/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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:
 *
 *   http://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 io.netty.buffer;

import io.netty.util.CharsetUtil;
import io.netty.util.Recycler;
import io.netty.util.Recycler.Handle;
import io.netty.util.concurrent.FastThreadLocal;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.SystemPropertyUtil;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.util.Locale;

import static io.netty.util.internal.MathUtil.isOutOfBounds;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.StringUtil.NEWLINE;
import static io.netty.util.internal.StringUtil.isSurrogate;

/**
 * A collection of utility methods that is related with handling {@link ByteBuf},
 * such as the generation of hex dump and swapping an integer's byte order.
 */
public final class ByteBufUtil {

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(ByteBufUtil.class);
    private static final FastThreadLocal<CharBuffer> CHAR_BUFFERS = new FastThreadLocal<CharBuffer>() {
        @Override
        protected CharBuffer initialValue() throws Exception {
            return CharBuffer.allocate(1024);
        }
    };

    private static final byte WRITE_UTF_UNKNOWN = (byte) '?';
    private static final int MAX_CHAR_BUFFER_SIZE;
    private static final int THREAD_LOCAL_BUFFER_SIZE;
    private static final int MAX_BYTES_PER_CHAR_UTF8 =
            (int) CharsetUtil.encoder(CharsetUtil.UTF_8).maxBytesPerChar();

    static final ByteBufAllocator DEFAULT_ALLOCATOR;

    static {
        String allocType = SystemPropertyUtil.get("io.netty.allocator.type", "unpooled").toLowerCase(Locale.US).trim();
        ByteBufAllocator alloc;
        if ("unpooled".equals(allocType)) {
            alloc = UnpooledByteBufAllocator.DEFAULT;
            logger.debug("-Dio.netty.allocator.type: {}", allocType);
        } else if ("pooled".equals(allocType)) {
            alloc = PooledByteBufAllocator.DEFAULT;
            logger.debug("-Dio.netty.allocator.type: {}", allocType);
        } else {
            alloc = UnpooledByteBufAllocator.DEFAULT;
            logger.debug("-Dio.netty.allocator.type: unpooled (unknown: {})", allocType);
        }

        DEFAULT_ALLOCATOR = alloc;

        THREAD_LOCAL_BUFFER_SIZE = SystemPropertyUtil.getInt("io.netty.threadLocalDirectBufferSize", 64 * 1024);
        logger.debug("-Dio.netty.threadLocalDirectBufferSize: {}", THREAD_LOCAL_BUFFER_SIZE);

        MAX_CHAR_BUFFER_SIZE = SystemPropertyUtil.getInt("io.netty.maxThreadLocalCharBufferSize", 16 * 1024);
        logger.debug("-Dio.netty.maxThreadLocalCharBufferSize: {}", MAX_CHAR_BUFFER_SIZE);
    }

    /**
     * Returns a <a href="http://en.wikipedia.org/wiki/Hex_dump">hex dump</a>
     * of the specified buffer's readable bytes.
     */
    public static String hexDump(ByteBuf buffer) {
        return hexDump(buffer, buffer.readerIndex(), buffer.readableBytes());
    }

    /**
     * Returns a <a href="http://en.wikipedia.org/wiki/Hex_dump">hex dump</a>
     * of the specified buffer's sub-region.
     */
    public static String hexDump(ByteBuf buffer, int fromIndex, int length) {
        return HexUtil.hexDump(buffer, fromIndex, length);
    }

    /**
<<<<<<< HEAD
=======
     * Returns a <a href="http://en.wikipedia.org/wiki/Hex_dump">hex dump</a>
     * of the specified byte array.
     */
    public static String hexDump(byte[] array) {
        return hexDump(array, 0, array.length);
    }

    /**
     * Returns a <a href="http://en.wikipedia.org/wiki/Hex_dump">hex dump</a>
     * of the specified byte array's sub-region.
     */
    public static String hexDump(byte[] array, int fromIndex, int length) {
        return HexUtil.hexDump(array, fromIndex, length);
    }

