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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.
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package org.aspectj.apache.bcel.classfile;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (https://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 */

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.aspectj.apache.bcel.Constants;
import org.aspectj.apache.bcel.classfile.annotation.AnnotationGen;
import org.aspectj.apache.bcel.classfile.annotation.RuntimeAnnos;
import org.aspectj.apache.bcel.classfile.annotation.RuntimeInvisAnnos;
import org.aspectj.apache.bcel.classfile.annotation.RuntimeInvisParamAnnos;
import org.aspectj.apache.bcel.classfile.annotation.RuntimeParamAnnos;
import org.aspectj.apache.bcel.classfile.annotation.RuntimeVisAnnos;
import org.aspectj.apache.bcel.classfile.annotation.RuntimeVisParamAnnos;
import org.aspectj.apache.bcel.generic.Type;
import org.aspectj.apache.bcel.util.ByteSequence;

/**
 * Utility functions that do not really belong to any class in particular.
 *
 * @version $Id: Utility.java,v 1.14 2009/09/28 16:39:46 aclement Exp $
 * @author M. Dahm
 *
 *         modified: Andy Clement 2-mar-05 Removed unnecessary static and optimized
 */
public abstract class Utility {

	/*
	 * The 'WIDE' instruction is used in the byte code to allow 16-bit wide indices for local variables. This opcode precedes an
	 * 'ILOAD', e.g.. The opcode immediately following takes an extra byte which is combined with the following byte to form a
	 * 16-bit value.
	 */
	private static boolean wide = false;

	/**
	 * Convert bit field of flags into string such as 'static final'.
	 *
	 * @param access_flags Access flags
	 * @return String representation of flags
	 */
	public static final String accessToString(int access_flags) {
		return accessToString(access_flags, false);
	}

	/**
	 * Convert bit field of flags into string such as 'static final'.
	 *
	 * Special case: Classes compiled with new compilers and with the 'ACC_SUPER' flag would be said to be "synchronized". This is
	 * because SUN used the same value for the flags 'ACC_SUPER' and 'ACC_SYNCHRONIZED'.
	 *
	 * @param access_flags Access flags
	 * @param for_class access flags are for class qualifiers ?
	 * @return String representation of flags
	 */
	public static final String accessToString(int access_flags, boolean for_class) {
		StringBuilder buf = new StringBuilder();

		int p = 0;
		for (int i = 0; p < Constants.MAX_ACC_FLAG; i++) { // Loop through known flags
			p = pow2(i);
			if ((access_flags & p) != 0) {
				// Special case: see comment at top of class...
				if (for_class && ((p == Constants.ACC_SUPER) || (p == Constants.ACC_INTERFACE))) {
					continue;
				}
				buf.append(Constants.ACCESS_NAMES[i]).append(" ");
			}
		}
		return buf.toString().trim();
	}

	/**
	 * @return "class" or "interface", depending on the ACC_INTERFACE flag
	 */
	public static final String classOrInterface(int access_flags) {
		return ((access_flags & Constants.ACC_INTERFACE) != 0) ? "interface" : "class";
	}

	/**
	 * Disassemble a byte array of JVM byte codes starting from code line 'index' and return the disassembled string representation.
	 * Decode only 'num' opcodes (including their operands), use -1 if you want to decompile everything.
	 *
	 * @param code byte code array
	 * @param constant_pool Array of constants
	 * @param index offset in `code' array (number of opcodes, not bytes!)
	 * @param length number of opcodes to decompile, -1 for all
	 * @param verbose be verbose, e.g. print constant pool index
	 * @return String representation of byte codes
	 */
	public static final String codeToString(byte[] code, ConstantPool constant_pool, int index, int length, boolean verbose) {
		StringBuilder buf = new StringBuilder(code.length * 20); // Should be sufficient
		ByteSequence stream = new ByteSequence(code);

		try {
			for (int i = 0; i < index; i++) {
				// Skip `index' lines of code
				codeToString(stream, constant_pool, verbose);
			}

