- All Known Implementing Classes:
public interface ObjectReuseAsIsExtension of
ObjectReaderthat supports reusing objects in packs.
ObjectReaderimplementations may also optionally implement this interface to support
PackWriterwith a means of copying an object that is already in pack encoding format directly into the output stream, without incurring decompression and recompression overheads.
All Methods Instance Methods Abstract Methods Modifier and Type Method Description
copyObjectAsIs(PackOutputStream out, ObjectToPack otp, boolean validate)Output a previously selected representation.
copyPackAsIs(PackOutputStream out, CachedPack pack)Append an entire pack's contents onto the output stream.
getCachedPacksAndUpdate(BitmapIndex.BitmapBuilder needBitmap)Obtain the available cached packs that match the bitmap and update the bitmap by removing the items that are in the CachedPack.
newObjectToPack(AnyObjectId objectId, int type)Allocate a new
PackWriterstate structure for an object.
selectObjectRepresentation(PackWriter packer, ProgressMonitor monitor, Iterable<ObjectToPack> objects)Select the best object representation for a packer.
writeObjects(PackOutputStream out, List<ObjectToPack> list)Write objects to the pack stream in roughly the order given.
ObjectToPack newObjectToPack(AnyObjectId objectId, int type)Allocate a new
PackWriterstate structure for an object.
PackWriterallocates these objects to keep track of the per-object state, and how to load the objects efficiently into the generated stream. Implementers may subclass this type with additional object state, such as to remember what file and offset contains the object's pack encoded data.
objectId- the id of the object that will be packed.
type- the Git type of the object that will be packed.
- a new instance for this object.
void selectObjectRepresentation(PackWriter packer, ProgressMonitor monitor, Iterable<ObjectToPack> objects) throws IOException, MissingObjectExceptionSelect the best object representation for a packer.
Implementations should iterate through all available representations of an object, and pass them in turn to the PackWriter though
PackWriter.select(ObjectToPack, StoredObjectRepresentation)so the writer can select the most suitable representation to reuse into the output stream.
If the implementation returns CachedPack from
getCachedPacksAndUpdate(BitmapBuilder)it must consider the representation of any object that is stored in any of the offered CachedPacks. PackWriter relies on this behavior to prune duplicate objects out of the pack stream when it selects a CachedPack and the object was also reached through the thin-pack enumeration.
The implementation may choose to consider multiple objects at once on concurrent threads, but must evaluate all representations of an object within the same thread.
packer- the packer that will write the object in the near future.
monitor- progress monitor, implementation should update the monitor once for each item in the iteration when selection is done.
objects- the objects that are being packed.
MissingObjectException- there is no representation available for the object, as it is no longer in the repository. Packing will abort.
IOException- the repository cannot be accessed. Packing will abort.
void writeObjects(PackOutputStream out, List<ObjectToPack> list) throws IOExceptionWrite objects to the pack stream in roughly the order given.
PackWriterinvokes this method to write out one or more objects, in approximately the order specified by the iteration over the list. A simple implementation of this method would just iterate the list and output each object:
for (ObjectToPack obj : list) out.writeObject(obj)However more sophisticated implementors may try to perform some (small) reordering to access objects that are stored close to each other at roughly the same time. Implementations may choose to write objects out of order, but this may increase pack file size due to using a larger header format to reach a delta base that is later in the stream. It may also reduce data locality for the reader, slowing down data access. Invoking
copyObjectAsIs(PackOutputStream, ObjectToPack, boolean)to be invoked recursively on
thisif the current object is scheduled for reuse.
out- the stream to write each object to.
list- the list of objects to write. Objects should be written in approximately this order. Implementors may resort the list elements in-place during writing if desired.
IOException- the stream cannot be written to, or one or more required objects cannot be accessed from the object database.
void copyObjectAsIs(PackOutputStream out, ObjectToPack otp, boolean validate) throws IOException, StoredObjectRepresentationNotAvailableExceptionOutput a previously selected representation.
PackWriterinvokes this method only if a representation previously given to it by
selectObjectRepresentationwas chosen for reuse into the output stream. The
otpargument is an instance created by this reader's own
newObjectToPack, and the representation data saved within it also originated from this reader.
Implementors must write the object header before copying the raw data to the output stream. The typical implementation is like:
MyToPack mtp = (MyToPack) otp; byte raw; if (validate) raw = validate(mtp); // throw SORNAE here, if at all else raw = readFast(mtp); out.writeHeader(mtp, mtp.inflatedSize); out.write(raw);
out- stream the object should be written to.
otp- the object's saved representation information.
validate- if true the representation must be validated and not be corrupt before being reused. If false, validation may be skipped as it will be performed elsewhere in the processing pipeline.
StoredObjectRepresentationNotAvailableException- the previously selected representation is no longer available. If thrown before
out.writeHeaderthe pack writer will try to find another representation, and write that one instead. If throw after
out.writeHeader, packing will abort.
IOException- the stream's write method threw an exception. Packing will abort.
void copyPackAsIs(PackOutputStream out, CachedPack pack) throws IOExceptionAppend an entire pack's contents onto the output stream.
The entire pack, excluding its header and trailing footer is sent.
out- stream to append the pack onto.
pack- the cached pack to send.
IOException- the pack cannot be read, or stream did not accept a write.
Collection<CachedPack> getCachedPacksAndUpdate(BitmapIndex.BitmapBuilder needBitmap) throws IOExceptionObtain the available cached packs that match the bitmap and update the bitmap by removing the items that are in the CachedPack.
A cached pack has known starting points and may be sent entirely as-is, with almost no effort on the sender's part.
needBitmap- the bitmap that contains all of the objects the client wants.
- the available cached packs.
IOException- the cached packs cannot be listed from the repository. Callers may choose to ignore this and continue as-if there were no cached packs.