使用 MonoTouch 反序列化 Protobuf 文件的问题

Question

我们目前面临的问题是，我们希望使用 MonoTouch 将当前在 Android (Monodroid) 和 Wp7 上运行的应用程序移植到 IOS。

这不是问题，但是使用 protobuf-net 框架反序列化数据总是会失败，并出现以下异常：

ProtoBuf.ProtoException: Invalid wire-type; this usually means you have over-written a file without truncating or setting the length; see http://stackoverflow.com/q/2152978/23354
  at ProtoBuf.ProtoReader.StartSubItem (ProtoBuf.ProtoReader reader) [0x00000] in <filename unknown>:0
  at ProtoBuf.BclHelpers.ReadGuid (ProtoBuf.ProtoReader source) [0x00000] in <filename unknown>:0
  at TpSerializer.Read (Application.Mobile.TpDataAccess.TimeEntryLoggingDao.Entities.ActiveTimeEntryDbo , ProtoBuf.ProtoReader ) [0x00000] in <filename unknown>:0
  at TpSerializer.Deserialize (Int32 , System.Object , ProtoBuf.ProtoReader ) [0x00000] in <filename unknown>:0
  at ProtoBuf.Meta.TypeModel.TryDeserializeAuxiliaryType (ProtoBuf.ProtoReader reader, DataFormat format, Int32 tag, System.Type type, System.Object& value, Boolean skipOtherFields, Boolean asListItem, Boolean autoCreate, Boolean insideList) [0x00000] in <filename unknown>:0
  at ProtoBuf.Meta.TypeModel.TryDeserializeList (ProtoBuf.Meta.TypeModel model, ProtoBuf.ProtoReader reader, DataFormat format, Int32 tag, System.Type listType, System.Type itemType, System.Object& value) [0x00000] in <filename unknown>:0
  at ProtoBuf.Meta.TypeModel.TryDeserializeAuxiliaryType (ProtoBuf.ProtoReader reader, DataFormat format, Int32 tag, System.Type type, System.Object& value, Boolean skipOtherFields, Boolean asListItem, Boolean autoCreate, Boolean insideList) [0x00000] in <filename unknown>:0
  at ProtoBuf.Meta.TypeModel.DeserializeCore (ProtoBuf.ProtoReader reader, System.Type type, System.Object value, Boolean noAutoCreate) [0x00000] in <filename unknown>:0
  at ProtoBuf.Meta.TypeModel.Deserialize (System.IO.Stream source, System.Object value, System.Type type, ProtoBuf.SerializationContext context) [0x00000] in <filename unknown>:0
  at ProtoBuf.Meta.TypeModel.Deserialize (System.IO.Stream source, System.Object value, System.Type type) [0x00000] in <filename unknown>:0
  at Application.Mobile.TpDataAccess.Core.CoreProtobufDao`2[System.Guid,Application.Mobile.TpDataAccess.TimeEntryDao.Entities.TimeEntryDbo].EnsureCollection () [0x00000] in <filename unknown>:0
  at Application.Mobile.TpDataAccess.TimeEntryDao.TimeEntryProtobufDao.PrepareAccess () [0x00000] in <filename unknown>:0
  at Application.Mobile.TpBusinessComponents.TimeEntryService.TimeEntryService.PrepareAccess () [0x00000] in <filename unknown>:0
  at App.TP.Mobile.AppDelegate.FinishedLaunching (MonoTouch.UIKit.UIApplication app, MonoTouch.Foundation.NSDictionary options) [0x00031] in /Users/Developer/Dropbox/Application Mobile/Application Mobile iOS Project/Application_Mobile/AppDelegate.cs:34
  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:38
  at App.TP.Mobile.Application.Main (System.String[] args) [0x00000] in /Users/Developer/Dropbox/Application Mobile/Application Mobile iOS Project/Application_Mobile/Main.cs:17

问题是我们没有改变实体，也没有改变我们存储数据的方式。

// and serialize
string file = Path.Combine(StoragePath, dataFileName);
using (var stm = new FileStream(file, FileMode.Create))
{
    foreach (var item in list)
        Serializer.Serialize(stm, item);
}

无论我们读取哪个实体，它都会失败：

string file = Path.Combine(StoragePath, dataFileName);
if (!File.Exists(file))
    return;

using (var stm = new FileStream(file, FileMode.Open))
{
    var list = (TClass[]) Serializer.Deserialize(stm, null, typeof(TClass[]));
    if (list == null)
        return;

    // transform array into dictionary
    for (int i = 0; i < list.Length; i++)
    {
        var entity = list[i];
        entities[primaryKeyFunction(entity)] = entity;
    }
}

我们正在使用以下 Protobuf-NET 环境。

• Protobuf-net r594 (unity dll)
• 预创建的序列化程序

保存数据不是问题，但加载失败。 非常感谢任何帮助。

谢谢 - 格哈德

Answer 1

一个不错的简单的。你已经序列化为Foo，反序列化为Foo[]。实际上，由于协议缓冲区是一种可附加格式，通过重复使用Serialize（到同一个文件），你实际上只写了一个Foo（但重复地覆盖了大部分成员)。

基本上，为了保留当前代码，您可以使用SerializeWithLengthPrefix 代替Serialize，即

foreach(var item in list)
{
    Serializer.SerializeWithLengthPrefix(stm, item,
        PrefixStyle.Base128, Serializer.ListItemTag);
}

但也可以简单地使用：

Serializer.Serialize(stm, list);

它们在语义上是相同的；在这两种情况下，你得到的是（以密集的二进制形式）：

[field 1, string]
[payload length of item 0]
[payload of item 0]
[field 1, string]
[payload length of item 1]
[payload of item 1]
...
[field 1, string]
[payload length of item n]
[payload of item n]

正是当你告诉 TClass[] 时，Deserialize 正在寻找什么