    /**
>>>>>>> e5386b0... Move Hex dump related util from ByteBufUtil to inner class
     * Calculates the hash code of the specified buffer.  This method is
     * useful when implementing a new buffer type.
     */
    public static int hashCode(ByteBuf buffer) {
        final int aLen = buffer.readableBytes();
        final int intCount = aLen >>> 2;
        final int byteCount = aLen & 3;

        int hashCode = 1;
        int arrayIndex = buffer.readerIndex();
        if (buffer.order() == ByteOrder.BIG_ENDIAN) {
            for (int i = intCount; i > 0; i --) {
                hashCode = 31 * hashCode + buffer.getInt(arrayIndex);
                arrayIndex += 4;
            }
        } else {
            for (int i = intCount; i > 0; i --) {
                hashCode = 31 * hashCode + swapInt(buffer.getInt(arrayIndex));
                arrayIndex += 4;
            }
        }

        for (int i = byteCount; i > 0; i --) {
            hashCode = 31 * hashCode + buffer.getByte(arrayIndex ++);
        }

        if (hashCode == 0) {
            hashCode = 1;
        }

        return hashCode;
    }

    /**
     * Returns {@code true} if and only if the two specified buffers are
     * identical to each other as described in {@code ChannelBuffer#equals(Object)}.
     * This method is useful when implementing a new buffer type.
     */
    public static boolean equals(ByteBuf bufferA, ByteBuf bufferB) {
        final int aLen = bufferA.readableBytes();
        if (aLen != bufferB.readableBytes()) {
            return false;
        }

        final int longCount = aLen >>> 3;
        final int byteCount = aLen & 7;

        int aIndex = bufferA.readerIndex();
        int bIndex = bufferB.readerIndex();

        if (bufferA.order() == bufferB.order()) {
            for (int i = longCount; i > 0; i --) {
                if (bufferA.getLong(aIndex) != bufferB.getLong(bIndex)) {
                    return false;
                }
                aIndex += 8;
                bIndex += 8;
            }
        } else {
            for (int i = longCount; i > 0; i --) {
                if (bufferA.getLong(aIndex) != swapLong(bufferB.getLong(bIndex))) {
                    return false;
                }
                aIndex += 8;
                bIndex += 8;
            }
        }

        for (int i = byteCount; i > 0; i --) {
            if (bufferA.getByte(aIndex) != bufferB.getByte(bIndex)) {
                return false;
            }
            aIndex ++;
            bIndex ++;
        }

        return true;
    }

    /**
     * Compares the two specified buffers as described in {@link ByteBuf#compareTo(ByteBuf)}.
     * This method is useful when implementing a new buffer type.
     */
    public static int compare(ByteBuf bufferA, ByteBuf bufferB) {
        final int aLen = bufferA.readableBytes();
        final int bLen = bufferB.readableBytes();
        final int minLength = Math.min(aLen, bLen);
        final int uintCount = minLength >>> 2;
        final int byteCount = minLength & 3;

        int aIndex = bufferA.readerIndex();
        int bIndex = bufferB.readerIndex();

        if (bufferA.order() == bufferB.order()) {
            for (int i = uintCount; i > 0; i --) {
                long va = bufferA.getUnsignedInt(aIndex);
                long vb = bufferB.getUnsignedInt(bIndex);
                if (va > vb) {
                    return 1;
                }
                if (va < vb) {
                    return -1;
                }
                aIndex += 4;
                bIndex += 4;
            }
        } else {
            for (int i = uintCount; i > 0; i --) {
                long va = bufferA.getUnsignedInt(aIndex);
                long vb = swapInt(bufferB.getInt(bIndex)) & 0xFFFFFFFFL;
                if (va > vb) {
                    return 1;
                }
                if (va < vb) {
                    return -1;
                }
                aIndex += 4;
                bIndex += 4;
            }
        }

        for (int i = byteCount; i > 0; i --) {
            short va = bufferA.getUnsignedByte(aIndex);
            short vb = bufferB.getUnsignedByte(bIndex);
            if (va > vb) {
                return 1;
            }
            if (va < vb) {
                return -1;
            }
            aIndex ++;
            bIndex ++;
        }

        return aLen - bLen;
    }

    /**
     * The default implementation of {@link ByteBuf#indexOf(int, int, byte)}.
     * This method is useful when implementing a new buffer type.
     */
    public static int indexOf(ByteBuf buffer, int fromIndex, int toIndex, byte value) {
        if (fromIndex <= toIndex) {
            return firstIndexOf(buffer, fromIndex, toIndex, value);
        } else {
            return lastIndexOf(buffer, fromIndex, toIndex, value);
        }
    }

