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1   /*
2    * Copyright 2011 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.io.hfile;
21  
22  import java.io.DataOutput;
23  import java.io.IOException;
24  
25  /**
26   * A way to write "inline" blocks into an {@link HFile}. Inline blocks are
27   * interspersed with data blocks. For example, Bloom filter chunks and
28   * leaf-level blocks of a multi-level block index are stored as inline blocks.
29   */
30  public interface InlineBlockWriter {
31  
32    /**
33     * Determines whether there is a new block to be written out.
34     *
35     * @param closing
36     *          whether the file is being closed, in which case we need to write
37     *          out all available data and not wait to accumulate another block
38     */
39    boolean shouldWriteBlock(boolean closing);
40  
41    /**
42     * Writes the block to the provided stream. Must not write any magic records.
43     * Called only if {@link #shouldWriteBlock(boolean)} returned true.
44     *
45     * @param out
46     *          a stream (usually a compressing stream) to write the block to
47     */
48    void writeInlineBlock(DataOutput out) throws IOException;
49  
50    /**
51     * Called after a block has been written, and its offset, raw size, and
52     * compressed size have been determined. Can be used to add an entry to a
53     * block index. If this type of inline blocks needs a block index, the inline
54     * block writer is responsible for maintaining it.
55     *
56     * @param offset the offset of the block in the stream
57     * @param onDiskSize the on-disk size of the block
58     * @param uncompressedSize the uncompressed size of the block
59     */
60    void blockWritten(long offset, int onDiskSize, int uncompressedSize);
61  
62    /**
63     * The type of blocks this block writer produces.
64     */
65    BlockType getInlineBlockType();
66  
67    /**
68     * @return true if inline blocks produced by this writer should be cached
69     */
70    boolean cacheOnWrite();
71  }