content: /*
   *
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.bookkeeper.bookie;
  
  import static org.apache.bookkeeper.bookie.BookieImpl.METAENTRY_ID_FENCE_KEY;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import java.io.IOException;
  import java.util.PrimitiveIterator.OfLong;
  import java.util.concurrent.CompletableFuture;
  import org.apache.bookkeeper.common.util.Watcher;
  
  /**
   * Implements a ledger inside a bookie. In particular, it implements operations
   * to write entries to a ledger and read entries from a ledger.
   */
  public abstract class LedgerDescriptor {
  
      static LedgerDescriptor create(byte[] masterKey,
                                     long ledgerId,
                                     LedgerStorage ledgerStorage) throws IOException {
          LedgerDescriptor ledger = new LedgerDescriptorImpl(masterKey, ledgerId, ledgerStorage);
          ledgerStorage.setMasterKey(ledgerId, masterKey);
          return ledger;
      }
  
      static LedgerDescriptor createReadOnly(long ledgerId,
                                             LedgerStorage ledgerStorage)
              throws IOException, Bookie.NoLedgerException {
          if (!ledgerStorage.ledgerExists(ledgerId)) {
              throw new Bookie.NoLedgerException(ledgerId);
          }
          return new LedgerDescriptorReadOnlyImpl(ledgerId, ledgerStorage);
      }
  
      static ByteBuf createLedgerFenceEntry(Long ledgerId) {
          ByteBuf bb = Unpooled.buffer(8 + 8);
          bb.writeLong(ledgerId);
          bb.writeLong(METAENTRY_ID_FENCE_KEY);
          return bb;
      }
  
      abstract void checkAccess(byte[] masterKey) throws BookieException, IOException;
  
      abstract long getLedgerId();
  
      abstract boolean setFenced() throws IOException;
      abstract boolean isFenced() throws IOException, BookieException;
      /**
       * When we fence a ledger, we need to first set ledger to fenced state in memory and
       * then log the fence entry in Journal so that we can rebuild the state.
       *
       * <p>We should satisfy the future only after we complete logging fence entry in Journal
       * @return
       */
      abstract CompletableFuture<Boolean> fenceAndLogInJournal(Journal journal) throws IOException;
  
      abstract long addEntry(ByteBuf entry) throws IOException, BookieException;
      abstract ByteBuf readEntry(long entryId) throws IOException, BookieException;
  
      abstract long getLastAddConfirmed() throws IOException, BookieException;
      abstract boolean waitForLastAddConfirmedUpdate(long previousLAC,
                                                     Watcher<LastAddConfirmedUpdateNotification> watcher)
          throws IOException;
      abstract void cancelWaitForLastAddConfirmedUpdate(Watcher<LastAddConfirmedUpdateNotification> watcher)
              throws IOException;
  
      abstract void setExplicitLac(ByteBuf entry) throws IOException;
  
      abstract  ByteBuf getExplicitLac() throws IOException, BookieException;
  
      abstract OfLong getListOfEntriesOfLedger(long ledgerId) throws IOException;
  }
  