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

   1 /*
   2  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
   3  *
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or
   7  * without modification, are permitted provided that the following
   8  * conditions are met:
   9  *
  10  * - Redistributions of source code must retain the above copyright
  11  *   notice, this list of conditions and the following disclaimer.
  12  *
  13  * - Redistributions in binary form must reproduce the above
  14  *   copyright notice, this list of conditions and the following
  15  *   disclaimer in the documentation and/or other materials provided
  16  *   with the distribution.
  17  *
  18  * - Neither the name of the Git Development Community nor the
  19  *   names of its contributors may be used to endorse or promote
  20  *   products derived from this software without specific prior
  21  *   written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  24  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  25  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  28  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  31  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  32  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  33  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  35  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 package org.spearce.jgit.revwalk;
  39
  40 import java.io.IOException;
  41
  42 import org.spearce.jgit.errors.IncorrectObjectTypeException;
  43 import org.spearce.jgit.errors.MissingObjectException;
  44
  45 /**
  46  * Produces commits for RevWalk to return to applications.
  47  * <p>
  48  * Implementations of this basic class provide the real work behind RevWalk.
  49  * Conceptually a Generator is an iterator or a queue, it returns commits until
  50  * there are no more relevant. Generators may be piped/stacked together to
  51  * create a more complex set of operations.
  52  *
  53  * @see PendingGenerator
  54  * @see StartGenerator
  55  */
  56 abstract class Generator {
  57         /** Commits are sorted by commit date and time, descending. */
  58         static final int SORT_COMMIT_TIME_DESC = 1 << 0;
  59
  60         /** Output may have {@link RevWalk#REWRITE} marked on it. */
  61         static final int HAS_REWRITE = 1 << 1;
  62
  63         /** Output needs {@link RewriteGenerator}. */
  64         static final int NEEDS_REWRITE = 1 << 2;
  65
  66         /** Topological ordering is enforced (all children before parents). */
  67         static final int SORT_TOPO = 1 << 3;
  68
  69         /** Output may have {@link RevWalk#UNINTERESTING} marked on it. */
  70         static final int HAS_UNINTERESTING = 1 << 4;
  71
  72         /**
  73          * Connect the supplied queue to this generator's own free list (if any).
  74          *
  75          * @param q
  76          *            another FIFO queue that wants to share our queue's free list.
  77          */
  78         void shareFreeList(final BlockRevQueue q) {
  79                 // Do nothing by default.
  80         }
  81
  82         /**
  83          * Obtain flags describing the output behavior of this generator.
  84          *
  85          * @return one or more of the constants declared in this class, describing
  86          *         how this generator produces its results.
  87          */
  88         abstract int outputType();
  89
  90         /**
  91          * Return the next commit to the application, or the next generator.
  92          *
  93          * @return next available commit; null if no more are to be returned.
  94          * @throws MissingObjectException
  95          * @throws IncorrectObjectTypeException
  96          * @throws IOException
  97          */
  98         abstract RevCommit next() throws MissingObjectException,
  99                         IncorrectObjectTypeException, IOException;
 100 }