/*
 * 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
 *
 *   https://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.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.CharArrayReader;
import java.io.CharArrayWriter;
import java.io.FilterReader;
import java.io.FilterWriter;
import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import org.apache.bcel.Const;
import org.apache.bcel.util.ByteSequence;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.input.BoundedInputStream;
import org.apache.commons.lang3.ArrayFill;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.StringUtils;

/**
 * Utility functions that do not really belong to any class in particular.
 */
// @since 6.0 methods are no longer final
public abstract class Utility {

    /**
     * Decode characters into bytes. Used by <a href="Utility.html#decode(java.lang.String, boolean)">decode()</a>
     */
    private static final class JavaReader extends FilterReader {

        JavaReader(final Reader in) {
            super(in);
        }

        @Override
        public int read() throws IOException {
            final int b = in.read();
            if (b != ESCAPE_CHAR) {
                return b;
            }
            final int i = in.read();
            if (i < 0) {
                return -1;
            }
            if (isHex(i)) { // Normal escape
                final int j = in.read();
                if (j < 0) {
                    return -1;
                }
                if (!isHex(j)) {
                    // Would otherwise reach Integer.parseInt and throw an undeclared NumberFormatException.
                    throw new IOException("Invalid escape sequence: expected a second hexadecimal digit after '" + ESCAPE_CHAR + (char) i + "'");
                }
                final char[] tmp = { (char) i, (char) j };
                return Integer.parseInt(new String(tmp), 16);
            }
            if (i >= MAP_CHAR.length || MAP_CHAR[i] == UNMAPPED) {
                // Reject instead of throwing an undeclared ArrayIndexOutOfBoundsException (i >= 256) or silently
                // aliasing every unmapped character to MAP_CHAR's default slot value (the '$A' encoding).
                throw new IOException("Invalid escape character after '" + ESCAPE_CHAR + "': 0x" + Integer.toHexString(i));
            }
            return MAP_CHAR[i];
        }

        @Override
        public int read(final char[] cbuf, final int off, final int len) throws IOException {
            for (int i = 0; i < len; i++) {
                final int ch = read();
                if (ch < 0) {
                    // Propagate end-of-stream instead of writing (char) -1 and over-reporting the read length.
                    return i > 0 ? i : -1;
                }
                cbuf[off + i] = (char) ch;
            }
            return len;
        }
    }

    /**
     * Encode bytes into valid Java identifier characters. Used by
     * <a href="Utility.html#encode(byte[], boolean)">encode()</a>
     */
    private static final class JavaWriter extends FilterWriter {

        JavaWriter(final Writer out) {
            super(out);
        }

        @Override
        public void write(final char[] cbuf, final int off, final int len) throws IOException {
            for (int i = 0; i < len; i++) {
                write(cbuf[off + i]);
            }
        }

        @Override
        public void write(final int b) throws IOException {
            if (isJavaIdentifierPart((char) b) && b != ESCAPE_CHAR) {
                out.write(b);
            } else {
                out.write(ESCAPE_CHAR); // Escape character
                // Special escape
                if (b >= 0 && b < FREE_CHARS) {
                    out.write(CHAR_MAP[b]);
                } else { // Normal escape
                    final char[] tmp = Integer.toHexString(b).toCharArray();
                    if (tmp.length == 1) {
                        out.write('0');
                        out.write(tmp[0]);
                    } else {
                        out.write(tmp[0]);
                        out.write(tmp[1]);
                    }
                }
            }
        }

        @Override
        public void write(final String str, final int off, final int len) throws IOException {
            write(str.toCharArray(), off, len);
        }
    }

    /*
     * Maximum nesting depth accepted by typeSignatureToString(). Signatures are attacker-controlled bytes from untrusted class files; without a limit, a deeply
     * nested generic signature such as "LA<LA<LA<...>;>;>;" drives one stack frame per nesting level and kills the calling thread with a StackOverflowError.
     */
    private static final int MAX_SIGNATURE_NESTING = 512;

    /**
     * The maximum number of bytes that {@link #decode(String, boolean)} will decompress. Guards against decompression bombs: the compressed input is
     * attacker-controlled and a small input can decompress to an enormous size.
     */
    private static final int MAX_DECODED_LENGTH = 64 * 1024 * 1024;

    /** Marker for {@link #MAP_CHAR} slots that do not correspond to a valid special escape character. */
    private static final int UNMAPPED = -1;

    /*
     * How many chars have been consumed during parsing in typeSignatureToString(). Read by methodSignatureToString(). Set
     * by side effect, but only internally.
     */
    private static final ThreadLocal<Integer> CONSUMER_CHARS = ThreadLocal.withInitial(() -> Integer.valueOf(0));

    /*
     * The 'WIDE' instruction is used in the byte code to allow 16-bit wide indices for local variables. This opcode
     * precedes an 'ILOAD', for example. The opcode immediately following takes an extra byte which is combined with the following
     * byte to form a 16-bit value. Read across consecutive codeToString() calls, so kept per-thread like CONSUMER_CHARS.
     */
    private static final ThreadLocal<Boolean> WIDE = ThreadLocal.withInitial(() -> Boolean.FALSE);

    // A-Z, g-z, _, $
    private static final int FREE_CHARS = 48;

    private static final int[] CHAR_MAP = new int[FREE_CHARS];

    private static final int[] MAP_CHAR = new int[256]; // Reverse map

    private static final char ESCAPE_CHAR = '$';

    static {
        Arrays.fill(MAP_CHAR, UNMAPPED);
        int j = 0;
        for (int i = 'A'; i <= 'Z'; i++) {
            CHAR_MAP[j] = i;
            MAP_CHAR[i] = j;
            j++;
        }
        for (int i = 'g'; i <= 'z'; i++) {
            CHAR_MAP[j] = i;
            MAP_CHAR[i] = j;
            j++;
        }
        CHAR_MAP[j] = '$';
        MAP_CHAR['$'] = j;
        j++;
        CHAR_MAP[j] = '_';
        MAP_CHAR['_'] = j;
    }

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

    /**
     * Convert bit field of flags into string such as 'static final'.
     * <p>
     * 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'.
     * </p>
     *
     * @param accessFlags Access flags.
     * @param forClass access flags are for class qualifiers ?.
     * @return String representation of flags.
     */
    public static String accessToString(final int accessFlags, final boolean forClass) {
        final StringBuilder buf = new StringBuilder();
        int p = 0;
        for (int i = 0; p < Const.MAX_ACC_FLAG_I; i++) { // Loop through known flags
            p = pow2(i);
            if ((accessFlags & p) != 0) {
                /*
                 * 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'.
                 */
                if (forClass && (p == Const.ACC_SUPER || p == Const.ACC_INTERFACE)) {
                    continue;
                }
                buf.append(Const.getAccessName(i)).append(" ");
            }
        }
        return buf.toString().trim();
    }

