1// Protocol Buffers - Google's data interchange format
2// Copyright 2008 Google Inc.  All rights reserved.
3// https://developers.google.com/protocol-buffers/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are
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8//
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10// notice, this list of conditions and the following disclaimer.
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13// in the documentation and/or other materials provided with the
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18//
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20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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30
31package com.google.protobuf;
32
33import java.io.IOException;
34import java.nio.ByteBuffer;
35
36/**
37 * Provides a number of unsafe byte operations to be used by advanced applications with high
38 * performance requirements. These methods are referred to as "unsafe" due to the fact that they
39 * potentially expose the backing buffer of a {@link ByteString} to the application.
40 *
41 * <p><strong>DISCLAIMER:</strong> The methods in this class should only be called if it is
42 * guaranteed that the buffer backing the {@link ByteString} will never change! Mutation of a
43 * {@link ByteString} can lead to unexpected and undesirable consequences in your application,
44 * and will likely be difficult to debug. Proceed with caution!
45 */
46@ExperimentalApi
47public final class UnsafeByteOperations {
48  private UnsafeByteOperations() {}
49
50  /**
51   * An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
52   *
53   * @param buffer the Java NIO buffer to be wrapped
54   * @return a {@link ByteString} backed by the provided buffer
55   */
56  public static ByteString unsafeWrap(ByteBuffer buffer) {
57    if (buffer.hasArray()) {
58      final int offset = buffer.arrayOffset();
59      return ByteString.wrap(buffer.array(), offset + buffer.position(), buffer.remaining());
60    } else {
61      return new NioByteString(buffer);
62    }
63  }
64
65  /**
66   * Writes the given {@link ByteString} to the provided {@link ByteOutput}. Calling this method may
67   * result in multiple operations on the target {@link ByteOutput}
68   * (i.e. for roped {@link ByteString}s).
69   *
70   * <p>This method exposes the internal backing buffer(s) of the {@link ByteString} to the {@link
71   * ByteOutput} in order to avoid additional copying overhead. It would be possible for a malicious
72   * {@link ByteOutput} to corrupt the {@link ByteString}. Use with caution!
73   *
74   * <p> NOTE: The {@link ByteOutput} <strong>MUST NOT</strong> modify the provided buffers. Doing
75   * so may result in corrupted data, which would be difficult to debug.
76   *
77   * @param bytes the {@link ByteString} to be written
78   * @param  output  the output to receive the bytes
79   * @throws IOException  if an I/O error occurs
80   */
81  public static void unsafeWriteTo(ByteString bytes, ByteOutput output) throws IOException {
82    bytes.writeTo(output);
83  }
84}
85