			for (int i = 0; stream.available() > 0; i++) {
				if ((length < 0) || (i < length)) {
					String indices = fillup(stream.getIndex() + ":", 6, true, ' ');
					buf.append(indices + codeToString(stream, constant_pool, verbose) + '\n');
				}
			}
		} catch (IOException e) {
			System.out.println(buf.toString());
			e.printStackTrace();
			throw new ClassFormatException("Byte code error: " + e);
		}

		return buf.toString();
	}

	/**
	 * Disassemble a stream of byte codes and return the string representation.
	 */
	public static final String codeToString(byte[] code, ConstantPool constant_pool, int index, int length) {
		return codeToString(code, constant_pool, index, length, true);
	}

	public static final String codeToString(ByteSequence bytes, ConstantPool constant_pool) throws IOException {
		return codeToString(bytes, constant_pool, true);
	}

	/**
	 * Shorten long class names, java/lang/String becomes String.
	 *
	 * @param str The long class name
	 * @return Compacted class name
	 */
	public static final String compactClassName(String str) {
		return compactClassName(str, true);
	}

	/**
	 * Shorten long class name str, i.e., chop off the prefix, if the class name starts with this string and the
	 * flag chopit is true. Slashes / are converted to dots ..
	 *
	 * @param str The long class name
	 * @param prefix The prefix the get rid off
	 * @param chopit Flag that determines whether chopping is executed or not
	 * @return Compacted class name
	 */
	public static final String compactClassName(String str, String prefix, boolean chopit) {
		str = str.replace('/', '.');
		if (chopit) {
			int len = prefix.length();
			// If string starts with 'prefix' and contains no further dots
			if (str.startsWith(prefix)) {
				String result = str.substring(len);
				if (result.indexOf('.') == -1) {
					str = result;
				}
			}
		}
		return str;
	}

	/**
	 * Shorten long class names, java/lang/String becomes java.lang.String, e.g.. If chopit is
	 * true the prefix java.lang is also removed.
	 *
	 * @param str The long class name
	 * @param chopit Flag that determines whether chopping is executed or not
	 * @return Compacted class name
	 */
	public static final String compactClassName(String str, boolean chopit) {
		return compactClassName(str, "java.lang.", chopit);
	}

	public static final String methodSignatureToString(String signature, String name, String access) {
		return methodSignatureToString(signature, name, access, true);
	}

	public static final String methodSignatureToString(String signature, String name, String access, boolean chopit) {
		return methodSignatureToString(signature, name, access, chopit, null);
	}

	/**
	 * This method converts such a string into a Java type declaration like 'void main(String[])' and throws a
	 * 'ClassFormatException' when the parsed type is invalid.
	 */
	public static final String methodSignatureToString(String signature, String name, String access, boolean chopit,
			LocalVariableTable vars) throws ClassFormatException {
		StringBuilder buf = new StringBuilder("(");
		String type;
		int index;
		int var_index = (access.contains("static")) ? 0 : 1;

		try { // Read all declarations between for `(' and `)'
			if (signature.charAt(0) != '(') {
				throw new ClassFormatException("Invalid method signature: " + signature);
			}

			index = 1; // current string position

			while (signature.charAt(index) != ')') {
				ResultHolder rh = signatureToStringInternal(signature.substring(index), chopit);
				String param_type = rh.getResult();
				buf.append(param_type);

				if (vars != null) {
					LocalVariable l = vars.getLocalVariable(var_index);

					if (l != null) {
						buf.append(" " + l.getName());
					}
				} else {
					buf.append(" arg" + var_index);
				}

				if ("double".equals(param_type) || "long".equals(param_type)) {
					var_index += 2;
				} else {
					var_index++;
				}

				buf.append(", ");
				index += rh.getConsumedChars();
			}

			index++;

			// Read return type after `)'
			type = signatureToString(signature.substring(index), chopit);

		} catch (StringIndexOutOfBoundsException e) { // Should never occur
			throw new ClassFormatException("Invalid method signature: " + signature);
		}

		if (buf.length() > 1) {
			buf.setLength(buf.length() - 2);
		}

		buf.append(")");

		return access + ((access.length() > 0) ? " " : "") + // May be an empty string
				type + " " + name + buf.toString();
	}

