使用C#protobuf-net进行序列化时，如何将对象附加到文件? [英] How to append object to a file while serializing using c# protobuf-net?

问题描述

我得到了Protobuf-net的源代码，该源代码将对象序列化为文件.

var person = new Person {
        Id = 12345, Name = "Fred",
        Address = new Address {
            Line1 = "Flat 1",
            Line2 = "The Meadows"
        }
    };
    using (var file = File.Create("person.bin")) {
        ProtoBuf.Serializer.Serialize(file, person);
    }

但是假设我有两个要序列化为单个文件的Person实例.我该怎么办?

纯粹意义上，

解决方案

protobuf除文件末尾外没有任何终止符"(这是因为对象可以通过以下方式简单地合并/合并:连接斑点).

但是，我们可以插入自己的标记，例如，通过在每个对象前添加随后的数据长度作为前缀.

protobuf-net通过公开SerializeWithLengthPrefix方法对此进行了总结.有多种方法可以反序列化此方法，但是最简单的方法是DeserializeItems，它依次为您提供对象的流序列(从迭代器的流中懒惰地假脱机-因此非常适合非常大的序列).

有关信息，因此您可以看到它是如何实现的:如果使用PrefixStyle.Base128和正数fieldNumber，则在线看起来就好像您有包装对象一样像:

[ProtoContract]
public class DoesNotExist {
    [ProtoMember({fieldNumber})]
    public List<Person> People {get;set;}
}

主要区别在于没有实际的DoesNotExist类型/实例，并且没有创建List<T>-您只需获取Person实例.

I got a source code of Protobuf-net that serializes an object to a file.

var person = new Person {
        Id = 12345, Name = "Fred",
        Address = new Address {
            Line1 = "Flat 1",
            Line2 = "The Meadows"
        }
    };
    using (var file = File.Create("person.bin")) {
        ProtoBuf.Serializer.Serialize(file, person);
    }

But suppose i have two instance of Person that i want to serialize into a single file. how can i do that?

解决方案

protobuf, in the pure sense, does not have any "terminator" except the end of a file (this is so that objects can be merged/combined simply by concatenating the blobs).

However, we can inject our own markers, for example by prefixing every object with the length of the data that follows.

protobuf-net wraps this up by exposing a SerializeWithLengthPrefix method. There are various methods to deserialize from this, but the simplest is DeserializeItems, which gives you a streaming sequence of objects in turn (lazily spooling from the stream in the iterator - so it is perfectly suitable for very large sequences).

For info, so you can see how this is implemented: if you use PrefixStyle.Base128 and a positive fieldNumber, then on the wire this looks the same as if you had a wrapper object like:

[ProtoContract]
public class DoesNotExist {
    [ProtoMember({fieldNumber})]
    public List<Person> People {get;set;}
}

the key differences being that no actual DoesNotExist type/instance exists, and no List<T> is created - you just get the Person instances.

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