I am trying to learn some basics of event driven programming. So for an exercise I am trying to write a program that reads a large binary file and does something with it but without ever making a blocking call. I have come up with the following:
var fs = require('fs');
var BUFFER_SIZE = 1024;
var path_of_file = "somefile"
fs.open(path_of_file, 'r', (error_opening_file, fd) =>
{
if (error_opening_file)
{
console.log(error_opening_file.message);
return;
}
var buffer = new Buffer(BUFFER_SIZE);
fs.read(fd, buffer, 0, BUFFER_SIZE, 0, (error_reading_file, bytesRead, buffer) =>
{
if (error_reading_file)
{
console.log(error_reading_file.message);
return;
}
// do something e.g. print or write to another file
})
})
I know I need to put a while loop in order to read complete file but in the above code I am reading just the first 1024 bytes of the file and cannot formulate how to continue reading the file without using a blocking loop. How could we do it?
Use fs.createReadStream instead. This will call your callback over and over again until it has finished reading the file, so you don't have to block.
var fs = require('fs');
var readStream = fs.createReadStream('./test.exe');
readStream.on('data', function (chunk) {
console.log(chunk.length);
})