java二进制文件操作

发布于 2025-01-08 04:12:14 字数 283 浏览 1 评论 0原文

我有一堆不同的对象（和 objec 类型），我想将它们写入二进制文件。首先，我需要文件的结构如下：

`Object type1

obj1, obj2 ...

Object type2

obj1, obj2...

....

作为一个二进制文件，这不能帮助用户阅读它，但我想要一个结构，以便我可以搜索、删除或按类型添加对象，而不是解析整个文件。这是我不知道该怎么做的事情。这可能吗？

原文

I have a bunch of different objects(and objec types) that i want to write to a binary file. First of all i need the file to be structured like this:

`Object type1

obj1, obj2 ...

Object type2

obj1, obj2...

....

Being a binary file this doesn't help a user read it, but i want to have a structure so i can search, delete or add an object by it's type, not parsing the entire file. And this is something i don't know how to do. Is this even posible?

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只为一人 2025-01-15 04:12:14

您必须在文件的开头（或其他位置）维护一个标头来标记每个对象的位置和长度。

标头的类型和布局在很大程度上取决于您计划如何读取和写入文件。例如，如果您计划按名称检索对象，则文件中可以包含类似以下内容

object1 500 1050
object2 1550 800
object3 2350 2000
<some padding to cover 500 bytes>
<the 1050 bytes of object1><the 800 bytes of object2><the 2000 bytes of object3>

并知道 object1 从文件中的偏移量 400 开始，长度为 1050 字节。

由于您似乎想要存储不同类型的对象，因此您可能需要向标头添加一些附加数据。

请注意以下事项：

每次添加、删除或修改文件时，您都必须在标头中更新后续所有文件的偏移量（例如，如果我删除 object2，则 object3 的偏移量现在为 1550）。
如果您将标头与数据存储在同一个文件中，那么在计算偏移量时必须考虑标头的大小（这会使事情变得更加困难，我建议您将标头和二进制数据分开。
您将不得不每次您想要访问对象时，请考虑使用标准化格式来避免出现问题（YML 或 XML），

但我不知道有任何库可以帮助您实现此类功能。我很确定有一些。也许有人可以建议。另

一种解决方案是使用 ZipFile（Java 本身支持）之类的东西并将每个对象编写为不同的 ZipEntry，这样您就不必自己管理对象分离。不用担心知道您想要的确切 ZipEntry。

You will have to maintain a header at the beginning of the file (or somewhere else) to mark the position and length of each of your objects.

The kind and layout of the header depend a lot on how you plan to read and write into the file. For example if you plan to retrieve the objects by name, you could have in your file something like this

object1 500 1050
object2 1550 800
object3 2350 2000
<some padding to cover 500 bytes>
<the 1050 bytes of object1><the 800 bytes of object2><the 2000 bytes of object3>

And know that object1 starts at the offset 400 in the file, and has a length of 1050 bytes.

Since it seems that you have different types of objects that you want to store, you will probably need to add some additional data to your header.

Take care of the following:

Each time you add, delete or modifiy a file, you will have to update in the header the offset for all files that follow (for example if I remove object2, then the offset for object3 is now 1550).
If you store the header in the same file as the data, then you must take the size of the header into account when computing offsets (this will make things much harder, I suggest you keep the header and binary data separated.
You will have to read and parse the header each time you want to access an object. Consider using a standardized format for your header to avoid problems (YML or XML).

I'm not aware of any library that will help you implement such a feature but I'm pretty sure there are some. Maybe someone will be able to suggest one.

Another solution would be to use something like a ZipFile (which is natively supported by Java) and write each of your objects as a differenz ZipEntry. This way you won't have to manage object separation yourself, and will only need to worry about knowing the exact ZipEntry you want.

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