ByteBuffer调试工具类

心已赠人 2022-09-02 08:09 188阅读 0赞

## 需要先导入netty依赖 ##

<dependency>
      <groupId>io.netty</groupId>
      <artifactId>netty-all</artifactId>
      <version>4.1.51.Final</version>
    </dependency>

import java.nio.ByteBuffer;
    
    import io.netty.util.internal.MathUtil;
    import io.netty.util.internal.StringUtil;
    import io.netty.util.internal.MathUtil.*;
    
    
    /**
     * @author Panwen Chen
     * @date 2021/4/12 15:59
     */
    public class ByteBufferUtil {
        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(StringUtil.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;
                }
            }
        }
    
        /**
         * 打印所有内容
         * @param buffer
         */
        public static void debugAll(ByteBuffer buffer) {
            int oldlimit = buffer.limit();
            buffer.limit(buffer.capacity());
            StringBuilder origin = new StringBuilder(256);
            appendPrettyHexDump(origin, buffer, 0, buffer.capacity());
            System.out.println("+--------+-------------------- all ------------------------+----------------+");
            System.out.printf("position: [%d], limit: [%d]\n", buffer.position(), oldlimit);
            System.out.println(origin);
            buffer.limit(oldlimit);
        }
    
        /**
         * 打印可读取内容
         * @param buffer
         */
        public static void debugRead(ByteBuffer buffer) {
            StringBuilder builder = new StringBuilder(256);
            appendPrettyHexDump(builder, buffer, buffer.position(), buffer.limit() - buffer.position());
            System.out.println("+--------+-------------------- read -----------------------+----------------+");
            System.out.printf("position: [%d], limit: [%d]\n", buffer.position(), buffer.limit());
            System.out.println(builder);
        }
    
        private static void appendPrettyHexDump(StringBuilder dump, ByteBuffer buf, int offset, int length) {
            if (MathUtil.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(
                    "         +-------------------------------------------------+" +
                            StringUtil.NEWLINE + "         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |" +
                            StringUtil.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[getUnsignedByte(buf, j)]);
                }
                dump.append(" |");
    
                // ASCII dump
                for (int j = rowStartIndex; j < rowEndIndex; j++) {
                    dump.append(BYTE2CHAR[getUnsignedByte(buf, 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[getUnsignedByte(buf, j)]);
                }
                dump.append(HEXPADDING[remainder]);
                dump.append(" |");
    
                // Ascii dump
                for (int j = rowStartIndex; j < rowEndIndex; j++) {
                    dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]);
                }
                dump.append(BYTEPADDING[remainder]);
                dump.append('|');
            }
    
            dump.append(StringUtil.NEWLINE +
                    "+--------+-------------------------------------------------+----------------+");
        }
    
        private static void appendHexDumpRowPrefix(StringBuilder dump, int row, int rowStartIndex) {
            if (row < HEXDUMP_ROWPREFIXES.length) {
                dump.append(HEXDUMP_ROWPREFIXES[row]);
            } else {
                dump.append(StringUtil.NEWLINE);
                dump.append(Long.toHexString(rowStartIndex & 0xFFFFFFFFL | 0x100000000L));
                dump.setCharAt(dump.length() - 9, '|');
                dump.append('|');
            }
        }
    
        public static short getUnsignedByte(ByteBuffer buffer, int index) {
            return (short) (buffer.get(index) & 0xFF);
        }
    }

## 调用ByteBuffer的方法 ##

public class TestByteBuffer {
        public static void main(String[] args) {
            ByteBuffer buffer = ByteBuffer.allocate(10);
            // 向buffer中写入1个字节的数据
            buffer.put((byte)97);
            // 使用工具类，查看buffer状态
            ByteBufferUtil.debugAll(buffer);
    
            // 向buffer中写入4个字节的数据
            buffer.put(new byte[]{98, 99, 100, 101});
            ByteBufferUtil.debugAll(buffer);
    
            // 获取数据
            buffer.flip();
            ByteBufferUtil.debugAll(buffer);
            System.out.println(buffer.get());
            System.out.println(buffer.get());
            ByteBufferUtil.debugAll(buffer);
    
            // 使用compact切换模式
            buffer.compact();
            ByteBufferUtil.debugAll(buffer);
    
            // 再次写入
            buffer.put((byte)102);
            buffer.put((byte)103);
            ByteBufferUtil.debugAll(buffer);
        }
    }