src/main/java/com/google/devtools/build/lib/vfs/UnixFileSystem.java - bazel - Git at Google

 // Copyright 2014 Google Inc. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //    http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 package com.google.devtools.build.lib.vfs;

 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
 import com.google.devtools.build.lib.profiler.Profiler;
 import com.google.devtools.build.lib.profiler.ProfilerTask;
 import com.google.devtools.build.lib.unix.ErrnoFileStatus;
 import com.google.devtools.build.lib.unix.FilesystemUtils;
 import com.google.devtools.build.lib.unix.FilesystemUtils.Dirents;
 import com.google.devtools.build.lib.unix.FilesystemUtils.ReadTypes;

 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;

 /**
  * This class implements the FileSystem interface using direct calls to the
  * UNIX filesystem.
  */
 // Not final only for testing.
 @ThreadSafe
 public class UnixFileSystem extends AbstractFileSystem {

   public static final UnixFileSystem INSTANCE = new UnixFileSystem();
   /**
    * Eager implementation of FileStatus for file systems that have an atomic
    * stat(2) syscall. A proxy for {@link com.google.devtools.build.lib.unix.FileStatus}.
    * Note that isFile and getLastModifiedTime have slightly different meanings
    * between UNIX and VFS.
    */
   @VisibleForTesting
   protected static class UnixFileStatus implements FileStatus {

     private final com.google.devtools.build.lib.unix.FileStatus status;

     UnixFileStatus(com.google.devtools.build.lib.unix.FileStatus status) {
       this.status = status;
     }

     @Override
     public boolean isFile() { return !isDirectory() && !isSymbolicLink(); }

     @Override
     public boolean isDirectory() { return status.isDirectory(); }

     @Override
     public boolean isSymbolicLink() { return status.isSymbolicLink(); }

     @Override
     public long getSize() { return status.getSize(); }

     @Override
     public long getLastModifiedTime() {
       return (status.getLastModifiedTime() * 1000)
           + (status.getFractionalLastModifiedTime() / 1000000);
     }

     @Override
     public long getLastChangeTime() {
       return (status.getLastChangeTime() * 1000)
           + (status.getFractionalLastChangeTime() / 1000000);
     }

     @Override
     public long getNodeId() {
       // Note that we may want to include more information in this id number going forward,
       // especially the device number.
       return status.getInodeNumber();
     }

     int getPermissions() { return status.getPermissions(); }

     @Override
     public String toString() { return status.toString(); }
   }

   @Override
   protected Collection<Path> getDirectoryEntries(Path path) throws IOException {
     String name = path.getPathString();
     String[] entries;
     long startTime = Profiler.nanoTimeMaybe();
     try {
       entries = FilesystemUtils.readdir(name);
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_DIR, name);
     }
     Collection<Path> result = new ArrayList<>(entries.length);
     for (String entry : entries) {
       result.add(path.getChild(entry));
     }
     return result;
   }

   @Override
   protected PathFragment resolveOneLink(Path path) throws IOException {
     // Beware, this seemingly simple code belies the complex specification of
     // FileSystem.resolveOneLink().
     return stat(path, false).isSymbolicLink()
         ? readSymbolicLink(path)
         : null;
   }

   /**
    * Converts from {@link com.google.devtools.build.lib.unix.FilesystemUtils.Dirents.Type} to
    * {@link com.google.devtools.build.lib.vfs.Dirent.Type}.
    */
   private static Dirent.Type convertToDirentType(Dirents.Type type) {
     switch (type) {
       case FILE:
         return Dirent.Type.FILE;
       case DIRECTORY:
         return Dirent.Type.DIRECTORY;
       case SYMLINK:
         return Dirent.Type.SYMLINK;
       case UNKNOWN:
         return Dirent.Type.UNKNOWN;
       default:
         throw new IllegalArgumentException("Unknown type " + type);
     }
   }

   @Override
   protected Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
     String name = path.getPathString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       Dirents unixDirents = FilesystemUtils.readdir(name,
           followSymlinks ? ReadTypes.FOLLOW : ReadTypes.NOFOLLOW);
       Preconditions.checkState(unixDirents.hasTypes());
       List<Dirent> dirents = Lists.newArrayListWithCapacity(unixDirents.size());
       for (int i = 0; i < unixDirents.size(); i++) {
         dirents.add(new Dirent(unixDirents.getName(i),
             convertToDirentType(unixDirents.getType(i))));
       }
       return dirents;
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_DIR, name);
     }
   }

