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/*
* $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/message/BasicListHeaderIterator.java $
* $Revision: 584542 $
* $Date: 2007-10-14 06:29:34 -0700 (Sun, 14 Oct 2007) $
*
* ====================================================================
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.http.message;
import java.util.List;
import java.util.NoSuchElementException;
import org.apache.http.Header;
import org.apache.http.HeaderIterator;
/**
* Implementation of a {@link HeaderIterator} based on a {@link List}.
* For use by {@link HeaderGroup}.
*
* @version $Revision: 584542 $
*/
public class BasicListHeaderIterator implements HeaderIterator {
/**
* A list of headers to iterate over.
* Not all elements of this array are necessarily part of the iteration.
*/
protected final List allHeaders;
/**
* The position of the next header in {@link #allHeaders allHeaders}.
* Negative if the iteration is over.
*/
protected int currentIndex;
/**
* The position of the last returned header.
* Negative if none has been returned so far.
*/
protected int lastIndex;
/**
* The header name to filter by.
* <code>null</code> to iterate over all headers in the array.
*/
protected String headerName;
/**
* Creates a new header iterator.
*
* @param headers a list of headers over which to iterate
* @param name the name of the headers over which to iterate, or
* <code>null</code> for any
*/
public BasicListHeaderIterator(List headers, String name) {
if (headers == null) {
throw new IllegalArgumentException
("Header list must not be null.");
}
this.allHeaders = headers;
this.headerName = name;
this.currentIndex = findNext(-1);
this.lastIndex = -1;
}
/**
* Determines the index of the next header.
*
* @param from one less than the index to consider first,
* -1 to search for the first header
*
* @return the index of the next header that matches the filter name,
* or negative if there are no more headers
*/
protected int findNext(int from) {
if (from < -1)
return -1;
final int to = this.allHeaders.size()-1;
boolean found = false;
while (!found && (from < to)) {
from++;
found = filterHeader(from);
}
return found ? from : -1;
}
/**
* Checks whether a header is part of the iteration.
*
* @param index the index of the header to check
*
* @return <code>true</code> if the header should be part of the
* iteration, <code>false</code> to skip
*/
protected boolean filterHeader(int index) {
if (this.headerName == null)
return true;
// non-header elements, including null, will trigger exceptions
final String name = ((Header)this.allHeaders.get(index)).getName();
return this.headerName.equalsIgnoreCase(name);
}
// non-javadoc, see interface HeaderIterator
public boolean hasNext() {
return (this.currentIndex >= 0);
}
/**
* Obtains the next header from this iteration.
*
* @return the next header in this iteration
*
* @throws NoSuchElementException if there are no more headers
*/
public Header nextHeader()
throws NoSuchElementException {
final int current = this.currentIndex;
if (current < 0) {
throw new NoSuchElementException("Iteration already finished.");
}
this.lastIndex = current;
this.currentIndex = findNext(current);
return (Header) this.allHeaders.get(current);
}
/**
* Returns the next header.
* Same as {@link #nextHeader nextHeader}, but not type-safe.
*
* @return the next header in this iteration
*
* @throws NoSuchElementException if there are no more headers
*/
public final Object next()
throws NoSuchElementException {
return nextHeader();
}
/**
* Removes the header that was returned last.
*/
public void remove()
throws UnsupportedOperationException {
if (this.lastIndex < 0) {
throw new IllegalStateException("No header to remove.");
}
this.allHeaders.remove(this.lastIndex);
this.lastIndex = -1;
this.currentIndex--; // adjust for the removed element
}
}
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