/*
* Copyright (C) 2010, Sasa Zivkov <sasa.zivkov@sap.com>
* 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
* 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 Eclipse Foundation, Inc. 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
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package org.eclipse.jgit.notes;
import java.io.IOException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.AbbreviatedObjectId;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.MutableObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.merge.MergeStrategy;
import org.eclipse.jgit.merge.Merger;
import org.eclipse.jgit.merge.ThreeWayMergeStrategy;
import org.eclipse.jgit.merge.ThreeWayMerger;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.TreeWalk;
/**
* Three-way note tree merge.
* <p>
* Direct implementation of NoteMap merger without using {@link TreeWalk} and
* {@link AbstractTreeIterator}
*/
public class NoteMapMerger {
private static final FanoutBucket EMPTY_FANOUT = new FanoutBucket(0);
private static final LeafBucket EMPTY_LEAF = new LeafBucket(0);
private final Repository db;
private final NoteMerger noteMerger;
private final MergeStrategy nonNotesMergeStrategy;
private final ObjectReader reader;
private final ObjectInserter inserter;
private final MutableObjectId objectIdPrefix;
/**
* Constructs a NoteMapMerger with custom {@link NoteMerger} and custom
* {@link MergeStrategy}.
*
* @param db
* Git repository
* @param noteMerger
* note merger for merging conflicting changes on a note
* @param nonNotesMergeStrategy
* merge strategy for merging non-note entries
*/
public NoteMapMerger(Repository db, NoteMerger noteMerger,
MergeStrategy nonNotesMergeStrategy) {
this.db = db;
this.reader = db.newObjectReader();
this.inserter = db.newObjectInserter();
this.noteMerger = noteMerger;
this.nonNotesMergeStrategy = nonNotesMergeStrategy;
this.objectIdPrefix = new MutableObjectId();
}
/**
* Constructs a NoteMapMerger with {@link DefaultNoteMerger} as the merger
* for notes and the {@link MergeStrategy#RESOLVE} as the strategy for
* resolving conflicts on non-notes
*
* @param db
* Git repository
*/
public NoteMapMerger(Repository db) {
this(db, new DefaultNoteMerger(), MergeStrategy.RESOLVE);
}
/**
* Performs the merge.
*
* @param base
* base version of the note tree
* @param ours
* ours version of the note tree
* @param theirs
* theirs version of the note tree
* @return merge result as a new NoteMap
* @throws IOException
*/
public NoteMap merge(NoteMap base, NoteMap ours, NoteMap theirs)
throws IOException {
try {
InMemoryNoteBucket mergedBucket = merge(0, base.getRoot(),
ours.getRoot(), theirs.getRoot());
inserter.flush();
return NoteMap.newMap(mergedBucket, reader);
} finally {
reader.release();
inserter.release();
}
}
/**
* This method is called only when it is known that there is some difference
* between base, ours and theirs.
*
* @param treeDepth
* @param base
* @param ours
* @param theirs
* @return merge result as an InMemoryBucket
* @throws IOException
*/
private InMemoryNoteBucket merge(int treeDepth, InMemoryNoteBucket base,
InMemoryNoteBucket ours, InMemoryNoteBucket theirs)
throws IOException {
InMemoryNoteBucket result;
if (base instanceof FanoutBucket || ours instanceof FanoutBucket
|| theirs instanceof FanoutBucket) {
result = mergeFanoutBucket(treeDepth, asFanout(base),
asFanout(ours), asFanout(theirs));
} else {
result = mergeLeafBucket(treeDepth, (LeafBucket) base,
(LeafBucket) ours, (LeafBucket) theirs);
}
result.nonNotes = mergeNonNotes(nonNotes(base), nonNotes(ours),
nonNotes(theirs));
return result;
}
private FanoutBucket asFanout(InMemoryNoteBucket bucket) {
if (bucket == null)
return EMPTY_FANOUT;
if (bucket instanceof FanoutBucket)
return (FanoutBucket) bucket;
return ((LeafBucket) bucket).split();
}
private static NonNoteEntry nonNotes(InMemoryNoteBucket b) {
return b == null ? null : b.nonNotes;
}
private InMemoryNoteBucket mergeFanoutBucket(int treeDepth,
FanoutBucket base,
FanoutBucket ours, FanoutBucket theirs) throws IOException {
FanoutBucket result = new FanoutBucket(treeDepth * 2);
// walking through entries of base, ours, theirs