   @Override
   protected FileStatus stat(Path path, boolean followSymlinks) throws IOException {
     return statInternal(path, followSymlinks);
   }

   @VisibleForTesting
   protected UnixFileStatus statInternal(Path path, boolean followSymlinks) throws IOException {
     String name = path.getPathString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       return new UnixFileStatus(followSymlinks
                                       ? FilesystemUtils.stat(name)
                                       : FilesystemUtils.lstat(name));
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_STAT, name);
     }
   }

   // Like stat(), but returns null instead of throwing.
   // This is a performance optimization in the case where clients
   // catch and don't re-throw.
   @Override
   protected FileStatus statNullable(Path path, boolean followSymlinks) {
     String name = path.getPathString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       ErrnoFileStatus stat = followSymlinks
           ? FilesystemUtils.errnoStat(name)
           : FilesystemUtils.errnoLstat(name);
       return stat.hasError() ? null : new UnixFileStatus(stat);
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_STAT, name);
     }
   }

   @Override
   protected boolean exists(Path path, boolean followSymlinks) {
     return statNullable(path, followSymlinks) != null;
   }

   /**
    * Return true iff the {@code stat} of {@code path} resulted in an {@code ENOENT}
    * or {@code ENOTDIR} error.
    */
   @Override
   protected FileStatus statIfFound(Path path, boolean followSymlinks) throws IOException {
     String name = path.getPathString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       ErrnoFileStatus stat = followSymlinks
           ? FilesystemUtils.errnoStat(name)
           : FilesystemUtils.errnoLstat(name);
       if (!stat.hasError()) {
         return new UnixFileStatus(stat);
       }
       int errno = stat.getErrno();
       if (errno == ErrnoFileStatus.ENOENT || errno == ErrnoFileStatus.ENOTDIR) {
         return null;
       }
       // This should not return -- we are calling stat here just to throw the proper exception.
       // However, since there may be transient IO errors, we cannot guarantee that an exception will
       // be thrown.
       // TODO(bazel-team): Extract the exception-construction code and make it visible separately in
       // FilesystemUtils to avoid having to do a duplicate stat call.
       return stat(path, followSymlinks);
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_STAT, name);
     }
   }

   @Override
   protected boolean isDirectory(Path path, boolean followSymlinks) {
     FileStatus stat = statNullable(path, followSymlinks);
     return stat != null && stat.isDirectory();
   }

   @Override
   protected boolean isFile(Path path, boolean followSymlinks) {
     // Note, FileStatus.isFile means *regular* file whereas Path.isFile may
     // mean special file too, so we don't return FileStatus.isFile here.
     FileStatus status = statNullable(path, followSymlinks);
     return status != null && !(status.isSymbolicLink() || status.isDirectory());
   }

   @Override
   protected boolean isReadable(Path path) throws IOException {
     return (statInternal(path, true).getPermissions() & 0400) != 0;
   }

   @Override
   protected boolean isWritable(Path path) throws IOException {
     return (statInternal(path, true).getPermissions() & 0200) != 0;
   }

   @Override
   protected boolean isExecutable(Path path) throws IOException {
     return (statInternal(path, true).getPermissions() & 0100) != 0;
   }

   /**
    * Adds or remove the bits specified in "permissionBits" to the permission
    * mask of the file specified by {@code path}. If the argument {@code add} is
    * true, the specified permissions are added, otherwise they are removed.
    *
    * @throws IOException if there was an error writing the file's metadata
    */
   private void modifyPermissionBits(Path path, int permissionBits, boolean add)
     throws IOException {
     synchronized (path) {
       int oldMode = statInternal(path, true).getPermissions();
       int newMode = add ? (oldMode | permissionBits) : (oldMode & ~permissionBits);
       FilesystemUtils.chmod(path.toString(), newMode);
     }
   }

   @Override
   protected void setReadable(Path path, boolean readable) throws IOException {
     modifyPermissionBits(path, 0400, readable);
   }

