Java example source code file (WindowsChannelFactory.java)

This example Java source code file (WindowsChannelFactory.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

append, closehandle, create_new, filedescriptor, flags, illegalargumentexception, open_always, openoption, read, set, string, truncate_existing, unsupportedoperationexception, util, windowsexception

The WindowsChannelFactory.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.nio.channels.*;
import java.io.FileDescriptor;
import java.io.IOException;
import java.util.*;

import com.sun.nio.file.ExtendedOpenOption;

import sun.nio.ch.FileChannelImpl;
import sun.nio.ch.ThreadPool;
import sun.nio.ch.WindowsAsynchronousFileChannelImpl;
import sun.misc.SharedSecrets;
import sun.misc.JavaIOFileDescriptorAccess;

import static sun.nio.fs.WindowsNativeDispatcher.*;
import static sun.nio.fs.WindowsConstants.*;

/**
 * Factory to create FileChannels and AsynchronousFileChannels.
 */

class WindowsChannelFactory {
    private static final JavaIOFileDescriptorAccess fdAccess =
        SharedSecrets.getJavaIOFileDescriptorAccess();

    private WindowsChannelFactory() { }

    /**
     * Do not follow reparse points when opening an existing file. Do not fail
     * if the file is a reparse point.
     */
    static final OpenOption OPEN_REPARSE_POINT = new OpenOption() { };

    /**
     * Represents the flags from a user-supplied set of open options.
     */
    private static class Flags {
        boolean read;
        boolean write;
        boolean append;
        boolean truncateExisting;
        boolean create;
        boolean createNew;
        boolean deleteOnClose;
        boolean sparse;
        boolean overlapped;
        boolean sync;
        boolean dsync;

        // non-standard
        boolean shareRead = true;
        boolean shareWrite = true;
        boolean shareDelete = true;
        boolean noFollowLinks;
        boolean openReparsePoint;

        static Flags toFlags(Set<? extends OpenOption> options) {
            Flags flags = new Flags();
            for (OpenOption option: options) {
                if (option instanceof StandardOpenOption) {
                    switch ((StandardOpenOption)option) {
                        case READ : flags.read = true; break;
                        case WRITE : flags.write = true; break;
                        case APPEND : flags.append = true; break;
                        case TRUNCATE_EXISTING : flags.truncateExisting = true; break;
                        case CREATE : flags.create = true; break;
                        case CREATE_NEW : flags.createNew = true; break;
                        case DELETE_ON_CLOSE : flags.deleteOnClose = true; break;
                        case SPARSE : flags.sparse = true; break;
                        case SYNC : flags.sync = true; break;
                        case DSYNC : flags.dsync = true; break;
                        default: throw new UnsupportedOperationException();
                    }
                    continue;
                }
                if (option instanceof ExtendedOpenOption) {
                    switch ((ExtendedOpenOption)option) {
                        case NOSHARE_READ : flags.shareRead = false; break;
                        case NOSHARE_WRITE : flags.shareWrite = false; break;
                        case NOSHARE_DELETE : flags.shareDelete = false; break;
                        default: throw new UnsupportedOperationException();
                    }
                    continue;
                }
                if (option == LinkOption.NOFOLLOW_LINKS) {
                    flags.noFollowLinks = true;
                    continue;
                }
                if (option == OPEN_REPARSE_POINT) {
                    flags.openReparsePoint = true;
                    continue;
                }
                if (option == null)
                    throw new NullPointerException();
                throw new UnsupportedOperationException();
            }
            return flags;
        }
    }

    /**
     * Open/creates file, returning FileChannel to access the file
     *
     * @param   pathForWindows
     *          The path of the file to open/create
     * @param   pathToCheck
     *          The path used for permission checks (if security manager)
     */
    static FileChannel newFileChannel(String pathForWindows,
                                      String pathToCheck,
                                      Set<? extends OpenOption> options,
                                      long pSecurityDescriptor)
        throws WindowsException
    {
        Flags flags = Flags.toFlags(options);

        // default is reading; append => writing
        if (!flags.read && !flags.write) {
            if (flags.append) {
                flags.write = true;
            } else {
                flags.read = true;
            }
        }

        // validation
        if (flags.read && flags.append)
            throw new IllegalArgumentException("READ + APPEND not allowed");
        if (flags.append && flags.truncateExisting)
            throw new IllegalArgumentException("APPEND + TRUNCATE_EXISTING not allowed");

        FileDescriptor fdObj = open(pathForWindows, pathToCheck, flags, pSecurityDescriptor);
        return FileChannelImpl.open(fdObj, flags.read, flags.write, flags.append, null);
    }

    /**
     * Open/creates file, returning AsynchronousFileChannel to access the file
     *
     * @param   pathForWindows
     *          The path of the file to open/create
     * @param   pathToCheck
     *          The path used for permission checks (if security manager)
     * @param   pool
     *          The thread pool that the channel is associated with
     */
    static AsynchronousFileChannel newAsynchronousFileChannel(String pathForWindows,
                                                              String pathToCheck,
                                                              Set<? extends OpenOption> options,
                                                              long pSecurityDescriptor,
                                                              ThreadPool pool)
        throws IOException
    {
        Flags flags = Flags.toFlags(options);

