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.http.message;
29
30 import java.util.NoSuchElementException;
31
32 import org.apache.http.Header;
33 import org.apache.http.HeaderIterator;
34 import org.apache.http.util.Args;
35
36 /**
37 * Basic implementation of a {@link HeaderIterator}.
38 *
39 * @since 4.0
40 */
41 public class BasicHeaderIterator implements HeaderIterator {
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 protected final Header[] allHeaders;
50
51
52 /**
53 * The position of the next header in {@link #allHeaders allHeaders}.
54 * Negative if the iteration is over.
55 */
56 protected int currentIndex;
57
58
59 /**
60 * The header name to filter by.
61 * {@code null} to iterate over all headers in the array.
62 */
63 protected String headerName;
64
65
66
67 /**
68 * Creates a new header iterator.
69 *
70 * @param headers an array of headers over which to iterate
71 * @param name the name of the headers over which to iterate, or
72 * {@code null} for any
73 */
74 public BasicHeaderIterator(final Header[] headers, final String name) {
75 super();
76 this.allHeaders = Args.notNull(headers, "Header array");
77 this.headerName = name;
78 this.currentIndex = findNext(-1);
79 }
80
81
82 /**
83 * Determines the index of the next header.
84 *
85 * @param pos one less than the index to consider first,
86 * -1 to search for the first header
87 *
88 * @return the index of the next header that matches the filter name,
89 * or negative if there are no more headers
90 */
91 protected int findNext(final int pos) {
92 int from = pos;
93 if (from < -1) {
94 return -1;
95 }
96
97 final int to = this.allHeaders.length-1;
98 boolean found = false;
99 while (!found && (from < to)) {
100 from++;
101 found = filterHeader(from);
102 }
103 return found ? from : -1;
104 }
105
106
107 /**
108 * Checks whether a header is part of the iteration.
109 *
110 * @param index the index of the header to check
111 *
112 * @return {@code true} if the header should be part of the
113 * iteration, {@code false} to skip
114 */
115 protected boolean filterHeader(final int index) {
116 return (this.headerName == null) ||
117 this.headerName.equalsIgnoreCase(this.allHeaders[index].getName());
118 }
119
120
121 // non-javadoc, see interface HeaderIterator
122 @Override
123 public boolean hasNext() {
124 return (this.currentIndex >= 0);
125 }
126
127
128 /**
129 * Obtains the next header from this iteration.
130 *
131 * @return the next header in this iteration
132 *
133 * @throws NoSuchElementException if there are no more headers
134 */
135 @Override
136 public Header nextHeader()
137 throws NoSuchElementException {
138
139 final int current = this.currentIndex;
140 if (current < 0) {
141 throw new NoSuchElementException("Iteration already finished.");
142 }
143
144 this.currentIndex = findNext(current);
145
146 return this.allHeaders[current];
147 }
148
149
150 /**
151 * Returns the next header.
152 * Same as {@link #nextHeader nextHeader}, but not type-safe.
153 *
154 * @return the next header in this iteration
155 *
156 * @throws NoSuchElementException if there are no more headers
157 */
158 @Override
159 public final Object next()
160 throws NoSuchElementException {
161 return nextHeader();
162 }
163
164
165 /**
166 * Removing headers is not supported.
167 *
168 * @throws UnsupportedOperationException always
169 */
170 @Override
171 public void remove()
172 throws UnsupportedOperationException {
173
174 throw new UnsupportedOperationException
175 ("Removing headers is not supported.");
176 }
177 }