for (int i = 0; i < 256; i++) {
NoteBucket b = base.getBucket(i);
NoteBucket o = ours.getBucket(i);
NoteBucket t = theirs.getBucket(i);
if (equals(o, t))
addIfNotNull(result, i, o);
else if (equals(b, o))
addIfNotNull(result, i, t);
else if (equals(b, t))
addIfNotNull(result, i, o);
else {
objectIdPrefix.setByte(treeDepth, i);
InMemoryNoteBucket mergedBucket = merge(treeDepth + 1,
FanoutBucket.loadIfLazy(b, objectIdPrefix, reader),
FanoutBucket.loadIfLazy(o, objectIdPrefix, reader),
FanoutBucket.loadIfLazy(t, objectIdPrefix, reader));
result.setBucket(i, mergedBucket);
}
}
return result.contractIfTooSmall(objectIdPrefix, reader);
}
private static boolean equals(NoteBucket a, NoteBucket b) {
if (a == null && b == null)
return true;
return a != null && b != null && a.getTreeId().equals(b.getTreeId());
}
private void addIfNotNull(FanoutBucket b, int cell, NoteBucket child)
throws IOException {
if (child == null)
return;
if (child instanceof InMemoryNoteBucket)
b.setBucket(cell, ((InMemoryNoteBucket) child).writeTree(inserter));
else
b.setBucket(cell, child.getTreeId());
}
private InMemoryNoteBucket mergeLeafBucket(int treeDepth, LeafBucket bb,
LeafBucket ob, LeafBucket tb) throws MissingObjectException,
IOException {
bb = notNullOrEmpty(bb);
ob = notNullOrEmpty(ob);
tb = notNullOrEmpty(tb);
InMemoryNoteBucket result = new LeafBucket(treeDepth * 2);
int bi = 0, oi = 0, ti = 0;
while (bi < bb.size() || oi < ob.size() || ti < tb.size()) {
Note b = get(bb, bi), o = get(ob, oi), t = get(tb, ti);
Note min = min(b, o, t);
b = sameNoteOrNull(min, b);
o = sameNoteOrNull(min, o);
t = sameNoteOrNull(min, t);
if (sameContent(o, t))
result = addIfNotNull(result, o);
else if (sameContent(b, o))
result = addIfNotNull(result, t);
else if (sameContent(b, t))
result = addIfNotNull(result, o);
else
result = addIfNotNull(result,
noteMerger.merge(b, o, t, reader, inserter));
if (b != null)
bi++;
if (o != null)
oi++;
if (t != null)
ti++;
}
return result;
}
private static LeafBucket notNullOrEmpty(LeafBucket b) {
return b != null ? b : EMPTY_LEAF;
}
private static Note get(LeafBucket b, int i) {
return i < b.size() ? b.get(i) : null;
}
private static Note min(Note b, Note o, Note t) {
Note min = b;
if (min == null || (o != null && o.compareTo(min) < 0))
min = o;
if (min == null || (t != null && t.compareTo(min) < 0))
min = t;
return min;
}
private static Note sameNoteOrNull(Note min, Note other) {
return sameNote(min, other) ? other : null;
}
private static boolean sameNote(Note a, Note b) {
if (a == null && b == null)
return true;
return a != null && b != null && AnyObjectId.equals(a, b);
}
private static boolean sameContent(Note a, Note b) {
if (a == null && b == null)
return true;
return a != null && b != null
&& AnyObjectId.equals(a.getData(), b.getData());
}
private static InMemoryNoteBucket addIfNotNull(InMemoryNoteBucket result,
Note note) {
if (note != null)
return result.append(note);
else
return result;
}
private NonNoteEntry mergeNonNotes(NonNoteEntry baseList,
NonNoteEntry oursList, NonNoteEntry theirsList) throws IOException {
if (baseList == null && oursList == null && theirsList == null)
return null;
ObjectId baseId = write(baseList);
ObjectId oursId = write(oursList);
ObjectId theirsId = write(theirsList);
inserter.flush();
ObjectId resultTreeId;
if (nonNotesMergeStrategy instanceof ThreeWayMergeStrategy) {
ThreeWayMerger m = ((ThreeWayMergeStrategy) nonNotesMergeStrategy)
.newMerger(db, true);
m.setBase(baseId);
if (!m.merge(oursId, theirsId))
throw new NotesMergeConflictException(baseList, oursList,
theirsList);
resultTreeId = m.getResultTreeId();
} else {
Merger m = nonNotesMergeStrategy.newMerger(db, true);
if (!m.merge(new AnyObjectId[] { oursId, theirsId }))
throw new NotesMergeConflictException(baseList, oursList,
theirsList);
resultTreeId = m.getResultTreeId();
}
AbbreviatedObjectId none = AbbreviatedObjectId.fromString("");
return NoteParser.parse(none, resultTreeId, reader).nonNotes;
}
private ObjectId write(NonNoteEntry list)
throws IOException {
LeafBucket b = new LeafBucket(0);
b.nonNotes = list;
return b.writeTree(inserter);
}
}