tikhomirov@600: /*
tikhomirov@600:  * Copyright (c) 2013 TMate Software Ltd
tikhomirov@600:  *  
tikhomirov@600:  * This program is free software; you can redistribute it and/or modify
tikhomirov@600:  * it under the terms of the GNU General Public License as published by
tikhomirov@600:  * the Free Software Foundation; version 2 of the License.
tikhomirov@600:  *
tikhomirov@600:  * This program is distributed in the hope that it will be useful,
tikhomirov@600:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
tikhomirov@600:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
tikhomirov@600:  * GNU General Public License for more details.
tikhomirov@600:  *
tikhomirov@600:  * For information on how to redistribute this software under
tikhomirov@600:  * the terms of a license other than GNU General Public License
tikhomirov@600:  * contact TMate Software at support@hg4j.com
tikhomirov@600:  */
tikhomirov@600: package org.tmatesoft.hg.internal;
tikhomirov@600: 
tikhomirov@600: import static org.tmatesoft.hg.repo.HgRepository.BAD_REVISION;
tikhomirov@600: 
tikhomirov@600: import java.util.Arrays;
tikhomirov@600: 
tikhomirov@600: import org.tmatesoft.hg.core.Nodeid;
tikhomirov@628: import org.tmatesoft.hg.repo.HgInvalidControlFileException;
tikhomirov@628: import org.tmatesoft.hg.repo.HgInvalidRevisionException;
tikhomirov@600: import org.tmatesoft.hg.repo.HgRevisionMap;
tikhomirov@628: import org.tmatesoft.hg.repo.HgRuntimeException;
tikhomirov@600: 
tikhomirov@600: /**
tikhomirov@600:  * Lite alternative to {@link HgRevisionMap}, to speed up nodeid to index conversion without consuming too much memory.
tikhomirov@600:  * E.g. for a 100k revisions, {@link HgRevisionMap} consumes 3 * (N * sizeof(int)) for indexes plus 48 bytes per 
tikhomirov@600:  * Nodeid instance, total (12+48)*N = 6 mb of memory. {RevisionLookup} instead keeps only Nodeid hashes, (N * sizeof(int) = 400 kb),
tikhomirov@600:  * but is slower in lookup, O(N/2) to find potential match plus disk read operatin (or few, in an unlikely case of hash collisions).
tikhomirov@600:  * 
tikhomirov@600:  * @author Artem Tikhomirov
tikhomirov@600:  * @author TMate Software Ltd.
tikhomirov@600:  */
tikhomirov@600: public class RevisionLookup implements RevlogStream.Inspector {
tikhomirov@600: 	
tikhomirov@600: 	private final RevlogStream content;
tikhomirov@600: 	private int[] nodeidHashes;
tikhomirov@600: 
tikhomirov@600: 	public RevisionLookup(RevlogStream stream) {
tikhomirov@600: 		assert stream != null;
tikhomirov@600: 		content = stream;
tikhomirov@600: 	}
tikhomirov@600: 	
tikhomirov@628: 	public static RevisionLookup createFor(RevlogStream stream) throws HgRuntimeException {
tikhomirov@600: 		RevisionLookup rv = new RevisionLookup(stream);
tikhomirov@600: 		int revCount = stream.revisionCount();
tikhomirov@600: 		rv.prepare(revCount);
tikhomirov@600: 		if (revCount > 0) {
tikhomirov@600: 			stream.iterate(0, revCount - 1, false, rv);
tikhomirov@600: 		}
tikhomirov@600: 		return rv;
tikhomirov@600: 	}
tikhomirov@600: 
tikhomirov@600: 	public void prepare(int count) {
tikhomirov@600: 		nodeidHashes = new int[count];
tikhomirov@600: 		Arrays.fill(nodeidHashes, BAD_REVISION);
tikhomirov@600: 	}
tikhomirov@600: 	public void next(int index, byte[] nodeid) {
tikhomirov@600: 		nodeidHashes[index] = Nodeid.hashCode(nodeid);
tikhomirov@600: 	}
tikhomirov@600: 	public void next(int index, Nodeid nodeid) {
tikhomirov@600: 		nodeidHashes[index] = nodeid.hashCode();
tikhomirov@600: 	}
tikhomirov@628: 	public int findIndex(Nodeid nodeid) throws HgInvalidControlFileException, HgInvalidRevisionException {
tikhomirov@600: 		final int hash = nodeid.hashCode();
tikhomirov@600: 		for (int i = 0; i < nodeidHashes.length; i++) {
tikhomirov@600: 			if (nodeidHashes[i] == hash) {
tikhomirov@600: 				byte[] nodeidAtI = content.nodeid(i);
tikhomirov@600: 				if (nodeid.equalsTo(nodeidAtI)) {
tikhomirov@600: 					return i;
tikhomirov@600: 				}
tikhomirov@600: 			}
tikhomirov@600: 			// else: false match (only 4 head bytes matched, continue loop
tikhomirov@600: 		}
tikhomirov@600: 		return BAD_REVISION;
tikhomirov@600: 	}
tikhomirov@600: 
tikhomirov@600: 	public void next(int revisionIndex, int actualLen, int baseRevision, int linkRevision, int parent1Revision, int parent2Revision, byte[] nodeid, DataAccess data) {
tikhomirov@600: 		next(revisionIndex, nodeid);
tikhomirov@600: 	}
tikhomirov@600: }