1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27
28 package org.apache.hc.core5.http.message;
29
30 import java.util.Iterator;
31 import java.util.NoSuchElementException;
32
33 import org.apache.hc.core5.http.Header;
34 import org.apache.hc.core5.util.Args;
35
36 /**
37 * {@link java.util.Iterator} of {@link org.apache.hc.core5.http.Header}s.
38 *
39 * @since 4.0
40 */
41 public class BasicHeaderIterator implements Iterator<Header> {
42
43 /**
44 * An array of headers to iterate over.
45 * Not all elements of this array are necessarily part of the iteration.
46 * This array will never be modified by the iterator.
47 * Derived implementations are expected to adhere to this restriction.
48 */
49 private final Header[] allHeaders;
50
51 /**
52 * The position of the next header in {@link #allHeaders allHeaders}.
53 * Negative if the iteration is over.
54 */
55 private int currentIndex;
56
57 /**
58 * The header name to filter by.
59 * {@code null} to iterate over all headers in the array.
60 */
61 private final String headerName;
62
63 /**
64 * Creates a new header iterator.
65 *
66 * @param headers an array of headers over which to iterate
67 * @param name the name of the headers over which to iterate, or
68 * {@code null} for any
69 */
70 public BasicHeaderIterator(final Header[] headers, final String name) {
71 super();
72 this.allHeaders = Args.notNull(headers, "Header array");
73 this.headerName = name;
74 this.currentIndex = findNext(-1);
75 }
76
77 /**
78 * Determines the index of the next header.
79 *
80 * @param pos one less than the index to consider first,
81 * -1 to search for the first header
82 *
83 * @return the index of the next header that matches the filter name,
84 * or negative if there are no more headers
85 */
86 private int findNext(final int pos) {
87 int from = pos;
88 if (from < -1) {
89 return -1;
90 }
91
92 final int to = this.allHeaders.length-1;
93 boolean found = false;
94 while (!found && (from < to)) {
95 from++;
96 found = filterHeader(from);
97 }
98 return found ? from : -1;
99 }
100
101 /**
102 * Checks whether a header is part of the iteration.
103 *
104 * @param index the index of the header to check
105 *
106 * @return {@code true} if the header should be part of the
107 * iteration, {@code false} to skip
108 */
109 private boolean filterHeader(final int index) {
110 return (this.headerName == null) ||
111 this.headerName.equalsIgnoreCase(this.allHeaders[index].getName());
112 }
113
114 @Override
115 public boolean hasNext() {
116 return this.currentIndex >= 0;
117 }
118
119 /**
120 * Obtains the next header from this iteration.
121 *
122 * @return the next header in this iteration
123 *
124 * @throws NoSuchElementException if there are no more headers
125 */
126 @Override
127 public Header next() throws NoSuchElementException {
128
129 final int current = this.currentIndex;
130 if (current < 0) {
131 throw new NoSuchElementException("Iteration already finished.");
132 }
133
134 this.currentIndex = findNext(current);
135
136 return this.allHeaders[current];
137 }
138
139 /**
140 * Removing headers is not supported.
141 *
142 * @throws UnsupportedOperationException always
143 */
144 @Override
145 public void remove() throws UnsupportedOperationException {
146 throw new UnsupportedOperationException("Removing headers is not supported.");
147 }
148
149 }