   @Override
   protected void setWritable(Path path, boolean writable) throws IOException {
     modifyPermissionBits(path, 0200, writable);
   }

   @Override
   protected void setExecutable(Path path, boolean executable) throws IOException {
     modifyPermissionBits(path, 0111, executable);
   }

   @Override
   protected void chmod(Path path, int mode) throws IOException {
     synchronized (path) {
       FilesystemUtils.chmod(path.toString(), mode);
     }
   }

   @Override
   public boolean supportsModifications() {
     return true;
   }

   @Override
   public boolean supportsSymbolicLinks() {
     return true;
   }

   @Override
   protected boolean createDirectory(Path path) throws IOException {
     synchronized (path) {
       // Note: UNIX mkdir(2), FilesystemUtils.mkdir() and createDirectory all
       // have different ways of representing failure!
       if (FilesystemUtils.mkdir(path.toString(), 0777)) {
         return true; // successfully created
       }

       // false => EEXIST: something is already in the way (file/dir/symlink)
       if (isDirectory(path, false)) {
         return false; // directory already existed
       } else {
         throw new IOException(path + " (File exists)");
       }
     }
   }

   @Override
   protected void createSymbolicLink(Path linkPath, PathFragment targetFragment)
       throws IOException {
     synchronized (linkPath) {
       FilesystemUtils.symlink(targetFragment.toString(), linkPath.toString());
     }
   }

   @Override
   protected PathFragment readSymbolicLink(Path path) throws IOException {
     String name = path.toString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       return new PathFragment(FilesystemUtils.readlink(name));
     } catch (IOException e) {
       // EINVAL => not a symbolic link.  Anything else is a real error.
       throw e.getMessage().endsWith("(Invalid argument)") ? new NotASymlinkException(path) : e;
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_READLINK, name);
     }
   }

   @Override
   protected void renameTo(Path sourcePath, Path targetPath) throws IOException {
     synchronized (sourcePath) {
       FilesystemUtils.rename(sourcePath.toString(), targetPath.toString());
     }
   }

   @Override
   protected long getFileSize(Path path, boolean followSymlinks) throws IOException {
     return stat(path, followSymlinks).getSize();
   }

   @Override
   protected boolean delete(Path path) throws IOException {
     String name = path.toString();
     long startTime = Profiler.nanoTimeMaybe();
     synchronized (path) {
       try {
         return FilesystemUtils.remove(name);
       } finally {
         profiler.logSimpleTask(startTime, ProfilerTask.VFS_DELETE, name);
       }
     }
   }

   @Override
   protected long getLastModifiedTime(Path path, boolean followSymlinks) throws IOException {
     return stat(path, followSymlinks).getLastModifiedTime();
   }

   @Override
   protected boolean isSymbolicLink(Path path) {
     FileStatus stat = statNullable(path, false);
     return stat != null && stat.isSymbolicLink();
   }

   @Override
   protected void setLastModifiedTime(Path path, long newTime) throws IOException {
     synchronized (path) {
       if (newTime == -1L) { // "now"
         FilesystemUtils.utime(path.toString(), true, 0, 0);
       } else {
         // newTime > MAX_INT => -ve unixTime
         int unixTime = (int) (newTime / 1000);
         FilesystemUtils.utime(path.toString(), false, unixTime, unixTime);
       }
     }
   }

   @Override
   protected byte[] getxattr(Path path, String name) throws IOException {
     String pathName = path.toString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       return FilesystemUtils.getxattr(pathName, name);
     } catch (UnsupportedOperationException e) {
       // getxattr() syscall is not supported by the underlying filesystem (it returned ENOTSUP).
       // Per method contract, treat this as ENODATA.
       return null;
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_XATTR, pathName);
     }
   }

