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An unofficial backport of the JDK Classfile API to Java 17
/*
* Copyright (c) 2022, 2024, 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 io.github.dmlloyd.classfile.impl;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Function;
import io.github.dmlloyd.classfile.*;
import io.github.dmlloyd.classfile.attribute.BootstrapMethodsAttribute;
import io.github.dmlloyd.classfile.constantpool.*;
import static io.github.dmlloyd.classfile.ClassFile.TAG_CLASS;
import static io.github.dmlloyd.classfile.ClassFile.TAG_CONSTANTDYNAMIC;
import static io.github.dmlloyd.classfile.ClassFile.TAG_DOUBLE;
import static io.github.dmlloyd.classfile.ClassFile.TAG_FIELDREF;
import static io.github.dmlloyd.classfile.ClassFile.TAG_FLOAT;
import static io.github.dmlloyd.classfile.ClassFile.TAG_INTEGER;
import static io.github.dmlloyd.classfile.ClassFile.TAG_INTERFACEMETHODREF;
import static io.github.dmlloyd.classfile.ClassFile.TAG_INVOKEDYNAMIC;
import static io.github.dmlloyd.classfile.ClassFile.TAG_LONG;
import static io.github.dmlloyd.classfile.ClassFile.TAG_METHODHANDLE;
import static io.github.dmlloyd.classfile.ClassFile.TAG_METHODREF;
import static io.github.dmlloyd.classfile.ClassFile.TAG_METHODTYPE;
import static io.github.dmlloyd.classfile.ClassFile.TAG_MODULE;
import static io.github.dmlloyd.classfile.ClassFile.TAG_NAMEANDTYPE;
import static io.github.dmlloyd.classfile.ClassFile.TAG_PACKAGE;
import static io.github.dmlloyd.classfile.ClassFile.TAG_STRING;
import static io.github.dmlloyd.classfile.ClassFile.TAG_UTF8;
public final class ClassReaderImpl
implements ClassReader {
static final int CP_ITEM_START = 10;
private final byte[] buffer;
private final int metadataStart;
private final int classfileLength;
private final Function> attributeMapper;
private final int flags;
private final int thisClassPos;
private ClassEntry thisClass;
private Optional superclass;
private final int constantPoolCount;
private final int[] cpOffset;
final ClassFileImpl context;
final int interfacesPos;
final PoolEntry[] cp;
private ClassModel containedClass;
private List bsmEntries;
private BootstrapMethodsAttribute bootstrapMethodsAttribute;
ClassReaderImpl(byte[] classfileBytes,
ClassFileImpl context) {
this.buffer = classfileBytes;
this.classfileLength = classfileBytes.length;
this.context = context;
this.attributeMapper = this.context.attributeMapperOption().attributeMapper();
if (classfileLength < 4 || readInt(0) != 0xCAFEBABE) {
throw new IllegalArgumentException("Bad magic number");
}
if (readU2(6) > ClassFile.latestMajorVersion()) {
throw new IllegalArgumentException("Unsupported class file version: " + readU2(6));
}
int constantPoolCount = readU2(8);
int[] cpOffset = new int[constantPoolCount];
int p = CP_ITEM_START;
for (int i = 1; i < cpOffset.length; ++i) {
cpOffset[i] = p;
int tag = readU1(p);
++p;
switch (tag) {
// 2
case TAG_CLASS, TAG_METHODTYPE, TAG_MODULE, TAG_STRING, TAG_PACKAGE -> p += 2;
// 3
case TAG_METHODHANDLE -> p += 3;
// 4
case TAG_CONSTANTDYNAMIC, TAG_FIELDREF, TAG_FLOAT, TAG_INTEGER,
TAG_INTERFACEMETHODREF, TAG_INVOKEDYNAMIC, TAG_METHODREF,
TAG_NAMEANDTYPE -> p += 4;
// 8
case TAG_DOUBLE, TAG_LONG -> {
p += 8;
++i;
}
case TAG_UTF8 -> p += 2 + readU2(p);
default -> throw new ConstantPoolException(
"Bad tag (" + tag + ") at index (" + i + ") position (" + p + ")");
}
}
this.metadataStart = p;
this.cpOffset = cpOffset;
this.constantPoolCount = constantPoolCount;
