org.eclipse.jgit.storage.pack
Class PackWriter

java.lang.Object
  org.eclipse.jgit.storage.pack.PackWriter

public class PackWriter
extends Object

PackWriter class is responsible for generating pack files from specified set of objects from repository. This implementation produce pack files in format version 2.

Source of objects may be specified in two ways:

• (usually) by providing sets of interesting and uninteresting objects in repository - all interesting objects and their ancestors except uninteresting objects and their ancestors will be included in pack, or
• by providing iterator of RevObject specifying exact list and order of objects in pack

Typical usage consists of creating instance intended for some pack, configuring options, preparing the list of objects by calling preparePack(Iterator) or preparePack(ProgressMonitor, Collection, Collection), and finally producing the stream with writePack(ProgressMonitor, ProgressMonitor, OutputStream).

Class provide set of configurable options and ProgressMonitor support, as operations may take a long time for big repositories. Deltas searching algorithm is NOT IMPLEMENTED yet - this implementation relies only on deltas and objects reuse.

This class is not thread safe, it is intended to be used in one thread, with one instance per created pack. Subsequent calls to writePack result in undefined behavior.

Nested Class Summary

static interface	PackWriter.ObjectIdSet A collection of object ids.
static class	PackWriter.PackingPhase Possible states that a PackWriter can be in.
class	PackWriter.State Summary of the current state of a PackWriter.
static class	PackWriter.Statistics Summary of how PackWriter created the pack.

Constructor Summary

PackWriter(ObjectReader reader)
Create a writer to load objects from the specified reader.

PackWriter(PackConfig config, ObjectReader reader)
Create writer with a specified configuration.

PackWriter(Repository repo)
Create writer for specified repository.

PackWriter(Repository repo, ObjectReader reader)
Create writer for specified repository.

Method Summary

void	addObject(RevObject object) Include one object to the output file.
ObjectId	computeName() Computes SHA-1 of lexicographically sorted objects ids written in this pack, as used to name a pack file in repository.
void	excludeObjects(PackWriter.ObjectIdSet idx) Add a pack index whose contents should be excluded from the result.
ObjectToPack	get(AnyObjectId id) Lookup the ObjectToPack object for a given ObjectId.
static Iterable<PackWriter>	getInstances()
long	getObjectCount() Returns objects number in a pack file that was created by this writer.
ObjectIdOwnerMap<ObjectIdOwnerMap.Entry>	getObjectSet() Returns the object ids in the pack file that was created by this writer.
PackWriter.State	getState()
PackWriter.Statistics	getStatistics()
boolean	isDeltaBaseAsOffset() Check whether writer can store delta base as an offset (new style reducing pack size) or should store it as an object id (legacy style, compatible with old readers).
boolean	isIgnoreMissingUninteresting()
boolean	isReuseDeltaCommits() Check if the writer will reuse commits that are already stored as deltas.
boolean	isReuseValidatingObjects() Check if the writer validates objects before copying them.
boolean	isThin()
boolean	isUseCachedPacks()
void	preparePack(Iterator<RevObject> objectsSource) Prepare the list of objects to be written to the pack stream.
void	preparePack(ProgressMonitor countingMonitor, Collection<? extends ObjectId> want, Collection<? extends ObjectId> have) Deprecated. to be removed in 2.0; use the Set version of this method.
void	preparePack(ProgressMonitor countingMonitor, ObjectWalk walk, Collection<? extends ObjectId> interestingObjects, Collection<? extends ObjectId> uninterestingObjects) Deprecated. to be removed in 2.0; use the Set version of this method.
void	preparePack(ProgressMonitor countingMonitor, ObjectWalk walk, Set<? extends ObjectId> interestingObjects, Set<? extends ObjectId> uninterestingObjects) Prepare the list of objects to be written to the pack stream.
void	preparePack(ProgressMonitor countingMonitor, Set<? extends ObjectId> want, Set<? extends ObjectId> have) Prepare the list of objects to be written to the pack stream.
void	release() Release all resources used by this writer.
void	select(ObjectToPack otp, StoredObjectRepresentation next) Select an object representation for this writer.
void	setDeltaBaseAsOffset(boolean deltaBaseAsOffset) Set writer delta base format.
void	setIgnoreMissingUninteresting(boolean ignore)
void	setReuseDeltaCommits(boolean reuse) Set the writer to reuse existing delta versions of commits.
void	setReuseValidatingObjects(boolean validate) Enable (or disable) object validation during packing.
void	setShallowPack(int depth, Collection<? extends ObjectId> unshallow) Configure this pack for a shallow clone.
void	setTagTargets(Set<ObjectId> objects) Set the tag targets that should be hoisted earlier during packing.
void	setThin(boolean packthin)
void	setUseCachedPacks(boolean useCached)
boolean	willInclude(AnyObjectId id) Determine if the pack file will contain the requested object.
void	writeIndex(OutputStream indexStream) Create an index file to match the pack file just written.
void	writePack(ProgressMonitor compressMonitor, ProgressMonitor writeMonitor, OutputStream packStream) Write the prepared pack to the supplied stream.

