用Java读取结构化二进制文件的最佳方式 [英] Best way to read structured binary files with Java

问题描述

我必须使用Java来读取旧格式的二进制文件。

简而言之，文件具有由几个整数，字节和固定长度的char数组组成的标题，后面是一个也由整数和字符组成的记录列表。

在任何其他语言中，我将创建 struct s（C / C ++）或 s（Pascal / Delphi），它们是头和记录的逐字节表示。然后我会将 sizeof（header）个字节读入标头变量，并对记录执行相同操作。

这样的东西：（Delphi）

  type 
 THeader = record 
版本：整数; 
类型：字节; 
 BeginOfData：Integer; 
 ID：array [0..15] of Char; 
结束
 
 ... 
 
程序ReadData（S：TStream）; 
 var 
标题：THeader; 
 begin 
 S.ReadBuffer（Header，SizeOf（THeader））; 
 ... 
 end; 
  

做什么与Java类似的最好方法是什么？我必须自己读取每一个值，还有其他方式做这种块读吗？

解决方案

据我所知，Java强制您以字节读取文件，而不是阻止读取。如果您正在序列化Java对象，那将是一个不同的故事。

其他示例使用 DataInputStream 类与文件，但您也可以使用快捷方式： RandomAccessFile 类：

  RandomAccessFile in = new RandomAccessFile（filename，r）; 
 int version = in.readInt（）; 
 byte type = in.readByte（）; 
 int beginOfData = in.readInt（）; 
 byte [] tempId; 
 in.read（tempId，0，16）; 
 String id = new String（tempId）; 
  

请注意，您可以将responce对象转换为类，如果这样会更容易。 p>

I have to read a binary file in a legacy format with Java.

In a nutshell the file has a header consisting of several integers, bytes and fixed-length char arrays, followed by a list of records which also consist of integers and chars.

In any other language I would create structs (C/C++) or records (Pascal/Delphi) which are byte-by-byte representations of the header and the record. Then I'd read sizeof(header) bytes into a header variable and do the same for the records.

Something like this: (Delphi)

type
  THeader = record
    Version: Integer;
    Type: Byte;
    BeginOfData: Integer;
    ID: array[0..15] of Char;
  end;

...

procedure ReadData(S: TStream);
var
  Header: THeader;
begin
  S.ReadBuffer(Header, SizeOf(THeader));
  ...
end;

What is the best way to do something similar with Java? Do I have to read every single value on its own or is there any other way to do this kind of "block-read"?

解决方案

To my knowledge, Java forces you to read a file as bytes rather than being able to block read. If you were serializing Java objects, it'd be a different story.

The other examples shown use the DataInputStream class with a File, but you can also use a shortcut: The RandomAccessFile class:

RandomAccessFile in = new RandomAccessFile("filename", "r");
int version = in.readInt();
byte type = in.readByte();
int beginOfData = in.readInt();
byte[] tempId;
in.read(tempId, 0, 16);
String id = new String(tempId);

Note that you could turn the responce objects into a class, if that would make it easier.

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