/*
* Copyright (C) 2009, Google Inc.
* and other copyright owners as documented in the project's IP log.
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Distribution License v1.0 which
* accompanies this distribution, is reproduced below, and is
* available at http://www.eclipse.org/org/documents/edl-v10.php
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* - Neither the name of the Eclipse Foundation, Inc. nor the
* names of its contributors may be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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package org.eclipse.jgit.lib;
import java.io.IOException;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
/**
* Abstraction of arbitrary object storage.
* <p>
* An object database stores one or more Git objects, indexed by their unique
* {@link ObjectId}.
*/
public abstract class ObjectDatabase {
/** Initialize a new database instance for access. */
protected ObjectDatabase() {
// Protected to force extension.
}
/**
* Does this database exist yet?
*
* @return true if this database is already created; false if the caller
* should invoke {@link #create()} to create this database location.
*/
public boolean exists() {
return true;
}
/**
* Initialize a new object database at this location.
*
* @throws IOException
* the database could not be created.
*/
public void create() throws IOException {
// Assume no action is required.
}
/**
* Create a new {@code ObjectInserter} to insert new objects.
* <p>
* The returned inserter is not itself thread-safe, but multiple concurrent
* inserter instances created from the same {@code ObjectDatabase} must be
* thread-safe.
*
* @return writer the caller can use to create objects in this database.
*/
public abstract ObjectInserter newInserter();
/**
* Create a new {@code ObjectReader} to read existing objects.
* <p>
* The returned reader is not itself thread-safe, but multiple concurrent
* reader instances created from the same {@code ObjectDatabase} must be
* thread-safe.
*
* @return reader the caller can use to load objects from this database.
*/
public abstract ObjectReader newReader();
/**
* Close any resources held by this database.
*/
public abstract void close();
/**
* Does the requested object exist in this database?
* <p>
* This is a one-shot call interface which may be faster than allocating a
* {@link #newReader()} to perform the lookup.
*
* @param objectId
* identity of the object to test for existence of.
* @return true if the specified object is stored in this database.
* @throws IOException
* the object store cannot be accessed.
*/
public boolean has(final AnyObjectId objectId) throws IOException {
try (final ObjectReader or = newReader()) {
return or.has(objectId);
}
}
/**
* Open an object from this database.
* <p>
* This is a one-shot call interface which may be faster than allocating a
* {@link #newReader()} to perform the lookup.
*
* @param objectId
* identity of the object to open.
* @return a {@link ObjectLoader} for accessing the object.
* @throws MissingObjectException
* the object does not exist.
* @throws IOException
* the object store cannot be accessed.
*/
public ObjectLoader open(final AnyObjectId objectId)
throws IOException {
return open(objectId, ObjectReader.OBJ_ANY);
}
/**
* Open an object from this database.
* <p>
* This is a one-shot call interface which may be faster than allocating a
* {@link #newReader()} to perform the lookup.
*
* @param objectId
* identity of the object to open.
* @param typeHint
* hint about the type of object being requested, e.g.
* {@link Constants#OBJ_BLOB}; {@link ObjectReader#OBJ_ANY} if
* the object type is not known, or does not matter to the
* caller.
* @return a {@link ObjectLoader} for accessing the object.
* @throws MissingObjectException
* the object does not exist.
* @throws IncorrectObjectTypeException
* typeHint was not OBJ_ANY, and the object's actual type does
* not match typeHint.
* @throws IOException
* the object store cannot be accessed.
*/
public ObjectLoader open(AnyObjectId objectId, int typeHint)
throws MissingObjectException, IncorrectObjectTypeException,
IOException {
try (final ObjectReader or = newReader()) {
return or.open(objectId, typeHint);
}
}
/**
* Create a new cached database instance over this database. This instance might
* optimize queries by caching some information about database. So some modifications
* done after instance creation might fail to be noticed.
*
* @return new cached database instance
*/
public ObjectDatabase newCachedDatabase() {
return this;
}
}