ConstantPool.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 java.util.Iterator;
import org.apache.bcel.Const;
/**
* This class represents the constant pool, i.e., a table of constants, of a parsed classfile. It may contain null references, due to the JVM specification that
* skips an entry after an 8-byte constant (double, long) entry. Those interested in generating constant pools programmatically should see
* <a href="../generic/ConstantPoolGen.html"> ConstantPoolGen</a>.
*
* @see Constant
* @see org.apache.bcel.generic.ConstantPoolGen
*/
public class ConstantPool implements Cloneable, Node, Iterable<Constant> {
private static String escape(final String str) {
final int len = str.length();
final StringBuilder buf = new StringBuilder(len + 5);
final char[] ch = str.toCharArray();
for (int i = 0; i < len; i++) {
switch (ch[i]) {
case '\n':
buf.append("\\n");
break;
case '\r':
buf.append("\\r");
break;
case '\t':
buf.append("\\t");
break;
case '\b':
buf.append("\\b");
break;
case '"':
buf.append("\\\"");
break;
default:
buf.append(ch[i]);
}
}
return buf.toString();
}
private Constant[] constantPool;
/**
* @param constantPool Array of constants
*/
public ConstantPool(final Constant[] constantPool) {
this.constantPool = constantPool;
}
/**
* Reads constants from given input stream.
*
* @param input Input stream
* @throws IOException if problem in readUnsignedShort or readConstant
*/
public ConstantPool(final DataInput input) throws IOException {
byte tag;
final int constantPoolCount = input.readUnsignedShort();
constantPool = new Constant[constantPoolCount];
/*
* constantPool[0] is unused by the compiler and may be used freely by the implementation.
* constantPool[0] is currently unused by the implementation.
*/
for (int i = 1; i < constantPoolCount; i++) {
constantPool[i] = Constant.readConstant(input);
/*
* Quote from the JVM specification: "All eight byte constants take up two spots in the constant pool. If this is the n'th byte in the constant
* pool, then the next item will be numbered n+2"
*
* Thus we have to increment the index counter.
*/
tag = constantPool[i].getTag();
if (tag == Const.CONSTANT_Double || tag == Const.CONSTANT_Long) {
i++;
}
}
}
/**
* 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.visitConstantPool(this);
}
/**
* Resolves constant to a string representation.
*
* @param c Constant to be printed
* @return String representation
* @throws IllegalArgumentException if c is unknown constant type
*/
public String constantToString(Constant c) throws IllegalArgumentException {
String str;
int i;
final byte tag = c.getTag();
switch (tag) {
case Const.CONSTANT_Class:
i = ((ConstantClass) c).getNameIndex();
c = getConstantUtf8(i);
str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
break;
case Const.CONSTANT_String:
i = ((ConstantString) c).getStringIndex();
c = getConstantUtf8(i);
str = "\"" + escape(((ConstantUtf8) c).getBytes()) + "\"";
break;
case Const.CONSTANT_Utf8:
str = ((ConstantUtf8) c).getBytes();
break;
case Const.CONSTANT_Double:
str = String.valueOf(((ConstantDouble) c).getBytes());
break;
case Const.CONSTANT_Float:
str = String.valueOf(((ConstantFloat) c).getBytes());
break;
case Const.CONSTANT_Long:
str = String.valueOf(((ConstantLong) c).getBytes());
break;
case Const.CONSTANT_Integer:
str = String.valueOf(((ConstantInteger) c).getBytes());
break;
case Const.CONSTANT_NameAndType:
str = constantToString(((ConstantNameAndType) c).getNameIndex(), Const.CONSTANT_Utf8) + " "
+ constantToString(((ConstantNameAndType) c).getSignatureIndex(), Const.CONSTANT_Utf8);
break;
case Const.CONSTANT_InterfaceMethodref:
case Const.CONSTANT_Methodref:
case Const.CONSTANT_Fieldref:
str = constantToString(((ConstantCP) c).getClassIndex(), Const.CONSTANT_Class) + "."
