/*
    * Copyright (C) 2008, 2009, Google Inc.
    * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
    * Copyright (C) 2010, Matthias Sohn <matthias.sohn@sap.com>
    * Copyright (C) 2010, 2020, Christian Halstrick <christian.halstrick@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.dircache;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import java.io.ByteArrayOutputStream;
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.security.MessageDigest;
  import java.text.MessageFormat;
  import java.time.Instant;
  import java.util.Arrays;
  
  import org.eclipse.jgit.dircache.DirCache.DirCacheVersion;
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.FileMode;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.util.IO;
  import org.eclipse.jgit.util.MutableInteger;
  import org.eclipse.jgit.util.NB;
  import org.eclipse.jgit.util.SystemReader;
  
  /**
   * A single file (or stage of a file) in a
   * {@link org.eclipse.jgit.dircache.DirCache}.
   * <p>
   * An entry represents exactly one stage of a file. If a file path is unmerged
   * then multiple DirCacheEntry instances may appear for the same path name.
   */
  public class DirCacheEntry {
  	private static final byte[] nullpad = new byte[8];
  
  	/** The standard (fully merged) stage for an entry. */
  	public static final int STAGE_0 = 0;
  
  	/** The base tree revision for an entry. */
  	public static final int STAGE_1 = 1;
  
  	/** The first tree revision (usually called "ours"). */
  	public static final int STAGE_2 = 2;
  
  	/** The second tree revision (usually called "theirs"). */
  	public static final int STAGE_3 = 3;
  
  	private static final int P_CTIME = 0;
  
  	// private static final int P_CTIME_NSEC = 4;
  
  	private static final int P_MTIME = 8;
  
  	// private static final int P_MTIME_NSEC = 12;
  
  	// private static final int P_DEV = 16;
  
  	// private static final int P_INO = 20;
  
  	private static final int P_MODE = 24;
  
  	// private static final int P_UID = 28;
  
  	// private static final int P_GID = 32;
  
  	private static final int P_SIZE = 36;
  
  	private static final int P_OBJECTID = 40;
  
  	private static final int P_FLAGS = 60;
  	private static final int P_FLAGS2 = 62;
  
  	/** Mask applied to data in {@link #P_FLAGS} to get the name length. */
  	private static final int NAME_MASK = 0xfff;
  
  	private static final int INTENT_TO_ADD = 0x20000000;
  	private static final int SKIP_WORKTREE = 0x40000000;
  	private static final int EXTENDED_FLAGS = (INTENT_TO_ADD | SKIP_WORKTREE);
  
  	private static final int INFO_LEN = 62;
  	private static final int INFO_LEN_EXTENDED = 64;
  
  	private static final int EXTENDED = 0x40;
  	private static final int ASSUME_VALID = 0x80;
 
 	/** In-core flag signaling that the entry should be considered as modified. */
 	private static final int UPDATE_NEEDED = 0x1;
 
 	/** (Possibly shared) header information storage. */
 	private final byte[] info;
 
 	/** First location within {@link #info} where our header starts. */
 	private final int infoOffset;
 
 	/** Our encoded path name, from the root of the repository. */
 	final byte[] path;
 
 	/** Flags which are never stored to disk. */
 	private byte inCoreFlags;
 
 	DirCacheEntry(byte[] sharedInfo, MutableInteger infoAt, InputStream in,
 			MessageDigest md, Instant smudge, DirCacheVersion version,
 			DirCacheEntry previous)
 			throws IOException {
 		info = sharedInfo;
 		infoOffset = infoAt.value;
 
