更改 fs.createReadstream 的内容

Question

我有这样的要求，我正在阅读一个明确请求的文件，如下所示：

const fs = require('fs');
const os = require('os');
const path = require('path');
var express = require("express");
app = express();

app.get('/getdata', function (req, res) {
  var stream = fs.createReadStream('myFileLocation');// this location contains encrypted file
  let tempVariable = [];
  stream.on('data', function(chunk) {
        tempVariable += chunk;
    });
stream.on('end', function () {
    *****here I read tempVariable and using it I decrypt the file content and output a buffer (say,finalBuffer)****

})
stream.on('error', function (error) {
        res.writeHead(404, 'Not Found');
        res.end();
    });
stream.pipe(res);

那么我应该怎么做才能使 'finalBuffer' 在请求时可读，换句话说，如何使用 res(response) 传输 finalBuffer 数据。

Answer 1

终于找到了使用节点js流从缓冲区创建读取流的方法。我从 here 得到了精确的解决方案。我刚刚放了一些代码，比如

const fs = require('fs');
const os = require('os');
const path = require('path');
var express = require("express");
app = express();

app.get('/getdata', function (req, res) { // getdata means getting decrypted data


fs.readFile(file_location, function read(err, data) {
   // here I am performing my decryption logic which gives output say 
   //"decryptedBuffer"
   var stream = require("./index.js");
   stream.createReadStream(decryptedBuffer).pipe(res);

})
})

// index.js
'use strict';

var util = require('util');
var stream = require('stream');

module.exports.createReadStream = function (object, options) {
  return new MultiStream (object, options);
};

var MultiStream = function (object, options) {
  if (object instanceof Buffer || typeof object === 'string') {
    options = options || {};
    stream.Readable.call(this, {
      highWaterMark: options.highWaterMark,
      encoding: options.encoding
    });
  } else {
    stream.Readable.call(this, { objectMode: true });
  }
  this._object = object;
};

util.inherits(MultiStream, stream.Readable);

MultiStream.prototype._read = function () {
  this.push(this._object);
  this._object = null;
};

如果有人对此有任何疑问，请发表评论，我会尽力让 him/her 理解我的代码片段。

更改 fs.createReadstream 的内容

changing content of fs.createReadstream

pipe

filestream

node.js

express