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

    /**
     * Gets the class or interface type name.
     *
     * @param accessFlags The class flags.
     * @return "class" or "interface", depending on the ACC_INTERFACE flag.
     */
    public static String classOrInterface(final int accessFlags) {
        return (accessFlags & Const.ACC_INTERFACE) != 0 ? "interface" : "class";
    }

    /**
     * Clears a bit in a flag.
     *
     * @param flag The flag value.
     * @param i The bit position.
     * @return 'flag' with bit 'i' set to 0.
     */
    public static int clearBit(final int flag, final int i) {
        final int bit = pow2(i);
        return (flag & bit) == 0 ? flag : flag ^ bit;
    }

    /**
     * Disassembles byte code.
     *
     * @param code byte code array.
     * @param constantPool The constant pool.
     * @param index offset in code array.
     * @param length number of opcodes to decompile.
     * @return disassembled string representation.
     */
    public static String codeToString(final byte[] code, final ConstantPool constantPool, final int index, final int length) {
        return codeToString(code, constantPool, index, length, true);
    }

    /**
     * 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 constantPool Array of constants.
     * @param index offset in 'code' array <em>(number of opcodes, not bytes!)</em>.
     * @param length number of opcodes to decompile, -1 for all.
     * @param verbose be verbose, for example print constant pool index.
     * @return String representation of byte codes.
     */
    public static String codeToString(final byte[] code, final ConstantPool constantPool, final int index, final int length, final boolean verbose) {
        final StringBuilder buf = new StringBuilder(code.length * 20); // Should be sufficient // CHECKSTYLE IGNORE MagicNumber
        // Defend against a stale flag left behind by a previous (possibly truncated) disassembly on this thread.
        WIDE.set(Boolean.FALSE);
        try (ByteSequence stream = new ByteSequence(code)) {
            for (int i = 0; i < index; i++) {
                codeToString(stream, constantPool, verbose);
            }
            for (int i = 0; stream.available() > 0; i++) {
                if (length < 0 || i < length) {
                    final String indices = fillup(stream.getIndex() + ":", 6, true, ' ');
                    buf.append(indices).append(codeToString(stream, constantPool, verbose)).append('\n');
                }
            }
        } catch (final IOException e) {
            throw new ClassFormatException("Byte code error: " + buf.toString(), e);
        } finally {
            // A crafted code array can end right after a WIDE opcode (normal loop exit) or throw before the flag is
            // consumed; never leak the flag to the next disassembly on this thread, or that (unrelated) input is
            // mis-decoded from its first load/store/iinc/ret instruction onwards.
            WIDE.remove();
        }
        return buf.toString();
    }

    /**
     * Disassembles byte code.
     *
     * @param bytes stream of bytes.
     * @param constantPool The constant pool.
     * @return disassembled string representation.
     * @throws IOException Thrown if a failure from reading from the bytes argument occurs.
     */
    public static String codeToString(final ByteSequence bytes, final ConstantPool constantPool) throws IOException {
        return codeToString(bytes, constantPool, true);
    }

