如果在不同语言/体系结构的相同输入上运行，protobuf是否会生成按位的完美副本? [英] Will protobuf generate bitwise perfect copy if ran on the same input on different languages/architectures?

问题描述

如果我在多个机器(arm，x86，amd64等)上使用相同的 .proto 文件，并且使用以不同语言(c ++，python，java等)编写的实现，在不同配置中进行序列化时，同一条消息会导致完全相同的字节顺序吗?

If I use the same .proto file, across several machine (arm, x86, amd64 etc.) with implementations written in different languages (c++, python, java, etc.), will the same message result in the exact same byte sequence when serialized across those different configurations?

我想使用这些字节进行哈希处理，以确保同一消息在不同平台上生成时最终会具有完全相同的哈希值.

I would like to use these bytes for hashing to ensure that the same message, when generated on a different platform, would end up with the exact same hash.

推荐答案

通常但并非总是如此"

"Often, but not quite always"

您可能会产生差异的原因包括:

The reasons you might get variance include:

• 按数字顺序写入字段只是应该"，而不是必须"-

  序列化消息时，其已知字段应按字段编号顺序写入

  因此不要求字段按顺序排序(反序列化器必须能够处理无序字段是必须")；这在讨论意外/扩展字段时尤其适用；如果两个序列化选择不同的字段顺序，则字节将不同

  and it is not demanded that fields are thus ordered (it is a "must" that deserializers be able to handle out-of-order fields); this can apply especially when discussing unexpected/extension fields; if two serializations choose different field orders, the bytes will be different

  在大多数情况下，是的:它将是可靠且可重复的.但这不是实际的保证.

  In most common cases, yes: it'll be reliable and repeatable. But this is not an actual guarantee.

  尽管字节-应该仍然具有相同的语义-只是字节不相同，但是字节应该与兼容.使用哪种语言，框架，库，运行时或处理器都无关紧要.如果存在:那是一个错误.

  The bytes should be compatible, though - it'll still have the same semantics - just not the same bytes. It shouldn't matter what language, framework, library, runtime, or processor you use. If it does: that's a bug.

  这篇关于如果在不同语言/体系结构的相同输入上运行，protobuf是否会生成按位的完美副本?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！