267 lines
10 KiB
Java
267 lines
10 KiB
Java
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// Protocol Buffers - Google's data interchange format
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// Copyright 2008 Google Inc. All rights reserved.
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// http://code.google.com/p/protobuf/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package com.google.protobuf;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.Map;
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import com.google.protobuf.Descriptors.Descriptor;
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import com.google.protobuf.Descriptors.FieldDescriptor;
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/**
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* A table of known extensions, searchable by name or field number. When
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* parsing a protocol message that might have extensions, you must provide
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* an {@code ExtensionRegistry} in which you have registered any extensions
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* that you want to be able to parse. Otherwise, those extensions will just
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* be treated like unknown fields.
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*
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* <p>For example, if you had the {@code .proto} file:
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*
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* <pre>
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* option java_class = "MyProto";
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*
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* message Foo {
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* extensions 1000 to max;
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* }
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*
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* extend Foo {
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* optional int32 bar;
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* }
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* </pre>
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*
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* Then you might write code like:
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*
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* <pre>
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* ExtensionRegistry registry = ExtensionRegistry.newInstance();
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* registry.add(MyProto.bar);
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* MyProto.Foo message = MyProto.Foo.parseFrom(input, registry);
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* </pre>
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*
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* <p>Background:
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*
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* <p>You might wonder why this is necessary. Two alternatives might come to
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* mind. First, you might imagine a system where generated extensions are
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* automatically registered when their containing classes are loaded. This
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* is a popular technique, but is bad design; among other things, it creates a
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* situation where behavior can change depending on what classes happen to be
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* loaded. It also introduces a security vulnerability, because an
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* unprivileged class could cause its code to be called unexpectedly from a
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* privileged class by registering itself as an extension of the right type.
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*
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* <p>Another option you might consider is lazy parsing: do not parse an
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* extension until it is first requested, at which point the caller must
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* provide a type to use. This introduces a different set of problems. First,
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* it would require a mutex lock any time an extension was accessed, which
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* would be slow. Second, corrupt data would not be detected until first
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* access, at which point it would be much harder to deal with it. Third, it
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* could violate the expectation that message objects are immutable, since the
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* type provided could be any arbitrary message class. An unprivileged user
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* could take advantage of this to inject a mutable object into a message
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* belonging to privileged code and create mischief.
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*
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* @author kenton@google.com Kenton Varda
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*/
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public final class ExtensionRegistry extends ExtensionRegistryLite {
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/** Construct a new, empty instance. */
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public static ExtensionRegistry newInstance() {
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return new ExtensionRegistry();
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}
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/** Get the unmodifiable singleton empty instance. */
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public static ExtensionRegistry getEmptyRegistry() {
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return EMPTY;
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}
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/** Returns an unmodifiable view of the registry. */
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@Override
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public ExtensionRegistry getUnmodifiable() {
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return new ExtensionRegistry(this);
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}
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/** A (Descriptor, Message) pair, returned by lookup methods. */
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public static final class ExtensionInfo {
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/** The extension's descriptor. */
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public final FieldDescriptor descriptor;
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/**
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* A default instance of the extension's type, if it has a message type.
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* Otherwise, {@code null}.
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*/
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public final Message defaultInstance;
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private ExtensionInfo(final FieldDescriptor descriptor) {
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this.descriptor = descriptor;
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defaultInstance = null;
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}
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private ExtensionInfo(final FieldDescriptor descriptor,
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final Message defaultInstance) {
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this.descriptor = descriptor;
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this.defaultInstance = defaultInstance;
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}
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}
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/**
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* Find an extension by fully-qualified field name, in the proto namespace.
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* I.e. {@code result.descriptor.fullName()} will match {@code fullName} if
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* a match is found.
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*
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* @return Information about the extension if found, or {@code null}
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* otherwise.
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*/
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public ExtensionInfo findExtensionByName(final String fullName) {
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return extensionsByName.get(fullName);
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}
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/**
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* Find an extension by containing type and field number.
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*
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* @return Information about the extension if found, or {@code null}
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* otherwise.