 		IO.readFully(in, info, infoOffset, INFO_LEN);
 
 		int len;
 		if (isExtended()) {
 			len = INFO_LEN_EXTENDED;
 			IO.readFully(in, info, infoOffset + INFO_LEN, INFO_LEN_EXTENDED - INFO_LEN);
 
 			if ((getExtendedFlags() & ~EXTENDED_FLAGS) != 0)
 				throw new IOException(MessageFormat.format(JGitText.get()
 						.DIRCUnrecognizedExtendedFlags, String.valueOf(getExtendedFlags())));
 		} else
 			len = INFO_LEN;
 
 		infoAt.value += len;
 		md.update(info, infoOffset, len);
 
 		int toRemove = 0;
 		if (version == DirCacheVersion.DIRC_VERSION_PATHCOMPRESS) {
 			// Read variable int and update digest
 			int b = in.read();
 			md.update((byte) b);
 			toRemove = b & 0x7F;
 			while ((b & 0x80) != 0) {
 				toRemove++;
 				b = in.read();
 				md.update((byte) b);
 				toRemove = (toRemove << 7) | (b & 0x7F);
 			}
 			if (toRemove < 0
 					|| (previous != null && toRemove > previous.path.length)) {
 				if (previous == null) {
 					throw new IOException(MessageFormat.format(
 							JGitText.get().DIRCCorruptLengthFirst,
 							Integer.valueOf(toRemove)));
 				}
 				throw new IOException(MessageFormat.format(
 						JGitText.get().DIRCCorruptLength,
 						Integer.valueOf(toRemove), previous.getPathString()));
 			}
 		}
 		int pathLen = NB.decodeUInt16(info, infoOffset + P_FLAGS) & NAME_MASK;
 		int skipped = 0;
 		if (pathLen < NAME_MASK) {
 			path = new byte[pathLen];
 			if (version == DirCacheVersion.DIRC_VERSION_PATHCOMPRESS
 					&& previous != null) {
 				System.arraycopy(previous.path, 0, path, 0,
 						previous.path.length - toRemove);
 				IO.readFully(in, path, previous.path.length - toRemove,
 						pathLen - (previous.path.length - toRemove));
 				md.update(path, previous.path.length - toRemove,
 						pathLen - (previous.path.length - toRemove));
 				pathLen = pathLen - (previous.path.length - toRemove);
 			} else {
 				IO.readFully(in, path, 0, pathLen);
 				md.update(path, 0, pathLen);
 			}
 		} else if (version != DirCacheVersion.DIRC_VERSION_PATHCOMPRESS
 				|| previous == null || toRemove == previous.path.length) {
 			ByteArrayOutputStream tmp = new ByteArrayOutputStream();
 			byte[] buf = new byte[NAME_MASK];
 			IO.readFully(in, buf, 0, NAME_MASK);
 			tmp.write(buf);
 			readNulTerminatedString(in, tmp);
 			path = tmp.toByteArray();
 			pathLen = path.length;
 			md.update(path, 0, pathLen);
 			skipped = 1; // we already skipped 1 '\0' in readNulTerminatedString
 			md.update((byte) 0);
 		} else {
 			ByteArrayOutputStream tmp = new ByteArrayOutputStream();
 			tmp.write(previous.path, 0, previous.path.length - toRemove);
 			pathLen = readNulTerminatedString(in, tmp);
 			path = tmp.toByteArray();
 			md.update(path, previous.path.length - toRemove, pathLen);
 			skipped = 1; // we already skipped 1 '\0' in readNulTerminatedString
 			md.update((byte) 0);
 		}
 
 		try {
 			checkPath(path);
 		} catch (InvalidPathException e) {
 			CorruptObjectException p =
 				new CorruptObjectException(e.getMessage());
 			if (e.getCause() != null)
 				p.initCause(e.getCause());
 			throw p;
 		}
 
 		if (version == DirCacheVersion.DIRC_VERSION_PATHCOMPRESS) {
 			if (skipped == 0) {
 				int b = in.read();
 				if (b < 0) {
 					throw new EOFException(JGitText.get().shortReadOfBlock);
 				}
 				md.update((byte) b);
 			}
 		} else {
 			// Index records are padded out to the next 8 byte alignment
 			// for historical reasons related to how C Git read the files.
 			//
 			final int actLen = len + pathLen;
 			final int expLen = (actLen + 8) & ~7;
 			final int padLen = expLen - actLen - skipped;
 			if (padLen > 0) {
 				IO.skipFully(in, padLen);
 				md.update(nullpad, 0, padLen);
 			}
 		}
 		if (mightBeRacilyClean(smudge)) {
 			smudgeRacilyClean();
 		}
 	}
 