	/**
	 * Replace all occurences of old in str with new.
	 *
	 * @param str String to permute
	 * @param old String to be replaced
	 * @param new Replacement string
	 * @return new String object
	 */
	public static final String replace(String str, String old, String new_) {
		int index, old_index;
		StringBuilder buf = new StringBuilder();

		try {
			index = str.indexOf(old);
			if (index != -1) {
				old_index = 0;

				// While we have something to replace
				while ((index = str.indexOf(old, old_index)) != -1) {
					buf.append(str.substring(old_index, index)); // append prefix
					buf.append(new_); // append replacement
					old_index = index + old.length(); // Skip 'old'.length chars
				}

				buf.append(str.substring(old_index)); // append rest of string
				str = buf.toString();
			}
		} catch (StringIndexOutOfBoundsException e) {
			System.err.println(e);
		}

		return str;
	}

	/**
	 * Converts signature to string with all class names compacted.
	 *
	 * @param signature to convert
	 * @return Human readable signature
	 */
	public static final String signatureToString(String signature) {
		return signatureToString(signature, true);
	}

	public static final String signatureToString(String signature, boolean chopit) {
		ResultHolder rh = signatureToStringInternal(signature, chopit);
		return rh.getResult();
	}

	/**
	 * This method converts this string into a Java type declaration such as 'String[]' and throws a `ClassFormatException' when the
	 * parsed type is invalid.
	 */
	public static final ResultHolder signatureToStringInternal(String signature, boolean chopit) {
		int processedChars = 1; // This is the default, read just one char
		try {
			switch (signature.charAt(0)) {
			case 'B':
				return ResultHolder.BYTE;
			case 'C':
				return ResultHolder.CHAR;
			case 'D':
				return ResultHolder.DOUBLE;
			case 'F':
				return ResultHolder.FLOAT;
			case 'I':
				return ResultHolder.INT;
			case 'J':
				return ResultHolder.LONG;
			case 'L': { // Full class name
				int index = signature.indexOf(';'); // Look for closing ';'

				if (index < 0) {
					throw new ClassFormatException("Invalid signature: " + signature);
				}

				if (signature.length() > index + 1 && signature.charAt(index + 1) == '>') {
					index = index + 2;
				}

				int genericStart = signature.indexOf('<');
				if (genericStart != -1) {
					int genericEnd = signature.indexOf('>');
					// FIXME asc going to need a lot more work in here for generics
					ResultHolder rh = signatureToStringInternal(signature.substring(genericStart + 1, genericEnd), chopit);
					StringBuilder sb = new StringBuilder();
					sb.append(signature.substring(1, genericStart));
					sb.append("<").append(rh.getResult()).append(">");
					ResultHolder retval = new ResultHolder(compactClassName(sb.toString(), chopit), genericEnd + 1);
					return retval;
				} else {
					processedChars = index + 1; // "Lblabla;" `L' and `;' are removed
					ResultHolder retval = new ResultHolder(compactClassName(signature.substring(1, index), chopit), processedChars);
					return retval;
				}
			}

			case 'S':
				return ResultHolder.SHORT;
			case 'Z':
				return ResultHolder.BOOLEAN;

			case '[': { // Array declaration
				StringBuilder brackets;
				int consumedChars, n;

				brackets = new StringBuilder(); // Accumulate []'s
				// Count opening brackets and look for optional size argument
				for (n = 0; signature.charAt(n) == '['; n++) {
					brackets.append("[]");
				}
				consumedChars = n;
				ResultHolder restOfIt = signatureToStringInternal(signature.substring(n), chopit);
				consumedChars += restOfIt.getConsumedChars();
				brackets.insert(0, restOfIt.getResult());
				return new ResultHolder(brackets.toString(), consumedChars);
			}
			case 'V':
				return ResultHolder.VOID;

			default:
				throw new ClassFormatException("Invalid signature: `" + signature + "'");
			}
		} catch (StringIndexOutOfBoundsException e) { // Should never occur
			throw new ClassFormatException("Invalid signature: " + e + ":" + signature);
		}
	}

