package java.io;

import java.io.*;

public class PipedOutputStream extends OutputStream {

  // 與PipedOutputStream通信的PipedInputStream對象
  private PipedInputStream sink;

  // 構(gòu)造函數(shù)，指定配對的PipedInputStream
  public PipedOutputStream(PipedInputStream snk) throws IOException {
    connect(snk);
  }

  // 構(gòu)造函數(shù)
  public PipedOutputStream() {
  }

  // 將“管道輸出流” 和 “管道輸入流”連接。
  public synchronized void connect(PipedInputStream snk) throws IOException {
    if (snk == null) {
      throw new NullPointerException();
    } else if (sink != null || snk.connected) {
      throw new IOException("Already connected");
    }
    // 設置“管道輸入流”
    sink = snk;
    // 初始化“管道輸入流”的讀寫位置
    // int是PipedInputStream中定義的，代表“管道輸入流”的讀寫位置
    snk.in = -1;
    // 初始化“管道輸出流”的讀寫位置。
    // out是PipedInputStream中定義的，代表“管道輸出流”的讀寫位置
    snk.out = 0;
    // 設置“管道輸入流”和“管道輸出流”為已連接狀態(tài)
    // connected是PipedInputStream中定義的，用于表示“管道輸入流與管道輸出流”是否已經(jīng)連接
    snk.connected = true;
  }

  // 將int類型b寫入“管道輸出流”中。
  // 將b寫入“管道輸出流”之后，它會將b傳輸給“管道輸入流”
  public void write(int b) throws IOException {
    if (sink == null) {
      throw new IOException("Pipe not connected");
    }
    sink.receive(b);
  }

  // 將字節(jié)數(shù)組b寫入“管道輸出流”中。
  // 將數(shù)組b寫入“管道輸出流”之后，它會將其傳輸給“管道輸入流”
  public void write(byte b[], int off, int len) throws IOException {
    if (sink == null) {
      throw new IOException("Pipe not connected");
    } else if (b == null) {
      throw new NullPointerException();
    } else if ((off < 0) || (off > b.length) || (len < 0) ||
          ((off + len) > b.length) || ((off + len) < 0)) {
      throw new IndexOutOfBoundsException();
    } else if (len == 0) {
      return;
    }
    // “管道輸入流”接收數(shù)據(jù)
    sink.receive(b, off, len);
  }

  // 清空“管道輸出流”。
  // 這里會調(diào)用“管道輸入流”的notifyAll()；
  // 目的是讓“管道輸入流”放棄對當前資源的占有，讓其它的等待線程(等待讀取管道輸出流的線程)讀取“管道輸出流”的值。
  public synchronized void flush() throws IOException {
    if (sink != null) {
      synchronized (sink) {
        sink.notifyAll();
      }
    }
  }

  // 關(guān)閉“管道輸出流”。
  // 關(guān)閉之后，會調(diào)用receivedLast()通知“管道輸入流”它已經(jīng)關(guān)閉。
  public void close() throws IOException {
    if (sink != null) {
      sink.receivedLast();
    }
  }
}

package java.io;

public class PipedInputStream extends InputStream {
  // “管道輸出流”是否關(guān)閉的標記
  boolean closedByWriter = false;
  // “管道輸入流”是否關(guān)閉的標記
  volatile boolean closedByReader = false;
  // “管道輸入流”與“管道輸出流”是否連接的標記
  // 它在PipedOutputStream的connect()連接函數(shù)中被設置為true
  boolean connected = false;

  Thread readSide;  // 讀取“管道”數(shù)據(jù)的線程
  Thread writeSide;  // 向“管道”寫入數(shù)據(jù)的線程

  // “管道”的默認大小
  private static final int DEFAULT_PIPE_SIZE = 1024;

  protected static final int PIPE_SIZE = DEFAULT_PIPE_SIZE;

  // 緩沖區(qū)
  protected byte buffer[];

  //下一個寫入字節(jié)的位置。in==out代表滿，說明“寫入的數(shù)據(jù)”全部被讀取了。
  protected int in = -1;
  //下一個讀取字節(jié)的位置。in==out代表滿，說明“寫入的數(shù)據(jù)”全部被讀取了。
  protected int out = 0;

  // 構(gòu)造函數(shù)：指定與“管道輸入流”關(guān)聯(lián)的“管道輸出流”
  public PipedInputStream(PipedOutputStream src) throws IOException {
    this(src, DEFAULT_PIPE_SIZE);
  }