   @Override
   protected byte[] getMD5Digest(Path path) throws IOException {
     String name = path.toString();
     long startTime = Profiler.nanoTimeMaybe();
     try {
       return FilesystemUtils.md5sum(name).asBytes();
     } finally {
       profiler.logSimpleTask(startTime, ProfilerTask.VFS_MD5, name);
     }
   }
 }
	// Copyright 2014 Google Inc. All rights reserved.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.
	package com.google.devtools.build.lib.vfs;

	import com.google.common.annotations.VisibleForTesting;
	import com.google.common.base.Preconditions;
	import com.google.common.collect.Lists;
	import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
	import com.google.devtools.build.lib.profiler.Profiler;
	import com.google.devtools.build.lib.profiler.ProfilerTask;
	import com.google.devtools.build.lib.unix.ErrnoFileStatus;
	import com.google.devtools.build.lib.unix.FilesystemUtils;
	import com.google.devtools.build.lib.unix.FilesystemUtils.Dirents;
	import com.google.devtools.build.lib.unix.FilesystemUtils.ReadTypes;

	import java.io.IOException;
	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.List;

	/**
	* This class implements the FileSystem interface using direct calls to the
	* UNIX filesystem.
	*/
	// Not final only for testing.
	@ThreadSafe
	public class UnixFileSystem extends AbstractFileSystem {

	public static final UnixFileSystem INSTANCE = new UnixFileSystem();
	/**
	* Eager implementation of FileStatus for file systems that have an atomic
	* stat(2) syscall. A proxy for {@link com.google.devtools.build.lib.unix.FileStatus}.
	* Note that isFile and getLastModifiedTime have slightly different meanings
	* between UNIX and VFS.
	*/
	@VisibleForTesting
	protected static class UnixFileStatus implements FileStatus {

	private final com.google.devtools.build.lib.unix.FileStatus status;

	UnixFileStatus(com.google.devtools.build.lib.unix.FileStatus status) {
	this.status = status;
	}

	@Override
	public boolean isFile() { return !isDirectory() && !isSymbolicLink(); }

	@Override
	public boolean isDirectory() { return status.isDirectory(); }

	@Override
	public boolean isSymbolicLink() { return status.isSymbolicLink(); }

	@Override
	public long getSize() { return status.getSize(); }

	@Override
	public long getLastModifiedTime() {
	return (status.getLastModifiedTime() * 1000)
	+ (status.getFractionalLastModifiedTime() / 1000000);
	}

	@Override
	public long getLastChangeTime() {
	return (status.getLastChangeTime() * 1000)
	+ (status.getFractionalLastChangeTime() / 1000000);
	}

	@Override
	public long getNodeId() {
	// Note that we may want to include more information in this id number going forward,
	// especially the device number.
	return status.getInodeNumber();
	}

	int getPermissions() { return status.getPermissions(); }

	@Override
	public String toString() { return status.toString(); }
	}

	@Override
	protected Collection<Path> getDirectoryEntries(Path path) throws IOException {
	String name = path.getPathString();
	String[] entries;
	long startTime = Profiler.nanoTimeMaybe();
	try {
	entries = FilesystemUtils.readdir(name);
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_DIR, name);
	}
	Collection<Path> result = new ArrayList<>(entries.length);
	for (String entry : entries) {
	result.add(path.getChild(entry));
	}
	return result;
	}

	@Override
	protected PathFragment resolveOneLink(Path path) throws IOException {
	// Beware, this seemingly simple code belies the complex specification of
	// FileSystem.resolveOneLink().
	return stat(path, false).isSymbolicLink()
	? readSymbolicLink(path)
	: null;
	}

	/**
	* Converts from {@link com.google.devtools.build.lib.unix.FilesystemUtils.Dirents.Type} to
	* {@link com.google.devtools.build.lib.vfs.Dirent.Type}.
	*/
	private static Dirent.Type convertToDirentType(Dirents.Type type) {
	switch (type) {
	case FILE:
	return Dirent.Type.FILE;
	case DIRECTORY:
	return Dirent.Type.DIRECTORY;
	case SYMLINK:
	return Dirent.Type.SYMLINK;
	case UNKNOWN:
	return Dirent.Type.UNKNOWN;
	default:
	throw new IllegalArgumentException("Unknown type " + type);
	}
	}

