Class DirCache

java.lang.Object
org.eclipse.jgit.dircache.DirCache

public class DirCache extends Object
Support for the Git dircache (aka index file).

The index file keeps track of which objects are currently checked out in the working directory, and the last modified time of those working files. Changes in the working directory can be detected by comparing the modification times to the cached modification time within the index file.

Index files are also used during merges, where the merge happens within the index file first, and the working directory is updated as a post-merge step. Conflicts are stored in the index file to allow tool (and human) based resolutions to be easily performed.

  • Field Details

    • SIG_DIRC

      private static final byte[] SIG_DIRC
    • EXT_TREE

      private static final int EXT_TREE
      See Also:
    • NO_ENTRIES

      private static final DirCacheEntry[] NO_ENTRIES
    • NO_CHECKSUM

      private static final byte[] NO_CHECKSUM
    • ENT_CMP

      static final Comparator<DirCacheEntry> ENT_CMP
    • liveFile

      private final File liveFile
      Location of the current version of the index file.
    • sortedEntries

      private DirCacheEntry[] sortedEntries
      Individual file index entries, sorted by path name.
    • entryCnt

      private int entryCnt
      Number of positions within sortedEntries that are valid.
    • tree

      private DirCacheTree tree
      Cache tree for this index; null if the cache tree is not available.
    • myLock

      private LockFile myLock
      Our active lock (if we hold it); null if we don't have it locked.
    • snapshot

      private FileSnapshot snapshot
      Keep track of whether the index has changed or not
    • readIndexChecksum

      private byte[] readIndexChecksum
      index checksum when index was read from disk
    • writeIndexChecksum

      private byte[] writeIndexChecksum
      index checksum when index was written to disk
    • indexChangedListener

      private IndexChangedListener indexChangedListener
      listener to be informed on commit
    • repository

      private Repository repository
      Repository containing this index
    • version

      private DirCache.DirCacheVersion version
      If we read this index from disk, the original format.
  • Constructor Details

    • DirCache

      public DirCache(File indexLocation, FS fs)
      Create a new in-core index representation.

      The new index will be empty. Callers may wish to read from the on disk file first with read().

      Parameters:
      indexLocation - location of the index file on disk.
      fs - the file system abstraction which will be necessary to perform certain file system operations.
  • Method Details

    • cmp

      static int cmp(DirCacheEntry a, DirCacheEntry b)
    • cmp

      static int cmp(byte[] aPath, int aLen, DirCacheEntry b)
    • cmp

      static int cmp(byte[] aPath, int aLen, byte[] bPath, int bLen)
    • newInCore

      public static DirCache newInCore()
      Create a new empty index which is never stored on disk.
      Returns:
      an empty cache which has no backing store file. The cache may not be read or written, but it may be queried and updated (in memory).
    • read

      public static DirCache read(ObjectReader reader, AnyObjectId treeId) throws IOException
      Create a new in memory index read from the contents of a tree.
      Parameters:
      reader - reader to access the tree objects from a repository.
      treeId - tree to read. Must identify a tree, not a tree-ish.
      Returns:
      a new cache which has no backing store file, but contains the contents of treeId.
      Throws:
      IOException - one or more trees not available from the ObjectReader.
      Since:
      4.2
    • read

      public static DirCache read(Repository repository) throws CorruptObjectException, IOException
      Create a new in-core index representation and read an index from disk.

      The new index will be read before it is returned to the caller. Read failures are reported as exceptions and therefore prevent the method from returning a partially populated index.

      Parameters:
      repository - repository containing the index to read
      Returns:
      a cache representing the contents of the specified index file (if it exists) or an empty cache if the file does not exist.
      Throws:
      IOException - the index file is present but could not be read.
      CorruptObjectException - the index file is using a format or extension that this library does not support.
    • read

      public static DirCache read(File indexLocation, FS fs) throws CorruptObjectException, IOException
      Create a new in-core index representation and read an index from disk.

      The new index will be read before it is returned to the caller. Read failures are reported as exceptions and therefore prevent the method from returning a partially populated index.

      Parameters:
      indexLocation - location of the index file on disk.
      fs - the file system abstraction which will be necessary to perform certain file system operations.
      Returns:
      a cache representing the contents of the specified index file (if it exists) or an empty cache if the file does not exist.
      Throws:
      IOException - the index file is present but could not be read.
      CorruptObjectException - the index file is using a format or extension that this library does not support.
    • lock

      public static DirCache lock(File indexLocation, FS fs) throws CorruptObjectException, IOException
      Create a new in-core index representation, lock it, and read from disk.

