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 * Copyright (c) 2016, 2019, 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.
 *
 * 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
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package org.graalvm.compiler.replacements.classfile;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;

import jdk.internal.vm.compiler.collections.EconomicMap;
import jdk.internal.vm.compiler.collections.Equivalence;
import org.graalvm.compiler.api.replacements.SnippetReflectionProvider;
import org.graalvm.compiler.bytecode.Bytecode;
import org.graalvm.compiler.bytecode.BytecodeProvider;
import org.graalvm.compiler.serviceprovider.GraalServices;

import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.MetaAccessProvider;
import jdk.vm.ci.meta.ResolvedJavaField;
import jdk.vm.ci.meta.ResolvedJavaMethod;
import jdk.vm.ci.meta.ResolvedJavaType;

A BytecodeProvider that provides bytecode properties of a ResolvedJavaMethod as parsed from a class file. This avoids all 
instrumentation and any bytecode rewriting performed by the VM. This mechanism retrieves class files based on the name and ClassLoader of existing Class instances. It bypasses all VM parsing and verification of the class file and assumes the class files are well formed. As such, it should only be used for classes from a trusted source such as the boot class (or module) path. A combination of Class.forName(String) and an existing MetaAccessProvider is used to resolve constant pool references. This opens up the opportunity for linkage errors if the referee is structurally changed through redefinition (e.g., a referred to method is renamed or deleted). This will result in an appropriate LinkageError being thrown. The only way to avoid this is to have a completely isolated jdk.vm.ci.meta implementation for parsing snippet/intrinsic bytecodes. /**
 * A {@link BytecodeProvider} that provides bytecode properties of a {@link ResolvedJavaMethod} as
 * parsed from a class file. This avoids all {@linkplain java.lang.instrument.Instrumentation
 * instrumentation} and any bytecode rewriting performed by the VM.
 *
 * This mechanism retrieves class files based on the name and {@link ClassLoader} of existing
 * {@link Class} instances. It bypasses all VM parsing and verification of the class file and
 * assumes the class files are well formed. As such, it should only be used for classes from a
 * trusted source such as the boot class (or module) path.
 *
 * A combination of {@link Class#forName(String)} and an existing {@link MetaAccessProvider} is used
 * to resolve constant pool references. This opens up the opportunity for linkage errors if the
 * referee is structurally changed through redefinition (e.g., a referred to method is renamed or
 * deleted). This will result in an appropriate {@link LinkageError} being thrown. The only way to
 * avoid this is to have a completely isolated {@code jdk.vm.ci.meta} implementation for parsing
 * snippet/intrinsic bytecodes.
 */
public final class ClassfileBytecodeProvider implements BytecodeProvider {

    private final ClassLoader loader;
    private final EconomicMap<Class<?>, Classfile> classfiles = EconomicMap.create(Equivalence.IDENTITY);
    private final EconomicMap<String, Class<?>> classes = EconomicMap.create();
    private final EconomicMap<ResolvedJavaType, FieldsCache> fields = EconomicMap.create();
    private final EconomicMap<ResolvedJavaType, MethodsCache> methods = EconomicMap.create();
    final MetaAccessProvider metaAccess;
    final SnippetReflectionProvider snippetReflection;

    public ClassfileBytecodeProvider(MetaAccessProvider metaAccess, SnippetReflectionProvider snippetReflection) {
        this.metaAccess = metaAccess;
        this.snippetReflection = snippetReflection;
        ClassLoader cl = getClass().getClassLoader();
        this.loader = cl == null ? ClassLoader.getSystemClassLoader() : cl;
    }

    public ClassfileBytecodeProvider(MetaAccessProvider metaAccess, SnippetReflectionProvider snippetReflection, ClassLoader loader) {
        this.metaAccess = metaAccess;
        this.snippetReflection = snippetReflection;
        this.loader = loader;
    }

