2 * Copyright 2017-present Open Networking Foundation
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
16 package io.atomix.storage.journal;
18 import java.util.NoSuchElementException;
23 public final class SegmentedJournalReader<E> implements JournalReader<E> {
24 private final SegmentedJournal<E> journal;
25 private JournalSegment<E> currentSegment;
26 private Indexed<E> previousEntry;
27 private JournalSegmentReader<E> currentReader;
28 private final Mode mode;
30 SegmentedJournalReader(SegmentedJournal<E> journal, long index, Mode mode) {
31 this.journal = journal;
33 currentSegment = journal.getSegment(index);
34 currentReader = currentSegment.createReader();
36 long nextIndex = getNextIndex();
37 while (index > nextIndex && hasNext()) {
39 nextIndex = getNextIndex();
44 public long getFirstIndex() {
45 return journal.getFirstSegment().index();
49 public long getCurrentIndex() {
50 long currentIndex = currentReader.getCurrentIndex();
51 if (currentIndex != 0) {
54 if (previousEntry != null) {
55 return previousEntry.index();
61 public Indexed<E> getCurrentEntry() {
62 Indexed<E> currentEntry = currentReader.getCurrentEntry();
63 if (currentEntry != null) {
70 public long getNextIndex() {
71 return currentReader.getNextIndex();
77 currentReader.close();
79 currentSegment = journal.getFirstSegment();
80 currentReader = currentSegment.createReader();
84 public void reset(long index) {
85 // If the current segment is not open, it has been replaced. Reset the segments.
86 if (!currentSegment.isOpen()) {
90 if (index < currentReader.getNextIndex()) {
92 } else if (index > currentReader.getNextIndex()) {
95 currentReader.reset(index);
100 * Rewinds the journal to the given index.
102 private void rewind(long index) {
103 if (currentSegment.index() >= index) {
104 JournalSegment<E> segment = journal.getSegment(index - 1);
105 if (segment != null) {
106 currentReader.close();
108 currentSegment = segment;
109 currentReader = currentSegment.createReader();
113 currentReader.reset(index);
114 previousEntry = currentReader.getCurrentEntry();
118 * Fast forwards the journal to the given index.
120 private void forward(long index) {
121 while (getNextIndex() < index && hasNext()) {
127 public boolean hasNext() {
128 if (mode == Mode.ALL) {
129 return hasNextEntry();
132 long nextIndex = getNextIndex();
133 long commitIndex = journal.getCommitIndex();
134 return nextIndex <= commitIndex && hasNextEntry();
137 private boolean hasNextEntry() {
138 if (currentReader.hasNext()) {
141 return moveToNextSegment() ? currentReader.hasNext() : false;
145 public Indexed<E> next() {
146 if (currentReader.hasNext()) {
147 previousEntry = currentReader.getCurrentEntry();
148 return currentReader.next();
150 if (moveToNextSegment()) {
151 return currentReader.next();
153 throw new NoSuchElementException();
157 public void close() {
158 currentReader.close();
159 journal.closeReader(this);
162 private boolean moveToNextSegment() {
163 final var nextSegment = journal.getNextSegment(currentSegment.index());
164 if (nextSegment == null || nextSegment.index() != getNextIndex()) {
168 previousEntry = currentReader.getCurrentEntry();
169 currentReader.close();
171 currentSegment = nextSegment;
172 currentReader = currentSegment.createReader();