/*
    * Copyright (C) 2010, Google Inc.
    * Copyright (C) 2010, Matthias Sohn <matthias.sohn@sap.com>
    * Copyright (C) 2010, Jens Baumgart <jens.baumgart@sap.com> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
   * SPDX-License-Identifier: BSD-3-Clause
   */
  
  package org.eclipse.jgit.util;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.nio.file.AtomicMoveNotSupportedException;
  import java.nio.file.CopyOption;
  import java.nio.file.Files;
  import java.nio.file.InvalidPathException;
  import java.nio.file.LinkOption;
  import java.nio.file.NoSuchFileException;
  import java.nio.file.Path;
  import java.nio.file.StandardCopyOption;
  import java.nio.file.StandardOpenOption;
  import java.nio.file.attribute.BasicFileAttributeView;
  import java.nio.file.attribute.BasicFileAttributes;
  import java.nio.file.attribute.FileTime;
  import java.nio.file.attribute.PosixFileAttributeView;
  import java.nio.file.attribute.PosixFileAttributes;
  import java.nio.file.attribute.PosixFilePermission;
  import java.text.MessageFormat;
  import java.text.Normalizer;
  import java.text.Normalizer.Form;
  import java.time.Instant;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Locale;
  import java.util.Random;
  import java.util.regex.Pattern;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.util.FS.Attributes;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * File Utilities
   */
  public class FileUtils {
  	private static final Logger LOG = LoggerFactory.getLogger(FileUtils.class);
  
  	private static final Random RNG = new Random();
  
  	/**
  	 * Option to delete given {@code File}
  	 */
  	public static final int NONE = 0;
  
  	/**
  	 * Option to recursively delete given {@code File}
  	 */
  	public static final int RECURSIVE = 1;
  
  	/**
  	 * Option to retry deletion if not successful
  	 */
  	public static final int RETRY = 2;
  
  	/**
  	 * Option to skip deletion if file doesn't exist
  	 */
  	public static final int SKIP_MISSING = 4;
  
  	/**
  	 * Option not to throw exceptions when a deletion finally doesn't succeed.
  	 * @since 2.0
  	 */
  	public static final int IGNORE_ERRORS = 8;
  
  	/**
  	 * Option to only delete empty directories. This option can be combined with
  	 * {@link #RECURSIVE}
  	 *
  	 * @since 3.0
  	 */
  	public static final int EMPTY_DIRECTORIES_ONLY = 16;
  
  	/**
  	 * Safe conversion from {@link java.io.File} to {@link java.nio.file.Path}.
  	 *
  	 * @param f
  	 *            {@code File} to be converted to {@code Path}
  	 * @return the path represented by the file
 	 * @throws java.io.IOException
 	 *             in case the path represented by the file is not valid (
 	 *             {@link java.nio.file.InvalidPathException})
 	 * @since 4.10
 	 */
 	public static Path toPath(File f) throws IOException {
 		try {
 			return f.toPath();
 		} catch (InvalidPathException ex) {
 			throw new IOException(ex);
 		}
 	}
 
 	/**
 	 * Delete file or empty folder
 	 *
 	 * @param f
 	 *            {@code File} to be deleted
 	 * @throws java.io.IOException
 	 *             if deletion of {@code f} fails. This may occur if {@code f}
 	 *             didn't exist when the method was called. This can therefore
 	 *             cause java.io.IOExceptions during race conditions when
 	 *             multiple concurrent threads all try to delete the same file.
 	 */
 	public static void delete(File f) throws IOException {
 		delete(f, NONE);
 	}
 
