org.eclipse.jgit.internal.storage.pack

Class PackWriter

java.lang.Object

org.eclipse.jgit.internal.storage.pack.PackWriter

All Implemented Interfaces:

AutoCloseable

public class PackWriter
extends Object
implements AutoCloseable

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 an instance, configuring options, preparing the list of objects by calling preparePack(Iterator) or preparePack(ProgressMonitor, Set, Set), and streaming with writePack(ProgressMonitor, ProgressMonitor, OutputStream). If the pack is being stored as a file the matching index can be written out after writing the pack by writeIndex(OutputStream). An optional bitmap index can be made by calling prepareBitmapIndex(ProgressMonitor) followed by writeBitmapIndex(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 as a single pass to produce one pack. Invoking methods multiple times or out of order is not supported as internal data structures are destroyed during certain phases to save memory when packing large repositories.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PackWriter.PackingPhase Possible states that a PackWriter can be in.
class	PackWriter.State Summary of the current state of a PackWriter.

Field Summary

Fields

Modifier and Type	Field and Description
static Set<ObjectId>	NONE Empty set of objects for preparePack().

Constructor Summary

Constructors

Constructor and Description
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(PackConfig config, ObjectReader reader, PackStatistics.Accumulator statsAccumulator) 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

Modifier and Type	Method and Description
void	addObject(RevObject object) Include one object to the output file.
void	close()
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(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.
int	getIndexVersion() Returns the index format version that will be written.
static Iterable<PackWriter>	getInstances() Get all allocated, non-released PackWriters instances.
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() Get snapshot of the current state of this PackWriter.
PackStatistics	getStatistics() Get statistics of what this PackWriter did in order to create the final pack stream.
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() Whether to ignore missing uninteresting objects
boolean	isIndexDisabled() Whether the index file cannot be created by this PackWriter.
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() Whether this writer is producing a thin pack.
boolean	isUseBitmaps() Whether to use bitmaps
boolean	isUseCachedPacks() Whether to reuse cached packs.
boolean	prepareBitmapIndex(ProgressMonitor pm) Prepares the bitmaps to be written to the bitmap index file.
void	preparePack(Iterator<RevObject> objectsSource) Prepare the list of objects to be written to the pack stream.
void	preparePack(ProgressMonitor countingMonitor, ObjectWalk walk, Set<? extends ObjectId> interestingObjects, Set<? extends ObjectId> uninterestingObjects, Set<? extends ObjectId> noBitmaps) 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	preparePack(ProgressMonitor countingMonitor, Set<? extends ObjectId> want, Set<? extends ObjectId> have, Set<? extends ObjectId> shallow) Prepare the list of objects to be written to the pack stream.
void	preparePack(ProgressMonitor countingMonitor, Set<? extends ObjectId> want, Set<? extends ObjectId> have, Set<? extends ObjectId> shallow, Set<? extends ObjectId> noBitmaps) Prepare the list of objects to be written to the pack stream.
void	select(ObjectToPack otp, StoredObjectRepresentation next) Select an object representation for this writer.
void	setClientShallowCommits(Set<ObjectId> clientShallowCommits) Records the set of shallow commits in the client.
void	setDeltaBaseAsOffset(boolean deltaBaseAsOffset) Set writer delta base format.
void	setFilterBlobLimit(long bytes)
void	setIgnoreMissingUninteresting(boolean ignore) Whether writer should ignore non existing uninteresting objects
void	setIndexDisabled(boolean noIndex) Whether to disable creation of the index file.
PackWriter	setObjectCountCallback(ObjectCountCallback callback) Set the ObjectCountCallback.
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) Whether writer may pack objects with delta base object not within set of objects to pack
void	setUseBitmaps(boolean useBitmaps) Whether to use bitmaps
void	setUseCachedPacks(boolean useCached) Whether to use cached packs
boolean	willInclude(AnyObjectId id) Determine if the pack file will contain the requested object.
void	writeBitmapIndex(OutputStream bitmapIndexStream) Create a bitmap index file to match the pack file just written.
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

Field Detail

NONE

public static final Set<ObjectId> NONE

Empty set of objects for preparePack().

