ObjectReader.java
/*
* Copyright (C) 2010, Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.lib;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.internal.revwalk.BitmappedObjectReachabilityChecker;
import org.eclipse.jgit.internal.revwalk.BitmappedReachabilityChecker;
import org.eclipse.jgit.internal.revwalk.PedestrianObjectReachabilityChecker;
import org.eclipse.jgit.internal.revwalk.PedestrianReachabilityChecker;
import org.eclipse.jgit.revwalk.ObjectReachabilityChecker;
import org.eclipse.jgit.revwalk.ObjectWalk;
import org.eclipse.jgit.revwalk.ReachabilityChecker;
import org.eclipse.jgit.revwalk.RevWalk;
/**
* Reads an {@link org.eclipse.jgit.lib.ObjectDatabase} for a single thread.
* <p>
* Readers that can support efficient reuse of pack encoded objects should also
* implement the companion interface
* {@link org.eclipse.jgit.internal.storage.pack.ObjectReuseAsIs}.
*/
public abstract class ObjectReader implements AutoCloseable {
/** Type hint indicating the caller doesn't know the type. */
public static final int OBJ_ANY = -1;
/**
* The threshold at which a file will be streamed rather than loaded
* entirely into memory.
* @since 4.6
*/
protected int streamFileThreshold;
/**
* Construct a new reader from the same data.
* <p>
* Applications can use this method to build a new reader from the same data
* source, but for an different thread.
*
* @return a brand new reader, using the same data source.
*/
public abstract ObjectReader newReader();
/**
* Obtain a unique abbreviation (prefix) of an object SHA-1.
*
* This method uses a reasonable default for the minimum length. Callers who
* don't care about the minimum length should prefer this method.
*
* The returned abbreviation would expand back to the argument ObjectId when
* passed to {@link #resolve(AbbreviatedObjectId)}, assuming no new objects
* are added to this repository between calls.
*
* @param objectId
* object identity that needs to be abbreviated.
* @return SHA-1 abbreviation.
* @throws java.io.IOException
* the object store cannot be read.
*/
public AbbreviatedObjectId abbreviate(AnyObjectId objectId)
throws IOException {
return abbreviate(objectId, 7);
}
/**
* Obtain a unique abbreviation (prefix) of an object SHA-1.
*
* The returned abbreviation would expand back to the argument ObjectId when
* passed to {@link #resolve(AbbreviatedObjectId)}, assuming no new objects
* are added to this repository between calls.
*
* The default implementation of this method abbreviates the id to the
* minimum length, then resolves it to see if there are multiple results.
* When multiple results are found, the length is extended by 1 and resolve
* is tried again.
*
* @param objectId
* object identity that needs to be abbreviated.
* @param len
* minimum length of the abbreviated string. Must be in the range
* [2, {@value Constants#OBJECT_ID_STRING_LENGTH}].
* @return SHA-1 abbreviation. If no matching objects exist in the
* repository, the abbreviation will match the minimum length.
* @throws java.io.IOException
* the object store cannot be read.
*/
public AbbreviatedObjectId abbreviate(AnyObjectId objectId, int len)
throws IOException {
if (len == Constants.OBJECT_ID_STRING_LENGTH)
return AbbreviatedObjectId.fromObjectId(objectId);
AbbreviatedObjectId abbrev = objectId.abbreviate(len);
Collection<ObjectId> matches = resolve(abbrev);
while (1 < matches.size() && len < Constants.OBJECT_ID_STRING_LENGTH) {
abbrev = objectId.abbreviate(++len);
List<ObjectId> n = new ArrayList<>(8);
for (ObjectId candidate : matches) {
if (abbrev.prefixCompare(candidate) == 0)
n.add(candidate);
}
if (1 < n.size())
matches = n;
else
matches = resolve(abbrev);
}
return abbrev;
}
/**
* Resolve an abbreviated ObjectId to its full form.
*
* This method searches for an ObjectId that begins with the abbreviation,
* and returns at least some matching candidates.
*
* If the returned collection is empty, no objects start with this
* abbreviation. The abbreviation doesn't belong to this repository, or the
* repository lacks the necessary objects to complete it.
