protobuf/src/ProtocolBuffers/FieldAccess/FieldAccessorTable.cs

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://github.com/jskeet/dotnet-protobufs/
// Original C++/Java/Python code:
// 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.
using System;
using Google.ProtocolBuffers.Descriptors;

namespace Google.ProtocolBuffers.FieldAccess {
  /// <summary>
  /// Provides access to fields in generated messages via reflection.
  /// This type is public to allow it to be used by generated messages, which
  /// create appropriate instances in the .proto file description class.
  /// TODO(jonskeet): See if we can hide it somewhere...
  /// </summary>
  public sealed class FieldAccessorTable<TMessage, TBuilder>
      where TMessage : IMessage<TMessage, TBuilder>
      where TBuilder : IBuilder<TMessage, TBuilder> {

    readonly IFieldAccessor<TMessage, TBuilder>[] accessors;

    readonly MessageDescriptor descriptor;

    public MessageDescriptor Descriptor { 
      get { return descriptor; }
    }

   /// <summary>
    /// Constructs a FieldAccessorTable for a particular message class.
    /// Only one FieldAccessorTable should be constructed per class.
    /// The property names should all actually correspond with the field descriptor's
    /// CSharpOptions.PropertyName property, but bootstrapping issues currently
    /// prevent us from using that. This may be addressed at a future time, in which case
    /// we can keep this constructor for backwards compatibility, just ignoring the parameter.
    /// TODO(jonskeet): Make it so.
    /// </summary>
    /// <param name="descriptor">The type's descriptor</param>
    /// <param name="propertyNames">The Pascal-case names of all the field-based properties in the message.</param>
    public FieldAccessorTable(MessageDescriptor descriptor, String[] propertyNames) {
      this.descriptor = descriptor;
      accessors = new IFieldAccessor<TMessage, TBuilder>[descriptor.Fields.Count];
      for (int i=0; i < accessors.Length; i++) {
        accessors[i] = CreateAccessor(descriptor.Fields[i], propertyNames[i]);
      }
    }

     /// <summary>
     /// Creates an accessor for a single field
     /// </summary>   
    private static IFieldAccessor<TMessage, TBuilder> CreateAccessor(FieldDescriptor field, string name) {
      if (field.IsRepeated) {
        switch (field.MappedType) {
          case MappedType.Message: return new RepeatedMessageAccessor<TMessage, TBuilder>(name);
          case MappedType.Enum: return new RepeatedEnumAccessor<TMessage, TBuilder>(field, name);
          default: return new RepeatedPrimitiveAccessor<TMessage, TBuilder>(name);
        }
      } else {
        switch (field.MappedType) {
          case MappedType.Message: return new SingleMessageAccessor<TMessage, TBuilder>(name);
          case MappedType.Enum: return new SingleEnumAccessor<TMessage, TBuilder>(field, name);
          default: return new SinglePrimitiveAccessor<TMessage, TBuilder>(name);
        }
      }
    }

    internal IFieldAccessor<TMessage, TBuilder> this[FieldDescriptor field] {
      get {
        if (field.ContainingType != descriptor) {
          throw new ArgumentException("FieldDescriptor does not match message type.");
        } else if (field.IsExtension) {
          // If this type had extensions, it would subclass ExtendableMessage,
          // which overrides the reflection interface to handle extensions.
          throw new ArgumentException("This type does not have extensions.");
        }
        return accessors[field.Index];
      }
    }
  }
}