	/**
	 * Return type of method signature as a byte value as defined in Constants
	 *
	 * @param signature in format described above
	 * @return type of method signature
	 * @see Constants
	 */
	public static final byte typeOfMethodSignature(String signature) throws ClassFormatException {
		int index;
		try {
			if (signature.charAt(0) != '(') {
				throw new ClassFormatException("Invalid method signature: " + signature);
			}
			index = signature.lastIndexOf(')') + 1;
			return typeOfSignature(signature.substring(index));
		} catch (StringIndexOutOfBoundsException e) {
			throw new ClassFormatException("Invalid method signature: " + signature);
		}
	}

	/**
	 * Convert (signed) byte to (unsigned) short value, i.e., all negative values become positive.
	 */
	private static final short byteToShort(byte b) {
		return (b < 0) ? (short) (256 + b) : (short) b;
	}

	/**
	 * Convert bytes into hexidecimal string
	 *
	 * @return bytes as hexidecimal string, e.g. 00 FA 12 ...
	 */
	public static final String toHexString(byte[] bytes) {
		StringBuilder buf = new StringBuilder();

		for (int i = 0; i < bytes.length; i++) {
			short b = byteToShort(bytes[i]);
			String hex = Integer.toString(b, 0x10);

			// Just one digit, so prepend 0
			if (b < 0x10) {
				buf.append('0');
			}

			buf.append(hex);

			if (i < bytes.length - 1) {
				buf.append(' ');
			}
		}

		return buf.toString();
	}

	/**
	 * Return a string for an integer justified left or right and filled up with 'fill' characters if necessary.
	 *
	 * @param i integer to format
	 * @param length length of desired string
	 * @param left_justify format left or right
	 * @param fill fill character
	 * @return formatted int
	 */
	public static final String format(int i, int length, boolean left_justify, char fill) {
		return fillup(Integer.toString(i), length, left_justify, fill);
	}

	/**
	 * Fillup char with up to length characters with char `fill' and justify it left or right.
	 *
	 * @param str string to format
	 * @param length length of desired string
	 * @param left_justify format left or right
	 * @param fill fill character
	 * @return formatted string
	 */
	public static final String fillup(String str, int length, boolean left_justify, char fill) {
		int len = length - str.length();
		char[] buf = new char[(len < 0) ? 0 : len];

		for (int j = 0; j < buf.length; j++) {
			buf[j] = fill;
		}

		if (left_justify) {
			return str + new String(buf);
		} else {
			return new String(buf) + str;
		}
	}

	/**
	 * Escape all occurences of newline chars '\n', quotes \", etc.
	 */
	public static final String convertString(String label) {
		char[] ch = label.toCharArray();
		StringBuilder buf = new StringBuilder();

		for (char c : ch) {
			switch (c) {
				case '\n':
					buf.append("\\n");
					break;
				case '\r':
					buf.append("\\r");
					break;
				case '\"':
					buf.append("\\\"");
					break;
				case '\'':
					buf.append("\\'");
					break;
				case '\\':
					buf.append("\\\\");
					break;
				default:
					buf.append(c);
					break;
			}
		}

		return buf.toString();
	}

	/**
	 * Converts a list of AnnotationGen objects into a set of attributes that can be attached to the class file.
	 *
	 * @param cp The constant pool gen where we can create the necessary name refs
	 * @param annotations A list of AnnotationGen objects
	 */
	public static Collection getAnnotationAttributes(ConstantPool cp, List annotations) {

		if (annotations.size() == 0) {
			return null;
		}

		try {
			int countVisible = 0;
			int countInvisible = 0;

			// put the annotations in the right output stream
			for (AnnotationGen a : annotations) {
				if (a.isRuntimeVisible()) {
					countVisible++;
				} else {
					countInvisible++;
				}
			}

			ByteArrayOutputStream rvaBytes = new ByteArrayOutputStream();
			ByteArrayOutputStream riaBytes = new ByteArrayOutputStream();
			DataOutputStream rvaDos = new DataOutputStream(rvaBytes);
			DataOutputStream riaDos = new DataOutputStream(riaBytes);

			rvaDos.writeShort(countVisible);
			riaDos.writeShort(countInvisible);