 	/**
 	 * Create an empty entry at stage 0.
 	 *
 	 * @param newPath
 	 *            name of the cache entry.
 	 * @throws java.lang.IllegalArgumentException
 	 *             If the path starts or ends with "/", or contains "//" either
 	 *             "\0". These sequences are not permitted in a git tree object
 	 *             or DirCache file.
 	 */
 	public DirCacheEntry(String newPath) {
 		this(Constants.encode(newPath), STAGE_0);
 	}
 
 	/**
 	 * Create an empty entry at the specified stage.
 	 *
 	 * @param newPath
 	 *            name of the cache entry.
 	 * @param stage
 	 *            the stage index of the new entry.
 	 * @throws java.lang.IllegalArgumentException
 	 *             If the path starts or ends with "/", or contains "//" either
 	 *             "\0". These sequences are not permitted in a git tree object
 	 *             or DirCache file.  Or if {@code stage} is outside of the
 	 *             range 0..3, inclusive.
 	 */
 	public DirCacheEntry(String newPath, int stage) {
 		this(Constants.encode(newPath), stage);
 	}
 
 	/**
 	 * Create an empty entry at stage 0.
 	 *
 	 * @param newPath
 	 *            name of the cache entry, in the standard encoding.
 	 * @throws java.lang.IllegalArgumentException
 	 *             If the path starts or ends with "/", or contains "//" either
 	 *             "\0". These sequences are not permitted in a git tree object
 	 *             or DirCache file.
 	 */
 	public DirCacheEntry(byte[] newPath) {
 		this(newPath, STAGE_0);
 	}
 
 	/**
 	 * Create an empty entry at the specified stage.
 	 *
 	 * @param path
 	 *            name of the cache entry, in the standard encoding.
 	 * @param stage
 	 *            the stage index of the new entry.
 	 * @throws java.lang.IllegalArgumentException
 	 *             If the path starts or ends with "/", or contains "//" either
 	 *             "\0". These sequences are not permitted in a git tree object
 	 *             or DirCache file.  Or if {@code stage} is outside of the
 	 *             range 0..3, inclusive.
 	 */
 	@SuppressWarnings("boxing")
 	public DirCacheEntry(byte[] path, int stage) {
 		checkPath(path);
 		if (stage < 0 || 3 < stage)
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().invalidStageForPath,
 					stage, toString(path)));
 
 		info = new byte[INFO_LEN];
 		infoOffset = 0;
 		this.path = path;
 
 		int flags = ((stage & 0x3) << 12);
 		if (path.length < NAME_MASK)
 			flags |= path.length;
 		else
 			flags |= NAME_MASK;
 		NB.encodeInt16(info, infoOffset + P_FLAGS, flags);
 	}
 
 	/**
 	 * Duplicate DirCacheEntry with same path and copied info.
 	 * <p>
 	 * The same path buffer is reused (avoiding copying), however a new info
 	 * buffer is created and its contents are copied.
 	 *
 	 * @param src
 	 *            entry to clone.
 	 * @since 4.2
 	 */
 	public DirCacheEntryf="../../../../org/eclipse/jgit/dircache/DirCacheEntry.html#DirCacheEntry">DirCacheEntry(DirCacheEntry src) {
 		path = src.path;
 		info = new byte[INFO_LEN];
 		infoOffset = 0;
 		System.arraycopy(src.info, src.infoOffset, info, 0, INFO_LEN);
 	}
 
 	private int readNulTerminatedString(InputStream in, OutputStream out)
 			throws IOException {
 		int n = 0;
 		for (;;) {
 			int c = in.read();
 			if (c < 0) {
 				throw new EOFException(JGitText.get().shortReadOfBlock);
 			}
 			if (c == 0) {
 				break;
 			}
 			out.write(c);
 			n++;
 		}
 		return n;
 	}
 