  // 構(gòu)造函數(shù)：指定與“管道輸入流”關(guān)聯(lián)的“管道輸出流”，以及“緩沖區(qū)大小”
  public PipedInputStream(PipedOutputStream src, int pipeSize)
      throws IOException {
     initPipe(pipeSize);
     connect(src);
  }

  // 構(gòu)造函數(shù)：默認緩沖區(qū)大小是1024字節(jié)
  public PipedInputStream() {
    initPipe(DEFAULT_PIPE_SIZE);
  }

  // 構(gòu)造函數(shù)：指定緩沖區(qū)大小是pipeSize
  public PipedInputStream(int pipeSize) {
    initPipe(pipeSize);
  }

  // 初始化“管道”：新建緩沖區(qū)大小
  private void initPipe(int pipeSize) {
     if (pipeSize <= 0) {
      throw new IllegalArgumentException("Pipe Size <= 0");
     }
     buffer = new byte[pipeSize];
  }

  // 將“管道輸入流”和“管道輸出流”綁定。
  // 實際上，這里調(diào)用的是PipedOutputStream的connect()函數(shù)
  public void connect(PipedOutputStream src) throws IOException {
    src.connect(this);
  }

  // 接收int類型的數(shù)據(jù)b。
  // 它只會在PipedOutputStream的write(int b)中會被調(diào)用
  protected synchronized void receive(int b) throws IOException {
    // 檢查管道狀態(tài)
    checkStateForReceive();
    // 獲取“寫入管道”的線程
    writeSide = Thread.currentThread();
    // 若“寫入管道”的數(shù)據(jù)正好全部被讀取完，則等待。
    if (in == out)
      awaitSpace();
    if (in < 0) {
      in = 0;
      out = 0;
    }
    // 將b保存到緩沖區(qū)
    buffer[in++] = (byte)(b & 0xFF);
    if (in >= buffer.length) {
      in = 0;
    }
  }

  // 接收字節(jié)數(shù)組b。
  synchronized void receive(byte b[], int off, int len) throws IOException {
    // 檢查管道狀態(tài)
    checkStateForReceive();
    // 獲取“寫入管道”的線程
    writeSide = Thread.currentThread();
    int bytesToTransfer = len;
    while (bytesToTransfer > 0) {
      // 若“寫入管道”的數(shù)據(jù)正好全部被讀取完，則等待。
      if (in == out)
        awaitSpace();
      int nextTransferAmount = 0;
      // 如果“管道中被讀取的數(shù)據(jù)，少于寫入管道的數(shù)據(jù)”；
      // 則設置nextTransferAmount=“buffer.length - in”
      if (out < in) {
        nextTransferAmount = buffer.length - in;
      } else if (in < out) { // 如果“管道中被讀取的數(shù)據(jù)，大于/等于寫入管道的數(shù)據(jù)”，則執(zhí)行后面的操作
        // 若in==-1(即管道的寫入數(shù)據(jù)等于被讀取數(shù)據(jù))，此時nextTransferAmount = buffer.length - in;
        // 否則，nextTransferAmount = out - in;
        if (in == -1) {
          in = out = 0;
          nextTransferAmount = buffer.length - in;
        } else {
          nextTransferAmount = out - in;
        }
      }
      if (nextTransferAmount > bytesToTransfer)
        nextTransferAmount = bytesToTransfer;
      // assert斷言的作用是，若nextTransferAmount <= 0，則終止程序。
      assert(nextTransferAmount > 0);
      // 將數(shù)據(jù)寫入到緩沖中
      System.arraycopy(b, off, buffer, in, nextTransferAmount);
      bytesToTransfer -= nextTransferAmount;
      off += nextTransferAmount;
      in += nextTransferAmount;
      if (in >= buffer.length) {
        in = 0;
      }
    }
  }

  // 檢查管道狀態(tài)
  private void checkStateForReceive() throws IOException {
    if (!connected) {
      throw new IOException("Pipe not connected");
    } else if (closedByWriter || closedByReader) {
      throw new IOException("Pipe closed");
    } else if (readSide != null && !readSide.isAlive()) {
      throw new IOException("Read end dead");
    }
  }

  // 等待。
  // 若“寫入管道”的數(shù)據(jù)正好全部被讀取完(例如，管道緩沖滿)，則執(zhí)行awaitSpace()操作；
  // 它的目的是讓“讀取管道的線程”管道產(chǎn)生讀取數(shù)據(jù)請求，從而才能繼續(xù)的向“管道”中寫入數(shù)據(jù)。
  private void awaitSpace() throws IOException {
    
