1// Protocol Buffers - Google's data interchange format
2// Copyright 2013 Google Inc.  All rights reserved.
3// http://code.google.com/p/protobuf/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are
7// met:
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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17// this software without specific prior written permission.
18//
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20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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30
31package com.google.protobuf.nano;
32
33import java.io.IOException;
34
35/**
36 * This class is used internally by the Protocol Buffer library and generated
37 * message implementations.  It is public only because those generated messages
38 * do not reside in the {@code protobuf} package.  Others should not use this
39 * class directly.
40 *
41 * This class contains constants and helper functions useful for dealing with
42 * the Protocol Buffer wire format.
43 *
44 * @author kenton@google.com Kenton Varda
45 */
46public final class WireFormatNano {
47  // Do not allow instantiation.
48  private WireFormatNano() {}
49
50  static final int WIRETYPE_VARINT           = 0;
51  static final int WIRETYPE_FIXED64          = 1;
52  static final int WIRETYPE_LENGTH_DELIMITED = 2;
53  static final int WIRETYPE_START_GROUP      = 3;
54  static final int WIRETYPE_END_GROUP        = 4;
55  static final int WIRETYPE_FIXED32          = 5;
56
57  static final int TAG_TYPE_BITS = 3;
58  static final int TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1;
59
60  /** Given a tag value, determines the wire type (the lower 3 bits). */
61  static int getTagWireType(final int tag) {
62    return tag & TAG_TYPE_MASK;
63  }
64
65  /** Given a tag value, determines the field number (the upper 29 bits). */
66  public static int getTagFieldNumber(final int tag) {
67    return tag >>> TAG_TYPE_BITS;
68  }
69
70  /** Makes a tag value given a field number and wire type. */
71  static int makeTag(final int fieldNumber, final int wireType) {
72    return (fieldNumber << TAG_TYPE_BITS) | wireType;
73  }
74
75  public static final int EMPTY_INT_ARRAY[] = {};
76  public static final long EMPTY_LONG_ARRAY[] = {};
77  public static final float EMPTY_FLOAT_ARRAY[] = {};
78  public static final double EMPTY_DOUBLE_ARRAY[] = {};
79  public static final boolean EMPTY_BOOLEAN_ARRAY[] = {};
80  public static final String EMPTY_STRING_ARRAY[] = {};
81  public static final byte[] EMPTY_BYTES_ARRAY[] = {};
82  public static final byte[] EMPTY_BYTES = {};
83
84  /**
85   * Parses an unknown field. This implementation skips the field.
86   *
87   * <p>Generated messages will call this for unknown fields if the store_unknown_fields
88   * option is off.
89   *
90   * @return {@literal true} unless the tag is an end-group tag.
91   */
92  public static boolean parseUnknownField(
93      final CodedInputByteBufferNano input,
94      final int tag) throws IOException {
95    return input.skipField(tag);
96  }
97
98  /**
99   * Computes the array length of a repeated field. We assume that in the common case repeated
100   * fields are contiguously serialized but we still correctly handle interspersed values of a
101   * repeated field (but with extra allocations).
102   *
103   * Rewinds to current input position before returning.
104   *
105   * @param input stream input, pointing to the byte after the first tag
106   * @param tag repeated field tag just read
107   * @return length of array
108   * @throws IOException
109   */
110  public static final int getRepeatedFieldArrayLength(
111      final CodedInputByteBufferNano input,
112      final int tag) throws IOException {
113    int arrayLength = 1;
114    int startPos = input.getPosition();
115    input.skipField(tag);
116    while (input.getBytesUntilLimit() > 0) {
117      int thisTag = input.readTag();
118      if (thisTag != tag) {
119        break;
120      }
121      input.skipField(tag);
122      arrayLength++;
123    }
124    input.rewindToPosition(startPos);
125    return arrayLength;
126  }
127
128}
129