jgit/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftree/RefTreeNames.java

/*
 * Copyright (C) 2016, 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
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 *
 * - Redistributions in binary form must reproduce the above
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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package org.eclipse.jgit.internal.storage.reftree;

import static org.eclipse.jgit.lib.RefDatabase.ALL;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;

/** Magic reference name logic for RefTrees. */
public class RefTreeNames {
	/**
	 * Suffix used on a {@link RefTreeDatabase#getTxnNamespace()} for user data.
	 * <p>
	 * A {@link RefTreeDatabase}'s namespace may include a subspace (e.g.
	 * {@code "refs/txn/stage/"}) containing commit objects from the usual user
	 * portion of the repository (e.g. {@code "refs/heads/"}). These should be
	 * packed by the garbage collector alongside other user content rather than
	 * with the RefTree.
	 */
	private static final String STAGE = "stage/"; //$NON-NLS-1$

	/**
	 * Determine if the reference is likely to be a RefTree.
	 *
	 * @param refdb
	 *            database instance.
	 * @param ref
	 *            reference name.
	 * @return {@code true} if the reference is a RefTree.
	 */
	public static boolean isRefTree(RefDatabase refdb, String ref) {
		if (refdb instanceof RefTreeDatabase) {
			RefTreeDatabase b = (RefTreeDatabase) refdb;
			if (ref.equals(b.getTxnCommitted())) {
				return true;
			}

			String namespace = b.getTxnNamespace();
			if (namespace != null
					&& ref.startsWith(namespace)
					&& !ref.startsWith(namespace + STAGE)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Snapshot all references from a RefTreeDatabase and its bootstrap.
	 * <p>
	 * There may be name conflicts with multiple {@link Ref} objects containing
	 * the same name in the returned collection.
	 *
	 * @param refdb
	 *            database instance.
	 * @return all known references.
	 * @throws IOException
	 *             references cannot be enumerated.
	 */
	public static Collection<Ref> allRefs(RefDatabase refdb)
			throws IOException {
		Collection<Ref> refs = refdb.getRefs(ALL).values();
		if (!(refdb instanceof RefTreeDatabase)) {
			return refs;
		}

		RefDatabase bootstrap = ((RefTreeDatabase) refdb).getBootstrap();
		Collection<Ref> br = bootstrap.getRefs(ALL).values();
		List<Ref> all = new ArrayList<>(refs.size() + br.size());
		all.addAll(refs);
		all.addAll(br);
		return all;
	}

	private RefTreeNames() {
	}
}