this.cp = new PoolEntry[constantPoolCount];
this.flags = readU2(p);
this.thisClassPos = p + 2;
p += 6;
this.interfacesPos = p;
}
public ClassFileImpl context() {
return context;
}
@Override
public Function> customAttributes() {
return attributeMapper;
}
@Override
public int size() {
return constantPoolCount;
}
@Override
public int flags() {
return flags;
}
@Override
public ClassEntry thisClassEntry() {
if (thisClass == null) {
thisClass = readEntry(thisClassPos, ClassEntry.class);
}
return thisClass;
}
@Override
public Optional superclassEntry() {
if (superclass == null) {
superclass = Optional.ofNullable(readEntryOrNull(thisClassPos + 2, ClassEntry.class));
}
return superclass;
}
public int thisClassPos() {
return thisClassPos;
}
@Override
public int classfileLength() {
return classfileLength;
}
//------ Bootstrap Method Table handling
@Override
public int bootstrapMethodCount() {
return bootstrapMethodsAttribute().bootstrapMethodsSize();
}
@Override
public BootstrapMethodEntryImpl bootstrapMethodEntry(int index) {
if (index < 0 || index >= bootstrapMethodCount()) {
throw new ConstantPoolException("Bad BSM index: " + index);
}
return bsmEntries().get(index);
}
private static IllegalArgumentException outOfBoundsError(IndexOutOfBoundsException cause) {
return new IllegalArgumentException("Reading beyond classfile bounds", cause);
}
@Override
public int readU1(int p) {
try {
return buffer[p] & 0xFF;
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public int readU2(int p) {
try {
int b1 = buffer[p] & 0xFF;
int b2 = buffer[p + 1] & 0xFF;
return (b1 << 8) + b2;
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public int readS1(int p) {
try {
return buffer[p];
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public int readS2(int p) {
try {
int b1 = buffer[p];
int b2 = buffer[p + 1] & 0xFF;
return (b1 << 8) + b2;
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public int readInt(int p) {
try {
int ch1 = buffer[p] & 0xFF;
int ch2 = buffer[p + 1] & 0xFF;
int ch3 = buffer[p + 2] & 0xFF;
int ch4 = buffer[p + 3] & 0xFF;
return (ch1 << 24) + (ch2 << 16) + (ch3 << 8) + ch4;
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public long readLong(int p) {
try {
return ((long) buffer[p + 0] << 56) + ((long) (buffer[p + 1] & 255) << 48) +
((long) (buffer[p + 2] & 255) << 40) + ((long) (buffer[p + 3] & 255) << 32) +
((long) (buffer[p + 4] & 255) << 24) + ((buffer[p + 5] & 255) << 16) + ((buffer[p + 6] & 255) << 8) +
(buffer[p + 7] & 255);
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public float readFloat(int p) {
return Float.intBitsToFloat(readInt(p));
}
@Override
public double readDouble(int p) {
return Double.longBitsToDouble(readLong(p));
}
@Override
public byte[] readBytes(int p, int len) {
try {
return Arrays.copyOfRange(buffer, p, p + len);
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
@Override
public void copyBytesTo(BufWriter buf, int p, int len) {
try {
buf.writeBytes(buffer, p, len);
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
BootstrapMethodsAttribute bootstrapMethodsAttribute() {
if (bootstrapMethodsAttribute == null) {
bootstrapMethodsAttribute
= containedClass.findAttribute(Attributes.bootstrapMethods())
.orElse(new UnboundAttribute.EmptyBootstrapAttribute());
}
return bootstrapMethodsAttribute;
}
List bsmEntries() {
if (bsmEntries == null) {
bsmEntries = new ArrayList<>();
BootstrapMethodsAttribute attr = bootstrapMethodsAttribute();