      The new index will be locked and then read before it is returned to the caller. Read failures are reported as exceptions and therefore prevent the method from returning a partially populated index. On read failure, the lock is released.

      Parameters:
      indexLocation - location of the index file on disk.
      fs - the file system abstraction which will be necessary to perform certain file system operations.
      Returns:
      a cache representing the contents of the specified index file (if it exists) or an empty cache if the file does not exist.
      Throws:
      IOException - the index file is present but could not be read, or the lock could not be obtained.
      CorruptObjectException - the index file is using a format or extension that this library does not support.
    • lock

      public static DirCache lock(Repository repository, IndexChangedListener indexChangedListener) throws CorruptObjectException, IOException
      Create a new in-core index representation, lock it, and read from disk.

      The new index will be locked and then read before it is returned to the caller. Read failures are reported as exceptions and therefore prevent the method from returning a partially populated index. On read failure, the lock is released.

      Parameters:
      repository - repository containing the index to lock and read
      indexChangedListener - listener to be informed when DirCache is committed
      Returns:
      a cache representing the contents of the specified index file (if it exists) or an empty cache if the file does not exist.
      Throws:
      IOException - the index file is present but could not be read, or the lock could not be obtained.
      CorruptObjectException - the index file is using a format or extension that this library does not support.
      Since:
      2.0
    • lock

      public static DirCache lock(File indexLocation, FS fs, IndexChangedListener indexChangedListener) throws CorruptObjectException, IOException
      Create a new in-core index representation, lock it, and read from disk.

      The new index will be locked and then read before it is returned to the caller. Read failures are reported as exceptions and therefore prevent the method from returning a partially populated index. On read failure, the lock is released.

      Parameters:
      indexLocation - location of the index file on disk.
      fs - the file system abstraction which will be necessary to perform certain file system operations.
      indexChangedListener - listener to be informed when DirCache is committed
      Returns:
      a cache representing the contents of the specified index file (if it exists) or an empty cache if the file does not exist.
      Throws:
      IOException - the index file is present but could not be read, or the lock could not be obtained.
      CorruptObjectException - the index file is using a format or extension that this library does not support.
    • builder

      public DirCacheBuilder builder()
      Create a new builder to update this cache.

      Callers should add all entries to the builder, then use DirCacheBuilder.finish() to update this instance.

      Returns:
      a new builder instance for this cache.
    • editor

      public DirCacheEditor editor()
      Create a new editor to recreate this cache.

      Callers should add commands to the editor, then use DirCacheEditor.finish() to update this instance.

      Returns:
      a new builder instance for this cache.
    • getVersion

    • replace

      void replace(DirCacheEntry[] e, int cnt)
    • read

      public void read() throws IOException, CorruptObjectException
      Read the index from disk, if it has changed on disk.

      This method tries to avoid loading the index if it has not changed since the last time we consulted it. A missing index file will be treated as though it were present but had no file entries in it.

      Throws:
      IOException - the index file is present but could not be read. This DirCache instance may not be populated correctly.
      CorruptObjectException - the index file is using a format or extension that this library does not support.
    • isOutdated

      public boolean isOutdated() throws IOException
      Whether the memory state differs from the index file
      Returns:
      true if the memory state differs from the index file
      Throws:
      IOException
    • clear

      public void clear()
      Empty this index, removing all entries.
    • readFrom

      private void readFrom(InputStream inStream) throws IOException, CorruptObjectException
      Throws:
      IOException
      CorruptObjectException
    • skipOptionalExtension

      private void skipOptionalExtension(InputStream in, MessageDigest md, byte[] hdr, long sz) throws IOException
      Throws:
      IOException
    • formatExtensionName

      private static String formatExtensionName(byte[] hdr)
    • is_DIRC

      private static boolean is_DIRC(byte[] hdr)
    • lock

      public boolean lock() throws IOException
      Try to establish an update lock on the cache file.
      Returns:
      true if the lock is now held by the caller; false if it is held by someone else.
      Throws:
      IOException - the output file could not be created. The caller does not hold the lock.
    • write

      public void write() throws IOException
      Write the entry records from memory to disk.

      The cache must be locked first by calling lock() and receiving true as the return value. Applications are encouraged to lock the index, then invoke read() to ensure the in-memory data is current, prior to updating the in-memory entries.

      Once written the lock is closed and must be either committed with commit() or rolled back with unlock().

