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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  package com.google.protobuf;  // This is a lie.
19  
20  /**
21   * Helper class to extract byte arrays from {@link ByteString} without copy.
22   * <p>
23   * Without this protobufs would force us to copy every single byte array out
24   * of the objects de-serialized from the wire (which already do one copy, on
25   * top of the copies the JVM does to go from kernel buffer to C buffer and
26   * from C buffer to JVM buffer).
27   *
28   * @since 0.96.1
29   */
30  public final class HBaseZeroCopyByteString extends LiteralByteString {
31    // Gotten from AsyncHBase code base with permission.
32    /** Private constructor so this class cannot be instantiated. */
33    private HBaseZeroCopyByteString() {
34      super(null);
35      throw new UnsupportedOperationException("Should never be here.");
36    }
37  
38    /**
39     * Wraps a byte array in a {@link ByteString} without copying it.
40     * @param array array to be wrapped
41     * @return wrapped array
42     */
43    public static ByteString wrap(final byte[] array) {
44      return new LiteralByteString(array);
45    }
46  
47    /**
48     * Wraps a subset of a byte array in a {@link ByteString} without copying it.
49     * @param array array to be wrapped
50     * @param offset from
51     * @param length length
52     * @return wrapped array
53     */
54    public static ByteString wrap(final byte[] array, int offset, int length) {
55      return new BoundedByteString(array, offset, length);
56    }
57  
58    // TODO:
59    // ZeroCopyLiteralByteString.wrap(this.buf, 0, this.count);
60  
61    /**
62     * Extracts the byte array from the given {@link ByteString} without copy.
63     * @param buf A buffer from which to extract the array.  This buffer must be
64     * actually an instance of a {@code LiteralByteString}.
65     * @return byte[] representation
66     */
67    public static byte[] zeroCopyGetBytes(final ByteString buf) {
68      if (buf instanceof LiteralByteString) {
69        return ((LiteralByteString) buf).bytes;
70      }
71      throw new UnsupportedOperationException("Need a LiteralByteString, got a "
72                                              + buf.getClass().getName());
73    }
74  }