python到Java校验和计算

Question

我收到了这个生成文件校验和的python脚本:

import sys,os

if __name__=="__main__":
#filename=os.path.abspath(sys.argv[1])
#filename=r"H:\Javier Ortiz\559-7 From Pump.bin"
cksum=0
offset=0
pfi=open(filename,'rb')
while 1:
  icks=0
  chunk=pfi.read(256)
  if not chunk:  break     #if EOF exit loop

  for iter in chunk:
    icks+=ord(iter)
    print ord(iter)
  cksum=(cksum+icks) & 0xffff
pfi.close()
print "cksum=0x%4.4x"%cksum

而我正在尝试将其转换为Java,但我没有得到相同的结果.

这是我的Java代码:

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class ChecksumCalculator {

private ChecksumCalculator() {
}

public static int getChecksum(File file) {
    int cksum = 0;
    FileInputStream fis = null;
    BufferedInputStream bis = null;
    DataInputStream dis = null;
    try {
        fis = new FileInputStream(file);

        // Here BufferedInputStream is added for fast reading.
        bis = new BufferedInputStream(fis);
        dis = new DataInputStream(bis);
        byte[] buffer = new byte[256];
        // dis.available() returns 0 if the file does not have more lines.
        while (dis.read(buffer) != -1) {
            int icks = 0;
            for (byte b : buffer) {
                icks += b & 0xff;
                System.out.println(b & 0xff);
            }
            cksum = (cksum + icks) & 0xffff;
            System.out.println("Checksum: " + cksum);
        }

        // dispose all the resources after using them.
        fis.close();
        bis.close();
        dis.close();
        return cksum;
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        return -1;
    } catch (IOException e) {
        e.printStackTrace();
        return -1;
    }
}

static public void main(String[] s) {
    System.out.println("0x" + getChecksum(new File("H:\\Javier Ortiz\\559-7 From Pump.bin")));
}

}

但是我在文件上得到了不同的结果.例如,如果我在只包含单词test的普通txt文件上运行它,它会给出以下结果:

python:cksum = 0x01c0 java:cksum = 0x448

任何的想法？

Answer 1

您的Python版本以十六进制格式打印校验和,而Java版本以十进制格式打印.您也应该使您的Java版本以十六进制格式打印.0x1c0 == 448.

要cksum=0x%4.4x像在Python版本中一样使用格式字符串,请使用:

System.out.printf("cksum=0x%4.4x%n", ...);

甚至更好

System.out.printf("cksum=%#04x%n", ...);

此外,你不需要DataInputStream这个.只需使用bis.read(buffer)而不是dis.read(buffer).