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/*
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* Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package org.graalvm.compiler.replacements.classfile;
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import java.io.DataInputStream;
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import java.io.IOException;
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import java.lang.reflect.Modifier;
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import java.util.ArrayList;
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import java.util.List;
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import org.graalvm.compiler.replacements.classfile.ClassfileConstant.Utf8;
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import jdk.vm.ci.meta.ResolvedJavaMethod;
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import jdk.vm.ci.meta.ResolvedJavaType;
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/**
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* Container for objects representing the {@code Code} attributes parsed from a class file.
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*
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* @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.3">Code
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* attributes</a>
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* @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4">Constant
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* Pool</a>
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*/
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public class Classfile {
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private final ResolvedJavaType type;
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private final List<ClassfileBytecode> codeAttributes;
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private static final int MAJOR_VERSION_JAVA_MIN = 51; // JDK7
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private static final int MAJOR_VERSION_JAVA_MAX = 57; // JDK13
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private static final int MAGIC = 0xCAFEBABE;
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/**
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* Creates a {@link Classfile} by parsing the class file bytes for {@code type} loadable from
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* {@code context}.
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*
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* @throws NoClassDefFoundError if there is an IO error while parsing the class file
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*/
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public Classfile(ResolvedJavaType type, DataInputStream stream, ClassfileBytecodeProvider context) throws IOException {
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this.type = type;
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// magic
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int magic = stream.readInt();
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assert magic == MAGIC;
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int minor = stream.readUnsignedShort();
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int major = stream.readUnsignedShort();
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if (major < MAJOR_VERSION_JAVA_MIN || major > MAJOR_VERSION_JAVA_MAX) {
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throw new UnsupportedClassVersionError("Unsupported class file version: " + major + "." + minor);
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}
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ClassfileConstantPool cp = new ClassfileConstantPool(stream, context);
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// access_flags, this_class, super_class
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skipFully(stream, 6);
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// interfaces
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skipFully(stream, stream.readUnsignedShort() * 2);
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// fields
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skipFields(stream);
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// methods
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codeAttributes = readMethods(stream, cp);
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// attributes
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skipAttributes(stream);
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}
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public ClassfileBytecode getCode(String name, String descriptor) {
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for (ClassfileBytecode code : codeAttributes) {
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ResolvedJavaMethod method = code.getMethod();
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if (method.getName().equals(name) && method.getSignature().toMethodDescriptor().equals(descriptor)) {
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return code;
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}
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}
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throw new NoSuchMethodError(type.toJavaName() + "." + name + descriptor);
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}
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private static void skipAttributes(DataInputStream stream) throws IOException {
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int attributesCount;
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attributesCount = stream.readUnsignedShort();
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for (int i = 0; i < attributesCount; i++) {
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skipFully(stream, 2); // name_index
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int attributeLength = stream.readInt();
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skipFully(stream, attributeLength);
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}
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}
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static void skipFully(DataInputStream stream, int n) throws IOException {
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long skipped = 0;
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do {
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long s = stream.skip(n - skipped);
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skipped += s;
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if (s == 0 && skipped != n) {
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// Check for EOF (i.e., truncated class file)
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if (stream.read() == -1) {
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throw new IOException("truncated stream");
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}
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skipped++;
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}
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} while (skipped != n);
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}
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private ClassfileBytecode findCodeAttribute(DataInputStream stream, ClassfileConstantPool cp, String name, String descriptor, boolean isStatic) throws IOException {
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int attributesCount;
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attributesCount = stream.readUnsignedShort();
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ClassfileBytecode code = null;
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for (int i = 0; i < attributesCount; i++) {
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String attributeName = cp.get(Utf8.class, stream.readUnsignedShort()).value;
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int attributeLength = stream.readInt();
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if (code == null && attributeName.equals("Code")) {
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ResolvedJavaMethod method = cp.context.findMethod(type, name, descriptor, isStatic);
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// Even if we will discard the Code attribute (see below), we still
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// need to parse it to reach the following class file content.
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code = new ClassfileBytecode(method, stream, cp);
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if (method == null) {
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// This is a method hidden from reflection
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// (see sun.reflect.Reflection.filterMethods)
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code = null;
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}
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} else {
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skipFully(stream, attributeLength);
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}
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}
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return code;
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}
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private static void skipFields(DataInputStream stream) throws IOException {
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int count = stream.readUnsignedShort();
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for (int i = 0; i < count; i++) {
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skipFully(stream, 6); // access_flags, name_index, descriptor_index
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skipAttributes(stream);
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}
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}
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private List<ClassfileBytecode> readMethods(DataInputStream stream, ClassfileConstantPool cp) throws IOException {
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int count = stream.readUnsignedShort();
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List<ClassfileBytecode> result = new ArrayList<>(count);
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for (int i = 0; i < count; i++) {
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int accessFlags = stream.readUnsignedShort();
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boolean isStatic = Modifier.isStatic(accessFlags);
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String name = cp.get(Utf8.class, stream.readUnsignedShort()).value;
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String descriptor = cp.get(Utf8.class, stream.readUnsignedShort()).value;
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ClassfileBytecode code = findCodeAttribute(stream, cp, name, descriptor, isStatic);
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if (code != null) {
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result.add(code);
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}
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}
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return result;
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}
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@Override
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public String toString() {
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return getClass().getSimpleName() + "<" + type.toJavaName() + ">";
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}
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}
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