1 /*

     2  * Copyright (c) 2019, 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 

    26 package sun.nio.ch;

    27 

    28 import java.io.FileDescriptor;

    29 import java.io.IOException;

    30 import java.nio.ByteBuffer;

    31 import java.nio.channels.AsynchronousCloseException;

    32 import java.nio.channels.ByteChannel;

    33 import java.nio.channels.ClosedChannelException;

    34 import java.nio.channels.NotYetConnectedException;

    35 import java.nio.channels.spi.AbstractInterruptibleChannel;

    36 import java.util.Objects;

    37 import java.util.concurrent.locks.ReentrantLock;

    38 

    39 import static java.util.concurrent.TimeUnit.NANOSECONDS;

    40 

    41 class UnixDomainSocketChannelImpl

    42     extends AbstractInterruptibleChannel

    43     implements ByteChannel

    44 {

    45     // Used to make native read and write calls

    46     private static final NativeDispatcher nd = new SocketDispatcher();

    47 

    48     // Our file descriptor object

    49     private final FileDescriptor fd;

    50     // Lock held by current reading or connecting thread

    51     private final ReentrantLock readLock = new ReentrantLock();

    52 

    53     // Lock held by current writing or connecting thread

    54     private final ReentrantLock writeLock = new ReentrantLock();

    55 

    56     // Lock for managing close state

    57     private final Object stateLock = new Object();

    58 

    59     // Channel state

    60     private static final int ST_INUSE = 0;

    61     private static final int ST_CLOSING = 1;

    62     private static final int ST_CLOSED = 2;

    63     private int state;

    64 

    65     // IDs of native threads doing reads and writes, for signalling

    66     private long readerThread;

    67     private long writerThread;

    68 

    69     UnixDomainSocketChannelImpl(FileDescriptor fd)

    70         throws IOException

    71     {

    72         this.fd = fd;

    73     }

    74 

    75     /**

    76      * Checks that the channel is open.

    77      *

    78      * @throws ClosedChannelException if channel is closed (or closing)

    79      */

    80     private void ensureOpen() throws ClosedChannelException {

    81         if (!isOpen())

    82             throw new ClosedChannelException();

    83     }

    84 

    85     /**

    86      * Closes the socket if there are no I/O operations in progress

    87      */

    88     private boolean tryClose() throws IOException {

    89         assert Thread.holdsLock(stateLock) && state == ST_CLOSING;

    90         if (readerThread == 0 && writerThread == 0) {

    91             state = ST_CLOSED;

    92             nd.close(fd);

    93             return true;

    94         } else {

    95             return false;

    96         }

    97     }

    98 

    99     /**

   100      * Complete closure of pre-closed socket (release the file descriptor)

   101      */

   102     private void tryFinishClose() {

   103         try {

   104             tryClose();

   105         } catch (IOException ignore) { }

   106     }

   107 

   108     /**

   109      * Marks the beginning of a read operation

   110      *

   111      * @throws ClosedChannelException if the channel is closed

   112      * @throws NotYetConnectedException if the channel is not yet connected

   113      */

   114     private void beginRead() throws ClosedChannelException {

   115         // set hook for Thread.interrupt

   116         begin();

   117         synchronized (stateLock) {

   118             ensureOpen();

   119             readerThread = NativeThread.current();

   120         }

   121     }

   122 

   123     /**

   124      * Marks the end of a read operation that may have blocked.

   125      *

   126      * @throws AsynchronousCloseException if the channel was closed due to this

   127      * thread being interrupted on a blocking read operation.

   128      */

   129     private void endRead(boolean completed)

   130         throws AsynchronousCloseException

   131     {

   132         synchronized (stateLock) {

   133             readerThread = 0;

   134             if (state == ST_CLOSING) {

   135                 tryFinishClose();

   136             }

   137         }

   138         end(completed);

   139     }

   140 

   141     @Override

   142     public int read(ByteBuffer buf) throws IOException {

   143         Objects.requireNonNull(buf);

   144 

   145         readLock.lock();

   146         try {

   147             int n = 0;

   148             try {

   149                 beginRead();

   150                 n = IOUtil.read(fd, buf, -1, nd);

   151                 while (IOStatus.okayToRetry(n) && isOpen()) {

   152                     park(Net.POLLIN, 0L);

   153                     n = IOUtil.read(fd, buf, -1, nd);

   154                 }

   155             } finally {

   156                 endRead(n > 0);

   157             }

   158             return n;

   159         } finally {

   160             readLock.unlock();

   161         }

   162     }

   163 

   164     /**

   165      * Marks the beginning of a write operation that might block.

   166      *

   167      * @throws ClosedChannelException if the channel is closed

   168      * @throws NotYetConnectedException if the channel is not yet connected

   169      */

   170     private void beginWrite() throws ClosedChannelException {

   171         begin();

   172         synchronized (stateLock) {

   173             // set hook for Thread.interrupt

   174             ensureOpen();

   175             writerThread = NativeThread.current();

   176         }

   177     }

   178 

   179     /**

   180      * Marks the end of a write operation that may have blocked.

   181      *

   182      * @throws AsynchronousCloseException if the channel was closed due to this

   183      * thread being interrupted on a blocking write operation.

   184      */

   185     private void endWrite(boolean completed)

   186         throws AsynchronousCloseException

   187     {

   188         synchronized (stateLock) {

   189             writerThread = 0;

   190             if (state == ST_CLOSING) {

   191                 tryFinishClose();

   192             }

   193         }

   194         end(completed);

   195     }

   196 

   197     void park(int event, long nanos) throws IOException {

   198         long millis;

   199         if (nanos <= 0) {

   200             millis = -1;

   201         } else {

   202             millis = NANOSECONDS.toMillis(nanos);

   203         }

   204         Net.poll(fd, event, millis);

   205     }

   206 

   207     @Override

   208     public int write(ByteBuffer buf) throws IOException {

   209         Objects.requireNonNull(buf);

   210 

   211         writeLock.lock();

   212         try {

   213             int n = 0;

   214             try {

   215                 beginWrite();

   216                 n = IOUtil.write(fd, buf, -1, nd);

   217                 while (IOStatus.okayToRetry(n) && isOpen()) {

   218                     park(Net.POLLOUT, 0L);

   219                     n = IOUtil.write(fd, buf, -1, nd);

   220                 }

   221             } finally {

   222                 endWrite(n > 0);

   223             }

   224             return n;

   225         } finally {

   226             writeLock.unlock();

   227         }

   228     }

   229 

   230     /**

   231      * Closes this channel

   232      *

   233      * If there is an I/O operation in progress then the socket is pre-closed

   234      * and the I/O threads signalled, in which case the final close is deferred

   235      * until all I/O operations complete.

   236      */

   237     @Override

   238     protected void implCloseChannel() throws IOException {

   239         synchronized (stateLock) {

   240             assert state == ST_INUSE;

   241             state = ST_CLOSING;

   242             if (!tryClose()) {

   243                 long reader = readerThread;

   244                 long writer = writerThread;

   245                 if (reader != 0 || writer != 0) {

   246                     nd.preClose(fd);

   247                     if (reader != 0)

   248                         NativeThread.signal(reader);

   249                     if (writer != 0)

   250                         NativeThread.signal(writer);

   251                 }

   252             }

   253         }

   254     }

   255 

   256     @Override

   257     public String toString() {

   258         StringBuilder sb = new StringBuilder();

   259         sb.append(this.getClass().getSuperclass().getName());

   260         sb.append('[');

   261         if (!isOpen())

   262             sb.append("closed");

   263         sb.append(']');

   264         return sb.toString();

   265     }

   266 }