    /**
     * Disassemble a stream of byte codes and return the string representation.
     *
     * @param bytes stream of bytes.
     * @param constantPool Array of constants.
     * @param verbose be verbose, for example print constant pool index.
     * @return String representation of byte code.
     * @throws IOException Thrown if a failure from reading from the bytes argument occurs
     */
    public static String codeToString(final ByteSequence bytes, final ConstantPool constantPool, final boolean verbose) throws IOException {
        final short opcode = (short) bytes.readUnsignedByte();
        int defaultOffset = 0;
        final int low;
        final int high;
        final int npairs;
        final int index;
        final int vindex;
        final int constant;
        final int[] match;
        final int[] jumpTable;
        int noPadBytes = 0;
        final int offset;
        final StringBuilder buf = new StringBuilder(Const.getOpcodeName(opcode));
        /*
         * Special case: Skip (0-3) padding bytes, that is, the following bytes are 4-byte-aligned
         */
        if (opcode == Const.TABLESWITCH || opcode == Const.LOOKUPSWITCH) {
            final int remainder = bytes.getIndex() % 4;
            noPadBytes = remainder == 0 ? 0 : 4 - remainder;
            for (int i = 0; i < noPadBytes; i++) {
                final byte b;
                if ((b = bytes.readByte()) != 0) {
                    System.err.println("Warning: Padding byte != 0 in " + Const.getOpcodeName(opcode) + ":" + b);
                }
            }
            // Both cases have a field default_offset in common
            defaultOffset = bytes.readInt();
        }
        switch (opcode) {
        /*
         * Table switch has variable length arguments.
         */
        case Const.TABLESWITCH:
            low = bytes.readInt();
            high = bytes.readInt();
            offset = bytes.getIndex() - 12 - noPadBytes - 1;
            defaultOffset += offset;
            // Each jump table entry is a 4 byte offset, so a well-formed table cannot declare more entries than fit
            // into the remaining byte code; checking before allocating keeps a crafted low/high pair from forcing a
            // huge allocation.
            final long jumpTableLength = (long) high - low + 1;
            if (jumpTableLength < 0 || jumpTableLength * 4 > bytes.available()) {
                throw new ClassFormatException("Invalid TABLESWITCH: low = " + low + ", high = " + high + " but only " + bytes.available() + " bytes remain");
            }
            buf.append("\tdefault = ").append(defaultOffset).append(", low = ").append(low).append(", high = ").append(high).append("(");
            jumpTable = new int[(int) jumpTableLength];
            for (int i = 0; i < jumpTable.length; i++) {
                jumpTable[i] = offset + bytes.readInt();
                buf.append(jumpTable[i]);
                if (i < jumpTable.length - 1) {
                    buf.append(", ");
                }
            }
            buf.append(")");
            break;
        /*
         * Lookup switch has variable length arguments.
         */
        case Const.LOOKUPSWITCH: {
            npairs = bytes.readInt();
            offset = bytes.getIndex() - 8 - noPadBytes - 1;
            // Each match-offset pair is 8 bytes, see the TABLESWITCH check above.
            if (npairs < 0 || (long) npairs * 8 > bytes.available()) {
                throw new ClassFormatException("Invalid LOOKUPSWITCH: npairs = " + npairs + " but only " + bytes.available() + " bytes remain");
            }
            match = new int[npairs];
            jumpTable = new int[npairs];
            defaultOffset += offset;
            buf.append("\tdefault = ").append(defaultOffset).append(", npairs = ").append(npairs).append(" (");
            for (int i = 0; i < npairs; i++) {
                match[i] = bytes.readInt();
                jumpTable[i] = offset + bytes.readInt();
                buf.append("(").append(match[i]).append(", ").append(jumpTable[i]).append(")");
                if (i < npairs - 1) {
                    buf.append(", ");
                }
            }
            buf.append(")");
        }
            break;
        /*
         * Two address bytes + offset from start of byte stream form the jump target
         */
        case Const.GOTO:
        case Const.IFEQ:
        case Const.IFGE:
        case Const.IFGT:
        case Const.IFLE:
        case Const.IFLT:
        case Const.JSR:
        case Const.IFNE:
        case Const.IFNONNULL:
        case Const.IFNULL:
        case Const.IF_ACMPEQ:
        case Const.IF_ACMPNE:
        case Const.IF_ICMPEQ:
        case Const.IF_ICMPGE:
        case Const.IF_ICMPGT:
        case Const.IF_ICMPLE:
        case Const.IF_ICMPLT:
        case Const.IF_ICMPNE:
            buf.append("\t\t#").append(bytes.getIndex() - 1 + bytes.readShort());
            break;
        /*
         * 32-bit wide jumps
         */
        case Const.GOTO_W:
        case Const.JSR_W:
            buf.append("\t\t#").append(bytes.getIndex() - 1 + bytes.readInt());
            break;
        /*
         * Index byte references local variable (register)
         */
        case Const.ALOAD:
        case Const.ASTORE:
        case Const.DLOAD:
        case Const.DSTORE:
        case Const.FLOAD:
        case Const.FSTORE:
        case Const.ILOAD:
        case Const.ISTORE:
        case Const.LLOAD:
        case Const.LSTORE:
        case Const.RET:
            if (WIDE.get().booleanValue()) {
                vindex = bytes.readUnsignedShort();
                WIDE.set(Boolean.FALSE); // Clear flag
            } else {
                vindex = bytes.readUnsignedByte();
            }
            buf.append("\t\t%").append(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 Const.WIDE:
            WIDE.set(Boolean.TRUE);
            buf.append("\t(wide)");
            break;
        /*
         * Array of basic type.
         */
        case Const.NEWARRAY:
            buf.append("\t\t<").append(Const.getTypeName(bytes.readByte())).append(">");
            break;
        /*
         * Access object/class fields.
         */
        case Const.GETFIELD:
        case Const.GETSTATIC:
        case Const.PUTFIELD:
        case Const.PUTSTATIC:
            index = bytes.readUnsignedShort();
            buf.append("\t\t").append(constantPool.constantToString(index, Const.CONSTANT_Fieldref)).append(verbose ? " (" + index + ")" : "");
            break;
        /*
         * Operands are references to classes in constant pool
         */
        case Const.NEW:
        case Const.CHECKCAST:
            buf.append("\t");
            index = bytes.readUnsignedShort();
            buf.append("\t<").append(constantPool.constantToString(index, Const.CONSTANT_Class)).append(">").append(verbose ? " (" + index + ")" : "");
            break;
        case Const.INSTANCEOF:
            index = bytes.readUnsignedShort();
            buf.append("\t<").append(constantPool.constantToString(index, Const.CONSTANT_Class)).append(">").append(verbose ? " (" + index + ")" : "");
            break;
        /*
         * Operands are references to methods in constant pool
         */
        case Const.INVOKESPECIAL:
        case Const.INVOKESTATIC:
            index = bytes.readUnsignedShort();
            final Constant c = constantPool.getConstant(index);
            // With Java8 operand may be either a CONSTANT_Methodref
            // or a CONSTANT_InterfaceMethodref. (markro)
            buf.append("\t").append(constantPool.constantToString(index, c.getTag())).append(verbose ? " (" + index + ")" : "");
            break;
        case Const.INVOKEVIRTUAL:
            index = bytes.readUnsignedShort();
            buf.append("\t").append(constantPool.constantToString(index, Const.CONSTANT_Methodref)).append(verbose ? " (" + index + ")" : "");
            break;
        case Const.INVOKEINTERFACE:
            index = bytes.readUnsignedShort();
            final int nargs = bytes.readUnsignedByte(); // historical, redundant
            buf.append("\t").append(constantPool.constantToString(index, Const.CONSTANT_InterfaceMethodref)).append(verbose ? " (" + index + ")\t" : "")
                .append(nargs).append("\t").append(bytes.readUnsignedByte()); // Last byte is a reserved space
            break;
        case Const.INVOKEDYNAMIC:
            index = bytes.readUnsignedShort();
            buf.append("\t").append(constantPool.constantToString(index, Const.CONSTANT_InvokeDynamic)).append(verbose ? " (" + index + ")\t" : "")
                .append(bytes.readUnsignedByte()) // Thrid byte is a reserved space
                .append(bytes.readUnsignedByte()); // Last byte is a reserved space
            break;
        /*
         * Operands are references to items in constant pool
         */
        case Const.LDC_W:
        case Const.LDC2_W:
            index = bytes.readUnsignedShort();
            buf.append("\t\t").append(constantPool.constantToString(index, constantPool.getConstant(index).getTag()))
                .append(verbose ? " (" + index + ")" : "");
            break;
        case Const.LDC:
            index = bytes.readUnsignedByte();
            buf.append("\t\t").append(constantPool.constantToString(index, constantPool.getConstant(index).getTag()))
                .append(verbose ? " (" + index + ")" : "");
            break;
        /*
         * Array of references.
         */
        case Const.ANEWARRAY:
            index = bytes.readUnsignedShort();
            buf.append("\t\t<").append(compactClassName(constantPool.getConstantString(index, Const.CONSTANT_Class), false)).append(">")
                .append(verbose ? " (" + index + ")" : "");
            break;
        /*
         * Multidimensional array of references.
         */
        case Const.MULTIANEWARRAY: {
            index = bytes.readUnsignedShort();
            final int dimensions = bytes.readUnsignedByte();
            buf.append("\t<").append(compactClassName(constantPool.getConstantString(index, Const.CONSTANT_Class), false)).append(">\t").append(dimensions)
                .append(verbose ? " (" + index + ")" : "");
        }
            break;
        /*
         * Increment local variable.
         */
        case Const.IINC:
            if (WIDE.get().booleanValue()) {
                vindex = bytes.readUnsignedShort();
                constant = bytes.readShort();
                WIDE.set(Boolean.FALSE);
            } else {
                vindex = bytes.readUnsignedByte();
                constant = bytes.readByte();
            }
            buf.append("\t\t%").append(vindex).append("\t").append(constant);
            break;
        default:
            if (Const.getNoOfOperands(opcode) > 0) {
                for (int i = 0; i < Const.getOperandTypeCount(opcode); i++) {
                    buf.append("\t\t");
                    switch (Const.getOperandType(opcode, i)) {
                    case Const.T_BYTE:
                        buf.append(bytes.readByte());
                        break;
                    case Const.T_SHORT:
                        buf.append(bytes.readShort());
                        break;
                    case Const.T_INT:
                        buf.append(bytes.readInt());
                        break;
                    default: // Never reached
                        throw new IllegalStateException("Unreachable default case reached.");
                    }
                }
            }
        }
        return buf.toString();
    }

