org.spearce.jgit/src/org/spearce/jgit/revwalk/Generator.java

   1 /*
   2  *  Copyright (C) 2008  Shawn Pearce <spearce@spearce.org>
   3  *
   4  *  This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU General Public
   6  *  License, version 2, as published by the Free Software Foundation.
   7  *
   8  *  This library is distributed in the hope that it will be useful,
   9  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  *  General Public License for more details.
  12  *
  13  *  You should have received a copy of the GNU General Public
  14  *  License along with this library; if not, write to the Free Software
  15  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
  16  */
  17 package org.spearce.jgit.revwalk;
  18
  19 import java.io.IOException;
  20
  21 import org.spearce.jgit.errors.IncorrectObjectTypeException;
  22 import org.spearce.jgit.errors.MissingObjectException;
  23
  24 /**
  25  * Produces commits for RevWalk to return to applications.
  26  * <p>
  27  * Implementations of this basic class provide the real work behind RevWalk.
  28  * Conceptually a Generator is an iterator or a queue, it returns commits until
  29  * there are no more relevant. Generators may be piped/stacked together to
  30  * create a more complex set of operations.
  31  *
  32  * @see PendingGenerator
  33  * @see StartGenerator
  34  */
  35 abstract class Generator {
  36         /** Commits are sorted by commit date and time, descending. */
  37         static final int SORT_COMMIT_TIME_DESC = 1 << 0;
  38
  39         /** Output may have {@link RevWalk#REWRITE} marked on it. */
  40         static final int HAS_REWRITE = 1 << 1;
  41
  42         /** Output needs {@link RewriteGenerator}. */
  43         static final int NEEDS_REWRITE = 1 << 2;
  44
  45         /** Topological ordering is enforced (all children before parents). */
  46         static final int SORT_TOPO = 1 << 3;
  47
  48         /** Output may have {@link RevWalk#UNINTERESTING} marked on it. */
  49         static final int HAS_UNINTERESTING = 1 << 4;
  50
  51         /**
  52          * Connect the supplied queue to this generator's own free list (if any).
  53          *
  54          * @param q
  55          *            another FIFO queue that wants to share our queue's free list.
  56          */
  57         void shareFreeList(final BlockRevQueue q) {
  58                 // Do nothing by default.
  59         }
  60
  61         /**
  62          * Obtain flags describing the output behavior of this generator.
  63          *
  64          * @return one or more of the constants declared in this class, describing
  65          *         how this generator produces its results.
  66          */
  67         abstract int outputType();
  68
  69         /**
  70          * Return the next commit to the application, or the next generator.
  71          *
  72          * @return next available commit; null if no more are to be returned.
  73          * @throws MissingObjectException
  74          * @throws IncorrectObjectTypeException
  75          * @throws IOException
  76          */
  77         abstract RevCommit next() throws MissingObjectException,
  78                         IncorrectObjectTypeException, IOException;
  79 }