Java example source code file (UnixDirectoryStream.java)

This example Java source code file (UnixDirectoryStream.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

directoryiteratorexception, directorystream, illegalstateexception, ioexception, iterator, lock, override, path, reentrantreadwritelock, unixdirectoryiterator, unixdirectorystream, unixexception, unixpath, unsupportedoperationexception, util

The UnixDirectoryStream.java Java example source code

/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.nio.fs;

import java.nio.file.*;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.locks.*;
import java.io.IOException;
import static sun.nio.fs.UnixNativeDispatcher.*;

/**
 * Unix implementation of java.nio.file.DirectoryStream
 */

class UnixDirectoryStream
    implements DirectoryStream<Path>
{
    // path to directory when originally opened
    private final UnixPath dir;

    // directory pointer (returned by opendir)
    private final long dp;

    // filter (may be null)
    private final DirectoryStream.Filter<? super Path> filter;

    // used to coorindate closing of directory stream
    private final ReentrantReadWriteLock streamLock =
        new ReentrantReadWriteLock(true);

    // indicates if directory stream is open (synchronize on closeLock)
    private volatile boolean isClosed;

    // directory iterator
    private Iterator<Path> iterator;

    /**
     * Initializes a new instance
     */
    UnixDirectoryStream(UnixPath dir, long dp, DirectoryStream.Filter<? super Path> filter) {
        this.dir = dir;
        this.dp = dp;
        this.filter = filter;
    }

    protected final UnixPath directory() {
        return dir;
    }

    protected final Lock readLock() {
        return streamLock.readLock();
    }

    protected final Lock writeLock() {
        return streamLock.writeLock();
    }

    protected final boolean isOpen() {
        return !isClosed;
    }

    protected final boolean closeImpl() throws IOException {
        if (!isClosed) {
            isClosed = true;
            try {
                closedir(dp);
            } catch (UnixException x) {
                throw new IOException(x.errorString());
            }
            return true;
        } else {
            return false;
        }
    }

    @Override
    public void close()
        throws IOException
    {
        writeLock().lock();
        try {
            closeImpl();
        } finally {
            writeLock().unlock();
        }
    }

    protected final Iterator<Path> iterator(DirectoryStream ds) {
        if (isClosed) {
            throw new IllegalStateException("Directory stream is closed");
        }
        synchronized (this) {
            if (iterator != null)
                throw new IllegalStateException("Iterator already obtained");
            iterator = new UnixDirectoryIterator(ds);
            return iterator;
        }
    }

    @Override
    public Iterator<Path> iterator() {
        return iterator(this);
    }

    /**
     * Iterator implementation
     */
    private class UnixDirectoryIterator implements Iterator<Path> {
        private final DirectoryStream<Path> stream;

        // true when at EOF
        private boolean atEof;

        // next entry to return
        private Path nextEntry;

        UnixDirectoryIterator(DirectoryStream<Path> stream) {
            atEof = false;
            this.stream = stream;
        }

        // Return true if file name is "." or ".."
        private boolean isSelfOrParent(byte[] nameAsBytes) {
            if (nameAsBytes[0] == '.') {
                if ((nameAsBytes.length == 1) ||
                    (nameAsBytes.length == 2 && nameAsBytes[1] == '.')) {
                    return true;
                }
            }
            return false;
        }

        // Returns next entry (or null)
        private Path readNextEntry() {
            assert Thread.holdsLock(this);

            for (;;) {
                byte[] nameAsBytes = null;

                // prevent close while reading
                readLock().lock();
                try {
                    if (isOpen()) {
                        nameAsBytes = readdir(dp);
                    }
                } catch (UnixException x) {
                    IOException ioe = x.asIOException(dir);
                    throw new DirectoryIteratorException(ioe);
                } finally {
                    readLock().unlock();
                }

                // EOF
                if (nameAsBytes == null) {
                    atEof = true;
                    return null;
                }

                // ignore "." and ".."
                if (!isSelfOrParent(nameAsBytes)) {
                    Path entry = dir.resolve(nameAsBytes);

                    // return entry if no filter or filter accepts it
                    try {
                        if (filter == null || filter.accept(entry))
                            return entry;
                    } catch (IOException ioe) {
                        throw new DirectoryIteratorException(ioe);
                    }
                }
            }
        }

        @Override
        public synchronized boolean hasNext() {
            if (nextEntry == null && !atEof)
                nextEntry = readNextEntry();
            return nextEntry != null;
        }

        @Override
        public synchronized Path next() {
            Path result;
            if (nextEntry == null && !atEof) {
                result = readNextEntry();
            } else {
                result = nextEntry;
                nextEntry = null;
            }
            if (result == null)
                throw new NoSuchElementException();
            return result;
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }
}