 	/**
 	 * Delete file or folder
 	 *
 	 * @param f
 	 *            {@code File} to be deleted
 	 * @param options
 	 *            deletion options, {@code RECURSIVE} for recursive deletion of
 	 *            a subtree, {@code RETRY} to retry when deletion failed.
 	 *            Retrying may help if the underlying file system doesn't allow
 	 *            deletion of files being read by another thread.
 	 * @throws java.io.IOException
 	 *             if deletion of {@code f} fails. This may occur if {@code f}
 	 *             didn't exist when the method was called. This can therefore
 	 *             cause java.io.IOExceptions during race conditions when
 	 *             multiple concurrent threads all try to delete the same file.
 	 *             This exception is not thrown when IGNORE_ERRORS is set.
 	 */
 	public static void delete(File f, int options) throws IOException {
 		FS fs = FS.DETECTED;
 		if ((options & SKIP_MISSING) != 0 && !fs.exists(f))
 			return;
 
 		if ((options & RECURSIVE) != 0 && fs.isDirectory(f)) {
 			final File[] items = f.listFiles();
 			if (items != null) {
 				List<File> files = new ArrayList<>();
 				List<File> dirs = new ArrayList<>();
 				for (File c : items)
 					if (c.isFile())
 						files.add(c);
 					else
 						dirs.add(c);
 				// Try to delete files first, otherwise options
 				// EMPTY_DIRECTORIES_ONLY|RECURSIVE will delete empty
 				// directories before aborting, depending on order.
 				for (File file : files)
 					delete(file, options);
 				for (File d : dirs)
 					delete(d, options);
 			}
 		}
 
 		boolean delete = false;
 		if ((options & EMPTY_DIRECTORIES_ONLY) != 0) {
 			if (f.isDirectory()) {
 				delete = true;
 			} else if ((options & IGNORE_ERRORS) == 0) {
 				throw new IOException(MessageFormat.format(
 						JGitText.get().deleteFileFailed, f.getAbsolutePath()));
 			}
 		} else {
 			delete = true;
 		}
 
 		if (delete) {
 			Throwable t = null;
 			Path p = f.toPath();
 			try {
 				Files.delete(p);
 				return;
 			} catch (FileNotFoundException e) {
 				if ((options & (SKIP_MISSING | IGNORE_ERRORS)) == 0) {
 					throw new IOException(MessageFormat.format(
 							JGitText.get().deleteFileFailed,
 							f.getAbsolutePath()), e);
 				}
 				return;
 			} catch (IOException e) {
 				t = e;
 			}
 			if ((options & RETRY) != 0) {
 				for (int i = 1; i < 10; i++) {
 					try {
 						Thread.sleep(100);
 					} catch (InterruptedException ex) {
 						// ignore
 					}
 					try {
 						Files.deleteIfExists(p);
 						return;
 					} catch (IOException e) {
 						t = e;
 					}
 				}
 			}
 			if ((options & IGNORE_ERRORS) == 0) {
 				throw new IOException(MessageFormat.format(
 						JGitText.get().deleteFileFailed, f.getAbsolutePath()),
 						t);
 			}
 		}
 	}
 
 	/**
 	 * Rename a file or folder. If the rename fails and if we are running on a
 	 * filesystem where it makes sense to repeat a failing rename then repeat
 	 * the rename operation up to 9 times with 100ms sleep time between two
 	 * calls. Furthermore if the destination exists and is directory hierarchy
 	 * with only directories in it, the whole directory hierarchy will be
 	 * deleted. If the target represents a non-empty directory structure, empty
 	 * subdirectories within that structure may or may not be deleted even if
 	 * the method fails. Furthermore if the destination exists and is a file
 	 * then the file will be deleted and then the rename is retried.
 	 * <p>
 	 * This operation is <em>not</em> atomic.
 	 *
 	 * @see FS#retryFailedLockFileCommit()
 	 * @param src
 	 *            the old {@code File}
 	 * @param dst
 	 *            the new {@code File}
 	 * @throws java.io.IOException
 	 *             if the rename has failed
 	 * @since 3.0
 	 */
 	public static void rename(File src, File dst)
 			throws IOException {
 		rename(src, dst, StandardCopyOption.REPLACE_EXISTING);
 	}
 
