org.eclipse.jgit.internal.storage.dfs

Class DfsObjDatabase

java.lang.Object

org.eclipse.jgit.lib.ObjectDatabase

org.eclipse.jgit.internal.storage.dfs.DfsObjDatabase

public abstract class DfsObjDatabase
extends ObjectDatabase

Manages objects stored in DfsPackFile on a storage system.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DfsObjDatabase.PackSource Sources for a pack file.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	DfsObjDatabase(DfsRepository repository, DfsReaderOptions options) Initialize an object database for our repository.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	clearCache() Clears the cached list of packs, forcing them to be scanned again.
void	close() Close any resources held by this database.
protected void	commitPack(Collection<DfsPackDescription> desc, Collection<DfsPackDescription> replaces) Commit a pack and index pair that was written to the DFS.
protected abstract void	commitPackImpl(Collection<DfsPackDescription> desc, Collection<DfsPackDescription> replaces) Implementation of pack commit.
DfsPackFile[]	getCurrentPacks() List currently known pack files in the repository, without scanning.
DfsPackFile[]	getPacks() Scan and list all available pack files in the repository.
DfsReaderOptions	getReaderOptions()
protected DfsRepository	getRepository()
protected abstract List<DfsPackDescription>	listPacks() List the available pack files.
ObjectInserter	newInserter() Create a new ObjectInserter to insert new objects.
protected abstract DfsPackDescription	newPack(DfsObjDatabase.PackSource source) Generate a new unique name for a pack file.
ObjectReader	newReader() Create a new ObjectReader to read existing objects.
protected abstract ReadableChannel	openFile(DfsPackDescription desc, PackExt ext) Open a pack, pack index, or other related file for reading.
protected abstract void	rollbackPack(Collection<DfsPackDescription> desc) Try to rollback a pack creation.
protected abstract DfsOutputStream	writeFile(DfsPackDescription desc, PackExt ext) Open a pack, pack index, or other related file for writing.

Methods inherited from class org.eclipse.jgit.lib.ObjectDatabase

create, exists, has, newCachedDatabase, open, open

Methods inherited from class java.lang.Object

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

Constructor Detail

DfsObjDatabase

protected DfsObjDatabase(DfsRepository repository,
              DfsReaderOptions options)

Initialize an object database for our repository.

Parameters:

repository - repository owning this object database.

options - how readers should access the object database.

Method Detail

getReaderOptions

public DfsReaderOptions getReaderOptions()

Returns:

configured reader options, such as read-ahead.

newReader

public ObjectReader newReader()

Description copied from class: ObjectDatabase

Create a new ObjectReader to read existing objects.

The returned reader is not itself thread-safe, but multiple concurrent reader instances created from the same ObjectDatabase must be thread-safe.

Specified by:

newReader in class ObjectDatabase

Returns:

reader the caller can use to load objects from this database.

newInserter

public ObjectInserter newInserter()

Description copied from class: ObjectDatabase

Create a new ObjectInserter to insert new objects.

The returned inserter is not itself thread-safe, but multiple concurrent inserter instances created from the same ObjectDatabase must be thread-safe.

Specified by:

newInserter in class ObjectDatabase

Returns:

writer the caller can use to create objects in this database.

getPacks

public DfsPackFile[] getPacks()
                       throws IOException

Scan and list all available pack files in the repository.

Returns:

list of available packs. The returned array is shared with the implementation and must not be modified by the caller.

Throws:

IOException - the pack list cannot be initialized.

getRepository

protected DfsRepository getRepository()

Returns:

repository owning this object database.

getCurrentPacks

public DfsPackFile[] getCurrentPacks()

List currently known pack files in the repository, without scanning.

Returns:

list of available packs. The returned array is shared with the implementation and must not be modified by the caller.

newPack

protected abstract DfsPackDescription newPack(DfsObjDatabase.PackSource source)
                                       throws IOException

Generate a new unique name for a pack file.

Parameters:

source - where the pack stream is created.

Returns:

a unique name for the pack file. Must not collide with any other pack file name in the same DFS.

Throws:

IOException - a new unique pack description cannot be generated.

commitPack

protected void commitPack(Collection<DfsPackDescription> desc,
              Collection<DfsPackDescription> replaces)
                   throws IOException

Commit a pack and index pair that was written to the DFS.

Committing the pack/index pair makes them visible to readers. The JGit DFS code always writes the pack, then the index. This allows a simple commit process to do nothing if readers always look for both files to exist and the DFS performs atomic creation of the file (e.g. stream to a temporary file and rename to target on close).

During pack compaction or GC the new pack file may be replacing other older files. Implementations should remove those older files (if any) as part of the commit of the new file.

This method is a trivial wrapper around commitPackImpl(Collection, Collection) that calls the implementation and fires events.

Parameters:

desc - description of the new packs.

replaces - if not null, list of packs to remove.

Throws:

IOException - the packs cannot be committed. On failure a rollback must also be attempted by the caller.

commitPackImpl

protected abstract void commitPackImpl(Collection<DfsPackDescription> desc,
                  Collection<DfsPackDescription> replaces)
                                throws IOException

Implementation of pack commit.

Parameters:

desc - description of the new packs.

replaces - if not null, list of packs to remove.

Throws:

IOException - the packs cannot be committed.

See Also:

commitPack(Collection, Collection)

rollbackPack

protected abstract void rollbackPack(Collection<DfsPackDescription> desc)

Try to rollback a pack creation.

JGit DFS always writes the pack first, then the index. If the pack does not yet exist, then neither does the index. A safe DFS implementation would try to remove both files to ensure they are really gone.

A rollback does not support failures, as it only occurs when there is already a failure in progress. A DFS implementor may wish to log warnings/error messages when a rollback fails, but should not send new exceptions up the Java callstack.

Parameters:

desc - pack to delete.

listPacks

protected abstract List<DfsPackDescription> listPacks()
                                               throws IOException

List the available pack files.

The returned list must support random access and must be mutable by the caller. It is sorted in place using the natural sorting of the returned DfsPackDescription objects.

Returns:

available packs. May be empty if there are no packs.

Throws:

IOException - the packs cannot be listed and the object database is not functional to the caller.

openFile

protected abstract ReadableChannel openFile(DfsPackDescription desc,
                       PackExt ext)
                                     throws FileNotFoundException,
                                            IOException

Open a pack, pack index, or other related file for reading.

Parameters:

desc - description of pack related to the data that will be read. This is an instance previously obtained from listPacks(), but not necessarily from the same DfsObjDatabase instance.

ext - file extension that will be read i.e "pack" or "idx".

Returns:

channel to read the file.

Throws:

FileNotFoundException - the file does not exist.

IOException - the file cannot be opened.

writeFile

protected abstract DfsOutputStream writeFile(DfsPackDescription desc,
                        PackExt ext)
                                      throws IOException

Open a pack, pack index, or other related file for writing.

Parameters:

desc - description of pack related to the data that will be written. This is an instance previously obtained from newPack(PackSource).

ext - file extension that will be written i.e "pack" or "idx".

Returns:

channel to write the file.

Throws:

IOException - the file cannot be opened.

clearCache

protected void clearCache()

Clears the cached list of packs, forcing them to be scanned again.

close

public void close()

Description copied from class: ObjectDatabase

Close any resources held by this database.

Specified by:

close in class ObjectDatabase