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.List;
32 import java.util.NoSuchElementException;
33
34 import org.apache.hc.core5.http.Header;
35 import org.apache.hc.core5.util.Args;
36 import org.apache.hc.core5.util.Asserts;
37
38 /**
39 * {@link java.util.Iterator} of {@link org.apache.hc.core5.http.Header}s. For use by {@link HeaderGroup}.
40 *
41 * @since 4.0
42 */
43 class BasicListHeaderIterator implements Iterator<Header> {
44
45 /**
46 * A list of headers to iterate over.
47 * Not all elements of this array are necessarily part of the iteration.
48 */
49 private final List<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 position of the last returned header.
59 * Negative if none has been returned so far.
60 */
61 private int lastIndex;
62
63 /**
64 * The header name to filter by.
65 * {@code null} to iterate over all headers in the array.
66 */
67 private final String headerName;
68
69 /**
70 * Creates a new header iterator.
71 *
72 * @param headers a list of headers over which to iterate
73 * @param name the name of the headers over which to iterate, or
74 * {@code null} for any
75 */
76 public BasicListHeaderIterator(final List<Header> headers, final String name) {
77 super();
78 this.allHeaders = Args.notNull(headers, "Header list");
79 this.headerName = name;
80 this.currentIndex = findNext(-1);
81 this.lastIndex = -1;
82 }
83
84 /**
85 * Determines the index of the next header.
86 *
87 * @param pos one less than the index to consider first,
88 * -1 to search for the first header
89 *
90 * @return the index of the next header that matches the filter name,
91 * or negative if there are no more headers
92 */
93 protected int findNext(final int pos) {
94 int from = pos;
95 if (from < -1) {
96 return -1;
97 }
98
99 final int to = this.allHeaders.size()-1;
100 boolean found = false;
101 while (!found && (from < to)) {
102 from++;
103 found = filterHeader(from);
104 }
105 return found ? from : -1;
106 }
107
108 /**
109 * Checks whether a header is part of the iteration.
110 *
111 * @param index the index of the header to check
112 *
113 * @return {@code true} if the header should be part of the
114 * iteration, {@code false} to skip
115 */
116 private boolean filterHeader(final int index) {
117 if (this.headerName == null) {
118 return true;
119 }
120
121 // non-header elements, including null, will trigger exceptions
122 final String name = (this.allHeaders.get(index)).getName();
123
124 return this.headerName.equalsIgnoreCase(name);
125 }
126
127 @Override
128 public boolean hasNext() {
129 return this.currentIndex >= 0;
130 }
131
132 /**
133 * Obtains the next header from this iteration.
134 *
135 * @return the next header in this iteration
136 *
137 * @throws NoSuchElementException if there are no more headers
138 */
139 @Override
140 public Header next() throws NoSuchElementException {
141 final int current = this.currentIndex;
142 if (current < 0) {
143 throw new NoSuchElementException("Iteration already finished.");
144 }
145
146 this.lastIndex = current;
147 this.currentIndex = findNext(current);
148
149 return this.allHeaders.get(current);
150 }
151
152 /**
153 * Removes the header that was returned last.
154 */
155 @Override
156 public void remove() throws UnsupportedOperationException {
157 Asserts.check(this.lastIndex >= 0, "No header to remove");
158 this.allHeaders.remove(this.lastIndex);
159 this.lastIndex = -1;
160 this.currentIndex--; // adjust for the removed element
161 }
162
163 }