 	/**
 	 * Rename a file or folder using the passed
 	 * {@link java.nio.file.CopyOption}s. If the rename fails and if we are
 	 * running on a filesystem where it makes sense to repeat a failing rename
 	 * then repeat the rename operation up to 9 times with 100ms sleep time
 	 * between two calls. Furthermore if the destination exists and is a
 	 * directory hierarchy with only directories in it, the whole directory
 	 * hierarchy will be deleted. If the target represents a non-empty directory
 	 * structure, empty subdirectories within that structure may or may not be
 	 * deleted even if the method fails. Furthermore if the destination exists
 	 * and is a file then the file will be replaced if
 	 * {@link java.nio.file.StandardCopyOption#REPLACE_EXISTING} has been set.
 	 * If {@link java.nio.file.StandardCopyOption#ATOMIC_MOVE} has been set the
 	 * rename will be done atomically or fail with an
 	 * {@link java.nio.file.AtomicMoveNotSupportedException}
 	 *
 	 * @param src
 	 *            the old file
 	 * @param dst
 	 *            the new file
 	 * @param options
 	 *            options to pass to
 	 *            {@link java.nio.file.Files#move(java.nio.file.Path, java.nio.file.Path, CopyOption...)}
 	 * @throws java.nio.file.AtomicMoveNotSupportedException
 	 *             if file cannot be moved as an atomic file system operation
 	 * @throws java.io.IOException
 	 * @since 4.1
 	 */
 	public static void rename(final File src, final File dst,
 			CopyOption... options)
 					throws AtomicMoveNotSupportedException, IOException {
 		int attempts = FS.DETECTED.retryFailedLockFileCommit() ? 10 : 1;
 		while (--attempts >= 0) {
 			try {
 				Files.move(toPath(src), toPath(dst), options);
 				return;
 			} catch (AtomicMoveNotSupportedException e) {
 				throw e;
 			} catch (IOException e) {
 				try {
 					if (!dst.delete()) {
 						delete(dst, EMPTY_DIRECTORIES_ONLY | RECURSIVE);
 					}
 					// On *nix there is no try, you do or do not
 					Files.move(toPath(src), toPath(dst), options);
 					return;
 				} catch (IOException e2) {
 					// ignore and continue retry
 				}
 			}
 			try {
 				Thread.sleep(100);
 			} catch (InterruptedException e) {
 				throw new IOException(
 						MessageFormat.format(JGitText.get().renameFileFailed,
 								src.getAbsolutePath(), dst.getAbsolutePath()),
 						e);
 			}
 		}
 		throw new IOException(
 				MessageFormat.format(JGitText.get().renameFileFailed,
 						src.getAbsolutePath(), dst.getAbsolutePath()));
 	}
 
 	/**
 	 * Creates the directory named by this abstract pathname.
 	 *
 	 * @param d
 	 *            directory to be created
 	 * @throws java.io.IOException
 	 *             if creation of {@code d} fails. This may occur if {@code d}
 	 *             did exist when the method was called. This can therefore
 	 *             cause java.io.IOExceptions during race conditions when
 	 *             multiple concurrent threads all try to create the same
 	 *             directory.
 	 */
 	public static void mkdir(File d)
 			throws IOException {
 		mkdir(d, false);
 	}
 
 	/**
 	 * Creates the directory named by this abstract pathname.
 	 *
 	 * @param d
 	 *            directory to be created
 	 * @param skipExisting
 	 *            if {@code true} skip creation of the given directory if it
 	 *            already exists in the file system
 	 * @throws java.io.IOException
 	 *             if creation of {@code d} fails. This may occur if {@code d}
 	 *             did exist when the method was called. This can therefore
 	 *             cause java.io.IOExceptions during race conditions when
 	 *             multiple concurrent threads all try to create the same
 	 *             directory.
 	 */
 	public static void mkdir(File d, boolean skipExisting)
 			throws IOException {
 		if (!d.mkdir()) {
 			if (skipExisting && d.isDirectory())
 				return;
 			throw new IOException(MessageFormat.format(
 					JGitText.get().mkDirFailed, d.getAbsolutePath()));
 		}
 	}
 
 	/**
 	 * Creates the directory named by this abstract pathname, including any
 	 * necessary but nonexistent parent directories. Note that if this operation
 	 * fails it may have succeeded in creating some of the necessary parent
 	 * directories.
 	 *
 	 * @param d
 	 *            directory to be created
 	 * @throws java.io.IOException
 	 *             if creation of {@code d} fails. This may occur if {@code d}
 	 *             did exist when the method was called. This can therefore
 	 *             cause java.io.IOExceptions during race conditions when
 	 *             multiple concurrent threads all try to create the same
 	 *             directory.
 	 */
 	public static void mkdirs(File d) throws IOException {
 		mkdirs(d, false);
 	}
 
