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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// 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.io.IOException;
/**
* LazyFieldLite encapsulates the logic of lazily parsing message fields. It stores
* the message in a ByteString initially and then parse it on-demand.
*
* LazyField is thread-compatible e.g. concurrent read are safe, however,
* synchronizations are needed under read/write situations.
*
* This class is internal implementation detail, so you don't need to use it directly.
*
* @author xiangl@google.com (Xiang Li)
*/
public class LazyFieldLite {
private ByteString bytes;
private ExtensionRegistryLite extensionRegistry;
private volatile boolean isDirty = false;
protected volatile MessageLite value;
public LazyFieldLite(ExtensionRegistryLite extensionRegistry, ByteString bytes) {
this.extensionRegistry = extensionRegistry;
this.bytes = bytes;
}
public LazyFieldLite() {
}
public static LazyFieldLite fromValue(MessageLite value) {
LazyFieldLite lf = new LazyFieldLite();
lf.setValue(value);
return lf;
}
public boolean containsDefaultInstance() {
return value == null && bytes == null;
}
public void clear() {
bytes = null;
value = null;
extensionRegistry = null;
isDirty = true;
}
/**
* Returns message instance. At first time, serialized data is parsed by
* {@code defaultInstance.getParserForType()}.
*
* @param defaultInstance its message's default instance. It's also used to get parser for the
* message type.
*/
public MessageLite getValue(MessageLite defaultInstance) {
ensureInitialized(defaultInstance);
return value;
}
/**
* LazyField is not thread-safe for write access. Synchronizations are needed
* under read/write situations.
*/
public MessageLite setValue(MessageLite value) {
MessageLite originalValue = this.value;
this.value = value;
bytes = null;
isDirty = true;
return originalValue;
}
public void merge(LazyFieldLite value) {
if (value.containsDefaultInstance()) {
return;
}
if (bytes == null) {
this.bytes = value.bytes;
} else {
this.bytes.concat(value.toByteString());
}
isDirty = false;
}
public void setByteString(ByteString bytes, ExtensionRegistryLite extensionRegistry) {
this.bytes = bytes;
this.extensionRegistry = extensionRegistry;
isDirty = false;
}
public ExtensionRegistryLite getExtensionRegistry() {
return extensionRegistry;
}
/**
* Due to the optional field can be duplicated at the end of serialized
* bytes, which will make the serialized size changed after LazyField
* parsed. Be careful when using this method.
*/
public int getSerializedSize() {
if (isDirty) {
return value.getSerializedSize();
}
return bytes.size();
}
public ByteString toByteString() {
if (!isDirty) {
return bytes;
}
synchronized (this) {
if (!isDirty) {
return bytes;
}
if (value == null) {
bytes = ByteString.EMPTY;
} else {
bytes = value.toByteString();
}
isDirty = false;
return bytes;
}
}
protected void ensureInitialized(MessageLite defaultInstance) {
if (value != null) {
return;
}
synchronized (this) {
if (value != null) {
return;
}
try {
if (bytes != null) {
value = defaultInstance.getParserForType()
.parseFrom(bytes, extensionRegistry);
} else {
value = defaultInstance;
}
} catch (IOException e) {
// TODO(xiangl): Refactory the API to support the exception thrown from
// lazily load messages.
}
}
}
}
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