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

    /**
     * Shorten long class names, <em>java/lang/String</em> becomes <em>java.lang.String</em>, for example. If <em>chopit</em> is
     * <em>true</em> the prefix <em>java.lang</em> 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 String compactClassName(final String str, final boolean chopit) {
        return compactClassName(str, "java.lang.", chopit);
    }

    /**
     * Shorten long class name <em>str</em>, that is, chop off the <em>prefix</em>, if the class name starts with this string
     * and the flag <em>chopit</em> is true. Slashes <em>/</em> are converted to dots <em>.</em>.
     *
     * @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 String compactClassName(String str, final String prefix, final boolean chopit) {
        final int len = prefix.length();
        str = pathToPackage(str); // Is '/' on all systems, even DOS
        // If string starts with 'prefix' and contains no further dots
        if (chopit && str.startsWith(prefix) && str.substring(len).indexOf('.') == -1) {
            str = str.substring(len);
        }
        return str;
    }

    /**
     * Escape all occurrences of newline chars '\n', quotes \", etc.
     *
     * @param label The string to convert.
     * @return The converted string.
     */
    public static String convertString(final String label) {
        final char[] ch = label.toCharArray();
        final StringBuilder buf = new StringBuilder();
        for (final char element : ch) {
            switch (element) {
            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(element);
                break;
            }
        }
        return buf.toString();
    }

    private static int countBrackets(final String brackets) {
        final char[] chars = brackets.toCharArray();
        int count = 0;
        boolean open = false;
        for (final char c : chars) {
            switch (c) {
            case '[':
                if (open) {
                    throw new IllegalArgumentException("Illegally nested brackets:" + brackets);
                }
                open = true;
                break;
            case ']':
                if (!open) {
                    throw new IllegalArgumentException("Illegally nested brackets:" + brackets);
                }
                open = false;
                count++;
                break;
            default:
                // Don't care
                break;
            }
        }
        if (open) {
            throw new IllegalArgumentException("Illegally nested brackets:" + brackets);
        }
        return count;
    }

    /**
     * Decode a string back to a byte array.
     *
     * @param s The string to convert.
     * @param uncompress use gzip to uncompress the stream of bytes.
     * @return The decoded byte array.
     * @throws IOException Thrown if there's a gzip exception or the decompressed data exceeds {@code MAX_DECODED_LENGTH}.
     */
    public static byte[] decode(final String s, final boolean uncompress) throws IOException {
        final byte[] bytes;
        try (JavaReader jr = new JavaReader(new CharArrayReader(s.toCharArray())); ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
            int ch;
            while ((ch = jr.read()) >= 0) {
                bos.write(ch);
            }
            bytes = bos.toByteArray();
        }
        if (uncompress) {
            // @formatter:off
            try (BoundedInputStream gis = BoundedInputStream.builder()
                    .setInputStream(new GZIPInputStream(new ByteArrayInputStream(bytes)))
                    .setMaxCount(MAX_DECODED_LENGTH + 1).get()) {
                return IOUtils.toByteArray(gis);
            }
            // @formatter:on
        }
        return bytes;
    }

    /**
     * Encode byte array it into Java identifier string, that is, a string that only contains the following characters: (a, ...
     * z, A, ... Z, 0, ... 9, _, $). The encoding algorithm itself is not too clever: if the current byte's ASCII value
     * already is a valid Java identifier part, leave it as it is. Otherwise it writes the escape character($) followed by:
     *
     * <ul>
     * <li>the ASCII value as a hexadecimal string, if the value is not in the range 200..247</li>
     * <li>a Java identifier char not used in a lowercase hexadecimal string, if the value is in the range 200..247</li>
     * </ul>
     *
     * <p>
     * This operation inflates the original byte array by roughly 40-50%
     * </p>
     *
     * @param bytes The byte array to convert.
     * @param compress use gzip to minimize string.
     * @return The encoded string.
     * @throws IOException Thrown if there's a gzip exception.
     */
    public static String encode(byte[] bytes, final boolean compress) throws IOException {
        if (compress) {
            try (ByteArrayOutputStream baos = new ByteArrayOutputStream(); GZIPOutputStream gos = new GZIPOutputStream(baos)) {
                gos.write(bytes, 0, bytes.length);
                gos.close();
                bytes = baos.toByteArray();
            }
        }
        final CharArrayWriter caw = new CharArrayWriter();
        try (JavaWriter jw = new JavaWriter(caw)) {
            for (final byte b : bytes) {
                final int in = b & 0x000000ff; // Normalize to unsigned
                jw.write(in);
            }
        }
        return caw.toString();
    }

    /**
     * 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 leftJustify format left or right.
     * @param fill fill character.
     * @return formatted string.
     */
    public static String fillup(final String str, final int length, final boolean leftJustify, final char fill) {
        final int len = length - str.length();
        final char[] buf = ArrayFill.fill(new char[Math.max(len, 0)], fill);
        if (leftJustify) {
            return str + new String(buf);
        }
        return new String(buf) + str;
    }

    /**
     * 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 leftJustify format left or right.
     * @param fill fill character.
     * @return formatted int.
     */
    public static String format(final int i, final int length, final boolean leftJustify, final char fill) {
        return fillup(Integer.toString(i), length, leftJustify, fill);
    }

    /**
     * Parse Java type such as "char", or "java.lang.String[]" and return the signature in byte code format, for example "C" or
     * "[Ljava/lang/String;" respectively.
     *
     * @param type Java type.
     * @return byte code signature.
     */
    public static String getSignature(String type) {
        final StringBuilder buf = new StringBuilder();
        final char[] chars = type.toCharArray();
        boolean charFound = false;
        boolean delim = false;
        int index = -1;
        loop: for (int i = 0; i < chars.length; i++) {
            switch (chars[i]) {
            case ' ':
            case '\t':
            case '\n':
            case '\r':
            case '\f':
                if (charFound) {
                    delim = true;
                }
                break;
            case '[':
                if (!charFound) {
                    throw new IllegalArgumentException("Illegal type: " + type);
                }
                index = i;
                break loop;
            default:
                charFound = true;
                if (!delim) {
                    buf.append(chars[i]);
                }
            }
        }
        int brackets = 0;
        if (index > 0) {
            brackets = countBrackets(type.substring(index));
        }
        type = buf.toString();
        buf.setLength(0);
        for (int i = 0; i < brackets; i++) {
            buf.append('[');
        }
        boolean found = false;
        for (int i = Const.T_BOOLEAN; i <= Const.T_VOID && !found; i++) {
            if (Const.getTypeName(i).equals(type)) {
                found = true;
                buf.append(Const.getShortTypeName(i));
            }
        }
        if (!found) {
            buf.append('L').append(packageToPath(type)).append(';');
        }
        return buf.toString();
    }

    private static boolean isHex(final int i) {
        return i >= '0' && i <= '9' || i >= 'a' && i <= 'f';
    }

