Home | History | Annotate | Download | only in protobuf 
      1 // Protocol Buffers - Google's data interchange format
      2 // Copyright 2008 Google Inc.  All rights reserved.
      3 // http://code.google.com/p/protobuf/
      4 //
      5 // Redistribution and use in source and binary forms, with or without
      6 // modification, are permitted provided that the following conditions are
      7 // met:
      8 //
      9 //     * Redistributions of source code must retain the above copyright
     10 // notice, this list of conditions and the following disclaimer.
     11 //     * Redistributions in binary form must reproduce the above
     12 // copyright notice, this list of conditions and the following disclaimer
     13 // in the documentation and/or other materials provided with the
     14 // distribution.
     15 //     * Neither the name of Google Inc. nor the names of its
     16 // contributors may be used to endorse or promote products derived from
     17 // this software without specific prior written permission.
     18 //
     19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     30 
     31 package com.google.protobuf;
     32 
     33 import java.util.Collections;
     34 import java.util.HashMap;
     35 import java.util.Map;
     36 
     37 /**
     38  * Equivalent to {@link ExtensionRegistry} but supports only "lite" types.
     39  * <p>
     40  * If all of your types are lite types, then you only need to use
     41  * {@code ExtensionRegistryLite}.  Similarly, if all your types are regular
     42  * types, then you only need {@link ExtensionRegistry}.  Typically it does not
     43  * make sense to mix the two, since if you have any regular types in your
     44  * program, you then require the full runtime and lose all the benefits of
     45  * the lite runtime, so you might as well make all your types be regular types.
     46  * However, in some cases (e.g. when depending on multiple third-patry libraries
     47  * where one uses lite types and one uses regular), you may find yourself
     48  * wanting to mix the two.  In this case things get more complicated.
     49  * <p>
     50  * There are three factors to consider:  Whether the type being extended is
     51  * lite, whether the embedded type (in the case of a message-typed extension)
     52  * is lite, and whether the extension itself is lite.  Since all three are
     53  * declared in different files, they could all be different.  Here are all
     54  * the combinations and which type of registry to use:
     55  * <pre>
     56  *   Extended type     Inner type    Extension         Use registry
     57  *   =======================================================================
     58  *   lite              lite          lite              ExtensionRegistryLite
     59  *   lite              regular       lite              ExtensionRegistry
     60  *   regular           regular       regular           ExtensionRegistry
     61  *   all other combinations                            not supported
     62  * </pre>
     63  * <p>
     64  * Note that just as regular types are not allowed to contain lite-type fields,
     65  * they are also not allowed to contain lite-type extensions.  This is because
     66  * regular types must be fully accessible via reflection, which in turn means
     67  * that all the inner messages must also support reflection.  On the other hand,
     68  * since regular types implement the entire lite interface, there is no problem
     69  * with embedding regular types inside lite types.
     70  *
     71  * @author kenton (at) google.com Kenton Varda
     72  */
     73 public class ExtensionRegistryLite {
     74   /** Construct a new, empty instance. */
     75   public static ExtensionRegistryLite newInstance() {
     76     return new ExtensionRegistryLite();
     77   }
     78 
     79   /** Get the unmodifiable singleton empty instance. */
     80   public static ExtensionRegistryLite getEmptyRegistry() {
     81     return EMPTY;
     82   }
     83 
     84   /** Returns an unmodifiable view of the registry. */
     85   public ExtensionRegistryLite getUnmodifiable() {
     86     return new ExtensionRegistryLite(this);
     87   }
     88 
     89   /**
     90    * Find an extension by containing type and field number.
     91    *
     92    * @return Information about the extension if found, or {@code null}
     93    *         otherwise.
     94    */
     95   @SuppressWarnings("unchecked")
     96   public <ContainingType extends MessageLite>
     97       GeneratedMessageLite.GeneratedExtension<ContainingType, ?>
     98         findLiteExtensionByNumber(
     99           final ContainingType containingTypeDefaultInstance,
    100           final int fieldNumber) {
    101     return (GeneratedMessageLite.GeneratedExtension<ContainingType, ?>)
    102       extensionsByNumber.get(
    103         new ObjectIntPair(containingTypeDefaultInstance, fieldNumber));
    104   }
    105 
    106   /** Add an extension from a lite generated file to the registry. */
    107   public final void add(
    108       final GeneratedMessageLite.GeneratedExtension<?, ?> extension) {
    109     extensionsByNumber.put(
    110       new ObjectIntPair(extension.getContainingTypeDefaultInstance(),
    111                         extension.getNumber()),
    112       extension);
    113   }
    114 
    115   // =================================================================
    116   // Private stuff.
    117 
    118   // Constructors are package-private so that ExtensionRegistry can subclass
    119   // this.
    120 
    121   ExtensionRegistryLite() {
    122     this.extensionsByNumber =
    123         new HashMap<ObjectIntPair,
    124                     GeneratedMessageLite.GeneratedExtension<?, ?>>();
    125   }
    126 
    127   ExtensionRegistryLite(ExtensionRegistryLite other) {
    128     if (other == EMPTY) {
    129       this.extensionsByNumber = Collections.emptyMap();
    130     } else {
    131       this.extensionsByNumber =
    132         Collections.unmodifiableMap(other.extensionsByNumber);
    133     }
    134   }
    135 
    136   private final Map<ObjectIntPair,
    137                     GeneratedMessageLite.GeneratedExtension<?, ?>>
    138       extensionsByNumber;
    139 
    140   private ExtensionRegistryLite(boolean empty) {
    141     this.extensionsByNumber = Collections.emptyMap();
    142   }
    143   private static final ExtensionRegistryLite EMPTY =
    144     new ExtensionRegistryLite(true);
    145 
    146   /** A (Object, int) pair, used as a map key. */
    147   private static final class ObjectIntPair {
    148     private final Object object;
    149     private final int number;
    150 
    151     ObjectIntPair(final Object object, final int number) {
    152       this.object = object;
    153       this.number = number;
    154     }
    155 
    156     @Override
    157     public int hashCode() {
    158       return System.identityHashCode(object) * ((1 << 16) - 1) + number;
    159     }
    160     @Override
    161     public boolean equals(final Object obj) {
    162       if (!(obj instanceof ObjectIntPair)) {
    163         return false;
    164       }
    165       final ObjectIntPair other = (ObjectIntPair)obj;
    166       return object == other.object && number == other.number;
    167     }
    168   }
    169 }
    170