    /**
     * Toggles the endianness of the specified 16-bit short integer.
     */
    public static short swapShort(short value) {
        return Short.reverseBytes(value);
    }

    /**
     * Toggles the endianness of the specified 24-bit medium integer.
     */
    public static int swapMedium(int value) {
        int swapped = value << 16 & 0xff0000 | value & 0xff00 | value >>> 16 & 0xff;
        if ((swapped & 0x800000) != 0) {
            swapped |= 0xff000000;
        }
        return swapped;
    }

    /**
     * Toggles the endianness of the specified 32-bit integer.
     */
    public static int swapInt(int value) {
        return Integer.reverseBytes(value);
    }

    /**
     * Toggles the endianness of the specified 64-bit long integer.
     */
    public static long swapLong(long value) {
        return Long.reverseBytes(value);
    }

    /**
     * Read the given amount of bytes into a new {@link ByteBuf} that is allocated from the {@link ByteBufAllocator}.
     */
    public static ByteBuf readBytes(ByteBufAllocator alloc, ByteBuf buffer, int length) {
        boolean release = true;
        ByteBuf dst = alloc.buffer(length);
        try {
            buffer.readBytes(dst);
            release = false;
            return dst;
        } finally {
            if (release) {
                dst.release();
            }
        }
    }

    private static int firstIndexOf(ByteBuf buffer, int fromIndex, int toIndex, byte value) {
        fromIndex = Math.max(fromIndex, 0);
        if (fromIndex >= toIndex || buffer.capacity() == 0) {
            return -1;
        }

        return buffer.forEachByte(fromIndex, toIndex - fromIndex, new IndexOfProcessor(value));
    }

    private static int lastIndexOf(ByteBuf buffer, int fromIndex, int toIndex, byte value) {
        fromIndex = Math.min(fromIndex, buffer.capacity());
        if (fromIndex < 0 || buffer.capacity() == 0) {
            return -1;
        }

        return buffer.forEachByteDesc(toIndex, fromIndex - toIndex, new IndexOfProcessor(value));
    }

    /**
     * Encode a {@link CharSequence} in <a href="http://en.wikipedia.org/wiki/UTF-8">UTF-8</a> and write
     * it to a {@link ByteBuf} allocated with {@code alloc}.
     * @param alloc The allocator used to allocate a new {@link ByteBuf}.
     * @param seq The characters to write into a buffer.
     * @return The {@link ByteBuf} which contains the <a href="http://en.wikipedia.org/wiki/UTF-8">UTF-8</a> encoded
     * result.
     */
    public static ByteBuf writeUtf8(ByteBufAllocator alloc, CharSequence seq) {
        // UTF-8 uses max. 3 bytes per char, so calculate the worst case.
        ByteBuf buf = alloc.buffer(seq.length() * MAX_BYTES_PER_CHAR_UTF8);
        writeUtf8(buf, seq);
        return buf;
    }

    /**
     * Encode a {@link CharSequence} in <a href="http://en.wikipedia.org/wiki/UTF-8">UTF-8</a> and write
     * it to a {@link ByteBuf}.
     *
     * This method returns the actual number of bytes written.
     */
    public static int writeUtf8(ByteBuf buf, CharSequence seq) {
        final int len = seq.length();
        buf.ensureWritable(len * MAX_BYTES_PER_CHAR_UTF8);

        for (;;) {
            if (buf instanceof AbstractByteBuf) {
                return writeUtf8((AbstractByteBuf) buf, seq, len);
            } else if (buf instanceof WrappedByteBuf) {
                // Unwrap as the wrapped buffer may be an AbstractByteBuf and so we can use fast-path.
                buf = buf.unwrap();
            } else {
                byte[] bytes = seq.toString().getBytes(CharsetUtil.UTF_8);
                buf.writeBytes(bytes);
                return bytes.length;
            }
        }
    }

