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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package com.google.protobuf;
import java.util.List;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.RandomAccess;
/**
* An implementation of {@link LazyStringList} that wraps an ArrayList. Each
* element is either a ByteString or a String. It caches the last one requested
* which is most likely the one needed next. This minimizes memory usage while
* satisfying the most common use cases.
* <p>
* <strong>Note that this implementation is not synchronized.</strong>
* If multiple threads access an <tt>ArrayList</tt> instance concurrently,
* and at least one of the threads modifies the list structurally, it
* <i>must</i> be synchronized externally. (A structural modification is
* any operation that adds or deletes one or more elements, or explicitly
* resizes the backing array; merely setting the value of an element is not
* a structural modification.) This is typically accomplished by
* synchronizing on some object that naturally encapsulates the list.
* <p>
* If the implementation is accessed via concurrent reads, this is thread safe.
* Conversions are done in a thread safe manner. It's possible that the
* conversion may happen more than once if two threads attempt to access the
* same element and the modifications were not visible to each other, but this
* will not result in any corruption of the list or change in behavior other
* than performance.
*
* @author jonp@google.com (Jon Perlow)
*/
public class LazyStringArrayList extends AbstractList<String>
implements LazyStringList, RandomAccess {
public final static LazyStringList EMPTY = new UnmodifiableLazyStringList(
new LazyStringArrayList());
private final List<Object> list;
public LazyStringArrayList() {
list = new ArrayList<Object>();
}
public LazyStringArrayList(LazyStringList from) {
list = new ArrayList<Object>(from.size());
addAll(from);
}
public LazyStringArrayList(List<String> from) {
list = new ArrayList<Object>(from);
}
@Override
public String get(int index) {
Object o = list.get(index);
if (o instanceof String) {
return (String) o;
} else {
ByteString bs = (ByteString) o;
String s = bs.toStringUtf8();
if (bs.isValidUtf8()) {
list.set(index, s);
}
return s;
}
}
@Override
public int size() {
return list.size();
}
@Override
public String set(int index, String s) {
Object o = list.set(index, s);
return asString(o);
}
@Override
public void add(int index, String element) {
list.add(index, element);
modCount++;
}
@Override
public boolean addAll(Collection<? extends String> c) {
// The default implementation of AbstractCollection.addAll(Collection)
// delegates to add(Object). This implementation instead delegates to
// addAll(int, Collection), which makes a special case for Collections
// which are instances of LazyStringList.
return addAll(size(), c);
}
@Override
public boolean addAll(int index, Collection<? extends String> c) {
// When copying from another LazyStringList, directly copy the underlying
// elements rather than forcing each element to be decoded to a String.
Collection<?> collection = c instanceof LazyStringList
? ((LazyStringList) c).getUnderlyingElements() : c;
boolean ret = list.addAll(index, collection);
modCount++;
return ret;
}
@Override
public String remove(int index) {
Object o = list.remove(index);
modCount++;
return asString(o);
}
public void clear() {
list.clear();
modCount++;
}
// @Override
public void add(ByteString element) {
list.add(element);
modCount++;
}
// @Override
public ByteString getByteString(int index) {
Object o = list.get(index);
if (o instanceof String) {
ByteString b = ByteString.copyFromUtf8((String) o);
list.set(index, b);
return b;
} else {
return (ByteString) o;
}
}
private String asString(Object o) {
if (o instanceof String) {
return (String) o;
} else {
return ((ByteString) o).toStringUtf8();
}
}
public List<?> getUnderlyingElements() {
return Collections.unmodifiableList(list);
}
}
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