 	void write(OutputStream os, DirCacheVersion version, DirCacheEntry previous)
 			throws IOException {
 		final int len = isExtended() ? INFO_LEN_EXTENDED : INFO_LEN;
 		if (version != DirCacheVersion.DIRC_VERSION_PATHCOMPRESS) {
 			os.write(info, infoOffset, len);
 			os.write(path, 0, path.length);
 			// Index records are padded out to the next 8 byte alignment
 			// for historical reasons related to how C Git read the files.
 			//
 			int entryLen = len + path.length;
 			int expLen = (entryLen + 8) & ~7;
 			if (entryLen != expLen)
 				os.write(nullpad, 0, expLen - entryLen);
 		} else {
 			int pathCommon = 0;
 			int toRemove;
 			if (previous != null) {
 				// Figure out common prefix
 				int pathLen = Math.min(path.length, previous.path.length);
 				while (pathCommon < pathLen
 						&& path[pathCommon] == previous.path[pathCommon]) {
 					pathCommon++;
 				}
 				toRemove = previous.path.length - pathCommon;
 			} else {
 				toRemove = 0;
 			}
 			byte[] tmp = new byte[16];
 			int n = tmp.length;
 			tmp[--n] = (byte) (toRemove & 0x7F);
 			while ((toRemove >>>= 7) != 0) {
 				tmp[--n] = (byte) (0x80 | (--toRemove & 0x7F));
 			}
 			os.write(info, infoOffset, len);
 			os.write(tmp, n, tmp.length - n);
 			os.write(path, pathCommon, path.length - pathCommon);
 			os.write(0);
 		}
 	}
 
 	/**
 	 * Is it possible for this entry to be accidentally assumed clean?
 	 * <p>
 	 * The "racy git" problem happens when a work file can be updated faster
 	 * than the filesystem records file modification timestamps. It is possible
 	 * for an application to edit a work file, update the index, then edit it
 	 * again before the filesystem will give the work file a new modification
 	 * timestamp. This method tests to see if file was written out at the same
 	 * time as the index.
 	 *
 	 * @param smudge_s
 	 *            seconds component of the index's last modified time.
 	 * @param smudge_ns
 	 *            nanoseconds component of the index's last modified time.
 	 * @return true if extra careful checks should be used.
 	 * @deprecated use {@link #mightBeRacilyClean(Instant)} instead
 	 */
 	@Deprecated
 	public final boolean mightBeRacilyClean(int smudge_s, int smudge_ns) {
 		return mightBeRacilyClean(Instant.ofEpochSecond(smudge_s, smudge_ns));
 	}
 
 	/**
 	 * Is it possible for this entry to be accidentally assumed clean?
 	 * <p>
 	 * The "racy git" problem happens when a work file can be updated faster
 	 * than the filesystem records file modification timestamps. It is possible
 	 * for an application to edit a work file, update the index, then edit it
 	 * again before the filesystem will give the work file a new modification
 	 * timestamp. This method tests to see if file was written out at the same
 	 * time as the index.
 	 *
 	 * @param smudge
 	 *            index's last modified time.
 	 * @return true if extra careful checks should be used.
 	 * @since 5.1.9
 	 */
 	public final boolean mightBeRacilyClean(Instant smudge) {
 		// If the index has a modification time then it came from disk
 		// and was not generated from scratch in memory. In such cases
 		// the entry is 'racily clean' if the entry's cached modification
 		// time is equal to or later than the index modification time. In
 		// such cases the work file is too close to the index to tell if
 		// it is clean or not based on the modification time alone.
 		//
 		final int base = infoOffset + P_MTIME;
 		final int mtime = NB.decodeInt32(info, base);
 		if ((int) smudge.getEpochSecond() == mtime) {
 			return smudge.getNano() <= NB.decodeInt32(info, base + 4);
 		}
 		return false;
 	}
 