    @Override
    public Bytecode getBytecode(ResolvedJavaMethod method) {
        Classfile classfile = getClassfile(resolveToClass(method.getDeclaringClass().getName()));
        return classfile.getCode(method.getName(), method.getSignature().toMethodDescriptor());
    }

    @Override
    public boolean supportsInvokedynamic() {
        return false;
    }

    @Override
    public boolean shouldRecordMethodDependencies() {
        return false;
    }

    
Gets a Classfile created by parsing the class file bytes for c. 
Throws:
NoClassDefFoundError – if the class file cannot be found/**
     * Gets a {@link Classfile} created by parsing the class file bytes for {@code c}.
     *
     * @throws NoClassDefFoundError if the class file cannot be found
     */
    private synchronized Classfile getClassfile(Class<?> c) {
        assert !c.isPrimitive() && !c.isArray() : c;
        Classfile classfile = classfiles.get(c);
        if (classfile == null) {
            try {
                ResolvedJavaType type = metaAccess.lookupJavaType(c);
                try (InputStream in = GraalServices.getClassfileAsStream(c)) {
                    if (in != null) {
                        DataInputStream stream = new DataInputStream(in);
                        classfile = new Classfile(type, stream, this);
                        classfiles.put(c, classfile);
                        return classfile;
                    }
                }
                throw new NoClassDefFoundError(c.getName());
            } catch (IOException e) {
                throw (NoClassDefFoundError) new NoClassDefFoundError(c.getName()).initCause(e);
            }
        }
        return classfile;
    }

    synchronized Class<?> resolveToClass(String descriptor) {
        Class<?> c = classes.get(descriptor);
        if (c == null) {
            if (descriptor.length() == 1) {
                c = JavaKind.fromPrimitiveOrVoidTypeChar(descriptor.charAt(0)).toJavaClass();
            } else {
                int dimensions = 0;
                while (descriptor.charAt(dimensions) == '[') {
                    dimensions++;
                }
                String name;
                if (dimensions == 0 && descriptor.startsWith("L") && descriptor.endsWith(";")) {
                    name = descriptor.substring(1, descriptor.length() - 1).replace('/', '.');
                } else {
                    name = descriptor.replace('/', '.');
                }
                try {
                    c = Class.forName(name, true, loader);
                    classes.put(descriptor, c);
                } catch (ClassNotFoundException e) {
                    throw new NoClassDefFoundError(descriptor);
                }
            }
        }
        return c;
    }

    
Name and type of a field.
/**
     * Name and type of a field.
     */
    static final class FieldKey {
        final String name;
        final String type;

        FieldKey(String name, String type) {
            this.name = name;
            this.type = type;
        }

        @Override
        public String toString() {
            return name + ":" + type;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj instanceof FieldKey) {
                FieldKey that = (FieldKey) obj;
                return that.name.equals(this.name) && that.type.equals(this.type);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return name.hashCode() ^ type.hashCode();
        }
    }

    
Name and descriptor of a method.
/**
     * Name and descriptor of a method.
     */
    static final class MethodKey {
        final String name;
        final String descriptor;

        MethodKey(String name, String descriptor) {
            this.name = name;
            this.descriptor = descriptor;
        }

        @Override
        public String toString() {
            return name + ":" + descriptor;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj instanceof MethodKey) {
                MethodKey that = (MethodKey) obj;
                return that.name.equals(this.name) && that.descriptor.equals(this.descriptor);
            }
            return false;
        }

        @Override
        public int hashCode() {
            return name.hashCode() ^ descriptor.hashCode();
        }
    }

    
Method cache for a ResolvedJavaType. /**
     * Method cache for a {@link ResolvedJavaType}.
     */
    static final class MethodsCache {

        volatile EconomicMap<MethodKey, ResolvedJavaMethod> constructors;
        volatile EconomicMap<MethodKey, ResolvedJavaMethod> methods;