Methods inherited from class java.lang.Object

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

Constructor Detail

PackWriter

public PackWriter(Repository repo)

Create writer for specified repository.

Objects for packing are specified in preparePack(Iterator) or preparePack(ProgressMonitor, Collection, Collection).

Parameters:

repo - repository where objects are stored.

PackWriter

public PackWriter(ObjectReader reader)

Create a writer to load objects from the specified reader.

Objects for packing are specified in preparePack(Iterator) or preparePack(ProgressMonitor, Collection, Collection).

Parameters:

reader - reader to read from the repository with.

PackWriter

public PackWriter(Repository repo,
                  ObjectReader reader)

Create writer for specified repository.

Objects for packing are specified in preparePack(Iterator) or preparePack(ProgressMonitor, Collection, Collection).

Parameters:

repo - repository where objects are stored.

reader - reader to read from the repository with.

PackWriter

public PackWriter(PackConfig config,
                  ObjectReader reader)

Create writer with a specified configuration.

Objects for packing are specified in preparePack(Iterator) or preparePack(ProgressMonitor, Collection, Collection).

Parameters:

config - configuration for the pack writer.

reader - reader to read from the repository with.

Method Detail

getInstances

public static Iterable<PackWriter> getInstances()

Returns:

all allocated, non-released PackWriters instances.

isDeltaBaseAsOffset

public boolean isDeltaBaseAsOffset()

Check whether writer can store delta base as an offset (new style reducing pack size) or should store it as an object id (legacy style, compatible with old readers). Default setting:

Returns:

true if delta base is stored as an offset; false if it is stored as an object id.

setDeltaBaseAsOffset

public void setDeltaBaseAsOffset(boolean deltaBaseAsOffset)

Set writer delta base format. Delta base can be written as an offset in a pack file (new approach reducing file size) or as an object id (legacy approach, compatible with old readers). Default setting:

Parameters:

deltaBaseAsOffset - boolean indicating whether delta base can be stored as an offset.

isReuseDeltaCommits

public boolean isReuseDeltaCommits()

Check if the writer will reuse commits that are already stored as deltas.

Returns:

true if the writer would reuse commits stored as deltas, assuming delta reuse is already enabled.

setReuseDeltaCommits

public void setReuseDeltaCommits(boolean reuse)

Set the writer to reuse existing delta versions of commits.

Parameters:

reuse - if true, the writer will reuse any commits stored as deltas. By default the writer does not reuse delta commits.

isReuseValidatingObjects

public boolean isReuseValidatingObjects()

Check if the writer validates objects before copying them.

Returns:

true if validation is enabled; false if the reader will handle object validation as a side-effect of it consuming the output.

setReuseValidatingObjects

public void setReuseValidatingObjects(boolean validate)

Enable (or disable) object validation during packing.

Parameters:

validate - if true the pack writer will validate an object before it is put into the output. This additional validation work may be necessary to avoid propagating corruption from one local pack file to another local pack file.

isThin

public boolean isThin()

Returns:

true if this writer is producing a thin pack.

setThin

public void setThin(boolean packthin)

Parameters:

packthin - a boolean indicating whether writer may pack objects with delta base object not within set of objects to pack, but belonging to party repository (uninteresting/boundary) as determined by set; this kind of pack is used only for transport; true - to produce thin pack, false - otherwise.

isUseCachedPacks

public boolean isUseCachedPacks()

Returns:

true to reuse cached packs. If true index creation isn't available.

setUseCachedPacks

public void setUseCachedPacks(boolean useCached)

Parameters:

useCached - if set to true and a cached pack is present, it will be appended onto the end of a thin-pack, reducing the amount of working set space and CPU used by PackWriter. Enabling this feature prevents PackWriter from creating an index for the newly created pack, so its only suitable for writing to a network client, where the client will make the index.

isIgnoreMissingUninteresting

public boolean isIgnoreMissingUninteresting()

Returns:

true to ignore objects that are uninteresting and also not found on local disk; false to throw a MissingObjectException out of preparePack(ProgressMonitor, Collection, Collection) if an uninteresting object is not in the source repository. By default, true, permitting gracefully ignoring of uninteresting objects.

setIgnoreMissingUninteresting

public void setIgnoreMissingUninteresting(boolean ignore)

Parameters:

ignore - true if writer should ignore non existing uninteresting objects during construction set of objects to pack; false otherwise - non existing uninteresting objects may cause MissingObjectException

setTagTargets

public void setTagTargets(Set<ObjectId> objects)

Set the tag targets that should be hoisted earlier during packing.