			// put the annotations in the right output stream
			for (AnnotationGen a : annotations) {
				if (a.isRuntimeVisible()) {
					a.dump(rvaDos);
				} else {
					a.dump(riaDos);
				}
			}

			rvaDos.close();
			riaDos.close();

			byte[] rvaData = rvaBytes.toByteArray();
			byte[] riaData = riaBytes.toByteArray();

			int rvaIndex = -1;
			int riaIndex = -1;

			if (rvaData.length > 2) {
				rvaIndex = cp.addUtf8("RuntimeVisibleAnnotations");
			}
			if (riaData.length > 2) {
				riaIndex = cp.addUtf8("RuntimeInvisibleAnnotations");
			}

			List newAttributes = new ArrayList<>();
			if (rvaData.length > 2) {
				newAttributes.add(new RuntimeVisAnnos(rvaIndex, rvaData.length, rvaData, cp));
			}
			if (riaData.length > 2) {
				newAttributes.add(new RuntimeInvisAnnos(riaIndex, riaData.length, riaData, cp));
			}

			return newAttributes;
		} catch (IOException e) {
			System.err.println("IOException whilst processing annotations");
			e.printStackTrace();
		}
		return null;
	}

	/**
	 * Annotations against a class are stored in one of four attribute kinds: - RuntimeVisibleParameterAnnotations -
	 * RuntimeInvisibleParameterAnnotations
	 */
	// OPTIMIZE looks heavyweight?
	public static Attribute[] getParameterAnnotationAttributes(ConstantPool cp, List[] vec) {

		int visCount[] = new int[vec.length];
		int totalVisCount = 0;
		int invisCount[] = new int[vec.length];
		int totalInvisCount = 0;
		try {

			for (int i = 0; i < vec.length; i++) {
				List l = vec[i];
				if (l != null) {
					for (AnnotationGen element : l) {
						if (element.isRuntimeVisible()) {
							visCount[i]++;
							totalVisCount++;
						} else {
							invisCount[i]++;
							totalInvisCount++;
						}
					}
				}
			}

			// Lets do the visible ones
			ByteArrayOutputStream rvaBytes = new ByteArrayOutputStream();
			DataOutputStream rvaDos = new DataOutputStream(rvaBytes);
			rvaDos.writeByte(vec.length); // First goes number of parameters

			for (int i = 0; i < vec.length; i++) {
				rvaDos.writeShort(visCount[i]);
				if (visCount[i] > 0) {
					List l = vec[i];
					for (AnnotationGen element : l) {
						if (element.isRuntimeVisible()) {
							element.dump(rvaDos);
						}
					}
				}
			}
			rvaDos.close();

			// Lets do the invisible ones
			ByteArrayOutputStream riaBytes = new ByteArrayOutputStream();
			DataOutputStream riaDos = new DataOutputStream(riaBytes);
			riaDos.writeByte(vec.length); // First goes number of parameters

			for (int i = 0; i < vec.length; i++) {
				riaDos.writeShort(invisCount[i]);
				if (invisCount[i] > 0) {
					List l = vec[i];
					for (AnnotationGen element : l) {
						if (!element.isRuntimeVisible()) {
							element.dump(riaDos);
						}
					}
				}
			}
			riaDos.close();

			byte[] rvaData = rvaBytes.toByteArray();
			byte[] riaData = riaBytes.toByteArray();

			int rvaIndex = -1;
			int riaIndex = -1;

			if (totalVisCount > 0) {
				rvaIndex = cp.addUtf8("RuntimeVisibleParameterAnnotations");
			}
			if (totalInvisCount > 0) {
				riaIndex = cp.addUtf8("RuntimeInvisibleParameterAnnotations");
			}

