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.annotation.NotThreadSafe;
35
36 /**
37 * Basic implementation of a {@link HeaderIterator}.
38 *
39 * @since 4.0
40 */
41 @NotThreadSafe
42 public class BasicHeaderIterator implements HeaderIterator {
43
44 /**
45 * An array of headers to iterate over.
46 * Not all elements of this array are necessarily part of the iteration.
47 * This array will never be modified by the iterator.
48 * Derived implementations are expected to adhere to this restriction.
49 */
50 protected final Header[] allHeaders;
51
52
53 /**
54 * The position of the next header in {@link #allHeaders allHeaders}.
55 * Negative if the iteration is over.
56 */
57 protected int currentIndex;
58
59
60 /**
61 * The header name to filter by.
62 * <code>null</code> to iterate over all headers in the array.
63 */
64 protected String headerName;
65
66
67
68 /**
69 * Creates a new header iterator.
70 *
71 * @param headers an array of headers over which to iterate
72 * @param name the name of the headers over which to iterate, or
73 * <code>null</code> for any
74 */
75 public BasicHeaderIterator(Header[] headers, String name) {
76 if (headers == null) {
77 throw new IllegalArgumentException
78 ("Header array must not be null.");
79 }
80
81 this.allHeaders = headers;
82 this.headerName = name;
83 this.currentIndex = findNext(-1);
84 }
85
86
87 /**
88 * Determines the index of the next header.
89 *
90 * @param from one less than the index to consider first,
91 * -1 to search for the first header
92 *
93 * @return the index of the next header that matches the filter name,
94 * or negative if there are no more headers
95 */
96 protected int findNext(int from) {
97 if (from < -1)
98 return -1;
99
100 final int to = this.allHeaders.length-1;
101 boolean found = false;
102 while (!found && (from < to)) {
103 from++;
104 found = filterHeader(from);
105 }
106 return found ? from : -1;
107 }
108
109
110 /**
111 * Checks whether a header is part of the iteration.
112 *
113 * @param index the index of the header to check
114 *
115 * @return <code>true</code> if the header should be part of the
116 * iteration, <code>false</code> to skip
117 */
118 protected boolean filterHeader(int index) {
119 return (this.headerName == null) ||
120 this.headerName.equalsIgnoreCase(this.allHeaders[index].getName());
121 }
122
123
124 // non-javadoc, see interface HeaderIterator
125 public boolean hasNext() {
126 return (this.currentIndex >= 0);
127 }
128
129
130 /**
131 * Obtains the next header from this iteration.
132 *
133 * @return the next header in this iteration
134 *
135 * @throws NoSuchElementException if there are no more headers
136 */
137 public Header nextHeader()
138 throws NoSuchElementException {
139
140 final int current = this.currentIndex;
141 if (current < 0) {
142 throw new NoSuchElementException("Iteration already finished.");
143 }
144
145 this.currentIndex = findNext(current);
146
147 return this.allHeaders[current];
148 }
149
150
151 /**
152 * Returns the next header.
153 * Same as {@link #nextHeader nextHeader}, but not type-safe.
154 *
155 * @return the next header in this iteration
156 *
157 * @throws NoSuchElementException if there are no more headers
158 */
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 public void remove()
171 throws UnsupportedOperationException {
172
173 throw new UnsupportedOperationException
174 ("Removing headers is not supported.");
175 }
176 }