List list = attr.bootstrapMethods();
if (!list.isEmpty()) {
for (BootstrapMethodEntry bm : list) {
AbstractPoolEntry.MethodHandleEntryImpl handle = (AbstractPoolEntry.MethodHandleEntryImpl) bm.bootstrapMethod();
List args = bm.arguments();
int hash = BootstrapMethodEntryImpl.computeHashCode(handle, args);
bsmEntries.add(new BootstrapMethodEntryImpl(this, bsmEntries.size(), hash, handle, args));
}
}
}
return bsmEntries;
}
void setContainedClass(ClassModel containedClass) {
this.containedClass = containedClass;
}
ClassModel getContainedClass() {
return containedClass;
}
boolean writeBootstrapMethods(BufWriterImpl buf) {
Optional a
= containedClass.findAttribute(Attributes.bootstrapMethods());
if (a.isEmpty())
return false;
// BootstrapMethodAttribute implementations are all internal writable
((Util.Writable) a.get()).writeTo(buf);
return true;
}
void writeConstantPoolEntries(BufWriter buf) {
copyBytesTo(buf, ClassReaderImpl.CP_ITEM_START,
metadataStart - ClassReaderImpl.CP_ITEM_START);
}
// Constantpool
@Override
public PoolEntry entryByIndex(int index) {
return entryByIndex(index, PoolEntry.class);
}
private static boolean checkTag(int tag, Class cls) {
var type = switch (tag) {
// JVMS Table 4.4-B. Constant pool tags
case TAG_UTF8 -> AbstractPoolEntry.Utf8EntryImpl.class;
case TAG_INTEGER -> AbstractPoolEntry.IntegerEntryImpl.class;
case TAG_FLOAT -> AbstractPoolEntry.FloatEntryImpl.class;
case TAG_LONG -> AbstractPoolEntry.LongEntryImpl.class;
case TAG_DOUBLE -> AbstractPoolEntry.DoubleEntryImpl.class;
case TAG_CLASS -> AbstractPoolEntry.ClassEntryImpl.class;
case TAG_STRING -> AbstractPoolEntry.StringEntryImpl.class;
case TAG_FIELDREF -> AbstractPoolEntry.FieldRefEntryImpl.class;
case TAG_METHODREF -> AbstractPoolEntry.MethodRefEntryImpl.class;
case TAG_INTERFACEMETHODREF -> AbstractPoolEntry.InterfaceMethodRefEntryImpl.class;
case TAG_NAMEANDTYPE -> AbstractPoolEntry.NameAndTypeEntryImpl.class;
case TAG_METHODHANDLE -> AbstractPoolEntry.MethodHandleEntryImpl.class;
case TAG_METHODTYPE -> AbstractPoolEntry.MethodTypeEntryImpl.class;
case TAG_CONSTANTDYNAMIC -> AbstractPoolEntry.ConstantDynamicEntryImpl.class;
case TAG_INVOKEDYNAMIC -> AbstractPoolEntry.InvokeDynamicEntryImpl.class;
case TAG_MODULE -> AbstractPoolEntry.ModuleEntryImpl.class;
case TAG_PACKAGE -> AbstractPoolEntry.PackageEntryImpl.class;
default -> null;
};
return type != null && cls.isAssignableFrom(type);
}
static T checkType(PoolEntry e, int index, Class cls) {
if (cls.isInstance(e)) return cls.cast(e);
throw new ConstantPoolException("Not a " + cls.getSimpleName() + " at index: " + index);
}
@Override
public T entryByIndex(int index, Class cls) {
Objects.requireNonNull(cls);
if (index <= 0 || index >= constantPoolCount) {
throw new ConstantPoolException("Bad CP index: " + index);
}
PoolEntry info = cp[index];
if (info == null) {
int offset = cpOffset[index];
if (offset == 0) {
throw new ConstantPoolException("Unusable CP index: " + index);
}
int tag = readU1(offset);
if (!checkTag(tag, cls)) {
throw new ConstantPoolException(
"Bad tag (" + tag + ") at index (" + index + ") position (" + offset + "), expected " + cls.getSimpleName());
}
final int q = offset + 1;
info = switch (tag) {
case TAG_UTF8 -> new AbstractPoolEntry.Utf8EntryImpl(this, index, buffer, q + 2, readU2(q));
case TAG_INTEGER -> new AbstractPoolEntry.IntegerEntryImpl(this, index, readInt(q));
case TAG_FLOAT -> new AbstractPoolEntry.FloatEntryImpl(this, index, readFloat(q));