Callers may put objects into this set before invoking any of the preparePack methods to influence where an annotated tag's target is stored within the resulting pack. Typically these will be clustered together, and hoisted earlier in the file even if they are ancient revisions, allowing readers to find tag targets with better locality.

Parameters:

objects - objects that annotated tags point at.

setShallowPack

public void setShallowPack(int depth,
                           Collection<? extends ObjectId> unshallow)

Configure this pack for a shallow clone.

Parameters:

depth - maximum depth to traverse the commit graph

unshallow - objects which used to be shallow on the client, but are being extended as part of this fetch

getObjectCount

public long getObjectCount()
                    throws IOException

Returns objects number in a pack file that was created by this writer.

Returns:

number of objects in pack.

Throws:

IOException - a cached pack cannot supply its object count.

getObjectSet

public ObjectIdOwnerMap<ObjectIdOwnerMap.Entry> getObjectSet()
                                                      throws IOException

Returns the object ids in the pack file that was created by this writer. This method can only be invoked after writePack(ProgressMonitor, ProgressMonitor, OutputStream) has been invoked and completed successfully.

Returns:

number of objects in pack.

Throws:

IOException - a cached pack cannot supply its object ids.

excludeObjects

public void excludeObjects(PackWriter.ObjectIdSet idx)

Add a pack index whose contents should be excluded from the result.

Parameters:

idx - objects in this index will not be in the output pack.

preparePack

public void preparePack(Iterator<RevObject> objectsSource)
                 throws IOException

Prepare the list of objects to be written to the pack stream.

Iterator exactly determines which objects are included in a pack and order they appear in pack (except that objects order by type is not needed at input). This order should conform general rules of ordering objects in git - by recency and path (type and delta-base first is internally secured) and responsibility for guaranteeing this order is on a caller side. Iterator must return each id of object to write exactly once.

Parameters:

objectsSource - iterator of object to store in a pack; order of objects within each type is important, ordering by type is not needed; allowed types for objects are Constants.OBJ_COMMIT, Constants.OBJ_TREE, Constants.OBJ_BLOB and Constants.OBJ_TAG; objects returned by iterator may be later reused by caller as object id and type are internally copied in each iteration.

Throws:

IOException - when some I/O problem occur during reading objects.

preparePack

@Deprecated
public void preparePack(ProgressMonitor countingMonitor,
                                   Collection<? extends ObjectId> want,
                                   Collection<? extends ObjectId> have)
                 throws IOException

Deprecated. to be removed in 2.0; use the Set version of this method.

Prepare the list of objects to be written to the pack stream.

Basing on these 2 sets, another set of objects to put in a pack file is created: this set consists of all objects reachable (ancestors) from interesting objects, except uninteresting objects and their ancestors. This method uses class ObjectWalk extensively to find out that appropriate set of output objects and their optimal order in output pack. Order is consistent with general git in-pack rules: sort by object type, recency, path and delta-base first.

Parameters:

countingMonitor - progress during object enumeration.

want - collection of objects to be marked as interesting (start points of graph traversal).

have - collection of objects to be marked as uninteresting (end points of graph traversal).

Throws:

IOException - when some I/O problem occur during reading objects.

preparePack

@Deprecated
public void preparePack(ProgressMonitor countingMonitor,
                                   ObjectWalk walk,
                                   Collection<? extends ObjectId> interestingObjects,
                                   Collection<? extends ObjectId> uninterestingObjects)
                 throws IOException

Deprecated. to be removed in 2.0; use the Set version of this method.

Prepare the list of objects to be written to the pack stream.

Basing on these 2 sets, another set of objects to put in a pack file is created: this set consists of all objects reachable (ancestors) from interesting objects, except uninteresting objects and their ancestors. This method uses class ObjectWalk extensively to find out that appropriate set of output objects and their optimal order in output pack. Order is consistent with general git in-pack rules: sort by object type, recency, path and delta-base first.

Parameters:

countingMonitor - progress during object enumeration.

walk - ObjectWalk to perform enumeration.

interestingObjects - collection of objects to be marked as interesting (start points of graph traversal).

uninterestingObjects - collection of objects to be marked as uninteresting (end points of graph traversal).

