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Diffstat (limited to 'java/core/src/main/java/com/google/protobuf/LazyField.java')
-rw-r--r-- | java/core/src/main/java/com/google/protobuf/LazyField.java | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/java/core/src/main/java/com/google/protobuf/LazyField.java b/java/core/src/main/java/com/google/protobuf/LazyField.java new file mode 100644 index 00000000..5e0a485c --- /dev/null +++ b/java/core/src/main/java/com/google/protobuf/LazyField.java @@ -0,0 +1,154 @@ +// 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.util.Iterator; +import java.util.Map.Entry; + +/** + * LazyField encapsulates the logic of lazily parsing message fields. It stores + * the message in a ByteString initially and then parse it on-demand. + * + * Most of key methods are implemented in {@link LazyFieldLite} but this class + * can contain default instance of the message to provide {@code hashCode()}, + * {@code equals()} and {@code toString()}. + * + * @author xiangl@google.com (Xiang Li) + */ +public class LazyField extends LazyFieldLite { + + /** + * Carry a message's default instance which is used by {@code hashCode()}, {@code equals()} and + * {@code toString()}. + */ + private final MessageLite defaultInstance; + + public LazyField(MessageLite defaultInstance, + ExtensionRegistryLite extensionRegistry, ByteString bytes) { + super(extensionRegistry, bytes); + + this.defaultInstance = defaultInstance; + } + + @Override + public boolean containsDefaultInstance() { + return super.containsDefaultInstance() || value == defaultInstance; + } + + public MessageLite getValue() { + return getValue(defaultInstance); + } + + @Override + public int hashCode() { + return getValue().hashCode(); + } + + @Override + public boolean equals(Object obj) { + return getValue().equals(obj); + } + + @Override + public String toString() { + return getValue().toString(); + } + + // ==================================================== + + /** + * LazyEntry and LazyIterator are used to encapsulate the LazyField, when + * users iterate all fields from FieldSet. + */ + static class LazyEntry<K> implements Entry<K, Object> { + private Entry<K, LazyField> entry; + + private LazyEntry(Entry<K, LazyField> entry) { + this.entry = entry; + } + + // @Override + public K getKey() { + return entry.getKey(); + } + + // @Override + public Object getValue() { + LazyField field = entry.getValue(); + if (field == null) { + return null; + } + return field.getValue(); + } + + public LazyField getField() { + return entry.getValue(); + } + + // @Override + public Object setValue(Object value) { + if (!(value instanceof MessageLite)) { + throw new IllegalArgumentException( + "LazyField now only used for MessageSet, " + + "and the value of MessageSet must be an instance of MessageLite"); + } + return entry.getValue().setValue((MessageLite) value); + } + } + + static class LazyIterator<K> implements Iterator<Entry<K, Object>> { + private Iterator<Entry<K, Object>> iterator; + + public LazyIterator(Iterator<Entry<K, Object>> iterator) { + this.iterator = iterator; + } + + // @Override + public boolean hasNext() { + return iterator.hasNext(); + } + + @SuppressWarnings("unchecked") + // @Override + public Entry<K, Object> next() { + Entry<K, ?> entry = iterator.next(); + if (entry.getValue() instanceof LazyField) { + return new LazyEntry<K>((Entry<K, LazyField>) entry); + } + return (Entry<K, Object>) entry; + } + + // @Override + public void remove() { + iterator.remove(); + } + } +} |