Constructor Detail

PackWriter

public PackWriter(Repository repo)

Create writer for specified repository.

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

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, Set, Set).

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, Set, Set).

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, Set, Set).

Parameters:

config - configuration for the pack writer.

reader - reader to read from the repository with.

PackWriter

public PackWriter(PackConfig config,
                  ObjectReader reader,
                  @Nullable
                  PackStatistics.Accumulator statsAccumulator)

Create writer with a specified configuration.

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

Parameters:

config - configuration for the pack writer.

reader - reader to read from the repository with.

statsAccumulator - accumulator for statics

Method Detail

getInstances

public static Iterable<PackWriter> getInstances()

Get all allocated, non-released PackWriters instances.

Returns:

all allocated, non-released PackWriters instances.

setObjectCountCallback

public PackWriter setObjectCountCallback(ObjectCountCallback callback)

Set the ObjectCountCallback.

It should be set before calling writePack(ProgressMonitor, ProgressMonitor, OutputStream).

Parameters:

callback - the callback to set

Returns:

this object for chaining.

setClientShallowCommits

public void setClientShallowCommits(Set<ObjectId> clientShallowCommits)

Records the set of shallow commits in the client.

Parameters:

clientShallowCommits - the shallow commits in the client

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()

Whether this writer is producing a thin pack.

Returns:

true if this writer is producing a thin pack.

setThin

public void setThin(boolean packthin)

Whether writer may pack objects with delta base object not within set of objects to pack

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()

Whether to reuse cached packs.

Returns:

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

setUseCachedPacks

public void setUseCachedPacks(boolean useCached)

Whether to use cached packs

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.

isUseBitmaps

public boolean isUseBitmaps()

Whether to use bitmaps

Returns:

true to use bitmaps for ObjectWalks, if available.

setUseBitmaps

public void setUseBitmaps(boolean useBitmaps)

Whether to use bitmaps

Parameters:

useBitmaps - if set to true, bitmaps will be used when preparing a pack.

isIndexDisabled

public boolean isIndexDisabled()

Whether the index file cannot be created by this PackWriter.

Returns:

true if the index file cannot be created by this PackWriter.

setIndexDisabled

public void setIndexDisabled(boolean noIndex)

Whether to disable creation of the index file.

Parameters:

noIndex - true to disable creation of the index file.

isIgnoreMissingUninteresting

public boolean isIgnoreMissingUninteresting()

Whether to ignore missing uninteresting objects

Returns:

true to ignore objects that are uninteresting and also not found on local disk; false to throw a MissingObjectException out of preparePack(ProgressMonitor, Set, Set) 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)

Whether writer should ignore non existing uninteresting objects

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 of history to return. 1 means return only the "wants".

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

setFilterBlobLimit

public void setFilterBlobLimit(long bytes)

Parameters:

bytes - exclude blobs of size greater than this

Since:

5.0

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:

set of objects in pack.

Throws:

IOException - a cached pack cannot supply its object ids.

excludeObjects

public void excludeObjects(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(@NonNull
                        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

public void preparePack(ProgressMonitor countingMonitor,
                        @NonNull
                        Set<? extends ObjectId> want,
                        @NonNull
                        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). Must not be null.

have - collection of objects to be marked as uninteresting (end points of graph traversal). Pass NONE if all objects reachable from want are desired, such as when serving a clone.

Throws:

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

preparePack

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

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

Like preparePack(ProgressMonitor, Set, Set) but also allows specifying commits that should not be walked past ("shallow" commits). The caller is responsible for filtering out commits that should not be shallow any more ("unshallow" commits as in setShallowPack(int, java.util.Collection<? extends org.eclipse.jgit.lib.ObjectId>)) from the shallow set.

Parameters:

countingMonitor - progress during object enumeration.

want - objects of interest, ancestors of which will be included in the pack. Must not be null.

have - objects whose ancestors (up to and including shallow commits) do not need to be included in the pack because they are already available from elsewhere. Must not be null.

shallow - commits indicating the boundary of the history marked with have. Shallow commits have parents but those parents are considered not to be already available. Parents of shallow commits and earlier generations will be included in the pack if requested by want. Must not be null.

