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/*
* Copyright (C) 2010, Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.notes;
import static org.eclipse.jgit.lib.Constants.OBJECT_ID_STRING_LENGTH;
import static org.eclipse.jgit.lib.FileMode.REGULAR_FILE;
import java.io.IOException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectInserter.Formatter;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.TreeFormatter;
/**
* A note tree holding only notes, with no subtrees.
*
* The leaf bucket contains on average less than 256 notes, all of whom share
* the same leading prefix. If a notes branch has less than 256 notes, the top
* level tree of the branch should be a LeafBucket. Once a notes branch has more
* than 256 notes, the root should be a {@link FanoutBucket} and the LeafBucket
* will appear only as a cell of a FanoutBucket.
*
* Entries within the LeafBucket are stored sorted by ObjectId, and lookup is
* performed using binary search. As the entry list should contain fewer than
* 256 elements, the average number of compares to find an element should be
* less than 8 due to the O(log N) lookup behavior.
*
* A LeafBucket must be parsed from a tree object by {@link NoteParser}.
*/
class LeafBucket extends InMemoryNoteBucket {
static final int MAX_SIZE = 256;
/** All note blobs in this bucket, sorted sequentially. */
private Note[] notes;
/** Number of items in {@link #notes}. */
private int cnt;
LeafBucket(int prefixLen) {
super(prefixLen);
notes = new Note[4];
}
private int search(AnyObjectId objId) {
int low = 0;
int high = cnt;
while (low < high) {
int mid = (low + high) >>> 1;
int cmp = objId.compareTo(notes[mid]);
if (cmp < 0)
high = mid;
else if (cmp == 0)
return mid;
else
low = mid + 1;
}
return -(low + 1);
}
@Override
Note getNote(AnyObjectId objId, ObjectReader or) {
int idx = search(objId);
return 0 <= idx ? notes[idx] : null;
}
Note get(int index) {
return notes[index];
}
int size() {
return cnt;
}
@Override
Iterator<Note> iterator(AnyObjectId objId, ObjectReader reader) {
return new Iterator<Note>() {
private int idx;
@Override
public boolean hasNext() {
return idx < cnt;
}
@Override
public Note next() {
if (hasNext()) {
return notes[idx++];
}
throw new NoSuchElementException();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@Override
int estimateSize(AnyObjectId noteOn, ObjectReader or) throws IOException {
return cnt;
}
@Override
InMemoryNoteBucket set(AnyObjectId noteOn, AnyObjectId noteData,
ObjectReader or) throws IOException {
int p = search(noteOn);
if (0 <= p) {
if (noteData != null) {
notes[p].setData(noteData.copy());
return this;
}
System.arraycopy(notes, p + 1, notes, p, cnt - p - 1);
cnt--;
return 0 < cnt ? this : null;
} else if (noteData != null) {
if (shouldSplit()) {
return split().set(noteOn, noteData, or);
}
growIfFull();
p = -(p + 1);
if (p < cnt) {
System.arraycopy(notes, p, notes, p + 1, cnt - p);
}
notes[p] = new Note(noteOn, noteData.copy());
cnt++;
return this;
} else {
return this;
}
}
@Override
ObjectId writeTree(ObjectInserter inserter) throws IOException {
return inserter.insert(build());
}
@Override
ObjectId getTreeId() {
try (Formatter f = new ObjectInserter.Formatter()) {
return f.idFor(build());
}
}
private TreeFormatter build() {
byte[] nameBuf = new byte[OBJECT_ID_STRING_LENGTH];
int nameLen = OBJECT_ID_STRING_LENGTH - prefixLen;
TreeFormatter fmt = new TreeFormatter(treeSize(nameLen));
NonNoteEntry e = nonNotes;
for (int i = 0; i < cnt; i++) {
Note n = notes[i];
n.copyTo(nameBuf, 0);
while (e != null
&& e.pathCompare(nameBuf, prefixLen, nameLen, REGULAR_FILE) < 0) {
e.format(fmt);
e = e.next;
}
fmt.append(nameBuf, prefixLen, nameLen, REGULAR_FILE, n.getData());
}
for (; e != null; e = e.next)
e.format(fmt);
return fmt;
}
private int treeSize(int nameLen) {
int sz = cnt * TreeFormatter.entrySize(REGULAR_FILE, nameLen);
for (NonNoteEntry e = nonNotes; e != null; e = e.next)
sz += e.treeEntrySize();
return sz;
}
void parseOneEntry(AnyObjectId noteOn, AnyObjectId noteData) {
growIfFull();
notes[cnt++] = new Note(noteOn, noteData.copy());
}
@Override
InMemoryNoteBucket append(Note note) {
if (shouldSplit()) {
return split().append(note);
}
growIfFull();
notes[cnt++] = note;
return this;
}
private void growIfFull() {
if (notes.length == cnt) {
Note[] n = new Note[notes.length * 2];
System.arraycopy(notes, 0, n, 0, cnt);
notes = n;
}
}
private boolean shouldSplit() {
return MAX_SIZE <= cnt && prefixLen + 2 < OBJECT_ID_STRING_LENGTH;
}
FanoutBucket split() {
FanoutBucket n = new FanoutBucket(prefixLen);
for (int i = 0; i < cnt; i++)
n.append(notes[i]);
n.nonNotes = nonNotes;
return n;
}
}
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