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.List;
31 import java.util.NoSuchElementException;
32
33 import org.apache.http.Header;
34 import org.apache.http.HeaderIterator;
35 import org.apache.http.annotation.NotThreadSafe;
36 import org.apache.http.util.Args;
37 import org.apache.http.util.Asserts;
38
39 /**
40 * Implementation of a {@link HeaderIterator} based on a {@link List}.
41 * For use by {@link HeaderGroup}.
42 *
43 * @since 4.0
44 */
45 @NotThreadSafe
46 public class BasicListHeaderIterator implements HeaderIterator {
47
48 /**
49 * A list of headers to iterate over.
50 * Not all elements of this array are necessarily part of the iteration.
51 */
52 protected final List<Header> allHeaders;
53
54
55 /**
56 * The position of the next header in {@link #allHeaders allHeaders}.
57 * Negative if the iteration is over.
58 */
59 protected int currentIndex;
60
61
62 /**
63 * The position of the last returned header.
64 * Negative if none has been returned so far.
65 */
66 protected int lastIndex;
67
68
69 /**
70 * The header name to filter by.
71 * <code>null</code> to iterate over all headers in the array.
72 */
73 protected String headerName;
74
75
76
77 /**
78 * Creates a new header iterator.
79 *
80 * @param headers a list of headers over which to iterate
81 * @param name the name of the headers over which to iterate, or
82 * <code>null</code> for any
83 */
84 public BasicListHeaderIterator(final List<Header> headers, final String name) {
85 super();
86 this.allHeaders = Args.notNull(headers, "Header list");
87 this.headerName = name;
88 this.currentIndex = findNext(-1);
89 this.lastIndex = -1;
90 }
91
92
93 /**
94 * Determines the index of the next header.
95 *
96 * @param from one less than the index to consider first,
97 * -1 to search for the first header
98 *
99 * @return the index of the next header that matches the filter name,
100 * or negative if there are no more headers
101 */
102 protected int findNext(int from) {
103 if (from < -1) {
104 return -1;
105 }
106
107 final int to = this.allHeaders.size()-1;
108 boolean found = false;
109 while (!found && (from < to)) {
110 from++;
111 found = filterHeader(from);
112 }
113 return found ? from : -1;
114 }
115
116
117 /**
118 * Checks whether a header is part of the iteration.
119 *
120 * @param index the index of the header to check
121 *
122 * @return <code>true</code> if the header should be part of the
123 * iteration, <code>false</code> to skip
124 */
125 protected boolean filterHeader(final int index) {
126 if (this.headerName == null) {
127 return true;
128 }
129
130 // non-header elements, including null, will trigger exceptions
131 final String name = (this.allHeaders.get(index)).getName();
132
133 return this.headerName.equalsIgnoreCase(name);
134 }
135
136
137 // non-javadoc, see interface HeaderIterator
138 public boolean hasNext() {
139 return (this.currentIndex >= 0);
140 }
141
142
143 /**
144 * Obtains the next header from this iteration.
145 *
146 * @return the next header in this iteration
147 *
148 * @throws NoSuchElementException if there are no more headers
149 */
150 public Header nextHeader()
151 throws NoSuchElementException {
152
153 final int current = this.currentIndex;
154 if (current < 0) {
155 throw new NoSuchElementException("Iteration already finished.");
156 }
157
158 this.lastIndex = current;
159 this.currentIndex = findNext(current);
160
161 return this.allHeaders.get(current);
162 }
163
164
165 /**
166 * Returns the next header.
167 * Same as {@link #nextHeader nextHeader}, but not type-safe.
168 *
169 * @return the next header in this iteration
170 *
171 * @throws NoSuchElementException if there are no more headers
172 */
173 public final Object next()
174 throws NoSuchElementException {
175 return nextHeader();
176 }
177
178
179 /**
180 * Removes the header that was returned last.
181 */
182 public void remove()
183 throws UnsupportedOperationException {
184 Asserts.check(this.lastIndex >= 0, "No header to remove");
185 this.allHeaders.remove(this.lastIndex);
186 this.lastIndex = -1;
187 this.currentIndex--; // adjust for the removed element
188 }
189 }