    // 如果“管道中被讀取的數(shù)據(jù)，等于寫入管道的數(shù)據(jù)”時，
    // 則每隔1000ms檢查“管道狀態(tài)”，并喚醒管道操作：若有“讀取管道數(shù)據(jù)線程被阻塞”，則喚醒該線程。
    while (in == out) {
      checkStateForReceive();

      /* full: kick any waiting readers */
      notifyAll();
      try {
        wait(1000);
      } catch (InterruptedException ex) {
        throw new java.io.InterruptedIOException();
      }
    }
  }

  // 當PipedOutputStream被關(guān)閉時，被調(diào)用
  synchronized void receivedLast() {
    closedByWriter = true;
    notifyAll();
  }

  // 從管道(的緩沖)中讀取一個字節(jié)，并將其轉(zhuǎn)換成int類型
  public synchronized int read() throws IOException {
    if (!connected) {
      throw new IOException("Pipe not connected");
    } else if (closedByReader) {
      throw new IOException("Pipe closed");
    } else if (writeSide != null && !writeSide.isAlive()
          && !closedByWriter && (in < 0)) {
      throw new IOException("Write end dead");
    }

    readSide = Thread.currentThread();
    int trials = 2;
    while (in < 0) {
      if (closedByWriter) {
        /* closed by writer, return EOF */
        return -1;
      }
      if ((writeSide != null) && (!writeSide.isAlive()) && (--trials < 0)) {
        throw new IOException("Pipe broken");
      }
      /* might be a writer waiting */
      notifyAll();
      try {
        wait(1000);
      } catch (InterruptedException ex) {
        throw new java.io.InterruptedIOException();
      }
    }
    int ret = buffer[out++] & 0xFF;
    if (out >= buffer.length) {
      out = 0;
    }
    if (in == out) {
      /* now empty */
      in = -1;
    }

    return ret;
  }

  // 從管道(的緩沖)中讀取數(shù)據(jù)，并將其存入到數(shù)組b中
  public synchronized int read(byte b[], int off, int len) throws IOException {
    if (b == null) {
      throw new NullPointerException();
    } else if (off < 0 || len < 0 || len > b.length - off) {
      throw new IndexOutOfBoundsException();
    } else if (len == 0) {
      return 0;
    }

    /* possibly wait on the first character */
    int c = read();
    if (c < 0) {
      return -1;
    }
    b[off] = (byte) c;
    int rlen = 1;
    while ((in >= 0) && (len > 1)) {

      int available;

      if (in > out) {
        available = Math.min((buffer.length - out), (in - out));
      } else {
        available = buffer.length - out;
      }

      // A byte is read beforehand outside the loop
      if (available > (len - 1)) {
        available = len - 1;
      }
      System.arraycopy(buffer, out, b, off + rlen, available);
      out += available;
      rlen += available;
      len -= available;

      if (out >= buffer.length) {
        out = 0;
      }
      if (in == out) {
        /* now empty */
        in = -1;
      }
    }
    return rlen;
  }

  // 返回不受阻塞地從此輸入流中讀取的字節(jié)數(shù)。
  public synchronized int available() throws IOException {
    if(in < 0)
      return 0;
    else if(in == out)
      return buffer.length;
    else if (in > out)
      return in - out;
    else
      return in + buffer.length - out;
  }

  // 關(guān)閉管道輸入流
  public void close() throws IOException {
    closedByReader = true;
    synchronized (this) {
      in = -1;
    }
  }
}

import java.io.IOException;  
  
import java.io.PipedInputStream;  
  
@SuppressWarnings("all")  
/** 
 * 接收者線程 
 */  
public class Receiver extends Thread {  
    
  // 管道輸入流對象。
  // 它和“管道輸出流(PipedOutputStream)”對象綁定，
  // 從而可以接收“管道輸出流”的數(shù)據(jù)，再讓用戶讀取。
  private PipedInputStream in = new PipedInputStream();  
  
  // 獲得“管道輸入流”對象
  public PipedInputStream getInputStream(){  
    return in;  
  }  
    
  @Override
  public void run(){  
    readMessageOnce() ;
    //readMessageContinued() ;
  }