    // Fast-Path implementation
    private static int writeUtf8(AbstractByteBuf buffer, CharSequence seq, int len) {
        int oldWriterIndex = buffer.writerIndex;
        int writerIndex = oldWriterIndex;

        // We can use the _set methods as these not need to do any index checks and reference checks.
        // This is possible as we called ensureWritable(...) before.
        for (int i = 0; i < len; i++) {
            char c = seq.charAt(i);
            if (c < 0x80) {
                buffer._setByte(writerIndex++, (byte) c);
            } else if (c < 0x800) {
                buffer._setByte(writerIndex++, (byte) (0xc0 | (c >> 6)));
                buffer._setByte(writerIndex++, (byte) (0x80 | (c & 0x3f)));
            } else if (isSurrogate(c)) {
                if (!Character.isHighSurrogate(c)) {
                    buffer._setByte(writerIndex++, WRITE_UTF_UNKNOWN);
                    continue;
                }
                final char c2;
                try {
                    // Surrogate Pair consumes 2 characters. Optimistically try to get the next character to avoid
                    // duplicate bounds checking with charAt. If an IndexOutOfBoundsException is thrown we will
                    // re-throw a more informative exception describing the problem.
                    c2 = seq.charAt(++i);
                } catch (IndexOutOfBoundsException e) {
                    buffer._setByte(writerIndex++, WRITE_UTF_UNKNOWN);
                    break;
                }
                if (!Character.isLowSurrogate(c2)) {
                    buffer._setByte(writerIndex++, WRITE_UTF_UNKNOWN);
                    buffer._setByte(writerIndex++, Character.isHighSurrogate(c2) ? WRITE_UTF_UNKNOWN : c2);
                    continue;
                }
                int codePoint = Character.toCodePoint(c, c2);
                // See http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G2630.
                buffer._setByte(writerIndex++, (byte) (0xf0 | (codePoint >> 18)));
                buffer._setByte(writerIndex++, (byte) (0x80 | ((codePoint >> 12) & 0x3f)));
                buffer._setByte(writerIndex++, (byte) (0x80 | ((codePoint >> 6) & 0x3f)));
                buffer._setByte(writerIndex++, (byte) (0x80 | (codePoint & 0x3f)));
            } else {
                buffer._setByte(writerIndex++, (byte) (0xe0 | (c >> 12)));
                buffer._setByte(writerIndex++, (byte) (0x80 | ((c >> 6) & 0x3f)));
                buffer._setByte(writerIndex++, (byte) (0x80 | (c & 0x3f)));
            }
        }
        // update the writerIndex without any extra checks for performance reasons
        buffer.writerIndex = writerIndex;
        return writerIndex - oldWriterIndex;
    }

    /**
     * Encode a {@link CharSequence} in <a href="http://en.wikipedia.org/wiki/ASCII">ASCII</a> and write
     * it to a {@link ByteBuf} allocated with {@code alloc}.
     * @param alloc The allocator used to allocate a new {@link ByteBuf}.
     * @param seq The characters to write into a buffer.
     * @return The {@link ByteBuf} which contains the <a href="http://en.wikipedia.org/wiki/ASCII">ASCII</a> encoded
     * result.
     */
    public static ByteBuf writeAscii(ByteBufAllocator alloc, CharSequence seq) {
        // ASCII uses 1 byte per char
        ByteBuf buf = alloc.buffer(seq.length());
        writeAscii(buf, seq);
        return buf;
    }

