciesData.speciesCode = speciesCode.asSubclass(topClass);
	final List<Class<?>> types = speciesData.fieldTypes;
	speciesData.factories = this.findFactories(speciesCode, types);
	speciesData.getters = this.findGetters(speciesCode, types);
	speciesData.nominalGetters = this.makeNominalGetters(types, speciesData.getters);
	}

	private Field reflectSDField(Class<? extends T> speciesCode) {
	final Field field = reflectField(speciesCode, sdFieldName);
	assert(field.getType() == metaType);
	assert(Modifier.isStatic(field.getModifiers()));
	return field;
	}

	private S readSpeciesDataFromCode(Class<? extends T> speciesCode) {
	try {
	MemberName sdField = IMPL_LOOKUP.resolveOrFail(REF_getStatic, speciesCode, sdFieldName, metaType);
	Object base = MethodHandleNatives.staticFieldBase(sdField);
	long offset = MethodHandleNatives.staticFieldOffset(sdField);
	UNSAFE.loadFence();
	return metaType.cast(UNSAFE.getReference(base, offset));
	} catch (Error err) {
	throw err;
	} catch (Exception ex) {
	throw newInternalError("Failed to load speciesData from speciesCode: " + speciesCode.getName(), ex);
	} catch (Throwable t) {
	throw uncaughtException(t);
	}
	}

	protected S loadSpeciesDataFromCode(Class<? extends T> speciesCode) {
	if (speciesCode == topClass()) {
	return topSpecies;
	}
	S result = readSpeciesDataFromCode(speciesCode);
	if (result.outer() != ClassSpecializer.this) {
	throw newInternalError("wrong class");
	}
	return result;
	}

	protected void linkCodeToSpeciesData(Class<? extends T> speciesCode, ClassSpecializer<T,K,S>.SpeciesData speciesData, boolean salvage) {
	try {
	assert(readSpeciesDataFromCode(speciesCode) == null \|\|
	(salvage && readSpeciesDataFromCode(speciesCode).equals(speciesData)));

	MemberName sdField = IMPL_LOOKUP.resolveOrFail(REF_putStatic, speciesCode, sdFieldName, metaType);
	Object base = MethodHandleNatives.staticFieldBase(sdField);
	long offset = MethodHandleNatives.staticFieldOffset(sdField);
	UNSAFE.storeFence();
	UNSAFE.putReference(base, offset, speciesData);
	UNSAFE.storeFence();
	} catch (Error err) {
	throw err;
	} catch (Exception ex) {
	throw newInternalError("Failed to link speciesData to speciesCode: " + speciesCode.getName(), ex);
	} catch (Throwable t) {
	throw uncaughtException(t);
	}
	}

	/**
	* Field names in concrete species classes adhere to this pattern:
	* type + index, where type is a single character (L, I, J, F, D).
	* The factory subclass can customize this.
	* The name is purely cosmetic, since it applies to a private field.
	*/
	protected String chooseFieldName(Class<?> type, int index) {
	BasicType bt = BasicType.basicType(type);
	return "" + bt.basicTypeChar() + index;
	}

	MethodHandle findFactory(Class<? extends T> speciesCode, List<Class<?>> types) {
	final MethodType type = baseConstructorType().changeReturnType(topClass()).appendParameterTypes(types);
	try {
	return IMPL_LOOKUP.findStatic(speciesCode, "make", type);
	} catch (NoSuchMethodException \| IllegalAccessException \| IllegalArgumentException \| TypeNotPresentException e) {
	throw newInternalError(e);
	}
	}
	}

	/** Hook that virtualizes the Factory class, allowing subclasses to extend it. */
	protected Factory makeFactory() {
	return new Factory();
	}


	// Other misc helpers:
	private static final String MH = "java/lang/invoke/MethodHandle";
	private static final String MH_SIG = "L" + MH + ";";
	private static final String STABLE = "jdk/internal/vm/annotation/Stable";
	private static final String STABLE_SIG = "L" + STABLE + ";";
	private static final String[] E_THROWABLE = new String[] { "java/lang/Throwable" };
	static {
	assert(MH_SIG.equals(classSig(MethodHandle.class)));
	assert(MH.equals(classBCName(MethodHandle.class)));
	}

	static String methodSig(MethodType mt) {
	return mt.toMethodDescriptorString();
	}
	static String classSig(Class<?> cls) {
	if (cls.isPrimitive() \|\| cls.isArray())
	return MethodType.methodType(cls).toMethodDescriptorString().substring(2);
	return classSig(classBCName(cls));
	}
	static String classSig(String bcName) {
	assert(bcName.indexOf('.') < 0);
	assert(!bcName.endsWith(";"));
	assert(!bcName.startsWith("["));
	return "L" + bcName + ";";
	}
	static String classBCName(Class<?> cls) {
	return classBCName(className(cls));
	}
	static String classBCName(String str) {
	assert(str.indexOf('/') < 0) : str;
	return str.replace('.', '/');
	}
	static String className(Class<?> cls) {
	assert(!cls.isArray() && !cls.isPrimitive());
	return cls.getName();
	}
	}

Back to index...