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An unofficial backport of the JDK Classfile API to Java 17
/*
* Copyright (c) 2023, 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 io.github.dmlloyd.classfile.CodeBuilder;
import io.github.dmlloyd.classfile.CodeElement;
import io.github.dmlloyd.classfile.Label;
import io.github.dmlloyd.classfile.Opcode;
import io.github.dmlloyd.classfile.TypeKind;
import io.github.dmlloyd.classfile.components.CodeStackTracker;
import io.github.dmlloyd.classfile.instruction.*;
import java.util.*;
import java.util.function.Consumer;
public final class CodeStackTrackerImpl implements CodeStackTracker {
private static record Item(TypeKind type, Item next) {
}
private final class Stack extends AbstractCollection {
private Item top;
private int count, realSize;
Stack(Item top, int count, int realSize) {
this.top = top;
this.count = count;
this.realSize = realSize;
}
@Override
public Iterator iterator() {
return new Iterator() {
Item i = top;
@Override
public boolean hasNext() {
return i != null;
}
@Override
public TypeKind next() {
if (i == null) {
throw new NoSuchElementException();
}
var t = i.type;
i = i.next;
return t;
}
};
}
@Override
public int size() {
return count;
}
private void push(TypeKind type) {
top = new Item(type, top);
realSize += type.slotSize();
count++;
if (maxSize != null && realSize > maxSize) maxSize = realSize;
}
private TypeKind pop() {
var t = top.type;
realSize -= t.slotSize();
count--;
top = top.next;
return t;
}
}
private Stack stack = new Stack(null, 0, 0);
private Integer maxSize = 0;
public CodeStackTrackerImpl(TypeKind... initialStack) {
for (int i = initialStack.length - 1; i >= 0; i--)
push(initialStack[i]);
}
@Override
public Optional> stack() {
return Optional.ofNullable(fork());
}
@Override
public Optional maxStackSize() {
return Optional.ofNullable(maxSize);
}
private final Map map = new HashMap<>();
private void push(TypeKind type) {
if (stack != null) {
if (type != TypeKind.VOID) stack.push(type);
} else {
maxSize = null;
}
}
private void pop(int i) {
if (stack != null) {
while (i-- > 0) stack.pop();
} else {
maxSize = null;
}
}
private Stack fork() {
return stack == null ? null : new Stack(stack.top, stack.count, stack.realSize);
}
private void withStack(Consumer c) {
if (stack != null) c.accept(stack);
else maxSize = null;
}
@Override
public void accept(CodeBuilder cb, CodeElement el) {
cb.with(el);
if (el instanceof ArrayLoadInstruction i) {
pop(2);push(i.typeKind());
}
else if (el instanceof ArrayStoreInstruction i)
pop(3);
else if (el instanceof BranchInstruction i) {
if (i.opcode() == Opcode.GOTO || i.opcode() == Opcode.GOTO_W) {
map.put(i.target(), stack);
stack = null;
} else {
pop(1);
map.put(i.target(), fork());
}
}
else if (el instanceof ConstantInstruction i)
push(i.typeKind());
else if (el instanceof ConvertInstruction i) {
pop(1);push(i.toType());
}
else if (el instanceof FieldInstruction i) {
switch (i.opcode()) {
case GETSTATIC ->
push(TypeKind.fromDescriptor(i.type().stringValue()));
case GETFIELD -> {
pop(1);push(TypeKind.fromDescriptor(i.type().stringValue()));
}
case PUTSTATIC ->
pop(1);
case PUTFIELD ->
pop(2);
}
}
else if (el instanceof InvokeDynamicInstruction i) {
var type = i.typeSymbol();
pop(type.parameterCount());
