/*
* reserved comment block
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*/
package com.sun.org.apache.bcel.internal.classfile;
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import com.sun.org.apache.bcel.internal.Constants;
import java.io.*;
/**
* 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
* programatically should see <a href="../generic/ConstantPoolGen.html">
* ConstantPoolGen</a>.
* @version $Id: ConstantPool.java,v 1.1.2.1 2005/07/31 23:46:35 jeffsuttor Exp $
* @see Constant
* @see com.sun.org.apache.bcel.internal.generic.ConstantPoolGen
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
*/
public class ConstantPool implements Cloneable, Node, Serializable {
private int constant_pool_count;
private Constant[] constant_pool;
/**
* @param constant_pool Array of constants
*/
public ConstantPool(Constant[] constant_pool)
{
setConstantPool(constant_pool);
}
/**
* Read constants from given file stream.
*
* @param file Input stream
* @throws IOException
* @throws ClassFormatException
*/
ConstantPool(DataInputStream file) throws IOException, ClassFormatException
{
byte tag;
constant_pool_count = file.readUnsignedShort();
constant_pool = new Constant[constant_pool_count];
/* constant_pool[0] is unused by the compiler and may be used freely
* by the implementation.
*/
for(int i=1; i < constant_pool_count; i++) {
constant_pool[i] = Constant.readConstant(file);
/* 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 = constant_pool[i].getTag();
if((tag == Constants.CONSTANT_Double) || (tag == Constants.CONSTANT_Long))
i++;
}
}
/**
* Called by objects that are traversing the nodes of the tree implicitely
* 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
*/
public void accept(Visitor v) {
v.visitConstantPool(this);
}
/**
* Resolve constant to a string representation.
*
* @param constant Constant to be printed
* @return String representation
*/
public String constantToString(Constant c)
throws ClassFormatException
{
String str;
int i;
byte tag = c.getTag();
switch(tag) {
case Constants.CONSTANT_Class:
i = ((ConstantClass)c).getNameIndex();
c = getConstant(i, Constants.CONSTANT_Utf8);
str = Utility.compactClassName(((ConstantUtf8)c).getBytes(), false);
break;
case Constants.CONSTANT_String:
i = ((ConstantString)c).getStringIndex();
c = getConstant(i, Constants.CONSTANT_Utf8);
str = "\"" + escape(((ConstantUtf8)c).getBytes()) + "\"";
break;
case Constants.CONSTANT_Utf8: str = ((ConstantUtf8)c).getBytes(); break;
case Constants.CONSTANT_Double: str = "" + ((ConstantDouble)c).getBytes(); break;
case Constants.CONSTANT_Float: str = "" + ((ConstantFloat)c).getBytes(); break;
case Constants.CONSTANT_Long: str = "" + ((ConstantLong)c).getBytes(); break;
case Constants.CONSTANT_Integer: str = "" + ((ConstantInteger)c).getBytes(); break;
case Constants.CONSTANT_NameAndType:
str = (constantToString(((ConstantNameAndType)c).getNameIndex(),
Constants.CONSTANT_Utf8) + " " +
constantToString(((ConstantNameAndType)c).getSignatureIndex(),
Constants.CONSTANT_Utf8));
break;
case Constants.CONSTANT_InterfaceMethodref: case Constants.CONSTANT_Methodref:
case Constants.CONSTANT_Fieldref:
str = (constantToString(((ConstantCP)c).getClassIndex(),
Constants.CONSTANT_Class) + "." +
constantToString(((ConstantCP)c).getNameAndTypeIndex(),
Constants.CONSTANT_NameAndType));
break;
default: // Never reached
throw new RuntimeException("Unknown constant type " + tag);
}
return str;
}
private static final String escape(String str) {
int len = str.length();
StringBuffer buf = new StringBuffer(len + 5);
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();
}
/**
* Retrieve 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(int index, byte tag)
throws ClassFormatException
{
Constant c = getConstant(index, tag);
return constantToString(c);
}
/**
* Dump constant pool to file stream in binary format.
*
* @param file Output file stream
* @throws IOException
*/
public void dump(DataOutputStream file) throws IOException
{
file.writeShort(constant_pool_count);
for(int i=1; i < constant_pool_count; i++)
if(constant_pool[i] != null)
constant_pool[i].dump(file);
}
/**
* Get constant from constant pool.
*
* @param index Index in constant pool
* @return Constant value
* @see Constant
*/
public Constant getConstant(int index) {
if (index >= constant_pool.length || index < 0)
throw new ClassFormatException("Invalid constant pool reference: " +
index + ". Constant pool size is: " +
constant_pool.length);
return constant_pool[index];
}
/**
* Get 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
*/
public Constant getConstant(int index, byte tag)
throws ClassFormatException
{
Constant c;
c = getConstant(index);
if(c == null)
throw new ClassFormatException("Constant pool at index " + index + " is null.");
if(c.getTag() == tag)
return c;
else
throw new ClassFormatException("Expected class `" + Constants.CONSTANT_NAMES[tag] +
"' at index " + index + " and got " + c);
}
/**
* @return Array of constants.
* @see Constant
*/
public Constant[] getConstantPool() { return constant_pool; }
/**
* Get 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 ClassFormatException
*/
public String getConstantString(int index, byte tag)
throws ClassFormatException
{
Constant c;
int i;
c = getConstant(index, tag);
/* This switch() is not that elegant, since the two 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 Constants.CONSTANT_Class: i = ((ConstantClass)c).getNameIndex(); break;
case Constants.CONSTANT_String: i = ((ConstantString)c).getStringIndex(); break;
default:
throw new RuntimeException("getConstantString called with illegal tag " + tag);
}
// Finally get the string from the constant pool
c = getConstant(i, Constants.CONSTANT_Utf8);
return ((ConstantUtf8)c).getBytes();
}
/**
* @return Length of constant pool.
*/
public int getLength()
{
return constant_pool_count;
}
/**
* @param constant Constant to set
*/
public void setConstant(int index, Constant constant) {
constant_pool[index] = constant;
}
/**
* @param constant_pool
*/
public void setConstantPool(Constant[] constant_pool) {
this.constant_pool = constant_pool;
constant_pool_count = (constant_pool == null)? 0 : constant_pool.length;
}
/**
* @return String representation.
*/
public String toString() {
StringBuffer buf = new StringBuffer();
for(int i=1; i < constant_pool_count; i++)
buf.append(i + ")" + constant_pool[i] + "\n");
return buf.toString();
}
/**
* @return deep copy of this constant pool
*/
public ConstantPool copy() {
ConstantPool c = null;
try {
c = (ConstantPool)clone();
} catch(CloneNotSupportedException e) {}
c.constant_pool = new Constant[constant_pool_count];
for(int i=1; i < constant_pool_count; i++) {
if(constant_pool[i] != null)
c.constant_pool[i] = constant_pool[i].copy();
}
return c;
}
}