 	/**
 	 * Force this entry to no longer match its working tree file.
 	 * <p>
 	 * This avoids the "racy git" problem by making this index entry no longer
 	 * match the file in the working directory. Later git will be forced to
 	 * compare the file content to ensure the file matches the working tree.
 	 */
 	public final void smudgeRacilyClean() {
 		// To mark an entry racily clean we set its length to 0 (like native git
 		// does). Entries which are not racily clean and have zero length can be
 		// distinguished from racily clean entries by checking P_OBJECTID
 		// against the SHA1 of empty content. When length is 0 and P_OBJECTID is
 		// different from SHA1 of empty content we know the entry is marked
 		// racily clean
 		final int base = infoOffset + P_SIZE;
 		Arrays.fill(info, base, base + 4, (byte) 0);
 	}
 
 	/**
 	 * Check whether this entry has been smudged or not
 	 * <p>
 	 * If a blob has length 0 we know its id, see
 	 * {@link org.eclipse.jgit.lib.Constants#EMPTY_BLOB_ID}. If an entry has
 	 * length 0 and an ID different from the one for empty blob we know this
 	 * entry was smudged.
 	 *
 	 * @return <code>true</code> if the entry is smudged, <code>false</code>
 	 *         otherwise
 	 */
 	public final boolean isSmudged() {
 		final int base = infoOffset + P_OBJECTID;
 		return (getLength() == 0) && (Constants.EMPTY_BLOB_ID.compareTo(info, base) != 0);
 	}
 
 	final byte[] idBuffer() {
 		return info;
 	}
 
 	final int idOffset() {
 		return infoOffset + P_OBJECTID;
 	}
 
 	/**
 	 * Is this entry always thought to be unmodified?
 	 * <p>
 	 * Most entries in the index do not have this flag set. Users may however
 	 * set them on if the file system stat() costs are too high on this working
 	 * directory, such as on NFS or SMB volumes.
 	 *
 	 * @return true if we must assume the entry is unmodified.
 	 */
 	public boolean isAssumeValid() {
 		return (info[infoOffset + P_FLAGS] & ASSUME_VALID) != 0;
 	}
 
 	/**
 	 * Set the assume valid flag for this entry,
 	 *
 	 * @param assume
 	 *            true to ignore apparent modifications; false to look at last
 	 *            modified to detect file modifications.
 	 */
 	public void setAssumeValid(boolean assume) {
 		if (assume)
 			info[infoOffset + P_FLAGS] |= (byte) ASSUME_VALID;
 		else
 			info[infoOffset + P_FLAGS] &= (byte) ~ASSUME_VALID;
 	}
 
 	/**
 	 * Whether this entry should be checked for changes
 	 *
 	 * @return {@code true} if this entry should be checked for changes
 	 */
 	public boolean isUpdateNeeded() {
 		return (inCoreFlags & UPDATE_NEEDED) != 0;
 	}
 
 	/**
 	 * Set whether this entry must be checked for changes
 	 *
 	 * @param updateNeeded
 	 *            whether this entry must be checked for changes
 	 */
 	public void setUpdateNeeded(boolean updateNeeded) {
 		if (updateNeeded)
 			inCoreFlags |= (byte) UPDATE_NEEDED;
 		else
 			inCoreFlags &= (byte) ~UPDATE_NEEDED;
 	}
 
 	/**
 	 * Get the stage of this entry.
 	 * <p>
 	 * Entries have one of 4 possible stages: 0-3.
 	 *
 	 * @return the stage of this entry.
 	 */
 	public int getStage() {
 		return (info[infoOffset + P_FLAGS] >>> 4) & 0x3;
 	}
 
 	/**
 	 * Sets the stage of an entry.
 	 *
 	 * @param stage
 	 *            to set, in the range [0..3]
 	 * @throws IllegalArgumentException
 	 *             if the stage is outside the range [0..3]
 	 * @since 5.10
 	 */
 	public void setStage(int stage) {
 		if ((stage & ~0x3) != 0) {
 			throw new IllegalArgumentException(
 					"Invalid stage, must be in range [0..3]"); //$NON-NLS-1$
 		}
 		byte flags = info[infoOffset + P_FLAGS];
 		info[infoOffset + P_FLAGS] = (byte) ((flags & 0xCF) | (stage << 4));
 	}
 