        // Overlapped I/O required
        flags.overlapped = true;

        // default is reading
        if (!flags.read && !flags.write) {
            flags.read = true;
        }

        // validation
        if (flags.append)
            throw new UnsupportedOperationException("APPEND not allowed");

        // open file for overlapped I/O
        FileDescriptor fdObj;
        try {
            fdObj = open(pathForWindows, pathToCheck, flags, pSecurityDescriptor);
        } catch (WindowsException x) {
            x.rethrowAsIOException(pathForWindows);
            return null;
        }

        // create the AsynchronousFileChannel
        try {
            return WindowsAsynchronousFileChannelImpl.open(fdObj, flags.read, flags.write, pool);
        } catch (IOException x) {
            // IOException is thrown if the file handle cannot be associated
            // with the completion port. All we can do is close the file.
            long handle = fdAccess.getHandle(fdObj);
            CloseHandle(handle);
            throw x;
        }
    }

    /**
     * Opens file based on parameters and options, returning a FileDescriptor
     * encapsulating the handle to the open file.
     */
    private static FileDescriptor open(String pathForWindows,
                                       String pathToCheck,
                                       Flags flags,
                                       long pSecurityDescriptor)
        throws WindowsException
    {
        // set to true if file must be truncated after open
        boolean truncateAfterOpen = false;

        // map options
        int dwDesiredAccess = 0;
        if (flags.read)
            dwDesiredAccess |= GENERIC_READ;
        if (flags.write)
            dwDesiredAccess |= GENERIC_WRITE;

        int dwShareMode = 0;
        if (flags.shareRead)
            dwShareMode |= FILE_SHARE_READ;
        if (flags.shareWrite)
            dwShareMode |= FILE_SHARE_WRITE;
        if (flags.shareDelete)
            dwShareMode |= FILE_SHARE_DELETE;

        int dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
        int dwCreationDisposition = OPEN_EXISTING;
        if (flags.write) {
            if (flags.createNew) {
                dwCreationDisposition = CREATE_NEW;
                // force create to fail if file is orphaned reparse point
                dwFlagsAndAttributes |= FILE_FLAG_OPEN_REPARSE_POINT;
            } else {
                if (flags.create)
                    dwCreationDisposition = OPEN_ALWAYS;
                if (flags.truncateExisting) {
                    // Windows doesn't have a creation disposition that exactly
                    // corresponds to CREATE + TRUNCATE_EXISTING so we use
                    // the OPEN_ALWAYS mode and then truncate the file.
                    if (dwCreationDisposition == OPEN_ALWAYS) {
                        truncateAfterOpen = true;
                    } else {
                        dwCreationDisposition = TRUNCATE_EXISTING;
                    }
                }
            }
        }

        if (flags.dsync || flags.sync)
            dwFlagsAndAttributes |= FILE_FLAG_WRITE_THROUGH;
        if (flags.overlapped)
            dwFlagsAndAttributes |= FILE_FLAG_OVERLAPPED;
        if (flags.deleteOnClose)
            dwFlagsAndAttributes |= FILE_FLAG_DELETE_ON_CLOSE;

        // NOFOLLOW_LINKS and NOFOLLOW_REPARSEPOINT mean open reparse point
        boolean okayToFollowLinks = true;
        if (dwCreationDisposition != CREATE_NEW &&
            (flags.noFollowLinks ||
             flags.openReparsePoint ||
             flags.deleteOnClose))
        {
            if (flags.noFollowLinks || flags.deleteOnClose)
                okayToFollowLinks = false;
            dwFlagsAndAttributes |= FILE_FLAG_OPEN_REPARSE_POINT;
        }

        // permission check
        if (pathToCheck != null) {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                if (flags.read)
                    sm.checkRead(pathToCheck);
                if (flags.write)
                    sm.checkWrite(pathToCheck);
                if (flags.deleteOnClose)
                    sm.checkDelete(pathToCheck);
            }
        }

        // open file
        long handle = CreateFile(pathForWindows,
                                 dwDesiredAccess,
                                 dwShareMode,
                                 pSecurityDescriptor,
                                 dwCreationDisposition,
                                 dwFlagsAndAttributes);

        // make sure this isn't a symbolic link.
        if (!okayToFollowLinks) {
            try {
                if (WindowsFileAttributes.readAttributes(handle).isSymbolicLink())
                    throw new WindowsException("File is symbolic link");
            } catch (WindowsException x) {
                CloseHandle(handle);
                throw x;
            }
        }

        // truncate file (for CREATE + TRUNCATE_EXISTING case)
        if (truncateAfterOpen) {
            try {
                SetEndOfFile(handle);
            } catch (WindowsException x) {
                CloseHandle(handle);
                throw x;
            }
        }

        // make the file sparse if needed
        if (dwCreationDisposition == CREATE_NEW && flags.sparse) {
            try {
                DeviceIoControlSetSparse(handle);
            } catch (WindowsException x) {
                // ignore as sparse option is hint
            }
        }

        // create FileDescriptor and return
        FileDescriptor fdObj = new FileDescriptor();
        fdAccess.setHandle(fdObj, handle);
        return fdObj;
    }
}