JS读取cpio文件内的一个文件

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

const cpio = require("cpio-stream");
/**
 * 解压获得CPIO升级包内的描述信息
 * @param {stream.Readable} file CPIO文件打开之后的Stream
 * @param {string} desc_name CPIO内包含描述信息的文件名
 * @return {Promise<string>}
 */
module.exports = function(file, desc_name) {
  let extract = cpio.extract();
  return new Promise((resolve, reject) => {
    extract.on("entry", function(header, stream, next) {
      // header is the tar header
      // stream is the content body (might be an empty stream)
      // call next when you are done with this entry
      let body = "";
      // 读取流文件内容
      stream.on("data", function(chunk) {
        if (header.name == desc_name) {
          body += chunk;
        }
      });
      // 读取流文件结束
      stream.on("end", function() {
        if (header.name == desc_name) {
          resolve(body);
        }
        next();
      });
      stream.resume(); // just auto drain the stream
    });
    extract.on("finish", function() {
      reject("all entries already read");
    });
    file.pipe(extract);
  });
};