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#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2015 Google Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
#endregion
using System;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using Google.Protobuf.Compatibility;
namespace Google.Protobuf.Reflection
{
/// <summary>
/// Accessor for single fields.
/// </summary>
internal sealed class SingleFieldAccessor : FieldAccessorBase
{
// All the work here is actually done in the constructor - it creates the appropriate delegates.
// There are various cases to consider, based on the property type (message, string/bytes, or "genuine" primitive)
// and proto2 vs proto3 for non-message types, as proto3 doesn't support "full" presence detection or default
// values.
private readonly Action<IMessage, object> setValueDelegate;
private readonly Action<IMessage> clearDelegate;
private readonly Func<IMessage, bool> hasDelegate;
internal SingleFieldAccessor(
[DynamicallyAccessedMembers(GeneratedClrTypeInfo.MessageAccessibility)]
Type messageType, PropertyInfo property, FieldDescriptor descriptor) : base(property, descriptor)
{
if (!property.CanWrite)
{
throw new ArgumentException("Not all required properties/methods available");
}
setValueDelegate = ReflectionUtil.CreateActionIMessageObject(property.GetSetMethod());
// Note: this looks worrying in that we access the containing oneof, which isn't valid until cross-linking
// is complete... but field accessors aren't created until after cross-linking.
// The oneof itself won't be cross-linked yet, but that's okay: the oneof accessor is created
// earlier.
// Message fields always support presence, via null checks.
if (descriptor.FieldType == FieldType.Message)
{
hasDelegate = message => GetValue(message) != null;
clearDelegate = message => SetValue(message, null);
}
// Oneof fields always support presence, via case checks.
// Note that clearing the field is a no-op unless that specific field is the current "case".
else if (descriptor.RealContainingOneof != null)
{
var oneofAccessor = descriptor.RealContainingOneof.Accessor;
hasDelegate = message => oneofAccessor.GetCaseFieldDescriptor(message) == descriptor;
clearDelegate = message =>
{
// Clear on a field only affects the oneof itself if the current case is the field we're accessing.
if (oneofAccessor.GetCaseFieldDescriptor(message) == descriptor)
{
oneofAccessor.Clear(message);
}
};
}
// Anything else that supports presence should have a "HasXyz" property and a "ClearXyz"
// method.
else if (descriptor.HasPresence)
{
MethodInfo hasMethod = messageType.GetRuntimeProperty("Has" + property.Name).GetMethod;
if (hasMethod == null)
{
throw new ArgumentException("Not all required properties/methods are available");
}
hasDelegate = ReflectionUtil.CreateFuncIMessageBool(hasMethod);
MethodInfo clearMethod = messageType.GetRuntimeMethod("Clear" + property.Name, ReflectionUtil.EmptyTypes);
if (clearMethod == null)
{
throw new ArgumentException("Not all required properties/methods are available");
}
clearDelegate = ReflectionUtil.CreateActionIMessage(clearMethod);
}
// Otherwise, we don't support presence.
else
{
hasDelegate = message => throw new InvalidOperationException("Presence is not implemented for this field");
// While presence isn't supported, clearing still is; it's just setting to a default value.
object defaultValue = GetDefaultValue(descriptor);
clearDelegate = message => SetValue(message, defaultValue);
}
}
private static object GetDefaultValue(FieldDescriptor descriptor) =>
descriptor.FieldType switch
{
FieldType.Bool => false,
FieldType.Bytes => ByteString.Empty,
FieldType.String => "",
FieldType.Double => 0.0,
FieldType.SInt32 or FieldType.Int32 or FieldType.SFixed32 or FieldType.Enum => 0,
FieldType.Fixed32 or FieldType.UInt32 => (uint)0,
FieldType.Fixed64 or FieldType.UInt64 => 0UL,
FieldType.SFixed64 or FieldType.Int64 or FieldType.SInt64 => 0L,
FieldType.Float => 0f,
FieldType.Message or FieldType.Group => null,
_ => throw new ArgumentException("Invalid field type"),
};
public override void Clear(IMessage message) => clearDelegate(message);
public override bool HasValue(IMessage message) => hasDelegate(message);
public override void SetValue(IMessage message, object value) => setValueDelegate(message, value);
}
}