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*/
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public ExtensionInfo findExtensionByNumber(final Descriptor containingType,
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final int fieldNumber) {
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return extensionsByNumber.get(
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new DescriptorIntPair(containingType, fieldNumber));
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}
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/** Add an extension from a generated file to the registry. */
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public void add(final GeneratedMessage.GeneratedExtension<?, ?> extension) {
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if (extension.getDescriptor().getJavaType() ==
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FieldDescriptor.JavaType.MESSAGE) {
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if (extension.getMessageDefaultInstance() == null) {
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throw new IllegalStateException(
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"Registered message-type extension had null default instance: " +
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extension.getDescriptor().getFullName());
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}
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add(new ExtensionInfo(extension.getDescriptor(),
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extension.getMessageDefaultInstance()));
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} else {
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add(new ExtensionInfo(extension.getDescriptor(), null));
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}
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}
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/** Add a non-message-type extension to the registry by descriptor. */
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public void add(final FieldDescriptor type) {
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if (type.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
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throw new IllegalArgumentException(
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"ExtensionRegistry.add() must be provided a default instance when " +
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"adding an embedded message extension.");
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}
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add(new ExtensionInfo(type, null));
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}
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/** Add a message-type extension to the registry by descriptor. */
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public void add(final FieldDescriptor type, final Message defaultInstance) {
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if (type.getJavaType() != FieldDescriptor.JavaType.MESSAGE) {
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throw new IllegalArgumentException(
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"ExtensionRegistry.add() provided a default instance for a " +
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"non-message extension.");
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}
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add(new ExtensionInfo(type, defaultInstance));
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}
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// =================================================================
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// Private stuff.
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private ExtensionRegistry() {
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this.extensionsByName = new HashMap<String, ExtensionInfo>();
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this.extensionsByNumber = new HashMap<DescriptorIntPair, ExtensionInfo>();
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}
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private ExtensionRegistry(ExtensionRegistry other) {
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super(other);
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this.extensionsByName = Collections.unmodifiableMap(other.extensionsByName);
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this.extensionsByNumber =
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Collections.unmodifiableMap(other.extensionsByNumber);
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}
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private final Map<String, ExtensionInfo> extensionsByName;
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private final Map<DescriptorIntPair, ExtensionInfo> extensionsByNumber;
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private ExtensionRegistry(boolean empty) {
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super(ExtensionRegistryLite.getEmptyRegistry());
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this.extensionsByName = Collections.<String, ExtensionInfo>emptyMap();
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this.extensionsByNumber =
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Collections.<DescriptorIntPair, ExtensionInfo>emptyMap();
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}
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private static final ExtensionRegistry EMPTY = new ExtensionRegistry(true);
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private void add(final ExtensionInfo extension) {
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if (!extension.descriptor.isExtension()) {
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throw new IllegalArgumentException(
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"ExtensionRegistry.add() was given a FieldDescriptor for a regular " +
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"(non-extension) field.");
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}
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extensionsByName.put(extension.descriptor.getFullName(), extension);
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extensionsByNumber.put(
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new DescriptorIntPair(extension.descriptor.getContainingType(),
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extension.descriptor.getNumber()),
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extension);
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final FieldDescriptor field = extension.descriptor;
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if (field.getContainingType().getOptions().getMessageSetWireFormat() &&
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field.getType() == FieldDescriptor.Type.MESSAGE &&
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field.isOptional() &&
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field.getExtensionScope() == field.getMessageType()) {
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// This is an extension of a MessageSet type defined within the extension
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// type's own scope. For backwards-compatibility, allow it to be looked
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// up by type name.
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extensionsByName.put(field.getMessageType().getFullName(), extension);
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}
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}
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/** A (GenericDescriptor, int) pair, used as a map key. */
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private static final class DescriptorIntPair {
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private final Descriptor descriptor;
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private final int number;
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DescriptorIntPair(final Descriptor descriptor, final int number) {
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this.descriptor = descriptor;
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this.number = number;
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}
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@Override
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public int hashCode() {
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return descriptor.hashCode() * ((1 << 16) - 1) + number;
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}
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@Override
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public boolean equals(final Object obj) {
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if (!(obj instanceof DescriptorIntPair)) {
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return false;
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}
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final DescriptorIntPair other = (DescriptorIntPair)obj;
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return descriptor == other.descriptor && number == other.number;
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}
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}
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}
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