  // 從“管道輸入流”中讀取1次數(shù)據(jù)
  public void readMessageOnce(){
    // 雖然buf的大小是2048個字節(jié)，但最多只會從“管道輸入流”中讀取1024個字節(jié)。
    // 因為，“管道輸入流”的緩沖區(qū)大小默認只有1024個字節(jié)。
    byte[] buf = new byte[2048];
    try {
      int len = in.read(buf);
      System.out.println(new String(buf,0,len));
      in.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
  // 從“管道輸入流”讀取>1024個字節(jié)時，就停止讀取
  public void readMessageContinued() {
    int total=0;
    while(true) {
      byte[] buf = new byte[1024];
      try {
        int len = in.read(buf);
        total += len;
        System.out.println(new String(buf,0,len));
        // 若讀取的字節(jié)總數(shù)>1024，則退出循環(huán)。
        if (total > 1024)
          break;
      } catch (IOException e) {
        e.printStackTrace();
      }
    }

    try {
      in.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

import java.io.IOException;  
  
import java.io.PipedOutputStream;  
@SuppressWarnings("all")
/** 
 * 發(fā)送者線程 
 */  
public class Sender extends Thread {  
    
  // 管道輸出流對象。
  // 它和“管道輸入流(PipedInputStream)”對象綁定，
  // 從而可以將數(shù)據(jù)發(fā)送給“管道輸入流”的數(shù)據(jù)，然后用戶可以從“管道輸入流”讀取數(shù)據(jù)。
  private PipedOutputStream out = new PipedOutputStream();

  // 獲得“管道輸出流”對象
  public PipedOutputStream getOutputStream(){
    return out;
  }  

  @Override
  public void run(){  
    writeShortMessage();
    //writeLongMessage();
  }  

  // 向“管道輸出流”中寫入一則較簡短的消息："this is a short message" 
  private void writeShortMessage() {
    String strInfo = "this is a short message" ;
    try {
      out.write(strInfo.getBytes());
      out.close();  
    } catch (IOException e) {  
      e.printStackTrace();  
    }  
  }
  // 向“管道輸出流”中寫入一則較長的消息
  private void writeLongMessage() {
    StringBuilder sb = new StringBuilder();
    // 通過for循環(huán)寫入1020個字節(jié)
    for (int i=0; i<102; i++)
      sb.append("0123456789");
    // 再寫入26個字節(jié)。
    sb.append("abcdefghijklmnopqrstuvwxyz");
    // str的總長度是1020+26=1046個字節(jié)
    String str = sb.toString();
    try {
      // 將1046個字節(jié)寫入到“管道輸出流”中
      out.write(str.getBytes());
      out.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.IOException;

@SuppressWarnings("all")  
/** 
 * 管道輸入流和管道輸出流的交互程序
 */  
public class PipedStreamTest {  
  
  public static void main(String[] args) {  
    Sender t1 = new Sender();  
      
    Receiver t2 = new Receiver();  
      
    PipedOutputStream out = t1.getOutputStream();  
 
    PipedInputStream in = t2.getInputStream();  

    try {  
      //管道連接。下面2句話的本質(zhì)是一樣。
      //out.connect(in);  
      in.connect(out);  
        
      /** 
       * Thread類的START方法： 
       * 使該線程開始執(zhí)行；Java 虛擬機調(diào)用該線程的 run 方法。  
       * 結(jié)果是兩個線程并發(fā)地運行；當前線程（從調(diào)用返回給 start 方法）和另一個線程（執(zhí)行其 run 方法）。  
       * 多次啟動一個線程是非法的。特別是當線程已經(jīng)結(jié)束執(zhí)行后，不能再重新啟動。  
       */
      t1.start();
      t2.start();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

public void write(byte b[]) throws IOException {
  write(b, 0, b.length);
}

public void run(){  
  writeShortMessage();
  //writeLongMessage();
} 

public void run(){  
  //writeShortMessage();
  writeLongMessage();
}

private static final int DEFAULT_PIPE_SIZE = 1024;
public PipedInputStream() {
  initPipe(DEFAULT_PIPE_SIZE);
}

private void initPipe(int pipeSize) {
   if (pipeSize <= 0) {
    throw new IllegalArgumentException("Pipe Size <= 0");
   }
   buffer = new byte[pipeSize];
}

public void run(){  
  readMessageOnce() ;
  //readMessageContinued() ;
}

public void run(){  
  //readMessageOnce() ;
  readMessageContinued() ;
}