 	/**
 	 * Creates the directory named by this abstract pathname, including any
 	 * necessary but nonexistent parent directories. Note that if this operation
 	 * fails it may have succeeded in creating some of the necessary parent
 	 * directories.
 	 *
 	 * @param d
 	 *            directory to be created
 	 * @param skipExisting
 	 *            if {@code true} skip creation of the given directory if it
 	 *            already exists in the file system
 	 * @throws java.io.IOException
 	 *             if creation of {@code d} fails. This may occur if {@code d}
 	 *             did exist when the method was called. This can therefore
 	 *             cause java.io.IOExceptions during race conditions when
 	 *             multiple concurrent threads all try to create the same
 	 *             directory.
 	 */
 	public static void mkdirs(File d, boolean skipExisting)
 			throws IOException {
 		if (!d.mkdirs()) {
 			if (skipExisting && d.isDirectory())
 				return;
 			throw new IOException(MessageFormat.format(
 					JGitText.get().mkDirsFailed, d.getAbsolutePath()));
 		}
 	}
 
 	/**
 	 * Atomically creates a new, empty file named by this abstract pathname if
 	 * and only if a file with this name does not yet exist. The check for the
 	 * existence of the file and the creation of the file if it does not exist
 	 * are a single operation that is atomic with respect to all other
 	 * filesystem activities that might affect the file.
 	 * <p>
 	 * Note: this method should not be used for file-locking, as the resulting
 	 * protocol cannot be made to work reliably. The
 	 * {@link java.nio.channels.FileLock} facility should be used instead.
 	 *
 	 * @param f
 	 *            the file to be created
 	 * @throws java.io.IOException
 	 *             if the named file already exists or if an I/O error occurred
 	 */
 	public static void createNewFile(File f) throws IOException {
 		if (!f.createNewFile())
 			throw new IOException(MessageFormat.format(
 					JGitText.get().createNewFileFailed, f));
 	}
 
 	/**
 	 * Create a symbolic link
 	 *
 	 * @param path
 	 *            the path of the symbolic link to create
 	 * @param target
 	 *            the target of the symbolic link
 	 * @return the path to the symbolic link
 	 * @throws java.io.IOException
 	 * @since 4.2
 	 */
 	public static Path createSymLink(File path, String target)
 			throws IOException {
 		Path nioPath = toPath(path);
 		if (Files.exists(nioPath, LinkOption.NOFOLLOW_LINKS)) {
 			BasicFileAttributes attrs = Files.readAttributes(nioPath,
 					BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
 			if (attrs.isRegularFile() || attrs.isSymbolicLink()) {
 				delete(path);
 			} else {
 				delete(path, EMPTY_DIRECTORIES_ONLY | RECURSIVE);
 			}
 		}
 		if (SystemReader.getInstance().isWindows()) {
 			target = target.replace('/', '\\');
 		}
 		Path nioTarget = toPath(new File(target));
 		return Files.createSymbolicLink(nioPath, nioTarget);
 	}
 
 	/**
 	 * Read target path of the symlink.
 	 *
 	 * @param path
 	 *            a {@link java.io.File} object.
 	 * @return target path of the symlink, or null if it is not a symbolic link
 	 * @throws java.io.IOException
 	 * @since 3.0
 	 */
 	public static String readSymLink(File path) throws IOException {
 		Path nioPath = toPath(path);
 		Path target = Files.readSymbolicLink(nioPath);
 		String targetString = target.toString();
 		if (SystemReader.getInstance().isWindows()) {
 			targetString = targetString.replace('\\', '/');
 		} else if (SystemReader.getInstance().isMacOS()) {
 			targetString = Normalizer.normalize(targetString, Form.NFC);
 		}
 		return targetString;
 	}
 
