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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.nio.ByteBuffer;
import java.util.Arrays;
import io.github.dmlloyd.classfile.BufWriter;
import io.github.dmlloyd.classfile.constantpool.ClassEntry;
import io.github.dmlloyd.classfile.constantpool.ConstantPool;
import io.github.dmlloyd.classfile.constantpool.ConstantPoolBuilder;
import io.github.dmlloyd.classfile.constantpool.PoolEntry;
public final class BufWriterImpl implements BufWriter {
private final ConstantPoolBuilder constantPool;
private final ClassFileImpl context;
private LabelContext labelContext;
private final ClassEntry thisClass;
private final int majorVersion;
byte[] elems;
int offset = 0;
public BufWriterImpl(ConstantPoolBuilder constantPool, ClassFileImpl context) {
this(constantPool, context, 64, null, 0);
}
public BufWriterImpl(ConstantPoolBuilder constantPool, ClassFileImpl context, int initialSize) {
this(constantPool, context, initialSize, null, 0);
}
public BufWriterImpl(ConstantPoolBuilder constantPool, ClassFileImpl context, int initialSize, ClassEntry thisClass, int majorVersion) {
this.constantPool = constantPool;
this.context = context;
elems = new byte[initialSize];
this.thisClass = thisClass;
this.majorVersion = majorVersion;
}
@Override
public ConstantPoolBuilder constantPool() {
return constantPool;
}
public LabelContext labelContext() {
return labelContext;
}
public void setLabelContext(LabelContext labelContext) {
this.labelContext = labelContext;
}
@Override
public boolean canWriteDirect(ConstantPool other) {
return constantPool.canWriteDirect(other);
}
public ClassEntry thisClass() {
return thisClass;
}
public int getMajorVersion() {
return majorVersion;
}
public ClassFileImpl context() {
return context;
}
@Override
public void writeU1(int x) {
reserveSpace(1);
elems[offset++] = (byte) x;
}
@Override
public void writeU2(int x) {
reserveSpace(2);
byte[] elems = this.elems;
int offset = this.offset;
elems[offset ] = (byte) (x >> 8);
elems[offset + 1] = (byte) x;
this.offset = offset + 2;
}
@Override
public void writeInt(int x) {
reserveSpace(4);
byte[] elems = this.elems;
int offset = this.offset;
elems[offset ] = (byte) (x >> 24);
elems[offset + 1] = (byte) (x >> 16);
elems[offset + 2] = (byte) (x >> 8);
elems[offset + 3] = (byte) x;
this.offset = offset + 4;
}
@Override
public void writeFloat(float x) {
writeInt(Float.floatToIntBits(x));
}
@Override
public void writeLong(long x) {
reserveSpace(8);
byte[] elems = this.elems;
int offset = this.offset;
elems[offset ] = (byte) (x >> 56);
elems[offset + 1] = (byte) (x >> 48);
elems[offset + 2] = (byte) (x >> 40);
elems[offset + 3] = (byte) (x >> 32);
elems[offset + 4] = (byte) (x >> 24);
elems[offset + 5] = (byte) (x >> 16);
elems[offset + 6] = (byte) (x >> 8);
elems[offset + 7] = (byte) x;
this.offset = offset + 8;
}
@Override
public void writeDouble(double x) {
writeLong(Double.doubleToLongBits(x));
}
@Override
public void writeBytes(byte[] arr) {
writeBytes(arr, 0, arr.length);
}
public void writeBytes(BufWriterImpl other) {
writeBytes(other.elems, 0, other.offset);
}
@Override
public void writeBytes(byte[] arr, int start, int length) {
reserveSpace(length);
System.arraycopy(arr, start, elems, offset, length);
offset += length;
}
@Override
public void patchInt(int offset, int size, int value) {
int prevOffset = this.offset;
this.offset = offset;
writeIntBytes(size, value);
this.offset = prevOffset;
}
@Override
public void writeIntBytes(int intSize, long intValue) {
reserveSpace(intSize);
for (int i = 0; i < intSize; i++) {
elems[offset++] = (byte) ((intValue >> 8 * (intSize - i - 1)) & 0xFF);
}
}
@Override
public void reserveSpace(int freeBytes) {
int minCapacity = offset + freeBytes;
if (minCapacity > elems.length) {
grow(minCapacity);
}
}
private void grow(int minCapacity) {
int newsize = elems.length * 2;
while (minCapacity > newsize) {
newsize *= 2;
}
elems = Arrays.copyOf(elems, newsize);
}
@Override
public int size() {
return offset;
}
public ByteBuffer asByteBuffer() {
return ByteBuffer.wrap(elems, 0, offset).slice();
}
public void copyTo(byte[] array, int bufferOffset) {
System.arraycopy(elems, 0, array, bufferOffset, size());
}
// writeIndex methods ensure that any CP info written
// is relative to the correct constant pool
@Override
public void writeIndex(PoolEntry entry) {
int idx = AbstractPoolEntry.maybeClone(constantPool, entry).index();
if (idx < 1 || idx > Character.MAX_VALUE)
throw new IllegalArgumentException(idx + " is not a valid index. Entry: " + entry);
writeU2(idx);
}
@Override
public void writeIndexOrZero(PoolEntry entry) {
if (entry == null || entry.index() == 0)
writeU2(0);
else
writeIndex(entry);
}
}