			List newAttributes = new ArrayList<>();

			if (totalVisCount > 0) {
				newAttributes.add(new RuntimeVisParamAnnos(rvaIndex, rvaData.length, rvaData, cp));
			}

			if (totalInvisCount > 0) {
				newAttributes.add(new RuntimeInvisParamAnnos(riaIndex, riaData.length, riaData, cp));
			}

			return newAttributes.toArray(Attribute.NoAttributes);
		} catch (IOException e) {
			System.err.println("IOException whilst processing parameter annotations");
			e.printStackTrace();
		}
		return null;
	}

	public static class ResultHolder {
		private String result;
		private int consumed;

		public static final ResultHolder BYTE = new ResultHolder("byte", 1);
		public static final ResultHolder CHAR = new ResultHolder("char", 1);
		public static final ResultHolder DOUBLE = new ResultHolder("double", 1);
		public static final ResultHolder FLOAT = new ResultHolder("float", 1);
		public static final ResultHolder INT = new ResultHolder("int", 1);
		public static final ResultHolder LONG = new ResultHolder("long", 1);
		public static final ResultHolder SHORT = new ResultHolder("short", 1);
		public static final ResultHolder BOOLEAN = new ResultHolder("boolean", 1);
		public static final ResultHolder VOID = new ResultHolder("void", 1);

		public ResultHolder(String s, int c) {
			result = s;
			consumed = c;
		}

		public String getResult() {
			return result;
		}

		public int getConsumedChars() {
			return consumed;
		}
	}

	/**
	 * Return type of signature as a byte value as defined in Constants
	 *
	 * @param signature in format described above
	 * @return type of signature
	 * @see Constants
	 */
	public static final byte typeOfSignature(String signature) throws ClassFormatException {
		try {
			switch (signature.charAt(0)) {
			case 'B':
				return Constants.T_BYTE;
			case 'C':
				return Constants.T_CHAR;
			case 'D':
				return Constants.T_DOUBLE;
			case 'F':
				return Constants.T_FLOAT;
			case 'I':
				return Constants.T_INT;
			case 'J':
				return Constants.T_LONG;
			case 'L':
				return Constants.T_REFERENCE;
			case '[':
				return Constants.T_ARRAY;
			case 'V':
				return Constants.T_VOID;
			case 'Z':
				return Constants.T_BOOLEAN;
			case 'S':
				return Constants.T_SHORT;
			default:
				throw new ClassFormatException("Invalid method signature: " + signature);
			}
		} catch (StringIndexOutOfBoundsException e) {
			throw new ClassFormatException("Invalid method signature: " + signature);
		}
	}

	public static final byte typeOfSignature(char c) throws ClassFormatException {
		switch (c) {
		case 'B':
			return Constants.T_BYTE;
		case 'C':
			return Constants.T_CHAR;
		case 'D':
			return Constants.T_DOUBLE;
		case 'F':
			return Constants.T_FLOAT;
		case 'I':
			return Constants.T_INT;
		case 'J':
			return Constants.T_LONG;
		case 'L':
			return Constants.T_REFERENCE;
		case '[':
			return Constants.T_ARRAY;
		case 'V':
			return Constants.T_VOID;
		case 'Z':
			return Constants.T_BOOLEAN;
		case 'S':
			return Constants.T_SHORT;
		default:
			throw new ClassFormatException("Invalid type of signature: " + c);
		}
	}

	/**
	 * Disassemble a stream of byte codes and return the string representation.
	 *
	 * @param bytes stream of bytes
	 * @param constant_pool Array of constants
	 * @param verbose be verbose, e.g. print constant pool index
	 * @return String representation of byte code
	 */
	public static final String codeToString(ByteSequence bytes, ConstantPool constant_pool, boolean verbose) throws IOException {
		short opcode = (short) bytes.readUnsignedByte();
		int default_offset = 0, low, high, npairs;
		int index, vindex, constant;
		int[] match, jump_table;
		int no_pad_bytes = 0, offset;
		StringBuilder buf = new StringBuilder(Constants.OPCODE_NAMES[opcode]);

		/*
		 * Special case: Skip (0-3) padding bytes, i.e., the following bytes are 4-byte-aligned
		 */
		if ((opcode == Constants.TABLESWITCH) || (opcode == Constants.LOOKUPSWITCH)) {
			int remainder = bytes.getIndex() % 4;
			no_pad_bytes = (remainder == 0) ? 0 : 4 - remainder;

			for (int i = 0; i < no_pad_bytes; i++) {
				byte b = bytes.readByte();
				if (b != 0) {
					System.err.println("Warning: Padding byte != 0 in " + Constants.OPCODE_NAMES[opcode] + ":" + b);
				}
			}

