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An unofficial backport of the JDK Classfile API to Java 17
/*
* Copyright (c) 2022, 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 static io.github.dmlloyd.classfile.ClassFile.ASTORE_3;
import static io.github.dmlloyd.classfile.ClassFile.ISTORE;
import static io.github.dmlloyd.classfile.ClassFile.LOOKUPSWITCH;
import static io.github.dmlloyd.classfile.ClassFile.TABLESWITCH;
import static io.github.dmlloyd.classfile.ClassFile.WIDE;
public final class RawBytecodeHelper {
public static final int ILLEGAL = -1;
private static final byte[] LENGTHS = new byte[] {
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 2, 3, 3, 2 | (4 << 4), 2 | (4 << 4), 2 | (4 << 4), 2 | (4 << 4), 2 | (4 << 4), 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2 | (4 << 4), 2 | (4 << 4), 2 | (4 << 4), 2 | (4 << 4), 2 | (4 << 4), 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3 | (6 << 4), 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2 | (4 << 4), 0, 0, 1, 1, 1,
1, 1, 1, 3, 3, 3, 3, 3, 3, 3, 5, 5, 3, 2, 3, 1, 1, 3, 3, 1, 1, 0, 4, 3, 3, 5, 5, 0, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 4, 4, 4, 2, 4, 3, 3, 0, 0, 1, 3, 2, 3, 3, 3, 1, 2, 1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};
public static boolean isStoreIntoLocal(int code) {
return (ISTORE <= code && code <= ASTORE_3);
}
public static int align(int n) {
return (n + 3) & ~3;
}
private final ByteBuffer bytecode;
public int bci, nextBci, endBci;
public int rawCode;
public boolean isWide;
public RawBytecodeHelper(ByteBuffer bytecode) {
this.bytecode = bytecode;
this.bci = 0;
this.nextBci = 0;
this.endBci = bytecode.capacity();
}
public boolean isLastBytecode() {
return nextBci >= endBci;
}
public int getShort(int bci) {
return bytecode.getShort(bci);
}
public int dest() {
return bci + getShort(bci + 1);
}
public int getInt(int bci) {
return bytecode.getInt(bci);
}
public int destW() {
return bci + getInt(bci + 1);
}
public int getIndexU1() {
return bytecode.get(bci + 1) & 0xff;
}
public int getU1(int bci) {
return bytecode.get(bci) & 0xff;
}
public int rawNext(int jumpTo) {
this.nextBci = jumpTo;
return rawNext();
}
public int rawNext() {
bci = nextBci;
int code = bytecode.get(bci) & 0xff;
int len = LENGTHS[code] & 0xf;
if (len > 0 && (bci <= endBci - len)) {
isWide = false;
nextBci += len;
if (nextBci <= bci) {
code = ILLEGAL;
}
rawCode = code;
return code;
} else {
len = switch (bytecode.get(bci) & 0xff) {
case WIDE -> {
if (bci + 1 >= endBci) {
yield -1;
}
yield LENGTHS[bytecode.get(bci + 1) & 0xff] >> 4;
}
case TABLESWITCH -> {
int aligned_bci = align(bci + 1);
if (aligned_bci + 3 * 4 >= endBci) {
yield -1;
}
int lo = bytecode.getInt(aligned_bci + 1 * 4);
int hi = bytecode.getInt(aligned_bci + 2 * 4);
int l = aligned_bci - bci + (3 + hi - lo + 1) * 4;
if (l > 0) yield l; else yield -1;
}
case LOOKUPSWITCH -> {
int aligned_bci = align(bci + 1);
if (aligned_bci + 2 * 4 >= endBci) {
yield -1;
}
int npairs = bytecode.getInt(aligned_bci + 4);
int l = aligned_bci - bci + (2 + 2 * npairs) * 4;
if (l > 0) yield l; else yield -1;
}
default ->
0;
};
if (len <= 0 || (bci > endBci - len) || (bci - len >= nextBci)) {
code = ILLEGAL;
} else {
nextBci += len;
isWide = false;
if (code == WIDE) {
if (bci + 1 >= endBci) {
code = ILLEGAL;
} else {
code = bytecode.get(bci + 1) & 0xff;
isWide = true;
}
}
}
rawCode = code;
return code;
}
}
public int getIndex() {
return (isWide) ? getIndexU2Raw(bci + 2) : getIndexU1();
}
public int getIndexU2() {
return getIndexU2Raw(bci + 1);
}
public int getIndexU2Raw(int bci) {
return bytecode.getShort(bci) & 0xffff;
}
}