1 /*

     2  * Copyright (c) 2018, 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 jdk.nio.zipfs;

    27 

    28 import java.io.IOException;

    29 import java.nio.ByteBuffer;

    30 import java.nio.channels.ClosedChannelException;

    31 import java.nio.channels.NonWritableChannelException;

    32 import java.nio.channels.SeekableByteChannel;

    33 import java.util.Arrays;

    34 import java.util.concurrent.locks.ReadWriteLock;

    35 import java.util.concurrent.locks.ReentrantReadWriteLock;

    36 

    37 public class ByteArrayChannel implements SeekableByteChannel {

    38 

    39     private final ReadWriteLock rwlock = new ReentrantReadWriteLock();

    40     private byte buf[];

    41 

    42     /*

    43      * The current position of this channel.

    44      */

    45     private int pos;

    46 

    47     /*

    48      * The index that is one greater than the last valid byte in the channel.

    49      */

    50     private int last;

    51 

    52     private boolean closed;

    53     private boolean readonly;

    54 

    55     /*

    56      * Creates a {@code ByteArrayChannel} with size {@code sz}.

    57      */

    58     ByteArrayChannel(int sz, boolean readonly) {

    59         this.buf = new byte[sz];

    60         this.pos = this.last = 0;

    61         this.readonly = readonly;

    62     }

    63 

    64     /*

    65      * Creates a ByteArrayChannel with its 'pos' at 0 and its 'last' at buf's end.

    66      * Note: no defensive copy of the 'buf', used directly.

    67      */

    68     ByteArrayChannel(byte[] buf, boolean readonly) {

    69         this.buf = buf;

    70         this.pos = 0;

    71         this.last = buf.length;

    72         this.readonly = readonly;

    73     }

    74 

    75     @Override

    76     public boolean isOpen() {

    77         return !closed;

    78     }

    79 

    80     @Override

    81     public long position() throws IOException {

    82         beginRead();

    83         try {

    84             ensureOpen();

    85             return pos;

    86         } finally {

    87             endRead();

    88         }

    89     }

    90 

    91     @Override

    92     public SeekableByteChannel position(long pos) throws IOException {

    93         beginWrite();

    94         try {

    95             ensureOpen();

    96             if (pos < 0 || pos >= Integer.MAX_VALUE)

    97                 throw new IllegalArgumentException("Illegal position " + pos);

    98             this.pos = Math.min((int)pos, last);

    99             return this;

   100         } finally {

   101             endWrite();

   102         }

   103     }

   104 

   105     @Override

   106     public int read(ByteBuffer dst) throws IOException {

   107         beginWrite();

   108         try {

   109             ensureOpen();

   110             if (pos == last)

   111                 return -1;

   112             int n = Math.min(dst.remaining(), last - pos);

   113             dst.put(buf, pos, n);

   114             pos += n;

   115             return n;

   116         } finally {

   117             endWrite();

   118         }

   119     }

   120 

   121     @Override

   122     public SeekableByteChannel truncate(long size) throws IOException {

   123         if (readonly)

   124             throw new NonWritableChannelException();

   125         ensureOpen();

   126         throw new UnsupportedOperationException();

   127     }

   128 

   129     @Override

   130     public int write(ByteBuffer src) throws IOException {

   131         if (readonly)

   132             throw new NonWritableChannelException();

   133         beginWrite();

   134         try {

   135             ensureOpen();

   136             int n = src.remaining();

   137             ensureCapacity(pos + n);

   138             src.get(buf, pos, n);

   139             pos += n;

   140             if (pos > last) {

   141                 last = pos;

   142             }

   143             return n;

   144         } finally {

   145             endWrite();

   146         }

   147     }

   148 

   149     @Override

   150     public long size() throws IOException {

   151         beginRead();

   152         try {

   153             ensureOpen();

   154             return last;

   155         } finally {

   156             endRead();

   157         }

   158     }

   159 

   160     @Override

   161     public void close() throws IOException {

   162         if (closed)

   163             return;

   164         beginWrite();

   165         try {

   166             closed = true;

   167             buf = null;

   168             pos = 0;

   169             last = 0;

   170         } finally {

   171             endWrite();

   172         }

   173     }

   174 

   175     /**

   176      * Creates a newly allocated byte array. Its size is the current

   177      * size of this channel and the valid contents of the buffer

   178      * have been copied into it.

   179      *

   180      * @return the current contents of this channel, as a byte array.

   181      */

   182     public byte[] toByteArray() {

   183         beginRead();

   184         try {

   185             // avoid copy if last == bytes.length?

   186             return Arrays.copyOf(buf, last);

   187         } finally {

   188             endRead();

   189         }

   190     }

   191 

   192     private void ensureOpen() throws IOException {

   193         if (closed)

   194             throw new ClosedChannelException();

   195     }

   196 

   197     private final void beginWrite() {

   198         rwlock.writeLock().lock();

   199     }

   200 

   201     private final void endWrite() {

   202         rwlock.writeLock().unlock();

   203     }

   204 

   205     private final void beginRead() {

   206         rwlock.readLock().lock();

   207     }

   208 

   209     private final void endRead() {

   210         rwlock.readLock().unlock();

   211     }

   212 

   213     private void ensureCapacity(int minCapacity) {

   214         // overflow-conscious code

   215         if (minCapacity - buf.length > 0) {

   216             grow(minCapacity);

   217         }

   218     }

   219 

   220     /**

   221      * The maximum size of array to allocate.

   222      * Some VMs reserve some header words in an array.

   223      * Attempts to allocate larger arrays may result in

   224      * OutOfMemoryError: Requested array size exceeds VM limit

   225      */

   226     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

   227 

   228     /**

   229      * Increases the capacity to ensure that it can hold at least the

   230      * number of elements specified by the minimum capacity argument.

   231      *

   232      * @param minCapacity the desired minimum capacity

   233      */

   234     private void grow(int minCapacity) {

   235         // overflow-conscious code

   236         int oldCapacity = buf.length;

   237         int newCapacity = oldCapacity << 1;

   238         if (newCapacity - minCapacity < 0)

   239             newCapacity = minCapacity;

   240         if (newCapacity - MAX_ARRAY_SIZE > 0)

   241             newCapacity = hugeCapacity(minCapacity);

   242         buf = Arrays.copyOf(buf, newCapacity);

   243     }

   244 

   245     private static int hugeCapacity(int minCapacity) {

   246         if (minCapacity < 0) // overflow

   247             throw new OutOfMemoryError();

   248         return (minCapacity > MAX_ARRAY_SIZE) ?

   249             Integer.MAX_VALUE :

   250             MAX_ARRAY_SIZE;

   251     }

   252 }