			// Both cases have a field default_offset in common
			default_offset = bytes.readInt();
		}

		switch (opcode) {
		/*
		 * Table switch has variable length arguments.
		 */
		case Constants.TABLESWITCH:
			low = bytes.readInt();
			high = bytes.readInt();

			offset = bytes.getIndex() - 12 - no_pad_bytes - 1;
			default_offset += offset;

			buf.append("\tdefault = " + default_offset + ", low = " + low + ", high = " + high + "(");

			jump_table = new int[high - low + 1];
			for (int i = 0; i < jump_table.length; i++) {
				jump_table[i] = offset + bytes.readInt();
				buf.append(jump_table[i]);
				if (i < jump_table.length - 1) {
					buf.append(", ");
				}
			}
			buf.append(")");
			break;

		/*
		 * Lookup switch has variable length arguments.
		 */
		case Constants.LOOKUPSWITCH: {

			npairs = bytes.readInt();
			offset = bytes.getIndex() - 8 - no_pad_bytes - 1;

			match = new int[npairs];
			jump_table = new int[npairs];
			default_offset += offset;

			buf.append("\tdefault = " + default_offset + ", npairs = " + npairs + " (");

			for (int i = 0; i < npairs; i++) {
				match[i] = bytes.readInt();
				jump_table[i] = offset + bytes.readInt();
				buf.append("(" + match[i] + ", " + jump_table[i] + ")");
				if (i < npairs - 1) {
					buf.append(", ");
				}
			}
			buf.append(")");
		}
			break;

		// Two address bytes + offset from start of byte stream form the jump target
		case Constants.GOTO:
		case Constants.IFEQ:
		case Constants.IFGE:
		case Constants.IFGT:
		case Constants.IFLE:
		case Constants.IFLT:
		case Constants.JSR:
		case Constants.IFNE:
		case Constants.IFNONNULL:
		case Constants.IFNULL:
		case Constants.IF_ACMPEQ:
		case Constants.IF_ACMPNE:
		case Constants.IF_ICMPEQ:
		case Constants.IF_ICMPGE:
		case Constants.IF_ICMPGT:
		case Constants.IF_ICMPLE:
		case Constants.IF_ICMPLT:
		case Constants.IF_ICMPNE:
			buf.append("\t\t#" + ((bytes.getIndex() - 1) + bytes.readShort()));
			break;

		// 32-bit wide jumps
		case Constants.GOTO_W:
		case Constants.JSR_W:
			buf.append("\t\t#" + ((bytes.getIndex() - 1) + bytes.readInt()));
			break;

		// Index byte references local variable (register)
		case Constants.ALOAD:
		case Constants.ASTORE:
		case Constants.DLOAD:
		case Constants.DSTORE:
		case Constants.FLOAD:
		case Constants.FSTORE:
		case Constants.ILOAD:
		case Constants.ISTORE:
		case Constants.LLOAD:
		case Constants.LSTORE:
		case Constants.RET:
			if (wide) {
				vindex = bytes.readUnsignedShort();
				wide = false; // Clear flag
			} else {
				vindex = bytes.readUnsignedByte();
			}
			buf.append("\t\t%" + vindex);
			break;

		/*
		 * Remember wide byte which is used to form a 16-bit address in the following instruction. Relies on that the method is
		 * called again with the following opcode.
		 */
		case Constants.WIDE:
			wide = true;
			buf.append("\t(wide)");
			break;

		// Array of basic type
		case Constants.NEWARRAY:
			buf.append("\t\t<" + Constants.TYPE_NAMES[bytes.readByte()] + ">");
			break;

		// Access object/class fields
		case Constants.GETFIELD:
		case Constants.GETSTATIC:
		case Constants.PUTFIELD:
		case Constants.PUTSTATIC:
			index = bytes.readUnsignedShort();
			buf.append("\t\t" + constant_pool.constantToString(index, Constants.CONSTANT_Fieldref)
					+ (verbose ? " (" + index + ")" : ""));
			break;

		// Operands are references to classes in constant pool
		case Constants.NEW:
		case Constants.CHECKCAST:
			buf.append("\t");
		case Constants.INSTANCEOF:
			index = bytes.readUnsignedShort();
			buf.append("\t<" + constant_pool.constantToString(index) + ">" + (verbose ? " (" + index + ")" : ""));
			break;