    /**
     * WARNING:
     *
     * There is some nomenclature confusion through much of the BCEL code base with respect to the terms Descriptor and
     * Signature. For the offical definitions see:
     *
     * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3"> Descriptors in The Java
     *      Virtual Machine Specification</a>
     *
     * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.9.1"> Signatures in The Java
     *      Virtual Machine Specification</a>
     *
     *      In brief, a descriptor is a string representing the type of a field or method. Signatures are similar, but more
     *      complex. Signatures are used to encode declarations written in the Java programming language that use types
     *      outside the type system of the Java Virtual Machine. They are used to describe the type of any class, interface,
     *      constructor, method or field whose declaration uses type variables or parameterized types.
     *
     *      To parse a descriptor, call typeSignatureToString. To parse a signature, call signatureToString.
     *
     *      Note that if the signature string is a single, non-generic item, the call to signatureToString reduces to a call
     *      to typeSignatureToString. Also note, that if you only wish to parse the first item in a longer signature string,
     *      you should call typeSignatureToString directly.
     */

    /**
     * Tests if a character is part of a Java identifier.
     *
     * @param ch The character to test if it's part of an identifier.
     * @return true, if character is one of (a, ... z, A, ... Z, 0, ... 9, _).
     */
    public static boolean isJavaIdentifierPart(final char ch) {
        return ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z' || ch >= '0' && ch <= '9' || ch == '_';
    }

    /**
     * Tests if a bit is set.
     *
     * @param flag The flag value.
     * @param i The bit position.
     * @return true, if bit 'i' in 'flag' is set.
     */
    public static boolean isSet(final int flag, final int i) {
        return (flag & pow2(i)) != 0;
    }

    /**
     * Converts argument list portion of method signature to string with all class names compacted.
     *
     * @param signature Method signature.
     * @return String Array of argument types.
     * @throws ClassFormatException Thrown if a class is malformed or cannot be interpreted as a class file
     */
    public static String[] methodSignatureArgumentTypes(final String signature) throws ClassFormatException {
        return methodSignatureArgumentTypes(signature, true);
    }

    /**
     * Converts argument list portion of method signature to string.
     *
     * @param signature Method signature.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return String Array of argument types.
     * @throws ClassFormatException Thrown if a class is malformed or cannot be interpreted as a class file
     */
    public static String[] methodSignatureArgumentTypes(final String signature, final boolean chopit) throws ClassFormatException {
        final List<String> vec = new ArrayList<>();
        int index;
        try {
            // Skip any type arguments to read argument declarations between '(' and ')'
            index = signature.indexOf('(') + 1;
            if (index <= 0) {
                throw new InvalidMethodSignatureException(signature);
            }
            while (signature.charAt(index) != ')') {
                vec.add(typeSignatureToString(signature.substring(index), chopit));
                // corrected concurrent private static field acess
                index += unwrap(CONSUMER_CHARS); // update position
            }
        } catch (final StringIndexOutOfBoundsException e) { // Should never occur
            throw new InvalidMethodSignatureException(signature, e);
        }
        return vec.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    /**
     * Converts return type portion of method signature to string with all class names compacted.
     *
     * @param signature Method signature.
     * @return String representation of method return type.
     * @throws ClassFormatException Thrown if a class is malformed or cannot be interpreted as a class file
     */
    public static String methodSignatureReturnType(final String signature) throws ClassFormatException {
        return methodSignatureReturnType(signature, true);
    }

    /**
     * Converts return type portion of method signature to string.
     *
     * @param signature Method signature.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return String representation of method return type.
     * @throws ClassFormatException Thrown if a class is malformed or cannot be interpreted as a class file
     */
    public static String methodSignatureReturnType(final String signature, final boolean chopit) throws ClassFormatException {
        try {
            // Read return type after ')'
            final int index = signature.lastIndexOf(')') + 1;
            if (index <= 0) {
                throw new InvalidMethodSignatureException(signature);
            }
            return typeSignatureToString(signature.substring(index), chopit);
        } catch (final StringIndexOutOfBoundsException e) { // Should never occur
            throw new InvalidMethodSignatureException(signature, e);
        }
    }

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

    /**
     * Converts method signature to string.
     *
     * @param signature to convert.
     * @param name of method.
     * @param access flags of method.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return Human readable signature.
     */
    public static String methodSignatureToString(final String signature, final String name, final String access, final boolean chopit) {
        return methodSignatureToString(signature, name, access, chopit, null);
    }

    /**
     * This method converts a method signature string into a Java type declaration like 'void main(String[])' and throws a
     * 'ClassFormatException' when the parsed type is invalid.
     *
     * @param signature Method signature.
     * @param name Method name.
     * @param access Method access rights.
     * @param chopit flag that determines whether chopping is executed or not.
     * @param vars The LocalVariableTable for the method.
     * @return Java type declaration.
     * @throws ClassFormatException Thrown if a class is malformed or cannot be interpreted as a class file
     */
    public static String methodSignatureToString(final String signature, final String name, final String access, final boolean chopit,
        final LocalVariableTable vars) throws ClassFormatException {
        final StringBuilder buf = new StringBuilder("(");
        final String type;
        int index;
        int varIndex = access.contains("static") ? 0 : 1;
        try {
            // Skip any type arguments to read argument declarations between '(' and ')'
            index = signature.indexOf('(') + 1;
            if (index <= 0) {
                throw new InvalidMethodSignatureException(signature);
            }
            while (signature.charAt(index) != ')') {
                final String paramType = typeSignatureToString(signature.substring(index), chopit);
                buf.append(paramType);
                if (vars != null) {
                    final LocalVariable l = vars.getLocalVariable(varIndex, 0);
                    if (l != null) {
                        buf.append(" ").append(l.getName());
                    }
                } else {
                    buf.append(" arg").append(varIndex);
                }
                if ("double".equals(paramType) || "long".equals(paramType)) {
                    varIndex += 2;
                } else {
                    varIndex++;
                }
                buf.append(", ");
                // corrected concurrent private static field acess
                index += unwrap(CONSUMER_CHARS); // update position
            }
            index++; // update position
            // Read return type after ')'
            type = typeSignatureToString(signature.substring(index), chopit);
        } catch (final StringIndexOutOfBoundsException e) { // Should never occur
            throw new InvalidMethodSignatureException(signature, e);
        }
        // ignore any throws information in the signature
        if (buf.length() > 1) {
            buf.setLength(buf.length() - 2);
        }
        buf.append(")");
        return access + (!access.isEmpty() ? " " : "") + // May be an empty string
            type + " " + name + buf.toString();
    }