Throws:

IOException - an I/O problem occurred while reading objects.

preparePack

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

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

Like preparePack(ProgressMonitor, Set, Set) but also allows specifying commits that should not be walked past ("shallow" commits). The caller is responsible for filtering out commits that should not be shallow any more ("unshallow" commits as in setShallowPack(int, java.util.Collection<? extends org.eclipse.jgit.lib.ObjectId>)) from the shallow set.

Parameters:

countingMonitor - progress during object enumeration.

want - objects of interest, ancestors of which will be included in the pack. Must not be null.

have - objects whose ancestors (up to and including shallow commits) do not need to be included in the pack because they are already available from elsewhere. Must not be null.

shallow - commits indicating the boundary of the history marked with have. Shallow commits have parents but those parents are considered not to be already available. Parents of shallow commits and earlier generations will be included in the pack if requested by want. Must not be null.

noBitmaps - collection of objects to be excluded from bitmap commit selection.

Throws:

IOException - an I/O problem occurred while reading objects.

preparePack

public void preparePack(ProgressMonitor countingMonitor,
                        @NonNull
                        ObjectWalk walk,
                        @NonNull
                        Set<? extends ObjectId> interestingObjects,
                        @NonNull
                        Set<? extends ObjectId> uninterestingObjects,
                        @NonNull
                        Set<? extends ObjectId> noBitmaps)
                 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). Must not be null.

uninterestingObjects - collection of objects to be marked as uninteresting (end points of graph traversal). Pass NONE if all objects reachable from want are desired, such as when serving a clone.

noBitmaps - collection of objects to be excluded from bitmap commit selection.

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.

getIndexVersion

public int getIndexVersion()

Returns the index format version that will be written.

This method can only be invoked after writePack(ProgressMonitor, ProgressMonitor, OutputStream) has been invoked and completed successfully.

Returns:

the index format version.

writeIndex

public void writeIndex(OutputStream indexStream)
                throws IOException

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

Called after writePack(ProgressMonitor, ProgressMonitor, OutputStream).

Writing an index is only required for local pack storage. Packs sent on the network do not need to create an index.

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.

writeBitmapIndex

public void writeBitmapIndex(OutputStream bitmapIndexStream)
                      throws IOException

Create a bitmap index file to match the pack file just written.

Called after prepareBitmapIndex(ProgressMonitor).

Parameters:

bitmapIndexStream - output for the bitmap 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.

Called after preparePack(ProgressMonitor, ObjectWalk, Set, Set, Set) or preparePack(ProgressMonitor, Set, Set).

Performs delta search if enabled and writes the pack stream.

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.

WriteAbortedException - the write operation is aborted by ObjectCountCallback .

getStatistics

public PackStatistics getStatistics()

Get statistics of what this PackWriter did in order to create the final pack stream.

Returns:

description of what this PackWriter did in order to create the final pack stream. This should only be invoked after the calls to create the pack/index/bitmap have completed.

getState

public PackWriter.State getState()

Get snapshot of the current state of this PackWriter.

Returns:

snapshot of the current state of this PackWriter.

close

public void close()

Release all resources used by this writer.

Specified by:

close in interface AutoCloseable

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.

prepareBitmapIndex

public boolean prepareBitmapIndex(ProgressMonitor pm)
                           throws IOException

Prepares the bitmaps to be written to the bitmap index file.

Bitmaps can be used to speed up fetches and clones by storing the entire object graph at selected commits. Writing a bitmap index is an optional feature that not all pack users may require.

Called after writeIndex(OutputStream).

To reduce memory internal state is cleared during this method, rendering the PackWriter instance useless for anything further than a call to write out the new bitmaps with writeBitmapIndex(OutputStream).

Parameters:

pm - progress monitor to report bitmap building work.

Returns:

whether a bitmap index may be written.

Throws:

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