    /**
     * Encode a {@link CharSequence} in <a href="http://en.wikipedia.org/wiki/ASCII">ASCII</a> and write it
     * to a {@link ByteBuf}.
     *
     * This method returns the actual number of bytes written.
     */
    public static int writeAscii(ByteBuf buf, CharSequence seq) {
        // ASCII uses 1 byte per char
        final int len = seq.length();
        buf.ensureWritable(len);
        for (;;) {
            if (buf instanceof AbstractByteBuf) {
                writeAscii((AbstractByteBuf) buf, seq, len);
                break;
            } else if (buf instanceof WrappedByteBuf) {
                // Unwrap as the wrapped buffer may be an AbstractByteBuf and so we can use fast-path.
                buf = buf.unwrap();
            } else {
                buf.writeBytes(seq.toString().getBytes(CharsetUtil.US_ASCII));
            }
        }
        return len;
    }

    // Fast-Path implementation
    private static void writeAscii(AbstractByteBuf buffer, CharSequence seq, int len) {
        int writerIndex = buffer.writerIndex;

        // We can use the _set methods as these not need to do any index checks and reference checks.
        // This is possible as we called ensureWritable(...) before.
        for (int i = 0; i < len; i++) {
            buffer._setByte(writerIndex++, (byte) seq.charAt(i));
        }
        // update the writerIndex without any extra checks for performance reasons
        buffer.writerIndex = writerIndex;
    }

    /**
     * Encode the given {@link CharBuffer} using the given {@link Charset} into a new {@link ByteBuf} which
     * is allocated via the {@link ByteBufAllocator}.
     */
    public static ByteBuf encodeString(ByteBufAllocator alloc, CharBuffer src, Charset charset) {
        return encodeString0(alloc, false, src, charset);
    }

    static ByteBuf encodeString0(ByteBufAllocator alloc, boolean enforceHeap, CharBuffer src, Charset charset) {
        final CharsetEncoder encoder = CharsetUtil.encoder(charset);
        int length = (int) ((double) src.remaining() * encoder.maxBytesPerChar());
        boolean release = true;
        final ByteBuf dst;
        if (enforceHeap) {
            dst = alloc.heapBuffer(length);
        } else {
            dst = alloc.buffer(length);
        }
        try {
            final ByteBuffer dstBuf = dst.internalNioBuffer(0, length);
            final int pos = dstBuf.position();
            CoderResult cr = encoder.encode(src, dstBuf, true);
            if (!cr.isUnderflow()) {
                cr.throwException();
            }
            cr = encoder.flush(dstBuf);
            if (!cr.isUnderflow()) {
                cr.throwException();
            }
            dst.writerIndex(dst.writerIndex() + dstBuf.position() - pos);
            release = false;
            return dst;
        } catch (CharacterCodingException x) {
            throw new IllegalStateException(x);
        } finally {
            if (release) {
                dst.release();
            }
        }
    }

    static String decodeString(ByteBuf src, int readerIndex, int len, Charset charset) {
        if (len == 0) {
            return StringUtil.EMPTY_STRING;
        }
        final CharsetDecoder decoder = CharsetUtil.decoder(charset);
        final int maxLength = (int) ((double) len * decoder.maxCharsPerByte());
        CharBuffer dst = CHAR_BUFFERS.get();
        if (dst.length() < maxLength) {
            dst = CharBuffer.allocate(maxLength);
            if (maxLength <= MAX_CHAR_BUFFER_SIZE) {
                CHAR_BUFFERS.set(dst);
            }
        } else {
            dst.clear();
        }
        if (src.nioBufferCount() == 1) {
            // Use internalNioBuffer(...) to reduce object creation.
            decodeString(decoder, src.internalNioBuffer(readerIndex, len), dst);
        } else {
            // We use a heap buffer as CharsetDecoder is most likely able to use a fast-path if src and dst buffers
            // are both backed by a byte array.
            ByteBuf buffer = src.alloc().heapBuffer(len);
            try {
                buffer.writeBytes(src, readerIndex, len);
                // Use internalNioBuffer(...) to reduce object creation.
                decodeString(decoder, buffer.internalNioBuffer(0, len), dst);
            } finally {
                // Release the temporary buffer again.
                buffer.release();
            }
        }
        return dst.flip().toString();
    }

    private static void decodeString(CharsetDecoder decoder, ByteBuffer src, CharBuffer dst) {
        try {
            CoderResult cr = decoder.decode(src, dst, true);
            if (!cr.isUnderflow()) {
                cr.throwException();
            }
            cr = decoder.flush(dst);
            if (!cr.isUnderflow()) {
                cr.throwException();
            }
        } catch (CharacterCodingException x) {
            throw new IllegalStateException(x);
        }
    }

