changing content of fs.createReadstream - node.js

Question

I have requirement such that I am reading a file on express request as follows:
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);
So what should I do to make the 'finalBuffer' readable on request,in other words, how to pipe the finalBuffer data with res(response).

Answer 1

Finally I got the way for creating read stream from a Buffer using stream of node js.
I got exact solution from here.
I have just put a little bit code like
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;
};
If anybody has some issue with this please comment I will try my best to make him/her understood my code snippet.