From 76b8a769ab47ff16200ae0ded835989cef92c726 Mon Sep 17 00:00:00 2001 From: "jieluo@google.com" Date: Sat, 19 Jul 2014 00:43:46 +0000 Subject: add LazyFieldLite.java --- .../java/com/google/protobuf/LazyFieldLite.java | 176 +++++++++++++++++++++ 1 file changed, 176 insertions(+) create mode 100644 java/src/main/java/com/google/protobuf/LazyFieldLite.java diff --git a/java/src/main/java/com/google/protobuf/LazyFieldLite.java b/java/src/main/java/com/google/protobuf/LazyFieldLite.java new file mode 100644 index 00000000..2c4d0dc6 --- /dev/null +++ b/java/src/main/java/com/google/protobuf/LazyFieldLite.java @@ -0,0 +1,176 @@ +// 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.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. + } + } + } +} -- cgit v1.2.3