*
* If the collection contains exactly one member, the abbreviation is
* (currently) unique within this database. There is a reasonably high
* probability that the returned id is what was previously abbreviated.
*
* If the collection contains 2 or more members, the abbreviation is not
* unique. In this case the implementation is only required to return at
* least 2 candidates to signal the abbreviation has conflicts. User
* friendly implementations should return as many candidates as reasonably
* possible, as the caller may be able to disambiguate further based on
* context. However since databases can be very large (e.g. 10 million
* objects) returning 625,000 candidates for the abbreviation "0" is simply
* unreasonable, so implementors should draw the line at around 256 matches.
*
* @param id
* abbreviated id to resolve to a complete identity. The
* abbreviation must have a length of at least 2.
* @return candidates that begin with the abbreviated identity.
* @throws java.io.IOException
* the object store cannot be read.
*/
public abstract Collection<ObjectId> resolve(AbbreviatedObjectId id)
throws IOException;
/**
* Does the requested object exist in this database?
*
* @param objectId
* identity of the object to test for existence of.
* @return true if the specified object is stored in this database.
* @throws java.io.IOException
* the object store cannot be accessed.
*/
public boolean has(AnyObjectId objectId) throws IOException {
return has(objectId, OBJ_ANY);
}
/**
* Does the requested object exist in this database?
*
* @param objectId
* identity of the object to test for existence of.
* @param typeHint
* hint about the type of object being requested, e.g.
* {@link org.eclipse.jgit.lib.Constants#OBJ_BLOB};
* {@link #OBJ_ANY} if the object type is not known, or does not
* matter to the caller.
* @return true if the specified object is stored in this database.
* @throws IncorrectObjectTypeException
* typeHint was not OBJ_ANY, and the object's actual type does
* not match typeHint.
* @throws java.io.IOException
* the object store cannot be accessed.
*/
public boolean has(AnyObjectId objectId, int typeHint) throws IOException {
try {
open(objectId, typeHint);
return true;
} catch (MissingObjectException notFound) {
return false;
}
}
/**
* Open an object from this database.
*
* @param objectId
* identity of the object to open.
* @return a {@link org.eclipse.jgit.lib.ObjectLoader} for accessing the
* object.
* @throws org.eclipse.jgit.errors.MissingObjectException
* the object does not exist.
* @throws java.io.IOException
* the object store cannot be accessed.
*/
public ObjectLoader open(AnyObjectId objectId)
throws MissingObjectException, IOException {
return open(objectId, OBJ_ANY);
}
/**
* Open an object from this database.
*
* @param objectId
* identity of the object to open.
* @param typeHint
* hint about the type of object being requested, e.g.
* {@link org.eclipse.jgit.lib.Constants#OBJ_BLOB};
* {@link #OBJ_ANY} if the object type is not known, or does not
* matter to the caller.
* @return a {@link org.eclipse.jgit.lib.ObjectLoader} for accessing the
* object.
* @throws org.eclipse.jgit.errors.MissingObjectException
* the object does not exist.
* @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
* typeHint was not OBJ_ANY, and the object's actual type does
* not match typeHint.
* @throws java.io.IOException
* the object store cannot be accessed.
*/
public abstract ObjectLoader open(AnyObjectId objectId, int typeHint)
throws MissingObjectException, IncorrectObjectTypeException,
IOException;
/**
* Returns IDs for those commits which should be considered as shallow.
*
* @return IDs of shallow commits
* @throws java.io.IOException
*/
public abstract Set<ObjectId> getShallowCommits() throws IOException;
/**
* Asynchronous object opening.
*
* @param objectIds
* objects to open from the object store. The supplied collection
* must not be modified until the queue has finished.
* @param reportMissing
* if true missing objects are reported by calling failure with a
* MissingObjectException. This may be more expensive for the
* implementation to guarantee. If false the implementation may
* choose to report MissingObjectException, or silently skip over
* the object with no warning.
* @return queue to read the objects from.