Throws:

IOException - when some I/O problem occur during reading objects.

preparePack

public void preparePack(ProgressMonitor countingMonitor,
                        Set<? extends ObjectId> want,
                        Set<? extends ObjectId> have)
                 throws IOException

Prepare the list of objects to be written to the pack stream.

Basing on these 2 sets, another set of objects to put in a pack file is created: this set consists of all objects reachable (ancestors) from interesting objects, except uninteresting objects and their ancestors. This method uses class ObjectWalk extensively to find out that appropriate set of output objects and their optimal order in output pack. Order is consistent with general git in-pack rules: sort by object type, recency, path and delta-base first.

Parameters:

countingMonitor - progress during object enumeration.

want - collection of objects to be marked as interesting (start points of graph traversal).

have - collection of objects to be marked as uninteresting (end points of graph traversal).

Throws:

IOException - when some I/O problem occur during reading objects.

preparePack

public void preparePack(ProgressMonitor countingMonitor,
                        ObjectWalk walk,
                        Set<? extends ObjectId> interestingObjects,
                        Set<? extends ObjectId> uninterestingObjects)
                 throws IOException

Prepare the list of objects to be written to the pack stream.

Basing on these 2 sets, another set of objects to put in a pack file is created: this set consists of all objects reachable (ancestors) from interesting objects, except uninteresting objects and their ancestors. This method uses class ObjectWalk extensively to find out that appropriate set of output objects and their optimal order in output pack. Order is consistent with general git in-pack rules: sort by object type, recency, path and delta-base first.

Parameters:

countingMonitor - progress during object enumeration.

walk - ObjectWalk to perform enumeration.

interestingObjects - collection of objects to be marked as interesting (start points of graph traversal).

uninterestingObjects - collection of objects to be marked as uninteresting (end points of graph traversal).

Throws:

IOException - when some I/O problem occur during reading objects.

willInclude

public boolean willInclude(AnyObjectId id)
                    throws IOException

Determine if the pack file will contain the requested object.

Parameters:

id - the object to test the existence of.

Returns:

true if the object will appear in the output pack file.

Throws:

IOException - a cached pack cannot be examined.

get

public ObjectToPack get(AnyObjectId id)

Lookup the ObjectToPack object for a given ObjectId.

Parameters:

id - the object to find in the pack.

Returns:

the object we are packing, or null.

computeName

public ObjectId computeName()

Computes SHA-1 of lexicographically sorted objects ids written in this pack, as used to name a pack file in repository.

Returns:

ObjectId representing SHA-1 name of a pack that was created.

writeIndex

public void writeIndex(OutputStream indexStream)
                throws IOException

Create an index file to match the pack file just written.

This method can only be invoked after writePack(ProgressMonitor, ProgressMonitor, OutputStream) has been invoked and completed successfully. Writing a corresponding index is an optional feature that not all pack users may require.

Parameters:

indexStream - output for the index data. Caller is responsible for closing this stream.

Throws:

IOException - the index data could not be written to the supplied stream.

writePack

public void writePack(ProgressMonitor compressMonitor,
                      ProgressMonitor writeMonitor,
                      OutputStream packStream)
               throws IOException

Write the prepared pack to the supplied stream.

At first, this method collects and sorts objects to pack, then deltas search is performed if set up accordingly, finally pack stream is written.

All reused objects data checksum (Adler32/CRC32) is computed and validated against existing checksum.

Parameters:

compressMonitor - progress monitor to report object compression work.

writeMonitor - progress monitor to report the number of objects written.

packStream - output stream of pack data. The stream should be buffered by the caller. The caller is responsible for closing the stream.

Throws:

IOException - an error occurred reading a local object's data to include in the pack, or writing compressed object data to the output stream.

getStatistics

public PackWriter.Statistics getStatistics()

Returns:

description of what this PackWriter did in order to create the final pack stream. The object is only available to callers after writePack(ProgressMonitor, ProgressMonitor, OutputStream)

getState

public PackWriter.State getState()

Returns:

snapshot of the current state of this PackWriter.

release

public void release()

Release all resources used by this writer.

addObject

public void addObject(RevObject object)
               throws IncorrectObjectTypeException

Include one object to the output file.

Objects are written in the order they are added. If the same object is added twice, it may be written twice, creating a larger than necessary file.

Parameters:

object - the object to add.

Throws:

IncorrectObjectTypeException - the object is an unsupported type.

select

public void select(ObjectToPack otp,
                   StoredObjectRepresentation next)

Select an object representation for this writer.

An ObjectReader implementation should invoke this method once for each representation available for an object, to allow the writer to find the most suitable one for the output.

Parameters:

otp - the object being packed.

next - the next available representation from the repository.