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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.io;
20  
21  import java.io.IOException;
22  
23  import org.apache.hadoop.hbase.Cell;
24  import org.apache.hadoop.hbase.classification.InterfaceAudience;
25  import org.apache.hadoop.hbase.classification.InterfaceStability;
26  
27  /**
28   * Accepts a stream of Cells. This can be used to build a block of cells during compactions
29   * and flushes, or to build a byte[] to send to the client. This could be backed by a
30   * List<KeyValue>, but more efficient implementations will append results to a
31   * byte[] to eliminate overhead, and possibly encode the cells further.
32   * <p>To read Cells, use {@link org.apache.hadoop.hbase.CellScanner}
33   * @see org.apache.hadoop.hbase.CellScanner
34   */
35  @InterfaceAudience.Private
36  @InterfaceStability.Evolving
37  public interface CellOutputStream {
38    /**
39     * Implementation must copy the entire state of the Cell. If the written Cell is modified
40     * immediately after the write method returns, the modifications must have absolutely no effect
41     * on the copy of the Cell that was added in the write.
42     * @param cell Cell to write out
43     * @throws IOException
44     */
45    void write(Cell cell) throws IOException;
46  
47    /**
48     * Let the implementation decide what to do.  Usually means writing accumulated data into a
49     * byte[] that can then be read from the implementation to be sent to disk, put in the block
50     * cache, or sent over the network.
51     * @throws IOException
52     */
53    void flush() throws IOException;
54  }