問題描述

我使用以下 matlab 代碼創建了一個二進制文件:

I have created a binary file using the following matlab code:

x is an array of int32 numbers
n is the length of x

fid = fopen("binary_file.dat", "wb");
fwrite(fid, n, 'int32');
fwrite(fid, x, 'int32');
fclose(fid);

我可以使用下面的 C 代碼來讀取這個文件:

I can use the following C code to read this file:

fp = fopen("binary_file.dat", "rb");
int n;
fread(&n, 4, 1, fp);//read 4 bytes
int *x = new int[n];
for (int i = 0; i < n; i++)
{
int t;
fread(&t,4, 1,fp);//read 4 bytes
x[i] = t;
}
......

上面的 C 代碼可以讀取正確的結果.但是，我現在想用 JAVA 讀取這樣的二進制文件.我的代碼如下所示:

The above C code can read correct results. However, I now want to read such binary file in JAVA. My code is shown as follows:

DataInputStream data_in = new DataInputStream(
             new BufferedInputStream(
                    new FileInputStream(
                new File("binary_file.dat"))));
while(true)
{
   try {
      int t = data_in.readInt();//read 4 bytes
      System.out.println(t);
   } catch (EOFException eof) {
    break;
   }
}
data_in.close();

它確實在 n+1 次循環后終止，但結果不正確.誰能幫幫我.非常感謝！

It DOES terminates after n+1 loops, but the results are not correct. Can anybody help me out. Thanks very much!

推薦答案

我猜這是字節序問題，即你的二進制文件寫成小端整數(可能是因為您使用的是 Intel 或類似的 CPU).

As I was guessing it is an endianness issue, i.e. your binary file is written as little-endian integers (probably, because you are using a Intel or similar CPU).

然而，Java 代碼正在讀取大端整數，無論??它在什么 CPU 上運行.

The Java code, however, is reading big-endian integers, no matter what CPU it is running on.

為了顯示問題，以下代碼將讀取您的數據并將整數顯示為字節序轉換前后的十六進制數.

To show the problem the following code will read your data and display the integers as hex number before and after endianness conversion.

import java.io.*;

class TestBinaryFileReading {

  static public void main(String[] args) throws IOException {  
    DataInputStream data_in = new DataInputStream(
        new BufferedInputStream(
            new FileInputStream(new File("binary_file.dat"))));
    while(true) {
      try {
        int t = data_in.readInt();//read 4 bytes

        System.out.printf("%08X ",t); 

        // change endianness "manually":
        t = (0x000000ff & (t>>24)) | 
            (0x0000ff00 & (t>> 8)) | 
            (0x00ff0000 & (t<< 8)) | 
            (0xff000000 & (t<<24));
        System.out.printf("%08X",t); 
        System.out.println();
      } 
      catch (java.io.EOFException eof) {
        break;
      }
    } 
    data_in.close();
  }
}

如果您不想手動"更改字節順序，請參閱此問題的答案問題:
將小端文件轉換為大端

If you don't want to do change endianness "manually", see answers to this question:
convert little Endian file into big Endian

這篇關于如何使用 JAVA 讀取 C/Matlab 創建的二進制文件的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！