/*
* JBoss, Home of Professional Open Source.
*
* Copyright 2012 Red Hat, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jboss.classfilewriter.attributes;
import org.jboss.classfilewriter.ClassMethod;
import org.jboss.classfilewriter.code.CodeAttribute;
import org.jboss.classfilewriter.code.StackEntry;
import org.jboss.classfilewriter.code.StackEntryType;
import org.jboss.classfilewriter.code.StackFrame;
import org.jboss.classfilewriter.code.StackFrameType;
import org.jboss.classfilewriter.constpool.ConstPool;
import org.jboss.classfilewriter.util.ByteArrayDataOutputStream;
import org.jboss.classfilewriter.util.LazySize;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map.Entry;
/**
* A JDK 6 StackMap sttribute.
*
*TODO: this will currently fall over if the code length, max locals or max stack is above 65535
*
* @author Stuart Douglas
*
*/
public class StackMapTableAttribute extends Attribute {
private static int FULL_FRAME = 255;
private static int SAME_FRAME_EXTENDED = 251;
public static final String NAME = "StackMapTable";
private final ClassMethod method;
public StackMapTableAttribute(ClassMethod classMethod, ConstPool constPool) {
super(NAME, constPool);
method = classMethod;
}
@Override
public void writeData(ByteArrayDataOutputStream stream) throws IOException {
// as we don't know the size yet we write everything to a byte stream first
// TODO: make this better
final CodeAttribute ca = method.getCodeAttribute();
// now we need to write the stack frames.
// for now we are going to write all frames as full frames
// TODO: optimise the frame creation
// write to dstream
LazySize size = stream.writeSize();
stream.writeShort(ca.getStackFrames().size());
int lastPos = -1;
for (Entry<Integer, StackFrame> entry : method.getCodeAttribute().getStackFrames().entrySet()) {
int offset = entry.getKey() - lastPos - 1;
lastPos = entry.getKey();
StackFrame frame = entry.getValue();
if (frame.getType() == StackFrameType.SAME_FRAME || frame.getType() == StackFrameType.SAME_FRAME_EXTENDED) {
writeSameFrame(stream, offset, lastPos, frame);
} else if (frame.getType() == StackFrameType.SAME_LOCALS_1_STACK && offset < (127 - 64)) {
writeSameLocals1Stack(stream, offset, lastPos, frame);
} else {
writeFullFrame(stream, offset, lastPos, entry.getValue());
}
}
size.markEnd();
}
private void writeSameLocals1Stack(DataOutputStream dstream, int offset, int lastPos, StackFrame frame) throws IOException {
dstream.writeByte(offset + 64);
frame.getStackState().getContents().get(0).write(dstream);
}
private void writeSameFrame(DataOutputStream dstream, int offset, int lastPos, StackFrame frame) throws IOException {
if (offset > 63) {
dstream.writeByte(SAME_FRAME_EXTENDED);
dstream.writeShort(offset);
} else {
dstream.writeByte(offset);
}
}
/**
* writes a full_frame to the stack map table
*/
private void writeFullFrame(DataOutputStream dstream, int offset, int position, StackFrame value) throws IOException {
dstream.writeByte(FULL_FRAME);
dstream.writeShort(offset);
List<StackEntry> realLocalVars = new ArrayList<StackEntry>(value.getLocalVariableState().getContents().size());
for (StackEntry i : value.getLocalVariableState().getContents()) {
if (i.getType() != StackEntryType.TOP) {
realLocalVars.add(i);
}
}
dstream.writeShort(realLocalVars.size());
for (StackEntry i : realLocalVars) {
i.write(dstream);
}
// TODO: this is inefficient, the stack should store the number of TOP values in each frame
List<StackEntry> realStack = new ArrayList<StackEntry>(value.getStackState().getContents().size());
for (StackEntry i : value.getStackState().getContents()) {
if (i.getType() != StackEntryType.TOP) {
realStack.add(i);
}
}
dstream.writeShort(realStack.size());
for (StackEntry i : realStack) {
i.write(dstream);
}
}
}