*/
public <T extends ObjectId> AsyncObjectLoaderQueue<T> open(
Iterable<T> objectIds, final boolean reportMissing) {
final Iterator<T> idItr = objectIds.iterator();
return new AsyncObjectLoaderQueue<>() {
private T cur;
@Override
public boolean next() throws MissingObjectException, IOException {
if (idItr.hasNext()) {
cur = idItr.next();
return true;
}
return false;
}
@Override
public T getCurrent() {
return cur;
}
@Override
public ObjectId getObjectId() {
return cur;
}
@Override
public ObjectLoader open() throws IOException {
return ObjectReader.this.open(cur, OBJ_ANY);
}
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
return true;
}
@Override
public void release() {
// Since we are sequential by default, we don't
// have any state to clean up if we terminate early.
}
};
}
/**
* Get only the size of an object.
* <p>
* The default implementation of this method opens an ObjectLoader.
* Databases are encouraged to override this if a faster access method is
* available to them.
*
* @param objectId
* identity of the object to open.
* @param typeHint
* hint about the type of object being requested, e.g.
* {@link org.eclipse.jgit.lib.Constants#OBJ_BLOB};
* {@link #OBJ_ANY} if the object type is not known, or does not
* matter to the caller.
* @return size of object in bytes.
* @throws org.eclipse.jgit.errors.MissingObjectException
* the object does not exist.
* @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
* typeHint was not OBJ_ANY, and the object's actual type does
* not match typeHint.
* @throws java.io.IOException
* the object store cannot be accessed.
*/
public long getObjectSize(AnyObjectId objectId, int typeHint)
throws MissingObjectException, IncorrectObjectTypeException,
IOException {
return open(objectId, typeHint).getSize();
}
/**
* Asynchronous object size lookup.
*
* @param objectIds
* objects to get the size of from the object store. The supplied
* collection must not be modified until the queue has finished.
* @param reportMissing
* if true missing objects are reported by calling failure with a
* MissingObjectException. This may be more expensive for the
* implementation to guarantee. If false the implementation may
* choose to report MissingObjectException, or silently skip over
* the object with no warning.
* @return queue to read object sizes from.
*/
public <T extends ObjectId> AsyncObjectSizeQueue<T> getObjectSize(
Iterable<T> objectIds, final boolean reportMissing) {
final Iterator<T> idItr = objectIds.iterator();
return new AsyncObjectSizeQueue<>() {
private T cur;
private long sz;
@Override
public boolean next() throws MissingObjectException, IOException {
if (idItr.hasNext()) {
cur = idItr.next();
sz = getObjectSize(cur, OBJ_ANY);
return true;
}
return false;
}
@Override
public T getCurrent() {
return cur;
}
@Override
public ObjectId getObjectId() {
return cur;
}
@Override
public long getSize() {
return sz;
}
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
return true;
}
@Override
public void release() {
// Since we are sequential by default, we don't
// have any state to clean up if we terminate early.
}
};
}
/**
* Advise the reader to avoid unreachable objects.
* <p>
* While enabled the reader will skip over anything previously proven to be
* unreachable. This may be dangerous in the face of concurrent writes.
*
* @param avoid
* true to avoid unreachable objects.
* @since 3.0
*/
public void setAvoidUnreachableObjects(boolean avoid) {
// Do nothing by default.
}
/**
* An index that can be used to speed up ObjectWalks.
*
* @return the index or null if one does not exist.
* @throws java.io.IOException
* when the index fails to load
* @since 3.0
*/
public BitmapIndex getBitmapIndex() throws IOException {
return null;
}
/**
* Create a reachability checker that will use bitmaps if possible.
*
* @param rw
* revwalk for use by the reachability checker
* @return the most efficient reachability checker for this repository.
* @throws IOException
* if it cannot open any of the underlying indices.
*
* @since 5.11
*/
@NonNull
public ReachabilityChecker createReachabilityChecker(RevWalk rw)
throws IOException {
if (getBitmapIndex() != null) {
return new BitmappedReachabilityChecker(rw);
}
return new PedestrianReachabilityChecker(true, rw);
}
/**
* Create an object reachability checker that will use bitmaps if possible.
*
* This reachability checker accepts any object as target. For checks
* exclusively between commits, use
* {@link #createReachabilityChecker(RevWalk)}.