+ constantToString(((ConstantCP) c).getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
break;
case Const.CONSTANT_MethodHandle:
// Note that the ReferenceIndex may point to a Fieldref, Methodref or
// InterfaceMethodref - so we need to peek ahead to get the actual type.
final ConstantMethodHandle cmh = (ConstantMethodHandle) c;
str = Const.getMethodHandleName(cmh.getReferenceKind()) + " "
+ constantToString(cmh.getReferenceIndex(), getConstant(cmh.getReferenceIndex()).getTag());
break;
case Const.CONSTANT_MethodType:
final ConstantMethodType cmt = (ConstantMethodType) c;
str = constantToString(cmt.getDescriptorIndex(), Const.CONSTANT_Utf8);
break;
case Const.CONSTANT_InvokeDynamic:
final ConstantInvokeDynamic cid = (ConstantInvokeDynamic) c;
str = cid.getBootstrapMethodAttrIndex() + ":" + constantToString(cid.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
break;
case Const.CONSTANT_Dynamic:
final ConstantDynamic cd = (ConstantDynamic) c;
str = cd.getBootstrapMethodAttrIndex() + ":" + constantToString(cd.getNameAndTypeIndex(), Const.CONSTANT_NameAndType);
break;
case Const.CONSTANT_Module:
i = ((ConstantModule) c).getNameIndex();
c = getConstantUtf8(i);
str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
break;
case Const.CONSTANT_Package:
i = ((ConstantPackage) c).getNameIndex();
c = getConstantUtf8(i);
str = Utility.compactClassName(((ConstantUtf8) c).getBytes(), false);
break;
default: // Never reached
throw new IllegalArgumentException("Unknown constant type " + tag);
}
return str;
}
/**
* Retrieves constant at 'index' from constant pool and resolve it to a string representation.
*
* @param index of constant in constant pool
* @param tag expected type
* @return String representation
*/
public String constantToString(final int index, final byte tag) {
return constantToString(getConstant(index, tag));
}
/**
* @return deep copy of this constant pool
*/
public ConstantPool copy() {
ConstantPool c = null;
try {
c = (ConstantPool) clone();
c.constantPool = new Constant[constantPool.length];
for (int i = 1; i < constantPool.length; i++) {
if (constantPool[i] != null) {
c.constantPool[i] = constantPool[i].copy();
}
}
} catch (final CloneNotSupportedException e) {
// TODO should this throw?
}
return c;
}
/**
* Dump constant pool to file stream in binary format.
*
* @param file Output file stream
* @throws IOException if problem in writeShort or dump
*/
public void dump(final DataOutputStream file) throws IOException {
/*
* Constants over the size of the constant pool shall not be written out. This is a redundant measure as the ConstantPoolGen should have already
* reported an error back in the situation.
*/
final int size = Math.min(constantPool.length, Const.MAX_CP_ENTRIES);
file.writeShort(size);
for (int i = 1; i < size; i++) {
if (constantPool[i] != null) {
constantPool[i].dump(file);
}
}
}
/**
* Gets constant from constant pool.
*
* @param index Index in constant pool
* @return Constant value
* @see Constant
* @throws ClassFormatException if index is invalid
*/
@SuppressWarnings("unchecked")
public <T extends Constant> T getConstant(final int index) throws ClassFormatException {
return (T) getConstant(index, Constant.class);
}
/**
* Gets constant from constant pool and check whether it has the expected type.
*
* @param index Index in constant pool
* @param tag Tag of expected constant, i.e., its type
* @return Constant value
* @see Constant
* @throws ClassFormatException if constant type does not match tag
*/
@SuppressWarnings("unchecked")
public <T extends Constant> T getConstant(final int index, final byte tag) throws ClassFormatException {
return (T) getConstant(index, tag, Constant.class);
}
/**
* Gets constant from constant pool and check whether it has the expected type.
*
* @param index Index in constant pool
* @param tag Tag of expected constant, i.e., its type
* @return Constant value
* @see Constant
* @throws ClassFormatException if constant type does not match tag
* @since 6.6.0
*/
public <T extends Constant> T getConstant(final int index, final byte tag, final Class<T> castTo) throws ClassFormatException {
final T c = getConstant(index);
if (c == null || c.getTag() != tag) {
throw new ClassFormatException("Expected class '" + Const.getConstantName(tag) + "' at index " + index + " and got " + c);
}
return c;
}
/**
* Gets constant from constant pool.
*
* @param <T> A {@link Constant} subclass
* @param index Index in constant pool
* @param castTo The {@link Constant} subclass to cast to.