    /**
     * Converts string containing the method return and argument types to a byte code method signature.
     *
     * @param ret Return type of method.
     * @param argv Types of method arguments.
     * @return Byte code representation of method signature.
     * @throws ClassFormatException Thrown if the signature is for Void
     */
    public static String methodTypeToSignature(final String ret, final String[] argv) throws ClassFormatException {
        final StringBuilder buf = new StringBuilder("(");
        String str;
        if (argv != null) {
            for (final String element : argv) {
                str = getSignature(element);
                if (str.endsWith("V")) {
                    throw new ClassFormatException("Invalid type: " + element);
                }
                buf.append(str);
            }
        }
        str = getSignature(ret);
        buf.append(")").append(str);
        return buf.toString();
    }

    /**
     * Converts '.'s to '/'s.
     *
     * @param name Source.
     * @return converted value.
     * @since 6.7.0
     */
    public static String packageToPath(final String name) {
        return name.replace('.', '/');
    }

    /**
     * Converts a path to a package name.
     *
     * @param str The source path.
     * @return A package name.
     * @since 6.6.0
     */
    public static String pathToPackage(final String str) {
        return str.replace('/', '.');
    }

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

    /**
     * Prints an array to a string.
     *
     * @param obj The array to print.
     * @return The string representation.
     */
    public static String printArray(final Object[] obj) {
        return printArray(obj, true);
    }

    /**
     * Prints an array to a string.
     *
     * @param obj The array to print.
     * @param braces whether to include braces.
     * @return The string representation.
     */
    public static String printArray(final Object[] obj, final boolean braces) {
        return printArray(obj, braces, false);
    }

    /**
     * Prints an array to a string.
     *
     * @param obj The array to print.
     * @param braces whether to include braces.
     * @param quote whether to quote elements.
     * @return The string representation.
     */
    public static String printArray(final Object[] obj, final boolean braces, final boolean quote) {
        if (obj == null) {
            return null;
        }
        final StringBuilder buf = new StringBuilder();
        if (braces) {
            buf.append('{');
        }
        for (int i = 0; i < obj.length; i++) {
            if (obj[i] != null) {
                buf.append(quote ? "\"" : "").append(obj[i]).append(quote ? "\"" : "");
            } else {
                buf.append("null");
            }
            if (i < obj.length - 1) {
                buf.append(", ");
            }
        }
        if (braces) {
            buf.append('}');
        }
        return buf.toString();
    }

    /**
     * Prints an array to a stream.
     *
     * @param out The output stream.
     * @param obj The array to print.
     */
    public static void printArray(final PrintStream out, final Object[] obj) {
        out.println(printArray(obj, true));
    }

    /**
     * Prints an array to a writer.
     *
     * @param out The output writer.
     * @param obj The array to print.
     */
    public static void printArray(final PrintWriter out, final Object[] obj) {
        out.println(printArray(obj, true));
    }

    /**
     * Replace all occurrences of <em>old</em> in <em>str</em> with <em>new</em>.
     *
     * @param str String to permute.
     * @param old String to be replaced.
     * @param new_ Replacement string.
     * @return new String object.
     */
    public static String replace(String str, final String old, final String new_) {
        int index;
        int oldIndex;
        try {
            if (str.contains(old)) { // 'old' found in str
                final StringBuilder buf = new StringBuilder();
                oldIndex = 0; // String start offset
                // While we have something to replace
                while ((index = str.indexOf(old, oldIndex)) != -1) {
                    buf.append(str, oldIndex, index); // append prefix
                    buf.append(new_); // append replacement
                    oldIndex = index + old.length(); // Skip 'old'.length chars
                }
                buf.append(str.substring(oldIndex)); // append rest of string
                str = buf.toString();
            }
        } catch (final StringIndexOutOfBoundsException e) { // Should not occur
            System.err.println(e);
        }
        return str;
    }

    /**
     * Map opcode names to opcode numbers. E.g., return Constants.ALOAD for "aload".
     *
     * @param name The opcode name.
     * @return The value.
     */
    public static short searchOpcode(final String name) {
        final String lcName = StringUtils.toRootLowerCase(name);
        for (short i = 0; i < Const.OPCODE_NAMES_LENGTH; i++) {
            if (Const.getOpcodeName(i).equals(lcName)) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Sets a bit in a flag.
     *
     * @param flag The flag value.
     * @param i The bit position.
     * @return 'flag' with bit 'i' set to 1.
     */
    public static int setBit(final int flag, final int i) {
        return flag | pow2(i);
    }

    /**
     * Converts a signature to a string with all class names compacted. Class, Method and Type signatures are supported.
     * Enum and Interface signatures are not supported.
     *
     * @param signature signature to convert.
     * @return String containg human readable signature.
     */
    public static String signatureToString(final String signature) {
        return signatureToString(signature, true);
    }

    /**
     * Converts a signature to a string. Class, Method and Type signatures are supported. Enum and Interface signatures are
     * not supported.
     *
     * @param signature signature to convert.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return String containg human readable signature.
     */
    public static String signatureToString(final String signature, final boolean chopit) {
        String type = "";
        String typeParams = "";
        int index = 0;
        if (signature.charAt(0) == '<') {
            // we have type parameters
            typeParams = typeParamTypesToString(signature, chopit);
            index += unwrap(CONSUMER_CHARS); // update position
        }
        if (signature.charAt(index) == '(') {
            // We have a Method signature.
            // add types of arguments
            type = typeParams + typeSignaturesToString(signature.substring(index), chopit, ')');
            index += unwrap(CONSUMER_CHARS); // update position
            // add return type
            type += typeSignatureToString(signature.substring(index), chopit);
            index += unwrap(CONSUMER_CHARS); // update position
            // ignore any throws information in the signature
            return type;
        }
        // Could be Class or Type...
        type = typeSignatureToString(signature.substring(index), chopit);
        index += unwrap(CONSUMER_CHARS); // update position
        if (typeParams.isEmpty() && index == signature.length()) {
            // We have a Type signature.
            return type;
        }
        // We have a Class signature.
        final StringBuilder typeClass = new StringBuilder(typeParams);
        typeClass.append(" extends ");
        typeClass.append(type);
        if (index < signature.length()) {
            typeClass.append(" implements ");
            typeClass.append(typeSignatureToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        while (index < signature.length()) {
            typeClass.append(", ");
            typeClass.append(typeSignatureToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        return typeClass.toString();
    }