	@Override
	protected Collection<Dirent> readdir(Path path, boolean followSymlinks) throws IOException {
	String name = path.getPathString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	Dirents unixDirents = FilesystemUtils.readdir(name,
	followSymlinks ? ReadTypes.FOLLOW : ReadTypes.NOFOLLOW);
	Preconditions.checkState(unixDirents.hasTypes());
	List<Dirent> dirents = Lists.newArrayListWithCapacity(unixDirents.size());
	for (int i = 0; i < unixDirents.size(); i++) {
	dirents.add(new Dirent(unixDirents.getName(i),
	convertToDirentType(unixDirents.getType(i))));
	}
	return dirents;
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_DIR, name);
	}
	}

	@Override
	protected FileStatus stat(Path path, boolean followSymlinks) throws IOException {
	return statInternal(path, followSymlinks);
	}

	@VisibleForTesting
	protected UnixFileStatus statInternal(Path path, boolean followSymlinks) throws IOException {
	String name = path.getPathString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	return new UnixFileStatus(followSymlinks
	? FilesystemUtils.stat(name)
	: FilesystemUtils.lstat(name));
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_STAT, name);
	}
	}

	// Like stat(), but returns null instead of throwing.
	// This is a performance optimization in the case where clients
	// catch and don't re-throw.
	@Override
	protected FileStatus statNullable(Path path, boolean followSymlinks) {
	String name = path.getPathString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	ErrnoFileStatus stat = followSymlinks
	? FilesystemUtils.errnoStat(name)
	: FilesystemUtils.errnoLstat(name);
	return stat.hasError() ? null : new UnixFileStatus(stat);
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_STAT, name);
	}
	}

	@Override
	protected boolean exists(Path path, boolean followSymlinks) {
	return statNullable(path, followSymlinks) != null;
	}

	/**
	* Return true iff the {@code stat} of {@code path} resulted in an {@code ENOENT}
	* or {@code ENOTDIR} error.
	*/
	@Override
	protected FileStatus statIfFound(Path path, boolean followSymlinks) throws IOException {
	String name = path.getPathString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	ErrnoFileStatus stat = followSymlinks
	? FilesystemUtils.errnoStat(name)
	: FilesystemUtils.errnoLstat(name);
	if (!stat.hasError()) {
	return new UnixFileStatus(stat);
	}
	int errno = stat.getErrno();
	if (errno == ErrnoFileStatus.ENOENT \|\| errno == ErrnoFileStatus.ENOTDIR) {
	return null;
	}
	// This should not return -- we are calling stat here just to throw the proper exception.
	// However, since there may be transient IO errors, we cannot guarantee that an exception will
	// be thrown.
	// TODO(bazel-team): Extract the exception-construction code and make it visible separately in
	// FilesystemUtils to avoid having to do a duplicate stat call.
	return stat(path, followSymlinks);
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_STAT, name);
	}
	}

	@Override
	protected boolean isDirectory(Path path, boolean followSymlinks) {
	FileStatus stat = statNullable(path, followSymlinks);
	return stat != null && stat.isDirectory();
	}

	@Override
	protected boolean isFile(Path path, boolean followSymlinks) {
	// Note, FileStatus.isFile means regular file whereas Path.isFile may
	// mean special file too, so we don't return FileStatus.isFile here.
	FileStatus status = statNullable(path, followSymlinks);
	return status != null && !(status.isSymbolicLink() \|\| status.isDirectory());
	}

	@Override
	protected boolean isReadable(Path path) throws IOException {
	return (statInternal(path, true).getPermissions() & 0400) != 0;
	}

	@Override
	protected boolean isWritable(Path path) throws IOException {
	return (statInternal(path, true).getPermissions() & 0200) != 0;
	}

	@Override
	protected boolean isExecutable(Path path) throws IOException {
	return (statInternal(path, true).getPermissions() & 0100) != 0;
	}

	/**
	* Adds or remove the bits specified in "permissionBits" to the permission
	* mask of the file specified by {@code path}. If the argument {@code add} is
	* true, the specified permissions are added, otherwise they are removed.
	*
	* @throws IOException if there was an error writing the file's metadata
	*/
	private void modifyPermissionBits(Path path, int permissionBits, boolean add)
	throws IOException {
	synchronized (path) {
	int oldMode = statInternal(path, true).getPermissions();
	int newMode = add ? (oldMode \| permissionBits) : (oldMode & ~permissionBits);
	FilesystemUtils.chmod(path.toString(), newMode);
	}
	}