 	/**
 	 * Returns whether this entry should be skipped from the working tree.
 	 *
 	 * @return true if this entry should be skipepd.
 	 */
 	public boolean isSkipWorkTree() {
 		return (getExtendedFlags() & SKIP_WORKTREE) != 0;
 	}
 
 	/**
 	 * Returns whether this entry is intent to be added to the Index.
 	 *
 	 * @return true if this entry is intent to add.
 	 */
 	public boolean isIntentToAdd() {
 		return (getExtendedFlags() & INTENT_TO_ADD) != 0;
 	}
 
 	/**
 	 * Returns whether this entry is in the fully-merged stage (0).
 	 *
 	 * @return true if this entry is merged
 	 * @since 2.2
 	 */
 	public boolean isMerged() {
 		return getStage() == STAGE_0;
 	}
 
 	/**
 	 * Obtain the raw {@link org.eclipse.jgit.lib.FileMode} bits for this entry.
 	 *
 	 * @return mode bits for the entry.
 	 * @see FileMode#fromBits(int)
 	 */
 	public int getRawMode() {
 		return NB.decodeInt32(info, infoOffset + P_MODE);
 	}
 
 	/**
 	 * Obtain the {@link org.eclipse.jgit.lib.FileMode} for this entry.
 	 *
 	 * @return the file mode singleton for this entry.
 	 */
 	public FileMode getFileMode() {
 		return FileMode.fromBits(getRawMode());
 	}
 
 	/**
 	 * Set the file mode for this entry.
 	 *
 	 * @param mode
 	 *            the new mode constant.
 	 * @throws java.lang.IllegalArgumentException
 	 *             If {@code mode} is
 	 *             {@link org.eclipse.jgit.lib.FileMode#MISSING},
 	 *             {@link org.eclipse.jgit.lib.FileMode#TREE}, or any other type
 	 *             code not permitted in a tree object.
 	 */
 	public void setFileMode(FileMode mode) {
 		switch (mode.getBits() & FileMode.TYPE_MASK) {
 		case FileMode.TYPE_MISSING:
 		case FileMode.TYPE_TREE:
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().invalidModeForPath, mode, getPathString()));
 		}
 		NB.encodeInt32(info, infoOffset + P_MODE, mode.getBits());
 	}
 
 	void setFileMode(int mode) {
 		NB.encodeInt32(info, infoOffset + P_MODE, mode);
 	}
 
 	/**
 	 * Get the cached creation time of this file, in milliseconds.
 	 *
 	 * @return cached creation time of this file, in milliseconds since the
 	 *         Java epoch (midnight Jan 1, 1970 UTC).
 	 */
 	public long getCreationTime() {
 		return decodeTS(P_CTIME);
 	}
 
 	/**
 	 * Set the cached creation time of this file, using milliseconds.
 	 *
 	 * @param when
 	 *            new cached creation time of the file, in milliseconds.
 	 */
 	public void setCreationTime(long when) {
 		encodeTS(P_CTIME, when);
 	}
 
 	/**
 	 * Get the cached last modification date of this file, in milliseconds.
 	 * <p>
 	 * One of the indicators that the file has been modified by an application
 	 * changing the working tree is if the last modification time for the file
 	 * differs from the time stored in this entry.
 	 *
 	 * @return last modification time of this file, in milliseconds since the
 	 *         Java epoch (midnight Jan 1, 1970 UTC).
 	 * @deprecated use {@link #getLastModifiedInstant()} instead
 	 */
 	@Deprecated
 	public long getLastModified() {
 		return decodeTS(P_MTIME);
 	}
 
 	/**
 	 * Get the cached last modification date of this file.
 	 * <p>
 	 * One of the indicators that the file has been modified by an application
 	 * changing the working tree is if the last modification time for the file
 	 * differs from the time stored in this entry.
 	 *
 	 * @return last modification time of this file.
 	 * @since 5.1.9
 	 */
 	public Instant getLastModifiedInstant() {
 		return decodeTSInstant(P_MTIME);
 	}
 
 	/**
 	 * Set the cached last modification date of this file, using milliseconds.
 	 *
 	 * @param when
 	 *            new cached modification date of the file, in milliseconds.
 	 * @deprecated use {@link #setLastModified(Instant)} instead
 	 */
 	@Deprecated
 	public void setLastModified(long when) {
 		encodeTS(P_MTIME, when);
 	}
 