*
* @param ow
* objectwalk for use by the reachability checker
* @return the most efficient object reachability checker for this
* repository.
*
* @throws IOException
* if it cannot open any of the underlying indices.
*
* @since 5.11
*/
@NonNull
public ObjectReachabilityChecker createObjectReachabilityChecker(
ObjectWalk ow) throws IOException {
if (getBitmapIndex() != null) {
return new BitmappedObjectReachabilityChecker(ow);
}
return new PedestrianObjectReachabilityChecker(ow);
}
/**
* Get the {@link org.eclipse.jgit.lib.ObjectInserter} from which this
* reader was created using {@code inserter.newReader()}
*
* @return the {@link org.eclipse.jgit.lib.ObjectInserter} from which this
* reader was created using {@code inserter.newReader()}, or null if
* this reader was not created from an inserter.
* @since 4.4
*/
@Nullable
public ObjectInserter getCreatedFromInserter() {
return null;
}
/**
* {@inheritDoc}
* <p>
* Release any resources used by this reader.
* <p>
* A reader that has been released can be used again, but may need to be
* released after the subsequent usage.
*
* @since 4.0
*/
@Override
public abstract void close();
/**
* Sets the threshold at which a file will be streamed rather than loaded
* entirely into memory
*
* @param threshold
* the new threshold
* @since 4.6
*/
public void setStreamFileThreshold(int threshold) {
streamFileThreshold = threshold;
}
/**
* Returns the threshold at which a file will be streamed rather than loaded
* entirely into memory
*
* @return the threshold in bytes
* @since 4.6
*/
public int getStreamFileThreshold() {
return streamFileThreshold;
}
/**
* Wraps a delegate ObjectReader.
*
* @since 4.4
*/
public abstract static class Filter extends ObjectReader {
/**
* @return delegate ObjectReader to handle all processing.
* @since 4.4
*/
protected abstract ObjectReader delegate();
@Override
public ObjectReader newReader() {
return delegate().newReader();
}
@Override
public AbbreviatedObjectId abbreviate(AnyObjectId objectId)
throws IOException {
return delegate().abbreviate(objectId);
}
@Override
public AbbreviatedObjectId abbreviate(AnyObjectId objectId, int len)
throws IOException {
return delegate().abbreviate(objectId, len);
}
@Override
public Collection<ObjectId> resolve(AbbreviatedObjectId id)
throws IOException {
return delegate().resolve(id);
}
@Override
public boolean has(AnyObjectId objectId) throws IOException {
return delegate().has(objectId);
}
@Override
public boolean has(AnyObjectId objectId, int typeHint) throws IOException {
return delegate().has(objectId, typeHint);
}
@Override
public ObjectLoader open(AnyObjectId objectId)
throws MissingObjectException, IOException {
return delegate().open(objectId);
}
@Override
public ObjectLoader open(AnyObjectId objectId, int typeHint)
throws MissingObjectException, IncorrectObjectTypeException,
IOException {
return delegate().open(objectId, typeHint);
}
@Override
public Set<ObjectId> getShallowCommits() throws IOException {
return delegate().getShallowCommits();
}
@Override
public <T extends ObjectId> AsyncObjectLoaderQueue<T> open(
Iterable<T> objectIds, boolean reportMissing) {
return delegate().open(objectIds, reportMissing);
}
@Override
public long getObjectSize(AnyObjectId objectId, int typeHint)
throws MissingObjectException, IncorrectObjectTypeException,
IOException {
return delegate().getObjectSize(objectId, typeHint);
}
@Override
public <T extends ObjectId> AsyncObjectSizeQueue<T> getObjectSize(
Iterable<T> objectIds, boolean reportMissing) {
return delegate().getObjectSize(objectIds, reportMissing);
}
@Override
public void setAvoidUnreachableObjects(boolean avoid) {
delegate().setAvoidUnreachableObjects(avoid);
}
@Override
public BitmapIndex getBitmapIndex() throws IOException {
return delegate().getBitmapIndex();
}
@Override
@Nullable
public ObjectInserter getCreatedFromInserter() {
return delegate().getCreatedFromInserter();
}
@Override
public void close() {
delegate().close();
}
}
}