 	/**
 	 * Create a temporary directory.
 	 *
 	 * @param prefix
 	 *            prefix string
 	 * @param suffix
 	 *            suffix string
 	 * @param dir
 	 *            The parent dir, can be null to use system default temp dir.
 	 * @return the temp dir created.
 	 * @throws java.io.IOException
 	 * @since 3.4
 	 */
 	public static File createTempDir(String prefix, String suffix, File dir)
 			throws IOException {
 		final int RETRIES = 1; // When something bad happens, retry once.
 		for (int i = 0; i < RETRIES; i++) {
 			File tmp = File.createTempFile(prefix, suffix, dir);
 			if (!tmp.delete())
 				continue;
 			if (!tmp.mkdir())
 				continue;
 			return tmp;
 		}
 		throw new IOException(JGitText.get().cannotCreateTempDir);
 	}
 
 	/**
 	 * Expresses <code>other</code> as a relative file path from
 	 * <code>base</code>. File-separator and case sensitivity are based on the
 	 * current file system.
 	 *
 	 * See also
 	 * {@link org.eclipse.jgit.util.FileUtils#relativizePath(String, String, String, boolean)}.
 	 *
 	 * @param base
 	 *            Base path
 	 * @param other
 	 *            Destination path
 	 * @return Relative path from <code>base</code> to <code>other</code>
 	 * @since 4.8
 	 */
 	public static String relativizeNativePath(String base, String other) {
 		return FS.DETECTED.relativize(base, other);
 	}
 
 	/**
 	 * Expresses <code>other</code> as a relative file path from
 	 * <code>base</code>. File-separator and case sensitivity are based on Git's
 	 * internal representation of files (which matches Unix).
 	 *
 	 * See also
 	 * {@link org.eclipse.jgit.util.FileUtils#relativizePath(String, String, String, boolean)}.
 	 *
 	 * @param base
 	 *            Base path
 	 * @param other
 	 *            Destination path
 	 * @return Relative path from <code>base</code> to <code>other</code>
 	 * @since 4.8
 	 */
 	public static String relativizeGitPath(String base, String other) {
 		return relativizePath(base, other, "/", false); //$NON-NLS-1$
 	}
 
 
 	/**
 	 * Expresses <code>other</code> as a relative file path from <code>base</code>
 	 * <p>
 	 * For example, if called with the two following paths :
 	 *
 	 * <pre>
 	 * <code>base = "c:\\Users\\jdoe\\eclipse\\git\\project"</code>
 	 * <code>other = "c:\\Users\\jdoe\\eclipse\\git\\another_project\\pom.xml"</code>
 	 * </pre>
 	 *
 	 * This will return "..\\another_project\\pom.xml".
 	 *
 	 * <p>
 	 * <b>Note</b> that this will return the empty String if <code>base</code>
 	 * and <code>other</code> are equal.
 	 * </p>
 	 *
 	 * @param base
 	 *            The path against which <code>other</code> should be
 	 *            relativized. This will be assumed to denote the path to a
 	 *            folder and not a file.
 	 * @param other
 	 *            The path that will be made relative to <code>base</code>.
 	 * @param dirSeparator
 	 *            A string that separates components of the path. In practice, this is "/" or "\\".
 	 * @param caseSensitive
 	 *            Whether to consider differently-cased directory names as distinct
 	 * @return A relative path that, when resolved against <code>base</code>,
 	 *         will yield the original <code>other</code>.
 	 * @since 4.8
 	 */
 	public static String relativizePath(String base, String other, String dirSeparator, boolean caseSensitive) {
 		if (base.equals(other))
 			return ""; //$NON-NLS-1$
 
 		final String[] baseSegments = base.split(Pattern.quote(dirSeparator));
 		final String[] otherSegments = other.split(Pattern
 				.quote(dirSeparator));
 
 		int commonPrefix = 0;
 		while (commonPrefix < baseSegments.length
 				&& commonPrefix < otherSegments.length) {
 			if (caseSensitive
 					&& baseSegments[commonPrefix]
 					.equals(otherSegments[commonPrefix]))
 				commonPrefix++;
 			else if (!caseSensitive
 					&& baseSegments[commonPrefix]
 							.equalsIgnoreCase(otherSegments[commonPrefix]))
 				commonPrefix++;
 			else
 				break;
 		}
 
 		final StringBuilder builder = new StringBuilder();
 		for (int i = commonPrefix; i < baseSegments.length; i++)
 			builder.append("..").append(dirSeparator); //$NON-NLS-1$
 		for (int i = commonPrefix; i < otherSegments.length; i++) {
 			builder.append(otherSegments[i]);
 			if (i < otherSegments.length - 1)
 				builder.append(dirSeparator);
 		}
 		return builder.toString();
 	}
 