 	/**
 	 * Set the cached last modification date of this file.
 	 *
 	 * @param when
 	 *            new cached modification date of the file.
 	 * @since 5.1.9
 	 */
 	public void setLastModified(Instant when) {
 		encodeTS(P_MTIME, when);
 	}
 
 	/**
 	 * Get the cached size (mod 4 GB) (in bytes) of this file.
 	 * <p>
 	 * One of the indicators that the file has been modified by an application
 	 * changing the working tree is if the size of the file (in bytes) differs
 	 * from the size stored in this entry.
 	 * <p>
 	 * Note that this is the length of the file in the working directory, which
 	 * may differ from the size of the decompressed blob if work tree filters
 	 * are being used, such as LF&lt;-&gt;CRLF conversion.
 	 * <p>
 	 * Note also that for very large files, this is the size of the on-disk file
 	 * truncated to 32 bits, i.e. modulo 4294967296. If that value is larger
 	 * than 2GB, it will appear negative.
 	 *
 	 * @return cached size of the working directory file, in bytes.
 	 */
 	public int getLength() {
 		return NB.decodeInt32(info, infoOffset + P_SIZE);
 	}
 
 	/**
 	 * Set the cached size (in bytes) of this file.
 	 *
 	 * @param sz
 	 *            new cached size of the file, as bytes. If the file is larger
 	 *            than 2G, cast it to (int) before calling this method.
 	 */
 	public void setLength(int sz) {
 		NB.encodeInt32(info, infoOffset + P_SIZE, sz);
 	}
 
 	/**
 	 * Set the cached size (in bytes) of this file.
 	 *
 	 * @param sz
 	 *            new cached size of the file, as bytes.
 	 */
 	public void setLength(long sz) {
 		setLength((int) sz);
 	}
 
 	/**
 	 * Obtain the ObjectId for the entry.
 	 * <p>
 	 * Using this method to compare ObjectId values between entries is
 	 * inefficient as it causes memory allocation.
 	 *
 	 * @return object identifier for the entry.
 	 */
 	public ObjectId getObjectId() {
 		return ObjectId.fromRaw(idBuffer(), idOffset());
 	}
 
 	/**
 	 * Set the ObjectId for the entry.
 	 *
 	 * @param id
 	 *            new object identifier for the entry. May be
 	 *            {@link org.eclipse.jgit.lib.ObjectId#zeroId()} to remove the
 	 *            current identifier.
 	 */
 	public void setObjectId(AnyObjectId id) {
 		id.copyRawTo(idBuffer(), idOffset());
 	}
 
 	/**
 	 * Set the ObjectId for the entry from the raw binary representation.
 	 *
 	 * @param bs
 	 *            the raw byte buffer to read from. At least 20 bytes after p
 	 *            must be available within this byte array.
 	 * @param p
 	 *            position to read the first byte of data from.
 	 */
 	public void setObjectIdFromRaw(byte[] bs, int p) {
 		final int n = Constants.OBJECT_ID_LENGTH;
 		System.arraycopy(bs, p, idBuffer(), idOffset(), n);
 	}
 
 	/**
 	 * Get the entry's complete path.
 	 * <p>
 	 * This method is not very efficient and is primarily meant for debugging
 	 * and final output generation. Applications should try to avoid calling it,
 	 * and if invoked do so only once per interesting entry, where the name is
 	 * absolutely required for correct function.
 	 *
 	 * @return complete path of the entry, from the root of the repository. If
 	 *         the entry is in a subtree there will be at least one '/' in the
 	 *         returned string.
 	 */
 	public String getPathString() {
 		return toString(path);
 	}
 
