• Netty——ByteBuffer的内部结构演示示例（1）

    目录

    一、pom.xml文件引入依赖

    		<dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.39.Final</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.18</version>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.5</version>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>19.0</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>3.11.3</version>
        </dependency>

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    二、编写工具类（此工具类复制即可使用）

    package com.example.nettytest.nio.day1;

import io.netty.util.internal.StringUtil;
import java.nio.ByteBuffer;
import static io.netty.util.internal.MathUtil.isOutOfBounds;
import static io.netty.util.internal.StringUtil.NEWLINE;

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(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);
    }

    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);
        buffer.put(new byte[]{97, 98, 99, 100});
        debugAll(buffer);
    }

    private static void appendPrettyHexDump(StringBuilder dump, ByteBuffer 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[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(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('|');
        }
    }

    public static short getUnsignedByte(ByteBuffer buffer, int index) {
        return (short) (buffer.get(index) & 0xFF);
    }
}

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    三、测试类示例演示（一）

    • 测试类

      package com.example.nettytest.nio.day1;

import java.nio.ByteBuffer;
import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll;

public class TestByteBufferReadWrite {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);
        /**
         * 写入十六进制的一个字节
         * */
        buffer.put((byte) 0x61); // 'a'
        debugAll(buffer);
    }
}

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    • 输出结果
      在这里插入图片描述

    四、测试类示例演示（二）

    • 测试类

      package com.example.nettytest.nio.day1;

import java.nio.ByteBuffer;
import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll;

public class TestByteBufferReadWrite {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);
        /**
         * 写入一个十六进制的字节数组
         * */
        buffer.put(new byte[]{0x62, 0x63, 0x64});
        debugAll(buffer);
    }
}

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    • 输出结果
      在这里插入图片描述

    五、测试类示例演示（三）

    • 测试类

      package com.example.nettytest.nio.day1;

import java.nio.ByteBuffer;

import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll;

public class TestByteBufferReadWrite {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);
        /**
         * 写入十六进制的一个字节
         * */
        buffer.put((byte) 0x61); // 'a'
        debugAll(buffer);
        /**
         * 写入一个十六进制的字节数组
         * */
        buffer.put(new byte[]{0x62, 0x63, 0x64}); // b  c  d
        debugAll(buffer);
        /**
         * 切换到读模式，读取一个字节（该十六进制字节读取后会转换成十进制并输出）
         * */
        buffer.flip();
        System.out.println(buffer.get());
        debugAll(buffer);
    }
}

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    • 输出结果
      在这里插入图片描述

    六、测试类示例演示（四）

    • 测试类

      package com.example.nettytest.nio.day1;

import java.nio.ByteBuffer;

import static com.example.nettytest.nio.day1.ByteBufferUtil.debugAll;

public class TestByteBufferReadWrite {
    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);
        /**
         * 写入十六进制的一个字节
         * */
        buffer.put((byte) 0x61); // 'a'
        debugAll(buffer);
        /**
         * 写入一个十六进制的字节数组
         * */
        buffer.put(new byte[]{0x62, 0x63, 0x64}); // b  c  d
        debugAll(buffer);
        /**
         * 切换到读模式，读取一个字节（该十六进制字节读取后会转换成十进制并输出）
         * */
        buffer.flip();
        System.out.println(buffer.get());
        debugAll(buffer);
        /**
         * 把未读完的部分向前压缩，然后切换至写模式
         * */
        buffer.compact();
        debugAll(buffer);
        buffer.put(new byte[]{0x65, 0x66});
        debugAll(buffer);
    }
}


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    • 输出结果
      在这里插入图片描述

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  • 原文地址：https://blog.csdn.net/li1325169021/article/details/125902638