import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.RandomAccessFile;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.MappedByteBuffer;

import java.nio.channels.FileChannel;

import java.nio.channels.FileChannel.MapMode;

import java.nio.charset.CharacterCodingException;

import java.nio.charset.Charset;

import java.nio.charset.CharsetDecoder;

import java.nio.charset.CharsetEncoder;

import java.nio.file.Paths;

import java.nio.file.StandardOpenOption;

import java.util.Map;

import java.util.Map.Entry;

import java.util.Set;

import org.junit.Test;

/*

 * 一、通道（Channel）：用于源节点与目标节点的连接。在 Java NIO 中负责缓冲区中数据的传输。Channel 本身不存储数据，因此需要配合缓冲区进行传输。

 *

 * 二、通道的主要实现类

 *     java.nio.channels.Channel 接口：

 *         |--FileChannel

 *         |--SocketChannel

 *         |--ServerSocketChannel

 *         |--DatagramChannel

 *

 * 三、获取通道

 * 1. Java 针对支持通道的类提供了 getChannel() 方法

 *         本地 IO：

 *         FileInputStream/FileOutputStream

 *         RandomAccessFile

 *

 *         网络IO：

 *         Socket

 *         ServerSocket

 *         DatagramSocket

 *

 * 2. 在 JDK 1.7 中的 NIO.2 针对各个通道提供了静态方法 open()

 * 3. 在 JDK 1.7 中的 NIO.2 的 Files 工具类的 newByteChannel()

 *

 * 四、通道之间的数据传输

 * transferFrom()

 * transferTo()

 *

 * 五、分散(Scatter)与聚集(Gather)

 * 分散读取（Scattering Reads）：将通道中的数据分散到多个缓冲区中

 * 聚集写入（Gathering Writes）：将多个缓冲区中的数据聚集到通道中

 *

 * 六、字符集：Charset

 * 编码：字符串 -> 字节数组

 * 解码：字节数组  -> 字符串

 *

 */

public class TestChannel {

    //字符集

    @Test

    public void test6() throws IOException{

        Charset cs1 = Charset.forName("GBK");

        //获取编码器

        CharsetEncoder ce = cs1.newEncoder();

        //获取解码器

        CharsetDecoder cd = cs1.newDecoder();

        CharBuffer cBuf = CharBuffer.allocate(1024);

        cBuf.put("尚硅谷威武！");

        cBuf.flip();

        //编码

        ByteBuffer bBuf = ce.encode(cBuf);

        for (int i = 0; i < 12; i++) {

            System.out.println(bBuf.get());

        }

        //解码

        bBuf.flip();

        CharBuffer cBuf2 = cd.decode(bBuf);

        System.out.println(cBuf2.toString());

        System.out.println("------------------------------------------------------");

        Charset cs2 = Charset.forName("GBK");

        bBuf.flip();

        CharBuffer cBuf3 = cs2.decode(bBuf);

        System.out.println(cBuf3.toString());

    }

    @Test

    public void test5(){

        Map<String, Charset> map = Charset.availableCharsets();

        Set<Entry<String, Charset>> set = map.entrySet();

        for (Entry<String, Charset> entry : set) {

            System.out.println(entry.getKey() + "=" + entry.getValue());

        }

    }

    //分散和聚集

    @Test

    public void test4() throws IOException{

        RandomAccessFile raf1 = new RandomAccessFile("1.txt", "rw");

        //1. 获取通道

        FileChannel channel1 = raf1.getChannel();

        //2. 分配指定大小的缓冲区

        ByteBuffer buf1 = ByteBuffer.allocate(100);

        ByteBuffer buf2 = ByteBuffer.allocate(1024);

        //3. 分散读取

        ByteBuffer[] bufs = {buf1, buf2};

        channel1.read(bufs);

        for (ByteBuffer byteBuffer : bufs) {

            byteBuffer.flip();

        }

        System.out.println(new String(bufs[0].array(), 0, bufs[0].limit()));

        System.out.println("-----------------");

        System.out.println(new String(bufs[1].array(), 0, bufs[1].limit()));

        //4. 聚集写入

        RandomAccessFile raf2 = new RandomAccessFile("2.txt", "rw");

        FileChannel channel2 = raf2.getChannel();

        channel2.write(bufs);

    }

    //通道之间的数据传输(直接缓冲区)

    @Test

    public void test3() throws IOException{

        FileChannel inChannel = FileChannel.open(Paths.get("d:/1.mkv"), StandardOpenOption.READ);

        FileChannel outChannel = FileChannel.open(Paths.get("d:/2.mkv"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);

//        inChannel.transferTo(0, inChannel.size(), outChannel);

        outChannel.transferFrom(inChannel, 0, inChannel.size());

        inChannel.close();

        outChannel.close();

    }

    //使用直接缓冲区完成文件的复制(内存映射文件)

    @Test

    public void test2() throws IOException{//2127-1902-1777

        long start = System.currentTimeMillis();

        FileChannel inChannel = FileChannel.open(Paths.get("d:/1.mkv"), StandardOpenOption.READ);

        FileChannel outChannel = FileChannel.open(Paths.get("d:/2.mkv"), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);

        //内存映射文件

        MappedByteBuffer inMappedBuf = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());

        MappedByteBuffer outMappedBuf = outChannel.map(MapMode.READ_WRITE, 0, inChannel.size());

        //直接对缓冲区进行数据的读写操作

        byte[] dst = new byte[inMappedBuf.limit()];

        inMappedBuf.get(dst);

        outMappedBuf.put(dst);

        inChannel.close();

        outChannel.close();

        long end = System.currentTimeMillis();

        System.out.println("耗费时间为：" + (end - start));

    }

    //利用通道完成文件的复制（非直接缓冲区）

    @Test

    public void test1(){//10874-10953

        long start = System.currentTimeMillis();

        FileInputStream fis = null;

        FileOutputStream fos = null;

        //①获取通道

        FileChannel inChannel = null;

        FileChannel outChannel = null;

        try {

            fis = new FileInputStream("d:/1.mkv");

            fos = new FileOutputStream("d:/2.mkv");

            inChannel = fis.getChannel();

            outChannel = fos.getChannel();

            //②分配指定大小的缓冲区

            ByteBuffer buf = ByteBuffer.allocate(1024);

            //③将通道中的数据存入缓冲区中

            while(inChannel.read(buf) != -1){

                buf.flip(); //切换读取数据的模式

                //④将缓冲区中的数据写入通道中

                outChannel.write(buf);

                buf.clear(); //清空缓冲区

            }

        } catch (IOException e) {

            e.printStackTrace();

        } finally {

            if(outChannel != null){

                try {

                    outChannel.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

            if(inChannel != null){

                try {

                    inChannel.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

            if(fos != null){

                try {

                    fos.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

            if(fis != null){

                try {

                    fis.close();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }

        long end = System.currentTimeMillis();

        System.out.println("耗费时间为：" + (end - start));

    }

}