/*
 * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 *
 * 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 Git Development Community 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
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.spearce.jgit.lib;

import java.io.IOException;

import org.spearce.jgit.errors.CorruptObjectException;

/** Reads a deltified object which uses an offset to find its base. */
class DeltaOfsPackedObjectLoader extends DeltaPackedObjectLoader {
	private final long deltaBase;

	DeltaOfsPackedObjectLoader(final PackFile pr,
			final long dataOffset, final long objectOffset, final int deltaSz,
			final long base) {
		super(pr, dataOffset, objectOffset, deltaSz);
		deltaBase = base;
	}

	protected PackedObjectLoader getBaseLoader(final WindowCursor curs)
			throws IOException {
		return pack.resolveBase(curs, deltaBase);
	}

	@Override
	public int getRawType() {
		return Constants.OBJ_OFS_DELTA;
	}

	@Override
	public ObjectId getDeltaBase() throws IOException {
		final ObjectId id = pack.findObjectForOffset(deltaBase);
		if (id == null)
			throw new CorruptObjectException(
					"Offset-written delta base for object not found in a pack");
		return id;
	}
}