    /**
     * Returns a multi-line hexadecimal dump of the specified {@link ByteBuf} that is easy to read by humans.
     */
    public static String prettyHexDump(ByteBuf buffer) {
        return prettyHexDump(buffer, buffer.readerIndex(), buffer.readableBytes());
    }

    /**
     * Returns a multi-line hexadecimal dump of the specified {@link ByteBuf} that is easy to read by humans,
     * starting at the given {@code offset} using the given {@code length}.
     */
    public static String prettyHexDump(ByteBuf buffer, int offset, int length) {
        return HexUtil.prettyHexDump(buffer, offset, length);
    }

    /**
     * Appends the prettified multi-line hexadecimal dump of the specified {@link ByteBuf} to the specified
     * {@link StringBuilder} that is easy to read by humans.
     */
    public static void appendPrettyHexDump(StringBuilder dump, ByteBuf buf) {
        appendPrettyHexDump(dump, buf, buf.readerIndex(), buf.readableBytes());
    }

    /**
     * Appends the prettified multi-line hexadecimal dump of the specified {@link ByteBuf} to the specified
     * {@link StringBuilder} that is easy to read by humans, starting at the given {@code offset} using
     * the given {@code length}.
     */
    public static void appendPrettyHexDump(StringBuilder dump, ByteBuf buf, int offset, int length) {
        HexUtil.appendPrettyHexDump(dump, buf, offset, length);
    }

    /* Separate class so that the expensive static initialization is only done when needed */
    private static final class HexUtil {

        private static final char[] BYTE2CHAR = new char[256];
        private static final char[] HEXDUMP_TABLE = new char[256 * 4];
        private static final String[] HEXPADDING = new String[16];
        private static final String[] HEXDUMP_ROWPREFIXES = new String[65536 >>> 4];
        private static final String[] BYTE2HEX = new String[256];
        private static final String[] BYTEPADDING = new String[16];

        static {
            final char[] DIGITS = "0123456789abcdef".toCharArray();
            for (int i = 0; i < 256; i ++) {
                HEXDUMP_TABLE[ i << 1     ] = DIGITS[i >>> 4 & 0x0F];
                HEXDUMP_TABLE[(i << 1) + 1] = DIGITS[i       & 0x0F];
            }

            int i;

            // Generate the lookup table for hex dump paddings
            for (i = 0; i < HEXPADDING.length; i ++) {
                int padding = HEXPADDING.length - i;
                StringBuilder buf = new StringBuilder(padding * 3);
                for (int j = 0; j < padding; j ++) {
                    buf.append("   ");
                }
                HEXPADDING[i] = buf.toString();
            }

            // Generate the lookup table for the start-offset header in each row (up to 64KiB).
            for (i = 0; i < HEXDUMP_ROWPREFIXES.length; i ++) {
                StringBuilder buf = new StringBuilder(12);
                buf.append(NEWLINE);
                buf.append(Long.toHexString(i << 4 & 0xFFFFFFFFL | 0x100000000L));
                buf.setCharAt(buf.length() - 9, '|');
                buf.append('|');
                HEXDUMP_ROWPREFIXES[i] = buf.toString();
            }

            // Generate the lookup table for byte-to-hex-dump conversion
            for (i = 0; i < BYTE2HEX.length; i ++) {
                BYTE2HEX[i] = ' ' + StringUtil.byteToHexStringPadded(i);
            }

            // Generate the lookup table for byte dump paddings
            for (i = 0; i < BYTEPADDING.length; i ++) {
                int padding = BYTEPADDING.length - i;
                StringBuilder buf = new StringBuilder(padding);
                for (int j = 0; j < padding; j ++) {
                    buf.append(' ');
                }
                BYTEPADDING[i] = buf.toString();
            }

