Module org.eclipse.jgit
Package org.eclipse.jgit.internal.storage.file

Interface PackIndex

All Superinterfaces:
Iterable<PackIndex.MutableEntry>, ObjectIdSet
public interface PackIndex extends Iterable<PackIndex.MutableEntry>, ObjectIdSet
Access path to locate objects by ObjectId in a Pack.

Indexes are strictly redundant information in that we can rebuild all of the data held in the index file from the on disk representation of the pack file itself, but it is faster to access for random requests because data is stored by ObjectId.

  • Method Details

    • open

      static PackIndex open(File idxFile) throws IOException
      Open an existing pack .idx file for reading.

      The format of the file will be automatically detected and a proper access implementation for that format will be constructed and returned to the caller. The file may or may not be held open by the returned instance.

      Parameters:
      idxFile - existing pack .idx to read.
      Returns:
      access implementation for the requested file.
      Throws:
      FileNotFoundException - the file does not exist.
      IOException - the file exists but could not be read due to security errors, unrecognized data version, or unexpected data corruption.

    • read

      static PackIndex read(InputStream fd) throws IOException, CorruptObjectException
      Read an existing pack index file from a buffered stream.

      The format of the file will be automatically detected and a proper access implementation for that format will be constructed and returned to the caller. The file may or may not be held open by the returned instance.

      Parameters:
      fd - stream to read the index file from. The stream must be buffered as some small IOs are performed against the stream. The caller is responsible for closing the stream.
      Returns:
      a copy of the index in-memory.
      Throws:
      IOException - the stream cannot be read.
      CorruptObjectException - the stream does not contain a valid pack index.

    • hasObject

      default boolean hasObject(AnyObjectId id)
      Determine if an object is contained within the pack file.
      Parameters:
      id - the object to look for. Must not be null.
      Returns:
      true if the object is listed in this index; false otherwise.

    • contains

      default boolean contains(AnyObjectId id)
      Description copied from interface: ObjectIdSet
      Returns true if the objectId is contained within the collection.
      Specified by:
      contains in interface ObjectIdSet
      Parameters:
      id - the objectId to find
      Returns:
      whether the collection contains the objectId.

    • iterator

      Iterator<PackIndex.MutableEntry> iterator()

      Provide iterator that gives access to index entries. Note, that iterator returns reference to mutable object, the same reference in each call - for performance reason. If client needs immutable objects, it must copy returned object on its own.

      Iterator returns objects in SHA-1 lexicographical order.

      Specified by:
      iterator in interface Iterable<PackIndex.MutableEntry>

    • getObjectCount

      long getObjectCount()
      Obtain the total number of objects described by this index.
      Returns:
      number of objects in this index, and likewise in the associated pack that this index was generated from.

    • getOffset64Count

      long getOffset64Count()
      Obtain the total number of objects needing 64 bit offsets.
      Returns:
      number of objects in this index using a 64 bit offset; that is an object positioned after the 2 GB position within the file.

    • getObjectId

      ObjectId getObjectId(long nthPosition)
      Get ObjectId for the n-th object entry returned by iterator().

      This method is a constant-time replacement for the following loop: 

       Iterator<MutableEntry> eItr = index.iterator();
 int curPosition = 0;
 while (eItr.hasNext() && curPosition++ < nthPosition)
        eItr.next();
 ObjectId result = eItr.next().toObjectId();
      Parameters:
      nthPosition - position within the traversal of iterator() that the caller needs the object for. The first returned PackIndex.MutableEntry is 0, the second is 1, etc.
      Returns:
      the ObjectId for the corresponding entry.

    • getObjectId

      default ObjectId getObjectId(int nthPosition)
      Get ObjectId for the n-th object entry returned by iterator().

      This method is a constant-time replacement for the following loop: 

       Iterator<MutableEntry> eItr = index.iterator();
 int curPosition = 0;
 while (eItr.hasNext() && curPosition++ < nthPosition)
        eItr.next();
 ObjectId result = eItr.next().toObjectId();
      Parameters:
      nthPosition - unsigned 32 bit position within the traversal of iterator() that the caller needs the object for. The first returned PackIndex.MutableEntry is 0, the second is 1, etc. Positions past 2**31-1 are negative, but still valid.
      Returns:
      the ObjectId for the corresponding entry.

    • getOffset

      long getOffset(long nthPosition)
      Get offset in a pack for the n-th object entry returned by iterator().
      Parameters:
      nthPosition - unsigned 32 bit position within the traversal of iterator() for which the caller needs the offset. The first returned PackIndex.MutableEntry is 0, the second is 1, etc. Positions past 2**31-1 are negative, but still valid.
      Returns:
      the offset in a pack for the corresponding entry.

    • findOffset

      long findOffset(AnyObjectId objId)
      Locate the file offset position for the requested object.
      Parameters:
      objId - name of the object to locate within the pack.
      Returns:
      offset of the object's header and compressed content; -1 if the object does not exist in this index and is thus not stored in the associated pack.

    • findPosition

      int findPosition(AnyObjectId objId)
      Locate the position of this id in the list of object-ids in the index
      Parameters:
      objId - name of the object to locate within the index
      Returns:
      position of the object-id in the lexicographically ordered list of ids stored in this index; -1 if the object does not exist in this index and is thus not stored in the associated pack.

    • findCRC32

      long findCRC32(AnyObjectId objId) throws MissingObjectException, UnsupportedOperationException
      Retrieve stored CRC32 checksum of the requested object raw-data (including header).
      Parameters:
      objId - id of object to look for
      Returns:
      CRC32 checksum of specified object (at 32 less significant bits)
      Throws:
      MissingObjectException - when requested ObjectId was not found in this index
      UnsupportedOperationException - when this index doesn't support CRC32 checksum

    • hasCRC32Support

      boolean hasCRC32Support()
      Check whether this index supports (has) CRC32 checksums for objects.
      Returns:
      true if CRC32 is stored, false otherwise

    • resolve

      void resolve(Set<ObjectId> matches, AbbreviatedObjectId id, int matchLimit) throws IOException
      Find objects matching the prefix abbreviation.
      Parameters:
      matches - set to add any located ObjectIds to. This is an output parameter.
      id - prefix to search for.
      matchLimit - maximum number of results to return. At most this many ObjectIds should be added to matches before returning.
      Throws:
      IOException - the index cannot be read.

    • getChecksum

      byte[] getChecksum()
      Get pack checksum
      Returns:
      the checksum of the pack; caller must not modify it
      Since:
      5.5