 	/**
 	 * Determine if an IOException is a Stale NFS File Handle
 	 *
 	 * @param ioe
 	 *            an {@link java.io.IOException} object.
 	 * @return a boolean true if the IOException is a Stale NFS FIle Handle
 	 * @since 4.1
 	 */
 	public static boolean isStaleFileHandle(IOException ioe) {
 		String msg = ioe.getMessage();
 		return msg != null
 				&& msg.toLowerCase(Locale.ROOT)
 						.matches("stale .*file .*handle"); //$NON-NLS-1$
 	}
 
 	/**
 	 * Determine if a throwable or a cause in its causal chain is a Stale NFS
 	 * File Handle
 	 *
 	 * @param throwable
 	 *            a {@link java.lang.Throwable} object.
 	 * @return a boolean true if the throwable or a cause in its causal chain is
 	 *         a Stale NFS File Handle
 	 * @since 4.7
 	 */
 	public static boolean isStaleFileHandleInCausalChain(Throwable throwable) {
 		while (throwable != null) {
 			if (throwable instanceof IOException
 					&& isStaleFileHandle((IOException) throwable)) {
 				return true;
 			}
 			throwable = throwable.getCause();
 		}
 		return false;
 	}
 
 	/**
 	 * @param file
 	 * @return {@code true} if the passed file is a symbolic link
 	 */
 	static boolean isSymlink(File file) {
 		return Files.isSymbolicLink(file.toPath());
 	}
 
 	/**
 	 * @param file
 	 * @return lastModified attribute for given file, not following symbolic
 	 *         links
 	 * @throws IOException
 	 * @deprecated use {@link #lastModifiedInstant(Path)} instead which returns
 	 *             FileTime
 	 */
 	@Deprecated
 	static long lastModified(File file) throws IOException {
 		return Files.getLastModifiedTime(toPath(file), LinkOption.NOFOLLOW_LINKS)
 				.toMillis();
 	}
 
 	/**
 	 * @param path
 	 * @return lastModified attribute for given file, not following symbolic
 	 *         links
 	 */
 	static Instant lastModifiedInstant(Path path) {
 		try {
 			return Files.getLastModifiedTime(path, LinkOption.NOFOLLOW_LINKS)
 					.toInstant();
 		} catch (NoSuchFileException e) {
 			LOG.debug(
 					"Cannot read lastModifiedInstant since path {} does not exist", //$NON-NLS-1$
 					path);
 			return Instant.EPOCH;
 		} catch (IOException e) {
 			LOG.error(MessageFormat
 					.format(JGitText.get().readLastModifiedFailed, path), e);
 			return Instant.ofEpochMilli(path.toFile().lastModified());
 		}
 	}
 
 	/**
 	 * Return all the attributes of a file, without following symbolic links.
 	 *
 	 * @param file
 	 * @return {@link BasicFileAttributes} of the file
 	 * @throws IOException in case of any I/O errors accessing the file
 	 *
 	 * @since 4.5.6
 	 */
 	static BasicFileAttributes fileAttributes(File file) throws IOException {
 		return Files.readAttributes(file.toPath(), BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
 	}
 
 	/**
 	 * @param file
 	 * @param time
 	 * @throws IOException
 	 */
 	@Deprecated
 	static void setLastModified(File file, long time) throws IOException {
 		Files.setLastModifiedTime(toPath(file), FileTime.fromMillis(time));
 	}
 
 	/**
 	 * @param path
 	 * @param time
 	 * @throws IOException
 	 */
 	static void setLastModified(Path path, Instant time)
 			throws IOException {
 		Files.setLastModifiedTime(path, FileTime.from(time));
 	}
 
 	/**
 	 * @param file
 	 * @return {@code true} if the given file exists, not following symbolic
 	 *         links
 	 */
 	static boolean exists(File file) {
 		return Files.exists(file.toPath(), LinkOption.NOFOLLOW_LINKS);
 	}
 