	@Override
	protected void setReadable(Path path, boolean readable) throws IOException {
	modifyPermissionBits(path, 0400, readable);
	}

	@Override
	protected void setWritable(Path path, boolean writable) throws IOException {
	modifyPermissionBits(path, 0200, writable);
	}

	@Override
	protected void setExecutable(Path path, boolean executable) throws IOException {
	modifyPermissionBits(path, 0111, executable);
	}

	@Override
	protected void chmod(Path path, int mode) throws IOException {
	synchronized (path) {
	FilesystemUtils.chmod(path.toString(), mode);
	}
	}

	@Override
	public boolean supportsModifications() {
	return true;
	}

	@Override
	public boolean supportsSymbolicLinks() {
	return true;
	}

	@Override
	protected boolean createDirectory(Path path) throws IOException {
	synchronized (path) {
	// Note: UNIX mkdir(2), FilesystemUtils.mkdir() and createDirectory all
	// have different ways of representing failure!
	if (FilesystemUtils.mkdir(path.toString(), 0777)) {
	return true; // successfully created
	}

	// false => EEXIST: something is already in the way (file/dir/symlink)
	if (isDirectory(path, false)) {
	return false; // directory already existed
	} else {
	throw new IOException(path + " (File exists)");
	}
	}
	}

	@Override
	protected void createSymbolicLink(Path linkPath, PathFragment targetFragment)
	throws IOException {
	synchronized (linkPath) {
	FilesystemUtils.symlink(targetFragment.toString(), linkPath.toString());
	}
	}

	@Override
	protected PathFragment readSymbolicLink(Path path) throws IOException {
	String name = path.toString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	return new PathFragment(FilesystemUtils.readlink(name));
	} catch (IOException e) {
	// EINVAL => not a symbolic link. Anything else is a real error.
	throw e.getMessage().endsWith("(Invalid argument)") ? new NotASymlinkException(path) : e;
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_READLINK, name);
	}
	}

	@Override
	protected void renameTo(Path sourcePath, Path targetPath) throws IOException {
	synchronized (sourcePath) {
	FilesystemUtils.rename(sourcePath.toString(), targetPath.toString());
	}
	}

	@Override
	protected long getFileSize(Path path, boolean followSymlinks) throws IOException {
	return stat(path, followSymlinks).getSize();
	}

	@Override
	protected boolean delete(Path path) throws IOException {
	String name = path.toString();
	long startTime = Profiler.nanoTimeMaybe();
	synchronized (path) {
	try {
	return FilesystemUtils.remove(name);
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_DELETE, name);
	}
	}
	}

	@Override
	protected long getLastModifiedTime(Path path, boolean followSymlinks) throws IOException {
	return stat(path, followSymlinks).getLastModifiedTime();
	}

	@Override
	protected boolean isSymbolicLink(Path path) {
	FileStatus stat = statNullable(path, false);
	return stat != null && stat.isSymbolicLink();
	}

	@Override
	protected void setLastModifiedTime(Path path, long newTime) throws IOException {
	synchronized (path) {
	if (newTime == -1L) { // "now"
	FilesystemUtils.utime(path.toString(), true, 0, 0);
	} else {
	// newTime > MAX_INT => -ve unixTime
	int unixTime = (int) (newTime / 1000);
	FilesystemUtils.utime(path.toString(), false, unixTime, unixTime);
	}
	}
	}

	@Override
	protected byte[] getxattr(Path path, String name) throws IOException {
	String pathName = path.toString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	return FilesystemUtils.getxattr(pathName, name);
	} catch (UnsupportedOperationException e) {
	// getxattr() syscall is not supported by the underlying filesystem (it returned ENOTSUP).
	// Per method contract, treat this as ENODATA.
	return null;
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_XATTR, pathName);
	}
	}

	@Override
	protected byte[] getMD5Digest(Path path) throws IOException {
	String name = path.toString();
	long startTime = Profiler.nanoTimeMaybe();
	try {
	return FilesystemUtils.md5sum(name).asBytes();
	} finally {
	profiler.logSimpleTask(startTime, ProfilerTask.VFS_MD5, name);
	}
	}
	}