StackMap.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.bcel.classfile;
import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Arrays;
import org.apache.bcel.Const;
import org.apache.bcel.util.Args;
/**
* This class represents a stack map attribute used for preverification of Java classes for the
* <a href="http://java.sun.com/j2me/"> Java 2 Micro Edition</a> (J2ME). This attribute is used by the
* <a href="http://java.sun.com/products/cldc/">KVM</a> and contained within the Code attribute of a method. See CLDC
* specification ���5.3.1.2
*
* <pre>
* StackMapTable_attribute {
* u2 attribute_name_index;
* u4 attribute_length;
* u2 number_of_entries;
* stack_map_frame entries[number_of_entries];
* }
* </pre>
*
* @see Code
* @see StackMapEntry
* @see StackMapType
*/
public final class StackMap extends Attribute {
private StackMapEntry[] table; // Table of stack map entries
/**
* Constructs object from input stream.
*
* @param nameIndex Index of name
* @param length Content length in bytes
* @param dataInput Input stream
* @param constantPool Array of constants
* @throws IOException if an I/O error occurs.
*/
StackMap(final int nameIndex, final int length, final DataInput dataInput, final ConstantPool constantPool) throws IOException {
this(nameIndex, length, (StackMapEntry[]) null, constantPool);
final int mapLength = dataInput.readUnsignedShort();
table = new StackMapEntry[mapLength];
for (int i = 0; i < mapLength; i++) {
table[i] = new StackMapEntry(dataInput, constantPool);
}
}
/*
* @param nameIndex Index of name
*
* @param length Content length in bytes
*
* @param map Table of stack map entries
*
* @param constantPool Array of constants
*/
public StackMap(final int nameIndex, final int length, final StackMapEntry[] table, final ConstantPool constantPool) {
super(Const.ATTR_STACK_MAP, nameIndex, length, constantPool);
this.table = table != null ? table : StackMapEntry.EMPTY_ARRAY;
Args.requireU2(this.table.length, "table.length");
}
/**
* Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
* I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
*
* @param v Visitor object
*/
@Override
public void accept(final Visitor v) {
v.visitStackMap(this);
}
/**
* @return deep copy of this attribute
*/
@Override
public Attribute copy(final ConstantPool constantPool) {
final StackMap c = (StackMap) clone();
c.table = new StackMapEntry[table.length];
Arrays.setAll(c.table, i -> table[i].copy());
c.setConstantPool(constantPool);
return c;
}
/**
* Dump stack map table attribute to file stream in binary format.
*
* @param file Output file stream
* @throws IOException if an I/O error occurs.
*/
@Override
public void dump(final DataOutputStream file) throws IOException {
super.dump(file);
file.writeShort(table.length);
for (final StackMapEntry entry : table) {
entry.dump(file);
}
}
public int getMapLength() {
return table.length;
}
/**
* @return Array of stack map entries
*/
public StackMapEntry[] getStackMap() {
return table;
}
/**
* @param table Array of stack map entries
*/
public void setStackMap(final StackMapEntry[] table) {
this.table = table != null ? table : StackMapEntry.EMPTY_ARRAY;
int len = 2; // Length of 'number_of_entries' field prior to the array of stack maps
for (final StackMapEntry element : this.table) {
len += element.getMapEntrySize();
}
setLength(len);
}
/**
* @return String representation.
*/
@Override
public String toString() {
final StringBuilder buf = new StringBuilder("StackMap(");
int runningOffset = -1; // no +1 on first entry
for (int i = 0; i < table.length; i++) {
runningOffset = table[i].getByteCodeOffset() + runningOffset + 1;
buf.append(String.format("%n@%03d %s", runningOffset, table[i]));
if (i < table.length - 1) {
buf.append(", ");
}
}
buf.append(')');
return buf.toString();
}
}