case TAG_LONG -> new AbstractPoolEntry.LongEntryImpl(this, index, readLong(q));
case TAG_DOUBLE -> new AbstractPoolEntry.DoubleEntryImpl(this, index, readDouble(q));
case TAG_CLASS -> new AbstractPoolEntry.ClassEntryImpl(this, index, readEntry(q, AbstractPoolEntry.Utf8EntryImpl.class));
case TAG_STRING -> new AbstractPoolEntry.StringEntryImpl(this, index, readEntry(q, AbstractPoolEntry.Utf8EntryImpl.class));
case TAG_FIELDREF -> new AbstractPoolEntry.FieldRefEntryImpl(this, index, readEntry(q, AbstractPoolEntry.ClassEntryImpl.class),
readEntry(q + 2, AbstractPoolEntry.NameAndTypeEntryImpl.class));
case TAG_METHODREF -> new AbstractPoolEntry.MethodRefEntryImpl(this, index, readEntry(q, AbstractPoolEntry.ClassEntryImpl.class),
readEntry(q + 2, AbstractPoolEntry.NameAndTypeEntryImpl.class));
case TAG_INTERFACEMETHODREF -> new AbstractPoolEntry.InterfaceMethodRefEntryImpl(this, index, readEntry(q, AbstractPoolEntry.ClassEntryImpl.class),
readEntry(q + 2, AbstractPoolEntry.NameAndTypeEntryImpl.class));
case TAG_NAMEANDTYPE -> new AbstractPoolEntry.NameAndTypeEntryImpl(this, index, readEntry(q, AbstractPoolEntry.Utf8EntryImpl.class),
readEntry(q + 2, AbstractPoolEntry.Utf8EntryImpl.class));
case TAG_METHODHANDLE -> new AbstractPoolEntry.MethodHandleEntryImpl(this, index, readU1(q),
readEntry(q + 1, AbstractPoolEntry.AbstractMemberRefEntry.class));
case TAG_METHODTYPE -> new AbstractPoolEntry.MethodTypeEntryImpl(this, index, readEntry(q, AbstractPoolEntry.Utf8EntryImpl.class));
case TAG_CONSTANTDYNAMIC -> new AbstractPoolEntry.ConstantDynamicEntryImpl(this, index, readU2(q), readEntry(q + 2, AbstractPoolEntry.NameAndTypeEntryImpl.class));
case TAG_INVOKEDYNAMIC -> new AbstractPoolEntry.InvokeDynamicEntryImpl(this, index, readU2(q), readEntry(q + 2, AbstractPoolEntry.NameAndTypeEntryImpl.class));
case TAG_MODULE -> new AbstractPoolEntry.ModuleEntryImpl(this, index, readEntry(q, AbstractPoolEntry.Utf8EntryImpl.class));
case TAG_PACKAGE -> new AbstractPoolEntry.PackageEntryImpl(this, index, readEntry(q, AbstractPoolEntry.Utf8EntryImpl.class));
default -> throw new ConstantPoolException(
"Bad tag (" + tag + ") at index (" + index + ") position (" + offset + ")");
};
cp[index] = info;
}
return checkType(info, index, cls);
}
public int skipAttributeHolder(int offset) {
int p = offset;
int cnt = readU2(p);
p += 2;
for (int i = 0; i < cnt; ++i) {
int len = readInt(p + 2);
p += 6;
if (len < 0 || len > classfileLength - p) {
throw new IllegalArgumentException("attribute " + readEntry(p - 6, Utf8Entry.class).stringValue() + " too big to handle");
}
p += len;
}
return p;
}
@Override
public PoolEntry readEntry(int pos) {
return entryByIndex(readU2(pos));
}
@Override
public T readEntry(int pos, Class cls) {
Objects.requireNonNull(cls);
return entryByIndex(readU2(pos), cls);
}
@Override
public PoolEntry readEntryOrNull(int pos) {
int index = readU2(pos);
if (index == 0) {
return null;
}
return entryByIndex(index);
}
@Override
public T readEntryOrNull(int offset, Class cls) {
Objects.requireNonNull(cls);
int index = readU2(offset);
if (index == 0) {
return null;
}
return entryByIndex(index, cls);
}
public boolean compare(BufWriterImpl bufWriter,
int bufWriterOffset,
int classReaderOffset,
int length) {
try {
return Arrays.equals(bufWriter.elems,
bufWriterOffset, bufWriterOffset + length,
buffer, classReaderOffset, classReaderOffset + length);
} catch (IndexOutOfBoundsException e) {
throw outOfBoundsError(e);
}
}
}