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using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Text;
using Google.ProtocolBuffers.Descriptors;
namespace Google.ProtocolBuffers {
/// <summary>
/// Base type for all generated extensions.
/// </summary>
/// <remarks>
/// The protocol compiler generates a static singleton instance of this
/// class for each extension. For exmaple, imagine a .proto file with:
/// <code>
/// message Foo {
/// extensions 1000 to max
/// }
///
/// extend Foo {
/// optional int32 bar;
/// }
/// </code>
/// Then MyProto.Foo.Bar has type GeneratedExtensionBase<MyProto.Foo,int>.
/// <para />
/// In general, users should ignore the details of this type, and
/// simply use the static singletons as parameters to the extension accessors
/// in ExtendableMessage and ExtendableBuilder.
/// The interface implemented by both GeneratedException and GeneratedRepeatException,
/// to make it easier to cope with repeats separately.
/// </remarks>
public abstract class GeneratedExtensionBase<TExtension> {
private readonly FieldDescriptor descriptor;
private readonly IMessage messageDefaultInstance;
protected GeneratedExtensionBase(FieldDescriptor descriptor, Type singularExtensionType) {
if (!descriptor.IsExtension) {
throw new ArgumentException("GeneratedExtension given a regular (non-extension) field.");
}
this.descriptor = descriptor;
if (descriptor.MappedType == MappedType.Message) {
PropertyInfo defaultInstanceProperty = singularExtensionType
.GetProperty("DefaultInstance", BindingFlags.Static | BindingFlags.Public);
if (defaultInstanceProperty == null) {
throw new ArgumentException("No public static DefaultInstance property for type " + typeof(TExtension).Name);
}
messageDefaultInstance = (IMessage)defaultInstanceProperty.GetValue(null, null);
}
}
public FieldDescriptor Descriptor {
get { return descriptor; }
}
/// <summary>
/// Returns the default message instance for extensions which are message types.
/// </summary>
public IMessage MessageDefaultInstance {
get { return messageDefaultInstance; }
}
public object SingularFromReflectionType(object value) {
switch (Descriptor.MappedType) {
case MappedType.Message:
if (value is TExtension) {
return value;
} else {
// It seems the copy of the embedded message stored inside the
// extended message is not of the exact type the user was
// expecting. This can happen if a user defines a
// GeneratedExtension manually and gives it a different type.
// This should not happen in normal use. But, to be nice, we'll
// copy the message to whatever type the caller was expecting.
return MessageDefaultInstance.WeakCreateBuilderForType()
.WeakMergeFrom((IMessage)value).WeakBuild();
}
case MappedType.Enum:
// Just return a boxed int - that can be unboxed to the enum
return ((EnumValueDescriptor) value).Number;
default:
return value;
}
}
/// <summary>
/// Converts from the type used by the native accessors to the type
/// used by reflection accessors. For example, the reflection accessors
/// for enums use EnumValueDescriptors but the native accessors use
/// the generated enum type.
/// </summary>
public object ToReflectionType(object value) {
if (descriptor.IsRepeated) {
if (descriptor.MappedType == MappedType.Enum) {
// Must convert the whole list.
IList<object> result = new List<object>();
foreach (object element in (IEnumerable) value) {
result.Add(SingularToReflectionType(element));
}
return result;
} else {
return value;
}
} else {
return SingularToReflectionType(value);
}
}
/// <summary>
/// Like ToReflectionType(object) but for a single element.
/// </summary>
internal Object SingularToReflectionType(object value) {
return descriptor.MappedType == MappedType.Enum
? descriptor.EnumType.FindValueByNumber((int) value)
: value;
}
public abstract object FromReflectionType(object value);
}
}
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