            // Generate the lookup table for byte-to-char conversion
            for (i = 0; i < BYTE2CHAR.length; i ++) {
                if (i <= 0x1f || i >= 0x7f) {
                    BYTE2CHAR[i] = '.';
                } else {
                    BYTE2CHAR[i] = (char) i;
                }
            }
        }

        private static String hexDump(ByteBuf buffer, int fromIndex, int length) {
            if (length < 0) {
              throw new IllegalArgumentException("length: " + length);
            }
            if (length == 0) {
              return "";
            }

            int endIndex = fromIndex + length;
            char[] buf = new char[length << 1];

            int srcIdx = fromIndex;
            int dstIdx = 0;
            for (; srcIdx < endIndex; srcIdx ++, dstIdx += 2) {
              System.arraycopy(
                  HEXDUMP_TABLE, buffer.getUnsignedByte(srcIdx) << 1,
                  buf, dstIdx, 2);
            }

            return new String(buf);
        }

        private static String hexDump(byte[] array, int fromIndex, int length) {
            if (length < 0) {
              throw new IllegalArgumentException("length: " + length);
            }
            if (length == 0) {
                return "";
            }

            int endIndex = fromIndex + length;
            char[] buf = new char[length << 1];

            int srcIdx = fromIndex;
            int dstIdx = 0;
            for (; srcIdx < endIndex; srcIdx ++, dstIdx += 2) {
                System.arraycopy(
                    HEXDUMP_TABLE, (array[srcIdx] & 0xFF) << 1,
                    buf, dstIdx, 2);
            }

            return new String(buf);
        }

        private static String prettyHexDump(ByteBuf buffer, int offset, int length) {
            if (length == 0) {
              return StringUtil.EMPTY_STRING;
            } else {
                int rows = length / 16 + (length % 15 == 0? 0 : 1) + 4;
                StringBuilder buf = new StringBuilder(rows * 80);
                appendPrettyHexDump(buf, buffer, offset, length);
                return buf.toString();
            }
        }

        private static void appendPrettyHexDump(StringBuilder dump, ByteBuf buf, int offset, int length) {
            if (isOutOfBounds(offset, length, buf.capacity())) {
                throw new IndexOutOfBoundsException(
                        "expected: " + "0 <= offset(" + offset + ") <= offset + length(" + length
                                                    + ") <= " + "buf.capacity(" + buf.capacity() + ')');
            }
            if (length == 0) {
                return;
            }
            dump.append(
                              "         +-------------------------------------------------+" +
                    NEWLINE + "         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |" +
                    NEWLINE + "+--------+-------------------------------------------------+----------------+");

            final int startIndex = offset;
            final int fullRows = length >>> 4;
            final int remainder = length & 0xF;

            // Dump the rows which have 16 bytes.
            for (int row = 0; row < fullRows; row ++) {
                int rowStartIndex = (row << 4) + startIndex;

                // Per-row prefix.
                appendHexDumpRowPrefix(dump, row, rowStartIndex);

                // Hex dump
                int rowEndIndex = rowStartIndex + 16;
                for (int j = rowStartIndex; j < rowEndIndex; j ++) {
                    dump.append(BYTE2HEX[buf.getUnsignedByte(j)]);
                }
                dump.append(" |");

                // ASCII dump
                for (int j = rowStartIndex; j < rowEndIndex; j ++) {
                    dump.append(BYTE2CHAR[buf.getUnsignedByte(j)]);
                }
                dump.append('|');
            }

            // Dump the last row which has less than 16 bytes.
            if (remainder != 0) {
                int rowStartIndex = (fullRows << 4) + startIndex;
                appendHexDumpRowPrefix(dump, fullRows, rowStartIndex);

                // Hex dump
                int rowEndIndex = rowStartIndex + remainder;
                for (int j = rowStartIndex; j < rowEndIndex; j ++) {
                    dump.append(BYTE2HEX[buf.getUnsignedByte(j)]);
                }
                dump.append(HEXPADDING[remainder]);
                dump.append(" |");

