src/java.base/share/classes/sun/nio/ch/UnixDomainSockets.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package sun.nio.ch;

import java.io.FileDescriptor;
import java.io.IOException;
import java.net.BindException;
import java.net.SocketAddress;
import java.net.UnixDomainSocketAddress;
import java.nio.channels.UnsupportedAddressTypeException;
import java.nio.file.FileSystems;
import java.nio.file.InvalidPathException;
import java.nio.file.Path;
import java.nio.file.spi.FileSystemProvider;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;
import sun.nio.fs.AbstractFileSystemProvider;

class UnixDomainSockets {
    private UnixDomainSockets() { }

    private static class UnnamedHolder {
        static final UnixDomainSocketAddress UNNAMED = UnixDomainSocketAddress.of("");
    }

    private static final boolean supported;

    private static final String tempDir = UnixDomainSocketsUtil.getTempDir();

    static boolean isSupported() {
        return supported;
    }

    static UnixDomainSocketAddress localAddress(FileDescriptor fd) throws IOException {
        String path = new String(localAddress0(fd), UnixDomainSocketsUtil.getCharset());
        return UnixDomainSocketAddress.of(path);
    }

    private static native byte[] localAddress0(FileDescriptor fd) throws IOException;

    static UnixDomainSocketAddress checkAddress(SocketAddress sa) {
        if (sa == null)
            throw new NullPointerException();
        if (!(sa instanceof UnixDomainSocketAddress))
            throw new UnsupportedAddressTypeException();
        return (UnixDomainSocketAddress) sa;
    }

    static byte[] getPathBytes(Path path) {
        FileSystemProvider provider = FileSystems.getDefault().provider();
        return ((AbstractFileSystemProvider) provider).getSunPathForSocketFile(path);
    }

    static FileDescriptor socket() throws IOException {
        return IOUtil.newFD(socket0());
    }

    static void bind(FileDescriptor fd, Path addr) throws IOException {
        byte[] path = getPathBytes(addr);
        if (path.length == 0) {
            throw new BindException("Server socket cannot bind to unnamed address");
        }
        bind0(fd, path);
    }

    private static Random getRandom() {
        try {
            return SecureRandom.getInstance("NativePRNGNonBlocking");
        } catch (NoSuchAlgorithmException e) {
            return new SecureRandom(); // This should not fail
        }
    }

    private static final Random random = getRandom();

    /**
     * Return a possible temporary name to bind to, which is different for each call
     * Name is of the form <temp dir>/socket_<random>
     */
    static UnixDomainSocketAddress generateTempName() throws IOException {
        String dir = UnixDomainSockets.tempDir;
        if (dir == null)
            throw new BindException("Could not locate temporary directory for sockets");
        int rnd = random.nextInt(Integer.MAX_VALUE);
        try {
            final Path path = Path.of(dir, "socket_" + rnd);
            if (path.getFileSystem().provider() != sun.nio.fs.DefaultFileSystemProvider.instance()) {
                throw new UnsupportedOperationException(
                        "Unix Domain Sockets not supported on non-default file system");
            }
            return UnixDomainSocketAddress.of(path);
        } catch (InvalidPathException e) {
            throw new BindException("Invalid temporary directory");
        }
    }

    static int connect(FileDescriptor fd, SocketAddress sa) throws IOException {
        return UnixDomainSockets.connect(fd, ((UnixDomainSocketAddress) sa).getPath());
    }

    static int connect(FileDescriptor fd, Path path) throws IOException {
        return connect0(fd, getPathBytes(path));
    }

    static int accept(FileDescriptor fd, FileDescriptor newfd, String[] paths)
        throws IOException
    {
        Object[] array  = new Object[1];
        int n = accept0(fd, newfd, array);
        if (n > 0) {
            byte[] bytes = (byte[]) array[0];
            paths[0] = new String(bytes, UnixDomainSocketsUtil.getCharset());
        }
        return n;
    }

    static UnixDomainSocketAddress unnamed() {
        return UnnamedHolder.UNNAMED;
    }

    private static native boolean init();

    private static native int socket0() throws IOException;

    private static native void bind0(FileDescriptor fd, byte[] path)
        throws IOException;

    private static native int connect0(FileDescriptor fd, byte[] path)
        throws IOException;

    private static native int accept0(FileDescriptor fd, FileDescriptor newfd, Object[] array)
        throws IOException;

    static {
        // Load all required native libs
        IOUtil.load();
        supported = init();
    }
}