* @return Constant value
* @see Constant
* @throws ClassFormatException if index is invalid
* @since 6.6.0
*/
public <T extends Constant> T getConstant(final int index, final Class<T> castTo) throws ClassFormatException {
if (index >= constantPool.length || index < 1) {
throw new ClassFormatException("Invalid constant pool reference using index: " + index + ". Constant pool size is: " + constantPool.length);
}
if (constantPool[index] != null && !castTo.isAssignableFrom(constantPool[index].getClass())) {
throw new ClassFormatException("Invalid constant pool reference at index: " + index +
". Expected " + castTo + " but was " + constantPool[index].getClass());
}
if (index > 1) {
final Constant prev = constantPool[index - 1];
if (prev != null && (prev.getTag() == Const.CONSTANT_Double || prev.getTag() == Const.CONSTANT_Long)) {
throw new ClassFormatException("Constant pool at index " + index + " is invalid. The index is unused due to the preceeding "
+ Const.getConstantName(prev.getTag()) + ".");
}
}
// Previous check ensures this won't throw a ClassCastException
final T c = castTo.cast(constantPool[index]);
if (c == null) {
throw new ClassFormatException("Constant pool at index " + index + " is null.");
}
return c;
}
/**
* Gets constant from constant pool and check whether it has the expected type.
*
* @param index Index in constant pool
* @return ConstantInteger value
* @see ConstantInteger
* @throws ClassFormatException if constant type does not match tag
*/
public ConstantInteger getConstantInteger(final int index) {
return getConstant(index, Const.CONSTANT_Integer, ConstantInteger.class);
}
/**
* @return Array of constants.
* @see Constant
*/
public Constant[] getConstantPool() {
return constantPool;
}
/**
* Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these classes have an index field that
* points to another entry of the constant pool of type 'ConstantUtf8' which contains the real data.
*
* @param index Index in constant pool
* @param tag Tag of expected constant, either ConstantClass or ConstantString
* @return Contents of string reference
* @see ConstantClass
* @see ConstantString
* @throws IllegalArgumentException if tag is invalid
*/
public String getConstantString(final int index, final byte tag) throws IllegalArgumentException {
int i;
/*
* This switch() is not that elegant, since the four classes have the same contents, they just differ in the name of the index field variable. But we
* want to stick to the JVM naming conventions closely though we could have solved these more elegantly by using the same variable name or by
* subclassing.
*/
switch (tag) {
case Const.CONSTANT_Class:
i = getConstant(index, ConstantClass.class).getNameIndex();
break;
case Const.CONSTANT_String:
i = getConstant(index, ConstantString.class).getStringIndex();
break;
case Const.CONSTANT_Module:
i = getConstant(index, ConstantModule.class).getNameIndex();
break;
case Const.CONSTANT_Package:
i = getConstant(index, ConstantPackage.class).getNameIndex();
break;
case Const.CONSTANT_Utf8:
return getConstantUtf8(index).getBytes();
default:
throw new IllegalArgumentException("getConstantString called with illegal tag " + tag);
}
// Finally get the string from the constant pool
return getConstantUtf8(i).getBytes();
}
/**
* Gets constant from constant pool and check whether it has the expected type.
*
* @param index Index in constant pool
* @return ConstantUtf8 value
* @see ConstantUtf8
* @throws ClassFormatException if constant type does not match tag
*/
public ConstantUtf8 getConstantUtf8(final int index) throws ClassFormatException {
return getConstant(index, Const.CONSTANT_Utf8, ConstantUtf8.class);
}
/**
* @return Length of constant pool.
*/
public int getLength() {
return constantPool == null ? 0 : constantPool.length;
}
@Override
public Iterator<Constant> iterator() {
return Arrays.stream(constantPool).iterator();
}
/**
* @param constant Constant to set
*/
public void setConstant(final int index, final Constant constant) {
constantPool[index] = constant;
}
/**
* @param constantPool
*/
public void setConstantPool(final Constant[] constantPool) {
this.constantPool = constantPool;
}
/**
* @return String representation.
*/
@Override
public String toString() {
final StringBuilder buf = new StringBuilder();
for (int i = 1; i < constantPool.length; i++) {
buf.append(i).append(")").append(constantPool[i]).append("\n");
}
return buf.toString();
}
}