      Throws:
      IOException - the output file could not be created. The caller no longer holds the lock.
    • writeTo

      void writeTo(File dir, OutputStream os) throws IOException
      Throws:
      IOException
    • commit

      public boolean commit()
      Commit this change and release the lock.

      If this method fails (returns false) the lock is still released.

      Returns:
      true if the commit was successful and the file contains the new data; false if the commit failed and the file remains with the old data.
      Throws:
      IllegalStateException - the lock is not held.
    • requireLocked

      private void requireLocked(LockFile tmp)
    • unlock

      public void unlock()
      Unlock this file and abort this change.

      The temporary file (if created) is deleted before returning.

    • findEntry

      public int findEntry(String path)
      Locate the position a path's entry is at in the index. For details refer to #findEntry(byte[], int).
      Parameters:
      path - the path to search for.
      Returns:
      if >= 0 then the return value is the position of the entry in the index; pass to getEntry(int) to obtain the entry information. If < 0 the entry does not exist in the index.
    • findEntry

      public int findEntry(byte[] p, int pLen)
      Locate the position a path's entry is at in the index.

      If there is at least one entry in the index for this path the position of the lowest stage is returned. Subsequent stages can be identified by testing consecutive entries until the path differs.

      If no path matches the entry -(position+1) is returned, where position is the location it would have gone within the index.

      Parameters:
      p - the byte array starting with the path to search for.
      pLen - the length of the path in bytes
      Returns:
      if >= 0 then the return value is the position of the entry in the index; pass to getEntry(int) to obtain the entry information. If < 0 the entry does not exist in the index.
      Since:
      3.4
    • findEntry

      int findEntry(int low, byte[] p, int pLen)
    • nextEntry

      public int nextEntry(int position)
      Determine the next index position past all entries with the same name.

      As index entries are sorted by path name, then stage number, this method advances the supplied position to the first position in the index whose path name does not match the path name of the supplied position's entry.

      Parameters:
      position - entry position of the path that should be skipped.
      Returns:
      position of the next entry whose path is after the input.
    • nextEntry

      int nextEntry(byte[] p, int pLen, int nextIdx)
    • getEntryCount

      public int getEntryCount()
      Total number of file entries stored in the index.

      This count includes unmerged stages for a file entry if the file is currently conflicted in a merge. This means the total number of entries in the index may be up to 3 times larger than the number of files in the working directory.

      Note that this value counts only files.

      Returns:
      number of entries available.
      See Also:
    • getEntry

      public DirCacheEntry getEntry(int i)
      Get a specific entry.
      Parameters:
      i - position of the entry to get.
      Returns:
      the entry at position i.
    • getEntry

      public DirCacheEntry getEntry(String path)
      Get a specific entry.
      Parameters:
      path - the path to search for.
      Returns:
      the entry for the given path.
    • getEntriesWithin

      public DirCacheEntry[] getEntriesWithin(String path)
      Recursively get all entries within a subtree.
      Parameters:
      path - the subtree path to get all entries within.
      Returns:
      all entries recursively contained within the subtree.
    • toArray

      void toArray(int i, DirCacheEntry[] dst, int off, int cnt)
    • getCacheTree

      public DirCacheTree getCacheTree(boolean build)
      Obtain (or build) the current cache tree structure.

      This method can optionally recreate the cache tree, without flushing the tree objects themselves to disk.

      Parameters:
      build - if true and the cache tree is not present in the index it will be generated and returned to the caller.
      Returns:
      the cache tree; null if there is no current cache tree available and build was false.
    • writeTree

      Write all index trees to the object store, returning the root tree.
      Parameters:
      ow - the writer to use when serializing to the store. The caller is responsible for flushing the inserter before trying to use the returned tree identity.
      Returns:
      identity for the root tree.
      Throws:
      UnmergedPathException - one or more paths contain higher-order stages (stage > 0), which cannot be stored in a tree object.
      IllegalStateException - one or more paths contain an invalid mode which should never appear in a tree object.
      IOException - an unexpected error occurred writing to the object store.
    • hasUnmergedPaths

      public boolean hasUnmergedPaths()
      Tells whether this index contains unmerged paths.
      Returns:
      true if this index contains unmerged paths. Means: at least one entry is of a stage different from 0. false will be returned if all entries are of stage 0.
    • registerIndexChangedListener

      private void registerIndexChangedListener(IndexChangedListener listener)
    • updateSmudgedEntries

      private void updateSmudgedEntries() throws IOException
      Update any smudged entries with information from the working tree.
      Throws:
      IOException