                // Ascii dump
                for (int j = rowStartIndex; j < rowEndIndex; j ++) {
                    dump.append(BYTE2CHAR[buf.getUnsignedByte(j)]);
                }
                dump.append(BYTEPADDING[remainder]);
                dump.append('|');
            }

            dump.append(NEWLINE +
                        "+--------+-------------------------------------------------+----------------+");
        }

        private static void appendHexDumpRowPrefix(StringBuilder dump, int row, int rowStartIndex) {
            if (row < HEXDUMP_ROWPREFIXES.length) {
                dump.append(HEXDUMP_ROWPREFIXES[row]);
            } else {
                dump.append(NEWLINE);
                dump.append(Long.toHexString(rowStartIndex & 0xFFFFFFFFL | 0x100000000L));
                dump.setCharAt(dump.length() - 9, '|');
                dump.append('|');
            }
        }
    }

    /**
     * Returns a cached thread-local direct buffer, if available.
     *
     * @return a cached thread-local direct buffer, if available.  {@code null} otherwise.
     */
    public static ByteBuf threadLocalDirectBuffer() {
        if (THREAD_LOCAL_BUFFER_SIZE <= 0) {
            return null;
        }

        if (PlatformDependent.hasUnsafe()) {
            return ThreadLocalUnsafeDirectByteBuf.newInstance();
        } else {
            return ThreadLocalDirectByteBuf.newInstance();
        }
    }

    static final class ThreadLocalUnsafeDirectByteBuf extends UnpooledUnsafeDirectByteBuf {

        private static final Recycler<ThreadLocalUnsafeDirectByteBuf> RECYCLER =
                new Recycler<ThreadLocalUnsafeDirectByteBuf>() {
                    @Override
                    protected ThreadLocalUnsafeDirectByteBuf newObject(Handle handle) {
                        return new ThreadLocalUnsafeDirectByteBuf(handle);
                    }
                };

        static ThreadLocalUnsafeDirectByteBuf newInstance() {
            ThreadLocalUnsafeDirectByteBuf buf = RECYCLER.get();
            buf.setRefCnt(1);
            return buf;
        }

        private final Handle handle;

        private ThreadLocalUnsafeDirectByteBuf(Handle handle) {
            super(UnpooledByteBufAllocator.DEFAULT, 256, Integer.MAX_VALUE);
            this.handle = handle;
        }

        @Override
        protected void deallocate() {
            if (capacity() > THREAD_LOCAL_BUFFER_SIZE) {
                super.deallocate();
            } else {
                clear();
                RECYCLER.recycle(this, handle);
            }
        }
    }

    static final class ThreadLocalDirectByteBuf extends UnpooledDirectByteBuf {

        private static final Recycler<ThreadLocalDirectByteBuf> RECYCLER = new Recycler<ThreadLocalDirectByteBuf>() {
            @Override
            protected ThreadLocalDirectByteBuf newObject(Handle handle) {
                return new ThreadLocalDirectByteBuf(handle);
            }
        };

        static ThreadLocalDirectByteBuf newInstance() {
            ThreadLocalDirectByteBuf buf = RECYCLER.get();
            buf.setRefCnt(1);
            return buf;
        }

        private final Handle handle;

        private ThreadLocalDirectByteBuf(Handle handle) {
            super(UnpooledByteBufAllocator.DEFAULT, 256, Integer.MAX_VALUE);
            this.handle = handle;
        }

        @Override
        protected void deallocate() {
            if (capacity() > THREAD_LOCAL_BUFFER_SIZE) {
                super.deallocate();
            } else {
                clear();
                RECYCLER.recycle(this, handle);
            }
        }
    }

    private static class IndexOfProcessor implements ByteBufProcessor {
        private final byte byteToFind;

        public IndexOfProcessor(byte byteToFind) {
            this.byteToFind = byteToFind;
        }

        @Override
        public boolean process(byte value) {
            return value != byteToFind;
        }
    }

    private ByteBufUtil() { }
}
