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 org.apache.hadoop.hbase.types;
19
20 import java.util.Iterator;
21 import java.util.NoSuchElementException;
22
23 import org.apache.hadoop.hbase.classification.InterfaceAudience;
24 import org.apache.hadoop.hbase.classification.InterfaceStability;
25 import org.apache.hadoop.hbase.util.PositionedByteRange;
26
27 /**
28 * An {@link Iterator} over encoded {@code Struct} members.
29 * <p>
30 * This iterates over each serialized {@code Struct} field from the specified
31 * {@code DataTypes<?>[]} definition. It allows you to read the field or skip
32 * over its serialized bytes using {@link #next()} and {@link #skip()},
33 * respectively. This is in contrast to the {@code Struct} method which allow
34 * you to {@link Struct#decode(PositionedByteRange)} or
35 * {@link Struct#skip(PositionedByteRange)} over the entire {@code Struct} at
36 * once.
37 * </p>
38 * <p>
39 * This iterator may also be used to read bytes from any {@code Struct} for
40 * which the specified {@code DataType<?>[]} is a prefix. For example, if the
41 * specified {@code Struct} definition has a {@link RawInteger} and a
42 * {@link RawStringTerminated} field, you may parse the serialized output
43 * of a {@code Struct} whose fields are {@link RawInteger},
44 * {@link RawStringTerminated}, and {@link RawBytes}. The iterator would
45 * return a number followed by a {@code String}. The trailing {@code byte[]}
46 * would be ignored.
47 * </p>
48 */
49 @InterfaceAudience.Public
50 @InterfaceStability.Evolving
51 public class StructIterator implements Iterator<Object> {
52
53 protected final PositionedByteRange src;
54 protected int idx = 0;
55 @SuppressWarnings("rawtypes")
56 protected final DataType[] types;
57
58 /**
59 * Construct {@code StructIterator} over the values encoded in {@code src}
60 * using the specified {@code types} definition.
61 * @param src The buffer from which to read encoded values.
62 * @param types The sequence of types to use as the schema for this
63 * {@code Struct}.
64 */
65 public StructIterator(PositionedByteRange src, @SuppressWarnings("rawtypes") DataType[] types) {
66 this.src = src;
67 this.types = types;
68 }
69
70 @Override
71 public boolean hasNext() {
72 // hasNext can return true when position == length in the case of a
73 // nullable field trailing a struct.
74 return idx < types.length && src.getPosition() <= src.getLength();
75 }
76
77 @Override
78 public void remove() { throw new UnsupportedOperationException(); }
79
80 @Override
81 public Object next() {
82 if (!hasNext()) throw new NoSuchElementException();
83 DataType<?> t = types[idx++];
84 if (src.getPosition() == src.getLength() && t.isNullable()) return null;
85 return t.decode(src);
86 }
87
88 /**
89 * Bypass the next encoded value.
90 * @return the number of bytes skipped.
91 */
92 public int skip() {
93 if (!hasNext()) throw new NoSuchElementException();
94 DataType<?> t = types[idx++];
95 if (src.getPosition() == src.getLength() && t.isNullable()) return 0;
96 return t.skip(src);
97 }
98 }