1 /*

     2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 package jdk.internal.jshell.tool;

    26 

    27 import java.io.IOException;

    28 import java.io.InputStream;

    29 import java.util.function.Consumer;

    30 

    31 public final class StopDetectingInputStream extends InputStream {

    32     public static final int INITIAL_SIZE = 128;

    33 

    34     private final Runnable stop;

    35     private final Consumer<Exception> errorHandler;

    36 

    37     private boolean initialized;

    38     private int[] buffer = new int[INITIAL_SIZE];

    39     private int start;

    40     private int end;

    41     private State state = State.WAIT;

    42 

    43     public StopDetectingInputStream(Runnable stop, Consumer<Exception> errorHandler) {

    44         this.stop = stop;

    45         this.errorHandler = errorHandler;

    46     }

    47 

    48     public synchronized InputStream setInputStream(InputStream input) {

    49         if (initialized)

    50             throw new IllegalStateException("Already initialized.");

    51         initialized = true;

    52 

    53         Thread reader = new Thread() {

    54             @Override

    55             public void run() {

    56                 try {

    57                     int read;

    58                     while (true) {

    59                         //to support external terminal editors, the "cmdin.read" must not run when

    60                         //an external editor is running. At the same time, it needs to run while the

    61                         //user's code is running (so Ctrl-C is detected). Hence waiting here until

    62                         //there is a confirmed need for input.

    63                         waitInputNeeded();

    64                         if ((read = input.read()) == (-1)) {

    65                             break;

    66                         }

    67                         if (read == 3 && state == StopDetectingInputStream.State.BUFFER) {

    68                             stop.run();

    69                         } else {

    70                             write(read);

    71                         }

    72                     }

    73                 } catch (IOException ex) {

    74                     errorHandler.accept(ex);

    75                 } finally {

    76                     state = StopDetectingInputStream.State.CLOSED;

    77                 }

    78             }

    79         };

    80         reader.setDaemon(true);

    81         reader.start();

    82 

    83         return this;

    84     }

    85 

    86     @Override

    87     public synchronized int read() {

    88         while (start == end) {

    89             if (state == State.CLOSED) {

    90                 return -1;

    91             }

    92             if (state == State.WAIT) {

    93                 state = State.READ;

    94             }

    95             notifyAll();

    96             try {

    97                 wait();

    98             } catch (InterruptedException ex) {

    99                 //ignore

   100             }

   101         }

   102         try {

   103             return buffer[start];

   104         } finally {

   105             start = (start + 1) % buffer.length;

   106         }

   107     }

   108 

   109     public synchronized void write(int b) {

   110         if (state != State.BUFFER) {

   111             state = State.WAIT;

   112         }

   113         int newEnd = (end + 1) % buffer.length;

   114         if (newEnd == start) {

   115             //overflow:

   116             int[] newBuffer = new int[buffer.length * 2];

   117             int rightPart = (end > start ? end : buffer.length) - start;

   118             int leftPart = end > start ? 0 : start - 1;

   119             System.arraycopy(buffer, start, newBuffer, 0, rightPart);

   120             System.arraycopy(buffer, 0, newBuffer, rightPart, leftPart);

   121             buffer = newBuffer;

   122             start = 0;

   123             end = rightPart + leftPart;

   124             newEnd = end + 1;

   125         }

   126         buffer[end] = b;

   127         end = newEnd;

   128         notifyAll();

   129     }

   130 

   131     public synchronized void setState(State state) {

   132         this.state = state;

   133         notifyAll();

   134     }

   135 

   136     private synchronized void waitInputNeeded() {

   137         while (state == State.WAIT) {

   138             try {

   139                 wait();

   140             } catch (InterruptedException ex) {

   141                 //ignore

   142             }

   143         }

   144     }

   145 

   146     public enum State {

   147         /* No reading from the input should happen. This is the default state. The StopDetectingInput

   148          * must be in this state when an external editor is being run, so that the external editor

   149          * can read from the input.

   150          */

   151         WAIT,

   152         /* A single input character should be read. Reading from the StopDetectingInput will move it

   153          * into this state, and the state will be automatically changed back to WAIT when a single

   154          * input character is obtained. This state is typically used while the user is editing the

   155          * input line.

   156          */

   157         READ,

   158         /* Continuously read from the input. Forward Ctrl-C ((int) 3) to the "stop" Runnable, buffer

   159          * all other input. This state is typically used while the user's code is running, to provide

   160          * the ability to detect Ctrl-C in order to stop the execution.

   161          */

   162         BUFFER,

   163         /* The input is closed.

   164         */

   165         CLOSED

   166     }

   167 

   168 }