org.eclipse.jgit.dircache
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.

Constructor Summary

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

Method Summary

DirCacheBuilder	builder() Create a new builder to update this cache.
void	clear() Empty this index, removing all entries.
boolean	commit() Commit this change and release the lock.
DirCacheEditor	editor() Create a new editor to recreate this cache.
int	findEntry(String path) Locate the position a path's entry is at in the index.
DirCacheTree	getCacheTree(boolean build) Obtain (or build) the current cache tree structure.
DirCacheEntry[]	getEntriesWithin(String path) Recursively get all entries within a subtree.
DirCacheEntry	getEntry(int i) Get a specific entry.
DirCacheEntry	getEntry(String path) Get a specific entry.
int	getEntryCount() Total number of file entries stored in the index.
boolean	hasUnmergedPaths() Tells whether this index contains unmerged paths.
boolean	isOutdated()
boolean	lock() Try to establish an update lock on the cache file.
static DirCache	lock(File indexLocation, FS fs) Create a new in-core index representation, lock it, and read from disk.
static DirCache	lock(File indexLocation, FS fs, IndexChangedListener indexChangedListener) Create a new in-core index representation, lock it, and read from disk.
static DirCache	lock(Repository repository, IndexChangedListener indexChangedListener) Create a new in-core index representation, lock it, and read from disk.
static DirCache	newInCore() Create a new empty index which is never stored on disk.
int	nextEntry(int position) Determine the next index position past all entries with the same name.
void	read() Read the index from disk, if it has changed on disk.
static DirCache	read(File indexLocation, FS fs) Create a new in-core index representation and read an index from disk.
static DirCache	read(Repository repository) Create a new in-core index representation and read an index from disk.
void	unlock() Unlock this file and abort this change.
void	write() Write the entry records from memory to disk.
ObjectId	writeTree(ObjectInserter ow) Write all index trees to the object store, returning the root tree.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

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 Detail

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(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.

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

Returns:

true if the memory state differs from the index file

Throws:

IOException

clear

public void clear()

Empty this index, removing all entries.

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.

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.

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.

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:

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.

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.

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(int)

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.

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

public ObjectId writeTree(ObjectInserter ow)
                   throws UnmergedPathException,
                          IOException

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.