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/*************************************************
*
* = PACKAGE
* JACE.ServiceConfigurator
*
* = FILENAME
* ClassReader.java
*
*@author Everett Anderson
*
*@see JACE.ServiceConfigurator
*@see JACE.ServiceConfigurator.ServiceLoader
*
*************************************************/
package JACE.ServiceConfigurator;
import JACE.OS.*;
import java.io.*;
import java.util.*;
/**
* <hr>
* <p><b>TITLE</b><br>
* Given a classfile name, this determines the qualified class name
* of what's inside (pacakage and class name together). It is necessary
* when users want to dynamically load classes, but don't provide the
* full name in svc.conf.
*/
public class ClassReader
{
// Types found in classfiles
public static final byte CONSTANT_Class = 7;
public static final byte CONSTANT_Fieldref = 9;
public static final byte CONSTANT_Methodref = 10;
public static final byte CONSTANT_InterfaceMethodref = 11;
public static final byte CONSTANT_String = 8;
public static final byte CONSTANT_Integer = 3;
public static final byte CONSTANT_Float = 4;
public static final byte CONSTANT_Long = 5;
public static final byte CONSTANT_Double = 6;
public static final byte CONSTANT_NameAndType = 12;
public static final byte CONSTANT_Utf8 = 1;
/** Returns a string that is the qualified class name of the
* given file. It returns null if there are any problems.
*
*@param fileName File to examine
*
*@return String that's the qualified class name of the
* given file (null on error)
*/
public static String getClassName(String fileName)
{
try {
// Open the .class file
FileInputStream fis = new FileInputStream(fileName);
DataInputStream dis = new DataInputStream(fis);
// Skip magic number and version numbers
dis.skipBytes(8);
// Find out how many entries are in the constant pool table
int count = dis.readUnsignedShort();
// Hash table to hold the text entries (possibilities for
// the class name)
Hashtable ht = new Hashtable();
// Vector that holds the index of the class name for each
// class record (the vector is indexed by placement in the
// table)
Vector vt = new Vector(count);
Integer noValue = new Integer(-1);
int type;
// Scan through all the entries
for (int i = 1; i < count; i++) {
// Read what type of entry this is
type = dis.readUnsignedByte();
switch (type) {
case CONSTANT_Class:
// Save the index of the class name
vt.addElement(new Integer(dis.readUnsignedShort()));
break;
case CONSTANT_Fieldref:
case CONSTANT_Methodref:
case CONSTANT_InterfaceMethodref:
case CONSTANT_Integer:
case CONSTANT_Float:
case CONSTANT_NameAndType:
// Skip the data
vt.addElement(noValue);
dis.skipBytes(4);
break;
case CONSTANT_String:
// Skip the data
vt.addElement(noValue);
dis.skipBytes(2);
break;
case CONSTANT_Long:
case CONSTANT_Double:
// Skip the data
vt.addElement(noValue);
dis.skipBytes(8);
// These take up two spots in the table
i++;
break;
case CONSTANT_Utf8:
vt.addElement(noValue);
// Save the text in the hash table
ht.put(new Integer(i), new String(dis.readUTF()));
break;
default:
ACE.DEBUG("Unknown type: " + type);
break;
}
}
// Skip the access flags
dis.skipBytes(2);
// Get index in table of this class
int classIdx = dis.readUnsignedShort();
// Get index in the table of the name of this class
Integer idx = (Integer)vt.elementAt(classIdx - 1);
// Put the result in period separated notation
String result = new String(((String)ht.get(idx)).replace('/', '.'));
return result;
} catch (IOException e) {
ACE.ERROR("" + e);
return null;
}
}
}
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