        ResolvedJavaMethod lookup(ResolvedJavaType type, String name, String descriptor) {
            MethodKey key = new MethodKey(name, descriptor);

            if (name.equals("<clinit>")) {
                // No need to cache <clinit> as it will be looked up at most once
                return type.getClassInitializer();
            }
            if (!name.equals("<init>")) {
                if (methods == null) {
                    // Racy initialization is safe since `methods` is volatile
                    methods = createMethodMap(type.getDeclaredMethods());
                }

                return methods.get(key);
            } else {
                if (constructors == null) {
                    // Racy initialization is safe since instanceFields is volatile
                    constructors = createMethodMap(type.getDeclaredConstructors());
                }
                return constructors.get(key);
            }
        }

        private static EconomicMap<MethodKey, ResolvedJavaMethod> createMethodMap(ResolvedJavaMethod[] methodArray) {
            EconomicMap<MethodKey, ResolvedJavaMethod> map = EconomicMap.create();
            for (ResolvedJavaMethod m : methodArray) {
                map.put(new MethodKey(m.getName(), m.getSignature().toMethodDescriptor()), m);
            }
            return map;
        }
    }

    
Field cache for a ResolvedJavaType. /**
     * Field cache for a {@link ResolvedJavaType}.
     */
    static final class FieldsCache {

        volatile EconomicMap<FieldKey, ResolvedJavaField> instanceFields;
        volatile EconomicMap<FieldKey, ResolvedJavaField> staticFields;

        ResolvedJavaField lookup(ResolvedJavaType type, String name, String fieldType, boolean isStatic) {
            FieldKey key = new FieldKey(name, fieldType);
            if (isStatic) {
                if (staticFields == null) {
                    // Racy initialization is safe since staticFields is volatile
                    staticFields = createFieldMap(type.getStaticFields());
                }
                return staticFields.get(key);
            } else {
                if (instanceFields == null) {
                    // Racy initialization is safe since instanceFields is volatile
                    instanceFields = createFieldMap(type.getInstanceFields(false));
                }
                return instanceFields.get(key);
            }
        }

        private static EconomicMap<FieldKey, ResolvedJavaField> createFieldMap(ResolvedJavaField[] fieldArray) {
            EconomicMap<FieldKey, ResolvedJavaField> map = EconomicMap.create();
            for (ResolvedJavaField f : fieldArray) {
                map.put(new FieldKey(f.getName(), f.getType().getName()), f);
            }
            return map;
        }
    }

    
Gets the methods cache for type. Synchronized since the cache is lazily created. /**
     * Gets the methods cache for {@code type}.
     *
     * Synchronized since the cache is lazily created.
     */
    private synchronized MethodsCache getMethods(ResolvedJavaType type) {
        MethodsCache methodsCache = methods.get(type);
        if (methodsCache == null) {
            methodsCache = new MethodsCache();
            methods.put(type, methodsCache);
        }
        return methodsCache;
    }

    
Gets the fields cache for type. Synchronized since the cache is lazily created. /**
     * Gets the fields cache for {@code type}.
     *
     * Synchronized since the cache is lazily created.
     */
    private synchronized FieldsCache getFields(ResolvedJavaType type) {
        FieldsCache fieldsCache = fields.get(type);
        if (fieldsCache == null) {
            fieldsCache = new FieldsCache();
            fields.put(type, fieldsCache);
        }
        return fieldsCache;
    }

    ResolvedJavaField findField(ResolvedJavaType type, String name, String fieldType, boolean isStatic) {
        return getFields(type).lookup(type, name, fieldType, isStatic);
    }

    ResolvedJavaMethod findMethod(ResolvedJavaType type, String name, String descriptor, boolean isStatic) {
        ResolvedJavaMethod method = getMethods(type).lookup(type, name, descriptor);
        if (method != null && method.isStatic() == isStatic) {
            return method;
        }
        return null;
    }
}