 	/**
 	 * Get a copy of the entry's raw path bytes.
 	 *
 	 * @return raw path bytes.
 	 * @since 3.4
 	 */
 	public byte[] getRawPath() {
 		return path.clone();
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * <p>
 	 * Use for debugging only !
 	 */
 	@SuppressWarnings("nls")
 	@Override
 	public String toString() {
 		return getFileMode() + " " + getLength() + " "
 				+ getLastModifiedInstant()
 				+ " " + getObjectId() + " " + getStage() + " "
 				+ getPathString() + "\n";
 	}
 
 	/**
 	 * Copy the ObjectId and other meta fields from an existing entry.
 	 * <p>
 	 * This method copies everything except the path from one entry to another,
 	 * supporting renaming.
 	 *
 	 * @param src
 	 *            the entry to copy ObjectId and meta fields from.
 	 */
 	public void copyMetaData(DirCacheEntry src) {
 		copyMetaData(src, false);
 	}
 
 	/**
 	 * Copy the ObjectId and other meta fields from an existing entry.
 	 * <p>
 	 * This method copies everything except the path and possibly stage from one
 	 * entry to another, supporting renaming.
 	 *
 	 * @param src
 	 *            the entry to copy ObjectId and meta fields from.
 	 * @param keepStage
 	 *            if true, the stage attribute will not be copied
 	 */
 	void copyMetaData(DirCacheEntry src, boolean keepStage) {
 		int origflags = NB.decodeUInt16(info, infoOffset + P_FLAGS);
 		int newflags = NB.decodeUInt16(src.info, src.infoOffset + P_FLAGS);
 		System.arraycopy(src.info, src.infoOffset, info, infoOffset, INFO_LEN);
 		final int pLen = origflags & NAME_MASK;
 		final int SHIFTED_STAGE_MASK = 0x3 << 12;
 		final int pStageShifted;
 		if (keepStage)
 			pStageShifted = origflags & SHIFTED_STAGE_MASK;
 		else
 			pStageShifted = newflags & SHIFTED_STAGE_MASK;
 		NB.encodeInt16(info, infoOffset + P_FLAGS, pStageShifted | pLen
 				| (newflags & ~NAME_MASK & ~SHIFTED_STAGE_MASK));
 	}
 
 	/**
 	 * @return true if the entry contains extended flags.
 	 */
 	boolean isExtended() {
 		return (info[infoOffset + P_FLAGS] & EXTENDED) != 0;
 	}
 
 	private long decodeTS(int pIdx) {
 		final int base = infoOffset + pIdx;
 		final int sec = NB.decodeInt32(info, base);
 		final int ms = NB.decodeInt32(info, base + 4) / 1000000;
 		return 1000L * sec + ms;
 	}
 
 	private Instant decodeTSInstant(int pIdx) {
 		final int base = infoOffset + pIdx;
 		final int sec = NB.decodeInt32(info, base);
 		final int nano = NB.decodeInt32(info, base + 4);
 		return Instant.ofEpochSecond(sec, nano);
 	}
 
 	private void encodeTS(int pIdx, long when) {
 		final int base = infoOffset + pIdx;
 		NB.encodeInt32(info, base, (int) (when / 1000));
 		NB.encodeInt32(info, base + 4, ((int) (when % 1000)) * 1000000);
 	}
 
 	private void encodeTS(int pIdx, Instant when) {
 		final int base = infoOffset + pIdx;
 		NB.encodeInt32(info, base, (int) when.getEpochSecond());
 		NB.encodeInt32(info, base + 4, when.getNano());
 	}
 
 	private int getExtendedFlags() {
 		if (isExtended()) {
 			return NB.decodeUInt16(info, infoOffset + P_FLAGS2) << 16;
 		}
 		return 0;
 	}
 
 	private static void checkPath(byte[] path) {
 		try {
 			SystemReader.getInstance().checkPath(path);
 		} catch (CorruptObjectException e) {
 			InvalidPathException p = new InvalidPathException(toString(path));
 			p.initCause(e);
 			throw p;
 		}
 	}
 
 	static String toString(byte[] path) {
 		return UTF_8.decode(ByteBuffer.wrap(path)).toString();
 	}
 
 	static int getMaximumInfoLength(boolean extended) {
 		return extended ? INFO_LEN_EXTENDED : INFO_LEN;
 	}
 }