javascript - Replacing fs.readFile with fs.createReadStream in Node.js -
i have code reading image directory , sending index.html.
i trying replace fs.readfile fs.createreadstream have no idea how implement can not find example.
here got (index.js)
var app = require('express')(); var http = require('http').server(app); var io = require('socket.io')(http); var fs = require('fs'); http.listen(3000, function () { console.log('listening on *:3000'); }); app.get('/', function (req, res) { res.sendfile(__dirname + '/public/views/index.html'); }); io.on('connection', function (socket) { fs.readfile(__dirname + '/public/images/image.png', function (err, buf){ socket.emit('image', { image: true, buffer: buf.tostring('base64') }); }); }); index.html
<!doctype html> <html> <body> <canvas id="canvas" width="200" height="100"> browser not support html5 canvas tag. </canvas> <script src="https://cdn.socket.io/socket.io-1.2.0.js"></script> <script> var socket = io(); var ctx = document.getelementbyid('canvas').getcontext('2d'); socket.on("image", function (info) { if (info.image) { var img = new image(); img.src = 'data:image/jpeg;base64,' + info.buffer; ctx.drawimage(img, 0, 0); } }); </script> </body > </html >
the below approach uses core modules , reads chunks stream.readable instance returned fs.createreadstream() , returns chunks buffer. isn't great of approach if you're not going stream chunks back. you're going hold file within buffer resides in memory, solution reasonably sized files.
io.on('connection', function (socket) { filetobuffer(__dirname + '/public/images/image.png', (err, imagebuffer) => { if (err) { socket.emit('error', err) } else { socket.emit('image', { image: true, buffer: imagebuffer.tostring('base64') }); } }); }); const filetobuffer = (filename, cb) => { let readstream = fs.createreadstream(filename); let chunks = []; // handle errors while reading readstream.on('error', err => { // handle error // file not read return cb(err); }); // listen data readstream.on('data', chunk => { chunks.push(chunk); }); // file done being read readstream.on('close', () => { // create buffer of image stream return cb(null, buffer.concat(chunks)); }); } http response stream example
its better idea use http streaming data since built protocol , you'd never need load data memory @ once since can pipe() file stream directly response.
this basic example without bells , whistles , demonstrate how pipe() stream.readable http.serverresponse. example uses express works exact same way using http or https node.js core api.
const express = require('express'); const fs = require('fs'); const server = express(); const port = process.env.port || 1337; server.get ('/image', (req, res) => { let readstream = fs.createreadstream(__dirname + '/public/images/image.png') // when stream done being read, end response readstream.on('close', () => { res.end() }) // stream chunks response readstream.pipe(res) }); server.listen(port, () => { console.log(`listening on ${port}`); });
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