// onjava/atunit/ClassNameFinder.java

// (c)2021 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// {java onjava.atunit.ClassNameFinder}

package onjava.atunit;

import java.io.*;

import java.nio.file.*;

import java.util.*;

import onjava.*;

public class ClassNameFinder {

public static String thisClass(byte[] classBytes) {

Map<Integer,Integer> offsetTable = new HashMap<>();

Map<Integer,String> classNameTable =

new HashMap<>();

try {

DataInputStream data = new DataInputStream(

new ByteArrayInputStream(classBytes));

int magic = data.readInt(); // 0xcafebabe

int minorVersion = data.readShort();

int majorVersion = data.readShort();

int constantPoolCount = data.readShort();

int[] constantPool = new int[constantPoolCount];

for(int i = 1; i < constantPoolCount; i++) {

int tag = data.read();

// int tableSize;

switch(tag) {

case 1: // UTF

int length = data.readShort();

char[] bytes = new char[length];

for(int k = 0; k < bytes.length; k++)

bytes[k] = (char)data.read();

String className = new String(bytes);

classNameTable.put(i, className);

break;

case 5: // LONG

case 6: // DOUBLE

data.readLong(); // discard 8 bytes

i++; // Special skip necessary

break;

case 7: // CLASS

int offset = data.readShort();

offsetTable.put(i, offset);

break;

case 8: // STRING

data.readShort(); // discard 2 bytes

break;

case 3: // INTEGER

case 4: // FLOAT

case 9: // FIELD_REF

case 10: // METHOD_REF

case 11: // INTERFACE_METHOD_REF

case 12: // NAME_AND_TYPE

case 18: // Invoke Dynamic

data.readInt(); // discard 4 bytes

break;

case 15: // Method Handle

data.readByte();

data.readShort();

break;

case 16: // Method Type

data.readShort();

break;

default:

throw

new RuntimeException("Bad tag " + tag);

}

}

short accessFlags = data.readShort();

String access = (accessFlags & 0x0001) == 0 ?

"nonpublic:" : "public:";

int thisClass = data.readShort();

int superClass = data.readShort();

return access + classNameTable.get(

offsetTable.get(thisClass)).replace('/', '.');

} catch(IOException | RuntimeException e) {

throw new RuntimeException(e);

}

}

// Demonstration:

public static void

main(String[] args) throws Exception {

PathMatcher matcher = FileSystems.getDefault()

.getPathMatcher("glob:**/*.class");

// Walk the entire tree:

Files.walk(Paths.get("."))

.filter(matcher::matches)

.map(p -> {

try {

return thisClass(Files.readAllBytes(p));

} catch(Exception e) {

throw new RuntimeException(e);

}

})

.filter(s -> s.startsWith("public:"))

// .filter(s -> s.indexOf('$') >= 0)

.map(s -> s.split(":")[1])

.filter(s -> !s.startsWith("enums."))

.filter(s -> s.contains("."))

.forEach(System.out::println);

}

}

/* Output:

onjava.ArrayShow

onjava.atunit.AtUnit$TestMethods

onjava.atunit.AtUnit

onjava.atunit.ClassNameFinder

onjava.atunit.Test

onjava.atunit.TestObjectCleanup

onjava.atunit.TestObjectCreate

onjava.atunit.TestProperty

onjava.BasicSupplier

onjava.CollectionMethodDifferences

onjava.ConvertTo

onjava.Count$Boolean

onjava.Count$Byte

onjava.Count$Character

onjava.Count$Double

onjava.Count$Float

onjava.Count$Integer

onjava.Count$Long

onjava.Count$Pboolean

onjava.Count$Pbyte

onjava.Count$Pchar

onjava.Count$Pdouble

onjava.Count$Pfloat

onjava.Count$Pint

onjava.Count$Plong

onjava.Count$Pshort

onjava.Count$Short

onjava.Count

onjava.CountingIntegerList

onjava.CountMap

onjava.Countries

onjava.Enums

onjava.FillMap

onjava.HTMLColors

onjava.MouseClick

onjava.Nap

onjava.Null

onjava.Operations

onjava.OSExecute

onjava.OSExecuteException

onjava.Pair

onjava.ProcessFiles$Strategy

onjava.ProcessFiles

onjava.Rand$Boolean

onjava.Rand$Byte

onjava.Rand$Character

onjava.Rand$Double

onjava.Rand$Float

onjava.Rand$Integer

onjava.Rand$Long

onjava.Rand$Pboolean

onjava.Rand$Pbyte

onjava.Rand$Pchar

onjava.Rand$Pdouble

onjava.Rand$Pfloat

onjava.Rand$Pint

onjava.Rand$Plong

onjava.Rand$Pshort

onjava.Rand$Short

onjava.Rand$String

onjava.Rand

onjava.Range

onjava.Repeat

onjava.RmDir

onjava.Sets

onjava.Stack

onjava.Suppliers

onjava.TimedAbort

onjava.Timer

onjava.Tuple

onjava.Tuple2

onjava.Tuple3

onjava.Tuple4

onjava.Tuple5

onjava.TypeCounter

*/