 	/**
 	 * @param file
 	 * @return {@code true} if the given file is hidden
 	 * @throws IOException
 	 */
 	static boolean isHidden(File file) throws IOException {
 		return Files.isHidden(toPath(file));
 	}
 
 	/**
 	 * Set a file hidden (on Windows)
 	 *
 	 * @param file
 	 *            a {@link java.io.File} object.
 	 * @param hidden
 	 *            a boolean.
 	 * @throws java.io.IOException
 	 * @since 4.1
 	 */
 	public static void setHidden(File file, boolean hidden) throws IOException {
 		Files.setAttribute(toPath(file), "dos:hidden", Boolean.valueOf(hidden), //$NON-NLS-1$
 				LinkOption.NOFOLLOW_LINKS);
 	}
 
 	/**
 	 * Get file length
 	 *
 	 * @param file
 	 *            a {@link java.io.File}.
 	 * @return length of the given file
 	 * @throws java.io.IOException
 	 * @since 4.1
 	 */
 	public static long getLength(File file) throws IOException {
 		Path nioPath = toPath(file);
 		if (Files.isSymbolicLink(nioPath))
 			return Files.readSymbolicLink(nioPath).toString()
 					.getBytes(UTF_8).length;
 		return Files.size(nioPath);
 	}
 
 	/**
 	 * @param file
 	 * @return {@code true} if the given file is a directory, not following
 	 *         symbolic links
 	 */
 	static boolean isDirectory(File file) {
 		return Files.isDirectory(file.toPath(), LinkOption.NOFOLLOW_LINKS);
 	}
 
 	/**
 	 * @param file
 	 * @return {@code true} if the given file is a file, not following symbolic
 	 *         links
 	 */
 	static boolean isFile(File file) {
 		return Files.isRegularFile(file.toPath(), LinkOption.NOFOLLOW_LINKS);
 	}
 
 	/**
 	 * Whether the given file can be executed.
 	 *
 	 * @param file
 	 *            a {@link java.io.File} object.
 	 * @return {@code true} if the given file can be executed.
 	 * @since 4.1
 	 */
 	public static boolean canExecute(File file) {
 		if (!isFile(file)) {
 			return false;
 		}
 		return Files.isExecutable(file.toPath());
 	}
 
 	/**
 	 * @param fs
 	 * @param file
 	 * @return non null attributes object
 	 */
 	static Attributes getFileAttributesBasic(FS fs, File file) {
 		try {
 			Path nioPath = toPath(file);
 			BasicFileAttributes readAttributes = nioPath
 					.getFileSystem()
 					.provider()
 					.getFileAttributeView(nioPath,
 							BasicFileAttributeView.class,
 							LinkOption.NOFOLLOW_LINKS).readAttributes();
 			Attributes attributes = new Attributes(fs, file,
 					true,
 					readAttributes.isDirectory(),
 					fs.supportsExecute() ? file.canExecute() : false,
 					readAttributes.isSymbolicLink(),
 					readAttributes.isRegularFile(), //
 					readAttributes.creationTime().toMillis(), //
 					readAttributes.lastModifiedTime().toInstant(),
 					readAttributes.isSymbolicLink() ? Constants
 							.encode(readSymLink(file)).length
 							: readAttributes.size());
 			return attributes;
 		} catch (IOException e) {
 			return new Attributes(file, fs);
 		}
 	}
 
 	/**
 	 * Get file system attributes for the given file.
 	 *
 	 * @param fs
 	 *            a {@link org.eclipse.jgit.util.FS} object.
 	 * @param file
 	 *            a {@link java.io.File}.
 	 * @return file system attributes for the given file.
 	 * @since 4.1
 	 */
 	public static Attributes getFileAttributesPosix(FS fs, File file) {
 		try {
 			Path nioPath = toPath(file);
 			PosixFileAttributes readAttributes = nioPath
 					.getFileSystem()
 					.provider()
 					.getFileAttributeView(nioPath,
 							PosixFileAttributeView.class,
 							LinkOption.NOFOLLOW_LINKS).readAttributes();
 			Attributes attributes = new Attributes(
 					fs,
 					file,
 					true, //
 					readAttributes.isDirectory(), //
 					readAttributes.permissions().contains(
 							PosixFilePermission.OWNER_EXECUTE),
 					readAttributes.isSymbolicLink(),
 					readAttributes.isRegularFile(), //
 					readAttributes.creationTime().toMillis(), //
 					readAttributes.lastModifiedTime().toInstant(),
 					readAttributes.size());
 			return attributes;
 		} catch (IOException e) {
 			return new Attributes(file, fs);
 		}
 	}
 
