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// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.server.edit.tree;
import static java.util.Objects.requireNonNull;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.eclipse.jgit.dircache.DirCache;
import org.eclipse.jgit.dircache.DirCacheBuilder;
import org.eclipse.jgit.dircache.DirCacheEditor;
import org.eclipse.jgit.dircache.DirCacheEntry;
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.revwalk.RevCommit;
/**
* A creator for a new Git tree. To create the new tree, the tree of another commit is taken as a
* basis and modified.
*/
public class TreeCreator {
private final RevCommit baseCommit;
private final List<TreeModification> treeModifications = new ArrayList<>();
public TreeCreator(RevCommit baseCommit) {
this.baseCommit = requireNonNull(baseCommit, "baseCommit is required");
}
/**
* Apply modifications to the tree which is taken as a basis. If this method is called multiple
* times, the modifications are applied subsequently in exactly the order they were provided.
*
* @param treeModifications modifications which should be applied to the base tree
*/
public void addTreeModifications(List<TreeModification> treeModifications) {
requireNonNull(treeModifications, "treeModifications must not be null");
this.treeModifications.addAll(treeModifications);
}
/**
* Creates the new tree. When this method is called, the specified base tree is read from the
* repository, the specified modifications are applied, and the resulting tree is written to the
* object store of the repository.
*
* @param repository the affected Git repository
* @return the {@code ObjectId} of the created tree
* @throws IOException if problems arise when accessing the repository
*/
public ObjectId createNewTreeAndGetId(Repository repository) throws IOException {
DirCache newTree = createNewTree(repository);
return writeAndGetId(repository, newTree);
}
private DirCache createNewTree(Repository repository) throws IOException {
DirCache newTree = readBaseTree(repository);
List<DirCacheEditor.PathEdit> pathEdits = getPathEdits(repository);
applyPathEdits(newTree, pathEdits);
return newTree;
}
private DirCache readBaseTree(Repository repository) throws IOException {
try (ObjectReader objectReader = repository.newObjectReader()) {
DirCache dirCache = DirCache.newInCore();
DirCacheBuilder dirCacheBuilder = dirCache.builder();
dirCacheBuilder.addTree(
new byte[0], DirCacheEntry.STAGE_0, objectReader, baseCommit.getTree());
dirCacheBuilder.finish();
return dirCache;
}
}
private List<DirCacheEditor.PathEdit> getPathEdits(Repository repository) throws IOException {
List<DirCacheEditor.PathEdit> pathEdits = new ArrayList<>();
for (TreeModification treeModification : treeModifications) {
pathEdits.addAll(treeModification.getPathEdits(repository, baseCommit));
}
return pathEdits;
}
private static void applyPathEdits(DirCache tree, List<DirCacheEditor.PathEdit> pathEdits) {
DirCacheEditor dirCacheEditor = tree.editor();
pathEdits.forEach(dirCacheEditor::add);
dirCacheEditor.finish();
}
private static ObjectId writeAndGetId(Repository repository, DirCache tree) throws IOException {
try (ObjectInserter objectInserter = repository.newObjectInserter()) {
ObjectId treeId = tree.writeTree(objectInserter);
objectInserter.flush();
return treeId;
}
}
}
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