    /**
     * Convert bytes into hexadecimal string
     *
     * @param bytes An array of bytes to convert to hexadecimal.
     * @return bytes as hexadecimal string, for example 00 fa 12 ...
     */
    public static String toHexString(final byte[] bytes) {
        final StringBuilder buf = new StringBuilder();
        for (int i = 0; i < bytes.length; i++) {
            final short b = byteToShort(bytes[i]);
            final String hex = Integer.toHexString(b);
            if (b < 0x10) {
                buf.append('0');
            }
            buf.append(hex);
            if (i < bytes.length - 1) {
                buf.append(' ');
            }
        }
        return buf.toString();
    }

    /**
     * Return type of method signature as a byte value as defined in <em>Constants</em>
     *
     * @param signature in format described above.
     * @return type of method signature.
     * @see Const
     * @throws ClassFormatException Thrown if signature is not a method signature
     */
    public static byte typeOfMethodSignature(final String signature) throws ClassFormatException {
        try {
            if (signature.charAt(0) != '(') {
                throw new InvalidMethodSignatureException(signature);
            }
            final int index = signature.lastIndexOf(')') + 1;
            return typeOfSignature(signature.substring(index));
        } catch (final StringIndexOutOfBoundsException e) {
            throw new InvalidMethodSignatureException(signature, e);
        }
    }

    /**
     * Return type of signature as a byte value as defined in <em>Constants</em>
     *
     * @param signature in format described above.
     * @return type of signature.
     * @see Const
     * @throws ClassFormatException Thrown if signature isn't a known type
     */
    public static byte typeOfSignature(final String signature) throws ClassFormatException {
        try {
            switch (signature.charAt(0)) {
            case 'B':
                return Const.T_BYTE;
            case 'C':
                return Const.T_CHAR;
            case 'D':
                return Const.T_DOUBLE;
            case 'F':
                return Const.T_FLOAT;
            case 'I':
                return Const.T_INT;
            case 'J':
                return Const.T_LONG;
            case 'L':
            case 'T':
                return Const.T_REFERENCE;
            case '[':
                return Const.T_ARRAY;
            case 'V':
                return Const.T_VOID;
            case 'Z':
                return Const.T_BOOLEAN;
            case 'S':
                return Const.T_SHORT;
            case '!':
            case '+':
            case '*':
                return typeOfSignature(signature.substring(1));
            default:
                throw new InvalidMethodSignatureException(signature);
            }
        } catch (final StringIndexOutOfBoundsException e) {
            throw new InvalidMethodSignatureException(signature, e);
        }
    }

    /**
     * Converts a type parameter list signature to a string.
     *
     * @param signature signature to convert.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return String containg human readable signature.
     */
    private static String typeParamTypesToString(final String signature, final boolean chopit) {
        // The first character is guranteed to be '<'
        final StringBuilder typeParams = new StringBuilder("<");
        int index = 1; // skip the '<'
        // get the first TypeParameter
        typeParams.append(typeParamTypeToString(signature.substring(index), chopit));
        index += unwrap(CONSUMER_CHARS); // update position
        // are there more TypeParameters?
        while (signature.charAt(index) != '>') {
            typeParams.append(", ");
            typeParams.append(typeParamTypeToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        wrap(CONSUMER_CHARS, index + 1); // account for the '>' char
        return typeParams.append(">").toString();
    }

    /**
     * Converts a type parameter signature to a string.
     *
     * @param signature signature to convert.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return String containg human readable signature.
     */
    private static String typeParamTypeToString(final String signature, final boolean chopit) {
        int index = signature.indexOf(':');
        if (index <= 0) {
            throw new ClassFormatException("Invalid type parameter signature: " + signature);
        }
        // get the TypeParameter identifier
        final StringBuilder typeParam = new StringBuilder(signature.substring(0, index));
        index++; // account for the ':'
        if (signature.charAt(index) != ':') {
            // we have a class bound
            typeParam.append(" extends ");
            typeParam.append(typeSignatureToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        // look for interface bounds
        while (signature.charAt(index) == ':') {
            index++; // skip over the ':'
            typeParam.append(" & ");
            typeParam.append(typeSignatureToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        wrap(CONSUMER_CHARS, index);
        return typeParam.toString();
    }

    /**
     * Converts a list of type signatures to a string.
     *
     * @param signature signature to convert.
     * @param chopit flag that determines whether chopping is executed or not.
     * @param term character indicating the end of the list.
     * @return String containg human readable signature.
     */
    private static String typeSignaturesToString(final String signature, final boolean chopit, final char term) {
        // The first character will be an 'open' that matches the 'close' contained in term.
        final StringBuilder typeList = new StringBuilder(signature.substring(0, 1));
        int index = 1; // skip the 'open' character
        // get the first Type in the list
        if (signature.charAt(index) != term) {
            typeList.append(typeSignatureToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        // are there more types in the list?
        while (signature.charAt(index) != term) {
            typeList.append(", ");
            typeList.append(typeSignatureToString(signature.substring(index), chopit));
            index += unwrap(CONSUMER_CHARS); // update position
        }
        wrap(CONSUMER_CHARS, index + 1); // account for the term char
        return typeList.append(term).toString();
    }

    /**
     *
     * This method converts a type signature string into a Java type declaration such as 'String[]' and throws a
     * 'ClassFormatException' when the parsed type is invalid.
     *
     * @param signature type signature.
     * @param chopit flag that determines whether chopping is executed or not.
     * @return string containing human readable type signature.
     * @throws ClassFormatException Thrown if a class is malformed or cannot be interpreted as a class file
     * @since 6.4.0
     */
    public static String typeSignatureToString(final String signature, final boolean chopit) throws ClassFormatException {
        return typeSignatureToString(signature, chopit, 0);
    }