 	/**
 	 * NFC normalize a file (on Mac), otherwise do nothing
 	 *
 	 * @param file
 	 *            a {@link java.io.File}.
 	 * @return on Mac: NFC normalized {@link java.io.File}, otherwise the passed
 	 *         file
 	 * @since 4.1
 	 */
 	public static File normalize(File file) {
 		if (SystemReader.getInstance().isMacOS()) {
 			// TODO: Would it be faster to check with isNormalized first
 			// assuming normalized paths are much more common
 			String normalized = Normalizer.normalize(file.getPath(),
 					Normalizer.Form.NFC);
 			return new File(normalized);
 		}
 		return file;
 	}
 
 	/**
 	 * On Mac: get NFC normalized form of given name, otherwise the given name.
 	 *
 	 * @param name
 	 *            a {@link java.lang.String} object.
 	 * @return on Mac: NFC normalized form of given name
 	 * @since 4.1
 	 */
 	public static String normalize(String name) {
 		if (SystemReader.getInstance().isMacOS()) {
 			if (name == null)
 				return null;
 			return Normalizer.normalize(name, Normalizer.Form.NFC);
 		}
 		return name;
 	}
 
 	/**
 	 * Best-effort variation of {@link java.io.File#getCanonicalFile()}
 	 * returning the input file if the file cannot be canonicalized instead of
 	 * throwing {@link java.io.IOException}.
 	 *
 	 * @param file
 	 *            to be canonicalized; may be {@code null}
 	 * @return canonicalized file, or the unchanged input file if
 	 *         canonicalization failed or if {@code file == null}
 	 * @throws java.lang.SecurityException
 	 *             if {@link java.io.File#getCanonicalFile()} throws one
 	 * @since 4.2
 	 */
 	public static File canonicalize(File file) {
 		if (file == null) {
 			return null;
 		}
 		try {
 			return file.getCanonicalFile();
 		} catch (IOException e) {
 			return file;
 		}
 	}
 
 	/**
 	 * Convert a path to String, replacing separators as necessary.
 	 *
 	 * @param file
 	 *            a {@link java.io.File}.
 	 * @return file's path as a String
 	 * @since 4.10
 	 */
 	public static String pathToString(File file) {
 		final String path = file.getPath();
 		if (SystemReader.getInstance().isWindows()) {
 			return path.replace('\\', '/');
 		}
 		return path;
 	}
 
 	/**
 	 * Touch the given file
 	 *
 	 * @param f
 	 *            the file to touch
 	 * @throws IOException
 	 * @since 5.1.8
 	 */
 	public static void touch(Path f) throws IOException {
 		try (FileChannel fc = FileChannel.open(f, StandardOpenOption.CREATE,
 				StandardOpenOption.APPEND, StandardOpenOption.SYNC)) {
 			// touch
 		}
 		Files.setLastModifiedTime(f, FileTime.from(Instant.now()));
 	}
 
 	/**
 	 * Compute a delay in a {@code min..max} interval with random jitter.
 	 *
 	 * @param last
 	 *            amount of delay waited before the last attempt. This is used
 	 *            to seed the next delay interval. Should be 0 if there was no
 	 *            prior delay.
 	 * @param min
 	 *            shortest amount of allowable delay between attempts.
 	 * @param max
 	 *            longest amount of allowable delay between attempts.
 	 * @return new amount of delay to wait before the next attempt.
 	 *
 	 * @since 5.6
 	 */
 	public static long delay(long last, long min, long max) {
 		long r = Math.max(0, last * 3 - min);
 		if (r > 0) {
 			int c = (int) Math.min(r + 1, Integer.MAX_VALUE);
 			r = RNG.nextInt(c);
 		}
 		return Math.max(Math.min(min + r, max), min);
 	}
 }