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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package org.graalvm.compiler.replacements.classfile;

import java.io.DataInputStream;
import java.io.IOException;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.List;

import org.graalvm.compiler.replacements.classfile.ClassfileConstant.Utf8;

import jdk.vm.ci.meta.ResolvedJavaMethod;
import jdk.vm.ci.meta.ResolvedJavaType;

Container for objects representing the Code attributes parsed from a class file.
See Also:
/** * Container for objects representing the {@code Code} attributes parsed from a class file. * * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.3">Code * attributes</a> * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4">Constant * Pool</a> */
public class Classfile { private final ResolvedJavaType type; private final List<ClassfileBytecode> codeAttributes; private static final int MAJOR_VERSION_JAVA_MIN = 51; // JDK7 private static final int MAJOR_VERSION_JAVA_MAX = 55; // JDK11 private static final int MAGIC = 0xCAFEBABE;
Creates a Classfile by parsing the class file bytes for type loadable from context.
Throws:
/** * Creates a {@link Classfile} by parsing the class file bytes for {@code type} loadable from * {@code context}. * * @throws NoClassDefFoundError if there is an IO error while parsing the class file */
public Classfile(ResolvedJavaType type, DataInputStream stream, ClassfileBytecodeProvider context) throws IOException { this.type = type; // magic int magic = stream.readInt(); assert magic == MAGIC; int minor = stream.readUnsignedShort(); int major = stream.readUnsignedShort(); if (major < MAJOR_VERSION_JAVA_MIN || major > MAJOR_VERSION_JAVA_MAX) { throw new UnsupportedClassVersionError("Unsupported class file version: " + major + "." + minor); } ClassfileConstantPool cp = new ClassfileConstantPool(stream, context); // access_flags, this_class, super_class skipFully(stream, 6); // interfaces skipFully(stream, stream.readUnsignedShort() * 2); // fields skipFields(stream); // methods codeAttributes = readMethods(stream, cp); // attributes skipAttributes(stream); } public ClassfileBytecode getCode(String name, String descriptor) { for (ClassfileBytecode code : codeAttributes) { ResolvedJavaMethod method = code.getMethod(); if (method.getName().equals(name) && method.getSignature().toMethodDescriptor().equals(descriptor)) { return code; } } throw new NoSuchMethodError(type.toJavaName() + "." + name + descriptor); } private static void skipAttributes(DataInputStream stream) throws IOException { int attributesCount; attributesCount = stream.readUnsignedShort(); for (int i = 0; i < attributesCount; i++) { skipFully(stream, 2); // name_index int attributeLength = stream.readInt(); skipFully(stream, attributeLength); } } static void skipFully(DataInputStream stream, int n) throws IOException { long skipped = 0; do { long s = stream.skip(n - skipped); skipped += s; if (s == 0 && skipped != n) { // Check for EOF (i.e., truncated class file) if (stream.read() == -1) { throw new IOException("truncated stream"); } skipped++; } } while (skipped != n); } private ClassfileBytecode findCodeAttribute(DataInputStream stream, ClassfileConstantPool cp, String name, String descriptor, boolean isStatic) throws IOException { int attributesCount; attributesCount = stream.readUnsignedShort(); ClassfileBytecode code = null; for (int i = 0; i < attributesCount; i++) { String attributeName = cp.get(Utf8.class, stream.readUnsignedShort()).value; int attributeLength = stream.readInt(); if (code == null && attributeName.equals("Code")) { ResolvedJavaMethod method = cp.context.findMethod(type, name, descriptor, isStatic); // Even if we will discard the Code attribute (see below), we still // need to parse it to reach the following class file content. code = new ClassfileBytecode(method, stream, cp); if (method == null) { // This is a method hidden from reflection // (see sun.reflect.Reflection.filterMethods) code = null; } } else { skipFully(stream, attributeLength); } } return code; } private static void skipFields(DataInputStream stream) throws IOException { int count = stream.readUnsignedShort(); for (int i = 0; i < count; i++) { skipFully(stream, 6); // access_flags, name_index, descriptor_index skipAttributes(stream); } } private List<ClassfileBytecode> readMethods(DataInputStream stream, ClassfileConstantPool cp) throws IOException { int count = stream.readUnsignedShort(); List<ClassfileBytecode> result = new ArrayList<>(count); for (int i = 0; i < count; i++) { int accessFlags = stream.readUnsignedShort(); boolean isStatic = Modifier.isStatic(accessFlags); String name = cp.get(Utf8.class, stream.readUnsignedShort()).value; String descriptor = cp.get(Utf8.class, stream.readUnsignedShort()).value; ClassfileBytecode code = findCodeAttribute(stream, cp, name, descriptor, isStatic); if (code != null) { result.add(code); } } return result; } @Override public String toString() { return getClass().getSimpleName() + "<" + type.toJavaName() + ">"; } }