push(TypeKind.from(type.returnType()));
}
else if (el instanceof InvokeInstruction i) {
var type = i.typeSymbol();
pop(type.parameterCount());
if (i.opcode() != Opcode.INVOKESTATIC) pop(1);
push(TypeKind.from(type.returnType()));
}
else if (el instanceof LoadInstruction i)
push(i.typeKind());
else if (el instanceof StoreInstruction i)
pop(1);
else if (el instanceof LookupSwitchInstruction i) {
map.put(i.defaultTarget(), stack);
for (var c : i.cases()) map.put(c.target(), fork());
stack = null;
}
else if (el instanceof MonitorInstruction i)
pop(1);
else if (el instanceof NewMultiArrayInstruction i) {
pop(i.dimensions());push(TypeKind.REFERENCE);
}
else if (el instanceof NewObjectInstruction i)
push(TypeKind.REFERENCE);
else if (el instanceof NewPrimitiveArrayInstruction i) {
pop(1);push(TypeKind.REFERENCE);
}
else if (el instanceof NewReferenceArrayInstruction i) {
pop(1);push(TypeKind.REFERENCE);
}
else if (el instanceof NopInstruction i) {}
else if (el instanceof OperatorInstruction i) {
switch (i.opcode()) {
case ARRAYLENGTH, INEG, LNEG, FNEG, DNEG -> pop(1);
default -> pop(2);
}
push(i.typeKind());
}
else if (el instanceof ReturnInstruction i)
stack = null;
else if (el instanceof StackInstruction i) {
switch (i.opcode()) {
case POP -> pop(1);
case POP2 -> withStack(s -> {
if (s.pop().slotSize() == 1) s.pop();
});
case DUP -> withStack(s -> {
var v = s.pop();s.push(v);s.push(v);
});
case DUP2 -> withStack(s -> {
var v1 = s.pop();
if (v1.slotSize() == 1) {
var v2 = s.pop();
s.push(v2);s.push(v1);
s.push(v2);s.push(v1);
} else {
s.push(v1);s.push(v1);
}
});
case DUP_X1 -> withStack(s -> {
var v1 = s.pop();
var v2 = s.pop();
s.push(v1);s.push(v2);s.push(v1);
});
case DUP_X2 -> withStack(s -> {
var v1 = s.pop();
var v2 = s.pop();
if (v2.slotSize() == 1) {
var v3 = s.pop();
s.push(v1);s.push(v3);s.push(v2);s.push(v1);
} else {
s.push(v1);s.push(v2);s.push(v1);
}
});
case DUP2_X1 -> withStack(s -> {
var v1 = s.pop();
var v2 = s.pop();
if (v1.slotSize() == 1) {
var v3 = s.pop();
s.push(v2);s.push(v1);s.push(v3);s.push(v2);s.push(v1);
} else {
s.push(v1);s.push(v2);s.push(v1);
}
});
case DUP2_X2 -> withStack(s -> {
var v1 = s.pop();
var v2 = s.pop();
if (v1.slotSize() == 1) {
var v3 = s.pop();
if (v3.slotSize() == 1) {
var v4 = s.pop();
s.push(v2);s.push(v1);s.push(v4);s.push(v3);s.push(v2);s.push(v1);
} else {
s.push(v2);s.push(v1);s.push(v3);s.push(v2);s.push(v1);
}
} else {
if (v2.slotSize() == 1) {
var v3 = s.pop();
s.push(v1);s.push(v3);s.push(v2);s.push(v1);
} else {
s.push(v1);s.push(v2);s.push(v1);
}
}
});
case SWAP -> withStack(s -> {
var v1 = s.pop();
var v2 = s.pop();
s.push(v1);s.push(v2);
});
}
}
else if (el instanceof TableSwitchInstruction i) {
map.put(i.defaultTarget(), stack);
for (var c : i.cases()) map.put(c.target(), fork());
stack = null;
}
else if (el instanceof ThrowInstruction i)
stack = null;
else if (el instanceof TypeCheckInstruction i) {
switch (i.opcode()) {
case CHECKCAST -> {
pop(1);push(TypeKind.REFERENCE);
}
case INSTANCEOF -> {
pop(1);push(TypeKind.INT);
}
}
}
else if (el instanceof ExceptionCatch i)
map.put(i.handler(), new Stack(new Item(TypeKind.REFERENCE, null), 1, 1));
else if (el instanceof LabelTarget i)
stack = map.getOrDefault(i.label(), stack);
}
}
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