Java implements method of parsing binary files

1. Requirements description, implementation details:

Parse the binary file files\case10\binary, which contains a string and a picture. The data file format is string data length (2 Bytes) + string content + picture data length (4 bytes) + picture data, the data length is the data byte length, with the high-order bit last, the string is UTF-8 encoded, please parse and output the string content, picture The file is saved as files\case10\test.png.

2. Implementation code:

package com.igen.case10;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

import java.io.IOException;
import java.io.InputStream;
import java.net.URISyntaxException;

/**

* 

* @ClassName Case10

* @Description TODO

*

* @author wjggwm

* @data 2017年2月7日 上午11:46:25

*/

public class Case10 {


static final String fileName = "/test.png";
static final String filePath = "D:/files/case10";
static final String sourceFileName = "binary";

public static void main(String[] args) {

try {
readFile(Case10.class.getResource(sourceFileName).toURI().getPath());

} catch (URISyntaxException e) {

e.printStackTrace();

}

}

/**

* 

* @Description 解析二进制文件

* @param sourceFileName

*

* @author wjggwm

* @data 2017年2月7日 上午11:47:12

*/

public static void readFile(String sourceFileName) {

InputStream in = null;

try {

in = new FileInputStream(sourceFileName);

 

// 读取字符串数据长度字节

byte[] txtLenByte = new byte[2];

in.read(txtLenByte);

int txtlen = byte2ToUnsignedShort(txtLenByte, 0);

 

// 读取字符串字节

byte[] txtByte = new byte[txtlen];

in.read(txtByte);

//字符串为UTF-8编码

String txt = new String(txtByte, "UTF-8");

// 输出字符串

System.out.println(txt);

 

// 读取图片数据长度

byte[] imgLenByte = new byte[4];

in.read(imgLenByte);

int imgLen = byte4ToInt(imgLenByte, 0);

 

// 读取图片数据

byte[] img = new byte[imgLen];

in.read(img);

// 生成图片文件

saveToImgByBytes(filePath, fileName, img);

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

} finally {

if (in != null) {

try {

in.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

 

}

 

/**

* 

* @Description 将字节写入文件

* @param imgName

* @param imgByte

*

* @author wjggwm

* @data 2017年2月7日 上午11:07:45

*/

public static void saveToImgByBytes(String filePath, String imgName, byte[] imgByte) {

try {

File dic = new File(filePath);

if (!dic.exists()) {

dic.mkdirs();

}

File image = new File(filePath + imgName);

if (!image.exists()) {

image.createNewFile();

}

FileOutputStream fos = new FileOutputStream(image);

fos.write(imgByte);

fos.flush();

fos.close();

} catch (Exception e) {

e.printStackTrace();

}

}

 

/**

* 

* @Description byte数组转换为无符号short整数

* @param bytes

* @param off

* @return

*

* @author wjggwm

* @data 2017年2月7日 上午11:05:58

*/

public static int byte2ToUnsignedShort(byte[] bytes, int off) {

// 注意高位在后面，即大小端问题

int low = bytes[off];

int high = bytes[off + 1];

return (high << 8 & 0xFF00) | (low & 0xFF);

}

 

/**

* 

* @Description byte数组转换为int整数

* @param bytes

* @param off

* @return

*

* @author wjggwm

* @data 2017年2月7日 上午11:07:23

*/

public static int byte4ToInt(byte[] bytes, int off) {

// 注意高位在后面，即大小端问题

int b3 = bytes[off] & 0xFF;

int b2 = bytes[off + 1] & 0xFF;

int b1 = bytes[off + 2] & 0xFF;

int b0 = bytes[off + 3] & 0xFF;

return (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;

}

}

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