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.metastore;
  
  import static org.apache.bookkeeper.metastore.InMemoryMetastoreTable.cloneValue;
  
  import com.google.common.collect.ImmutableSortedMap;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.SortedMap;
  import java.util.concurrent.ScheduledExecutorService;
  import org.apache.bookkeeper.metastore.MSException.Code;
  import org.apache.bookkeeper.versioning.Versioned;
  
  class InMemoryMetastoreCursor implements MetastoreCursor {
  
      private final ScheduledExecutorService scheduler;
      private final Iterator<Map.Entry<String, Versioned<Value>>> iter;
      private final Set<String> fields;
  
      public InMemoryMetastoreCursor(SortedMap<String, Versioned<Value>> map, Set<String> fields,
              ScheduledExecutorService scheduler) {
          // copy an map for iterator to avoid concurrent modification problem.
          this.iter = ImmutableSortedMap.copyOfSorted(map).entrySet().iterator();
          this.fields = fields;
          this.scheduler = scheduler;
      }
  
      @Override
      public boolean hasMoreEntries() {
          return iter.hasNext();
      }
  
      @Override
      public Iterator<MetastoreTableItem> readEntries(int numEntries)
      throws MSException {
          if (numEntries < 0) {
              throw MSException.create(Code.IllegalOp);
          }
          return unsafeReadEntries(numEntries);
      }
  
      @Override
      public void asyncReadEntries(final int numEntries, final ReadEntriesCallback cb, final Object ctx) {
          scheduler.submit(new Runnable() {
              @Override
              public void run() {
                  if (numEntries < 0) {
                      cb.complete(Code.IllegalOp.getCode(), null, ctx);
                      return;
                  }
                  Iterator<MetastoreTableItem> result = unsafeReadEntries(numEntries);
                  cb.complete(Code.OK.getCode(), result, ctx);
              }
          });
      }
  
      private Iterator<MetastoreTableItem> unsafeReadEntries(int numEntries) {
          List<MetastoreTableItem> entries = new ArrayList<MetastoreTableItem>();
          int nCount = 0;
          while (iter.hasNext() && nCount < numEntries) {
              Map.Entry<String, Versioned<Value>> entry = iter.next();
              Versioned<Value> value = entry.getValue();
              Versioned<Value> vv = cloneValue(value.getValue(), value.getVersion(), fields);
              String key = entry.getKey();
              entries.add(new MetastoreTableItem(key, vv));
              ++nCount;
          }
          return entries.iterator();
      }
  
      @Override
      public void close() throws IOException {
          // do nothing
      }
  }
  