ExtensionRegistryLite.java

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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
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package com.google.protobuf;
 
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
 
public class ExtensionRegistryLite {
 
  // Set true to enable lazy parsing feature for MessageSet.
  //
  // TODO(xiangl): Now we use a global flag to control whether enable lazy
  // parsing feature for MessageSet, which may be too crude for some
  // applications. Need to support this feature on smaller granularity.
  private static volatile boolean eagerlyParseMessageSets = false;
 
  // short circuit the ExtensionRegistryFactory via assumevalues trickery
  @SuppressWarnings("JavaOptionalSuggestions")
  private static boolean doFullRuntimeInheritanceCheck = true;
 
  // Visible for testing.
  static final String EXTENSION_CLASS_NAME = "com.google.protobuf.Extension";
 
  /* @Nullable */
  static Class<?> resolveExtensionClass() {
    try {
      return Class.forName(EXTENSION_CLASS_NAME);
    } catch (ClassNotFoundException e) {
      // See comment in ExtensionRegistryFactory on the potential expense of this.
      return null;
    }
  }
 
  /* @Nullable */
  private static final Class<?> extensionClass = resolveExtensionClass();
 
  public static boolean isEagerlyParseMessageSets() {
    return eagerlyParseMessageSets;
  }
 
  public static void setEagerlyParseMessageSets(boolean isEagerlyParse) {
    eagerlyParseMessageSets = isEagerlyParse;
  }
 
  public static ExtensionRegistryLite newInstance() {
    return doFullRuntimeInheritanceCheck
        ? ExtensionRegistryFactory.create()
        : new ExtensionRegistryLite();
  }
 
  private static volatile ExtensionRegistryLite emptyRegistry;
 
  public static ExtensionRegistryLite getEmptyRegistry() {
    ExtensionRegistryLite result = emptyRegistry;
    if (result == null) {
      synchronized (ExtensionRegistryLite.class) {
        result = emptyRegistry;
        if (result == null) {
          result =
              emptyRegistry =
                  doFullRuntimeInheritanceCheck
                      ? ExtensionRegistryFactory.createEmpty()
                      : EMPTY_REGISTRY_LITE;
        }
      }
    }
    return result;
  }
 
 
  public ExtensionRegistryLite getUnmodifiable() {
    return new ExtensionRegistryLite(this);
  }
 
  @SuppressWarnings("unchecked")
  public <ContainingType extends MessageLite>
      GeneratedMessageLite.GeneratedExtension<ContainingType, ?> findLiteExtensionByNumber(
          final ContainingType containingTypeDefaultInstance, final int fieldNumber) {
    return (GeneratedMessageLite.GeneratedExtension<ContainingType, ?>)
        extensionsByNumber.get(new ObjectIntPair(containingTypeDefaultInstance, fieldNumber));
  }
 
  public final void add(final GeneratedMessageLite.GeneratedExtension<?, ?> extension) {
    extensionsByNumber.put(
        new ObjectIntPair(extension.getContainingTypeDefaultInstance(), extension.getNumber()),
        extension);
  }
 
  public final void add(ExtensionLite<?, ?> extension) {
    if (GeneratedMessageLite.GeneratedExtension.class.isAssignableFrom(extension.getClass())) {
      add((GeneratedMessageLite.GeneratedExtension<?, ?>) extension);
    }
    if (doFullRuntimeInheritanceCheck && ExtensionRegistryFactory.isFullRegistry(this)) {
      try {
        this.getClass().getMethod("add", extensionClass).invoke(this, extension);
      } catch (Exception e) {
        throw new IllegalArgumentException(
            String.format("Could not invoke ExtensionRegistry#add for %s", extension), e);
      }
    }
  }
 
  // =================================================================
  // Private stuff.
 
  // Constructors are package-private so that ExtensionRegistry can subclass
  // this.
 
  ExtensionRegistryLite() {
    this.extensionsByNumber =
        new HashMap<ObjectIntPair, GeneratedMessageLite.GeneratedExtension<?, ?>>();
  }
 
  static final ExtensionRegistryLite EMPTY_REGISTRY_LITE = new ExtensionRegistryLite(true);
 
  ExtensionRegistryLite(ExtensionRegistryLite other) {
    if (other == EMPTY_REGISTRY_LITE) {
      this.extensionsByNumber = Collections.emptyMap();
    } else {
      this.extensionsByNumber = Collections.unmodifiableMap(other.extensionsByNumber);
    }
  }
 
  private final Map<ObjectIntPair, GeneratedMessageLite.GeneratedExtension<?, ?>>
      extensionsByNumber;
 
  ExtensionRegistryLite(boolean empty) {
    this.extensionsByNumber = Collections.emptyMap();
  }
 
  private static final class ObjectIntPair {
    private final Object object;
    private final int number;
 
    ObjectIntPair(final Object object, final int number) {
      this.object = object;
      this.number = number;
    }
 
    @Override
    public int hashCode() {
      return System.identityHashCode(object) * ((1 << 16) - 1) + number;
    }
 
    @Override
    public boolean equals(final Object obj) {
      if (!(obj instanceof ObjectIntPair)) {
        return false;
      }
      final ObjectIntPair other = (ObjectIntPair) obj;
      return object == other.object && number == other.number;
    }
  }
}