    /**
     * Recursive worker for {@link #typeSignatureToString(String, boolean)} carrying the current nesting depth.
     *
     * @param signature type signature.
     * @param chopit    flag that determines whether chopping is executed or not.
     * @param depth     current nesting depth.
     * @return string containing human readable type signature.
     * @throws ClassFormatException Thrown if the signature is malformed or nested deeper than {@code MAX_SIGNATURE_NESTING}.
     */
    private static String typeSignatureToString(final String signature, final boolean chopit, final int depth) throws ClassFormatException {
        if (depth > MAX_SIGNATURE_NESTING) {
            throw new ClassFormatException("Invalid signature: nesting depth exceeds " + MAX_SIGNATURE_NESTING);
        }
        // corrected concurrent private static field acess
        wrap(CONSUMER_CHARS, 1); // This is the default, read just one char like 'B'
        try {
            switch (signature.charAt(0)) {
            case 'B':
                return "byte";
            case 'C':
                return "char";
            case 'D':
                return "double";
            case 'F':
                return "float";
            case 'I':
                return "int";
            case 'J':
                return "long";
            case 'T': { // TypeVariableSignature
                final int index = signature.indexOf(';'); // Look for closing ';'
                if (index < 0) {
                    throw new ClassFormatException("Invalid type variable signature: " + signature);
                }
                // corrected concurrent private static field acess
                wrap(CONSUMER_CHARS, index + 1); // "Tblabla;" 'T' and ';' are removed
                return compactClassName(signature.substring(1, index), chopit);
            }
            case 'L': { // Full class name
                // should this be a while loop? can there be more than
                // one generic clause? (markro)
                int fromIndex = signature.indexOf('<'); // generic type?
                if (fromIndex < 0) {
                    fromIndex = 0;
                } else {
                    fromIndex = signature.indexOf('>', fromIndex);
                    if (fromIndex < 0) {
                        throw new ClassFormatException("Invalid signature: " + signature);
                    }
                }
                final int index = signature.indexOf(';', fromIndex); // Look for closing ';'
                if (index < 0) {
                    throw new ClassFormatException("Invalid signature: " + signature);
                }

                // check to see if there are any TypeArguments
                final int bracketIndex = signature.substring(0, index).indexOf('<');
                if (bracketIndex < 0) {
                    // just a class identifier
                    wrap(CONSUMER_CHARS, index + 1); // "Lblabla;" 'L' and ';' are removed
                    return compactClassName(signature.substring(1, index), chopit);
                }
                // but make sure we are not looking past the end of the current item
                fromIndex = signature.indexOf(';');
                if (fromIndex < 0) {
                    throw new ClassFormatException("Invalid signature: " + signature);
                }
                if (fromIndex < bracketIndex) {
                    // just a class identifier
                    wrap(CONSUMER_CHARS, fromIndex + 1); // "Lblabla;" 'L' and ';' are removed
                    return compactClassName(signature.substring(1, fromIndex), chopit);
                }

                // we have TypeArguments; build up partial result
                // as we recurse for each TypeArgument
                final StringBuilder type = new StringBuilder(compactClassName(signature.substring(1, bracketIndex), chopit)).append("<");
                int consumedChars = bracketIndex + 1; // Shadows global var

                // check for wildcards
                if (signature.charAt(consumedChars) == '+') {
                    type.append("? extends ");
                    consumedChars++;
                } else if (signature.charAt(consumedChars) == '-') {
                    type.append("? super ");
                    consumedChars++;
                }

                // get the first TypeArgument
                if (signature.charAt(consumedChars) == '*') {
                    type.append("?");
                    consumedChars++;
                } else {
                    type.append(typeSignatureToString(signature.substring(consumedChars), chopit, depth + 1));
                    // update our consumed count by the number of characters the for type argument
                    consumedChars = unwrap(CONSUMER_CHARS) + consumedChars;
                    wrap(CONSUMER_CHARS, consumedChars);
                }

                // are there more TypeArguments?
                while (signature.charAt(consumedChars) != '>') {
                    type.append(", ");
                    // check for wildcards
                    if (signature.charAt(consumedChars) == '+') {
                        type.append("? extends ");
                        consumedChars++;
                    } else if (signature.charAt(consumedChars) == '-') {
                        type.append("? super ");
                        consumedChars++;
                    }
                    if (signature.charAt(consumedChars) == '*') {
                        type.append("?");
                        consumedChars++;
                    } else {
                        type.append(typeSignatureToString(signature.substring(consumedChars), chopit, depth + 1));
                        // update our consumed count by the number of characters the for type argument
                        consumedChars = unwrap(CONSUMER_CHARS) + consumedChars;
                        wrap(CONSUMER_CHARS, consumedChars);
                    }
                }

                // process the closing ">"
                consumedChars++;
                type.append(">");

                if (signature.charAt(consumedChars) == '.') {
                    // we have a ClassTypeSignatureSuffix
                    type.append(".");
                    // convert SimpleClassTypeSignature to fake ClassTypeSignature
                    // and then recurse to parse it
                    type.append(typeSignatureToString("L" + signature.substring(consumedChars + 1), chopit, depth + 1));
                    // update our consumed count by the number of characters the for type argument
                    // note that this count includes the "L" we added, but that is ok
                    // as it accounts for the "." we didn't consume
                    consumedChars = unwrap(CONSUMER_CHARS) + consumedChars;
                    wrap(CONSUMER_CHARS, consumedChars);
                    return type.toString();
                }
                if (signature.charAt(consumedChars) != ';') {
                    throw new ClassFormatException("Invalid signature: " + signature);
                }
                wrap(CONSUMER_CHARS, consumedChars + 1); // remove final ";"
                return type.toString();
            }
            case 'S':
                return "short";
            case 'Z':
                return "boolean";
            case '[': { // Array declaration
                int n;
                final StringBuilder brackets = new StringBuilder(); // Accumulate []'s
                // Count opening brackets and look for optional size argument
                for (n = 0; signature.charAt(n) == '['; n++) {
                    brackets.append("[]");
                }
                final int consumedChars = n; // Remember value
                // The rest of the string denotes a '<field_type>'
                final String type = typeSignatureToString(signature.substring(n), chopit, depth + 1);
                // corrected concurrent private static field acess
                // consumed_chars += consumed_chars; is replaced by:
                final int temp = unwrap(CONSUMER_CHARS) + consumedChars;
                wrap(CONSUMER_CHARS, temp);
                return type + brackets.toString();
            }
            case 'V':
                return "void";
            default:
                throw new ClassFormatException("Invalid signature: '" + signature + "'");
            }
        } catch (final StringIndexOutOfBoundsException e) { // Should never occur
            throw new ClassFormatException("Invalid signature: " + signature, e);
        }
    }

    private static int unwrap(final ThreadLocal<Integer> tl) {
        return tl.get().intValue();
    }

    private static void wrap(final ThreadLocal<Integer> tl, final int value) {
        tl.set(Integer.valueOf(value));
    }

    /**
     * Constructs a Utility.
     *
     * @deprecated Will be private in the next major release.
     */
    public Utility() {
        // Default constructor for subclasses
    }

}