		// Operands are references to methods in constant pool
		case Constants.INVOKESPECIAL:
		case Constants.INVOKESTATIC:
		case Constants.INVOKEVIRTUAL:
			index = bytes.readUnsignedShort();
			buf.append("\t" + constant_pool.constantToString(index) + (verbose ? " (" + index + ")" : ""));
			break;

		case Constants.INVOKEINTERFACE:
			index = bytes.readUnsignedShort();
			int nargs = bytes.readUnsignedByte(); // historical, redundant
			buf.append("\t" + constant_pool.constantToString(index) + (verbose ? " (" + index + ")\t" : "") + nargs + "\t"
					+ bytes.readUnsignedByte()); // Last byte is a reserved
			// space
			break;

		case Constants.INVOKEDYNAMIC://https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-6.html#jvms-6.5.invokedynamic
			index = bytes.readUnsignedShort();
			bytes.readUnsignedShort(); // zeroes
			buf.append("\t" + constant_pool.constantToString(index) + (verbose ? " (" + index + ")" : ""));
			break;

		// Operands are references to items in constant pool
		case Constants.LDC_W:
		case Constants.LDC2_W:
			index = bytes.readUnsignedShort();
			buf.append("\t\t" + constant_pool.constantToString(index) + (verbose ? " (" + index + ")" : ""));
			break;

		case Constants.LDC:
			index = bytes.readUnsignedByte();
			buf.append("\t\t" + constant_pool.constantToString(index) + (verbose ? " (" + index + ")" : ""));
			break;

		// Array of references
		case Constants.ANEWARRAY:
			index = bytes.readUnsignedShort();
			buf.append("\t\t<" + compactClassName(constant_pool.getConstantString(index, Constants.CONSTANT_Class), false) + ">"
					+ (verbose ? " (" + index + ")" : ""));
			break;

		// Multidimensional array of references
		case Constants.MULTIANEWARRAY: {
			index = bytes.readUnsignedShort();
			int dimensions = bytes.readUnsignedByte();

			buf.append("\t<" + compactClassName(constant_pool.getConstantString(index, Constants.CONSTANT_Class), false) + ">\t"
					+ dimensions + (verbose ? " (" + index + ")" : ""));
		}
			break;

		// Increment local variable
		case Constants.IINC:
			if (wide) {
				vindex = bytes.readUnsignedShort();
				constant = bytes.readShort();
				wide = false;
			} else {
				vindex = bytes.readUnsignedByte();
				constant = bytes.readByte();
			}
			buf.append("\t\t%" + vindex + "\t" + constant);
			break;

		default:
			if ((Constants.iLen[opcode] - 1) > 0) {
				for (int i = 0; i < Constants.TYPE_OF_OPERANDS[opcode].length; i++) {
					buf.append("\t\t");
					switch (Constants.TYPE_OF_OPERANDS[opcode][i]) {
					case Constants.T_BYTE:
						buf.append(bytes.readByte());
						break;
					case Constants.T_SHORT:
						buf.append(bytes.readShort());
						break;
					case Constants.T_INT:
						buf.append(bytes.readInt());
						break;

					default: // Never reached
						System.err.println("Unreachable default case reached!");
						System.exit(-1);
					}
				}
			}
		}
		return buf.toString();
	}

	// private helpers
	private static final int pow2(int n) {
		return 1 << n;
	}

	/**
	 * Convert type to Java method signature, e.g. int[] f(java.lang.String x) becomes (Ljava/lang/String;)[I
	 *
	 * @param returnType what the method returns
	 * @param argTypes what are the argument types
	 * @return method signature for given type(s).
	 */
	public static String toMethodSignature(Type returnType, Type[] argTypes) {
		StringBuilder buf = new StringBuilder("(");
		int length = (argTypes == null) ? 0 : argTypes.length;
		for (int i = 0; i < length; i++) {
			buf.append(argTypes[i].getSignature());
		}
		buf.append(')');
		buf.append(returnType.getSignature());
		return buf.toString();
	}
}