create custom storage engine to get hash of file

customstorage.js

@@ -0,0 +1,71 @@
+var fs = require('fs');
+var os = require('os');
+var path = require('path');
+var crypto = require('crypto');
+var mkdirp = require('mkdirp');
+
+function getFilename (req, file, cb) {
+	crypto.pseudoRandomBytes(16, function (err, raw) {
+		cb(err, err ? undefined : raw.toString('hex'));
+	});
+}
+
+function getDestination (req, file, cb) {
+	cb(null, os.tmpdir());
+}
+
+function customStorage (opts) {
+	this.getFilename = (opts.filename || getFilename);
+
+	if (typeof opts.destination === 'string') {
+		mkdirp.sync(opts.destination);
+		this.getDestination = function ($0, $1, cb) { cb(null, opts.destination) };
+	} else {
+		this.getDestination = (opts.destination || getDestination);
+	}
+}
+
+customStorage.prototype._handleFile = function _handleFile (req, file, cb) {
+	var that = this;
+	var hash = crypto.createHash('sha256');
+
+	that.getDestination(req, file, function (err, destination) {
+		if (err) return cb(err);
+
+		that.getFilename(req, file, function (err, filename) {
+			if (err) return cb(err);
+
+			var finalPath = path.join(destination, filename);
+			var outStream = fs.createWriteStream(finalPath);
+
+			file.stream.pipe(outStream);
+			outStream.on('error', cb);
+			file.stream.on('data', function (chunk) {
+				hash.update(chunk);
+			});
+			outStream.on('finish', function () {
+				cb(null, {
+					destination: destination,
+					filename: filename,
+					path: finalPath,
+					size: outStream.bytesWritten,
+					hash: hash.digest('hex')
+				});
+			});
+		});
+	});
+}
+
+customStorage.prototype._removeFile = function _removeFile (req, file, cb) {
+	var path = file.path;
+
+	delete file.destination;
+	delete file.filename;
+	delete file.path;
+
+	fs.unlink(path, cb);
+}
+
+module.exports = function (opts) {
+	return new customStorage(opts);
+}

index.js

@@ -10,6 +10,7 @@ var consolidate = require('consolidate');
 var useragent = require('express-useragent');
 var mongoose = require('mongoose');
 
+var customstorage = require('./customstorage');
 var config = require('./config');
 
 var port = config.port;
@@ -26,10 +27,11 @@ var uploadRecord = mongoose.model('upload', {
 	ip: String,
 	originalFilename: String,
 	filename: String,
+	hash: String,
 	timestamp: Number
 });
 
-var storage = multer.diskStorage({
+var storage = customstorage({
 	destination: function (req, file, cb) {
 		cb(null, uploadPath)
 	},
@@ -93,6 +95,7 @@ app.post('/', (req, res) => {
 				ip: ip,
 				originalFilename: req.file.originalname,
 				filename: req.file.filename,
+				hash: req.file.hash,
 				timestamp: + new Date()
 			});