设计（二进制）文件格式时要注意什么？ [英] What are important points when designing a (binary) file format?

问题描述

当设计用于记录二进制数据的文件格式时，您认为格式应该具有什么属性？到目前为止，我已经提出了以下重点：

When designing a file format for recording binary data, what attributes would you think the format should have? So far, I've come up with the following important points:

• 开始时有一些魔术字节，能够识别文件（在具体情况下，这也有助于区分文件和遗留文件）


• 在开头有一个文件版本号，以便文件格式可以更改后，不会破坏兼容性


• 指定所有数据项的字节和大小;或者：包含一些空格来描述数据的字节/大小（我会倾向于前者）


• 可能为将来可能需要的进一步的每个文件属性预留一些空间？ / li>
  

• have some "magic bytes" at the beginning, to be able to recognize the files (in my specific case, this should also help to distinguish the files from "legacy" files)
• have a file version number at the beginning, so that the file format can be changed later without breaking compatibility
• specify the endianness and size of all data items; or: include some space to describe endianness/size of data (I would tend towards the former)
• possibly reserve some space for further per-file attributes that might be necessary in the future?

还有什么会使格式更具前瞻性，并尽量减少头痛？

What else would be useful to make the format more future-proof and minimize headache in the future?

推荐答案

查看 PNG规范。这种格式有一些非常好的理由背后。

Take a look at the PNG spec. This format has some very good rationale behind it.

另外，决定什么对您的未来格式很重要：紧凑性，兼容性，允许嵌入其他格式（不同的压缩算法）内它。另一个有趣的例子是 Google的协议缓冲区 ，其中传输的数据的大小是王。

Also, decide what's important for your future format: compactness, compatibility, allowing to embed other formats (different compression algorithms) inside it. Another interesting example would be the Google's protocol buffers, where size of the transferred data is the king.

关于字节顺序，我建议您选择一个选项并坚持使用，不允许不同的字节顺序。否则，读书和写书库只会变得更复杂和更慢。

As for endianness, I'd suggest you to pick one option and stick with it, not allowing different byte orders. Otherwise, reading and writing libraries will only get more complex and slower.

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